If you like this book, please consider + spreading the word or + + buying me a coffee + +
+ ``` +include-after: +- | + ```{=html} +
+
+
+ ```
+---
+```
+
+下面几个变量需要注意一下：
+
+- `header-includes` 变量包含将要嵌入 `` 标签的 HTML 文本。
+- 调用变量后的下一行必须是 `- |`。再往下一行必须以与 `|` 对齐的三个反引号开始，否则 Pandoc 将无法识别。`{= html}` 告诉 Pandoc 其中的内容是原始文本，不应该作为 Markdown 处理。（为此，需要检查 Pandoc 中的 `raw_attribute` 扩展是否已启用。要进行此检查，键入 `pandoc --list-extensions | grep raw` 并确保返回的列表包含名为 `+ raw_html` 的项目，加号表示已启用。）
+- 变量 `include-before` 在网页开头添加一些 HTML 文本，此处我请求读者帮忙宣传我的书或给我打赏。
+- `include-after` 变量在网页末尾添加原始 HTML 文本，同时显示我的图书许可证。
+
+这些只是其中一部分可用的变量，查看 HTML 中的模板变量（我的文章 [Pandoc简介][1] 中介绍了如何查看 LaTeX 的模版变量，查看 HTML 模版变量的过程是相同的）对其余变量进行了解。
+
+#### 将网页分成多章
+
+网页可以作为一个整体生成，这会产生一个包含所有内容的长页面；也可以分成多章，我认为这样会更容易阅读。我将解释如何将网页划分为多章，以便读者不会被长网页吓到。
+
+为了使网页易于在 GitHub Pages 上部署，需要创建一个名为 `docs` 的根文件夹（这是 GitHub Pages 默认用于渲染网页的根文件夹）。然后我们需要为 `docs` 下的每一章创建文件夹，将 HTML 内容放在各自的文件夹中，将文件内容放在名为 `index.html` 的文件中。
+
+例如，`about.md` 文件将转换成名为 `index.html` 的文件，该文件位于名为 `about`（`about/index.html`）的文件夹中。这样，当用户键入 `http://+
+
+
+ ` 和 `
` 来包裹文本，那么浏览器将识别 `` 和 `
` 中的文本是一个段落。我们这样做： + +``` +After all the battles we fought together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you.
+``` + +通过在 `` 和 `
`中编写段落，你创建了一个 HTML 元素。一个网页就是 HTML 元素的集合。 + +让我们首先来认识一些术语：`` 是开始标签，`
` 是结束标签，“p” 是标签名称。元素开始和结束标签之间的文本是元素的内容。 + +### “style” 属性 + +在上面，你将看到文本覆盖屏幕的整个宽度。 + +我们不希望这样。没有人想要阅读这么长的行。让我们设定段落宽度为 550px。 + +我们可以通过使用元素的 `style` 属性来实现。你可以在其 `style` 属性中定义元素的样式（例如，在我们的示例中为宽度）。以下行将在 `p` 元素上创建一个空样式属性： + +``` +...
+``` + +你看到那个空的 `""` 了吗？这就是我们定义元素外观的地方。现在我们要将宽度设置为 550px。我们这样做： + +``` ++ After all the battles we fought together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you. +
+``` + +我们将 `width` 属性设置为 `550px`，用冒号 `:` 分隔，以分号 `;` 结束。 + +另外，注意我们如何将 `` 和 `
` 放在单独的行中，文本内容用一个制表符缩进。像这样设置代码使其更具可读性。 + +### HTML 中的列表 + +接下来，蝙蝠侠希望列出他所钦佩的人的一些优点，例如： + +``` +You complete my darkness with your light. I love: +- the way you see good in the worst things +- the way you handle emotionally difficult situations +- the way you look at Justice +I have learned a lot from you. You have occupied a special place in my heart over time. +``` + +这看起来很简单。 + +让我们继续，在 `` 下面复制所需的文本： + +``` ++ After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you. +
++ You complete my darkness with your light. I love: + - the way you see good in the worse + - the way you handle emotionally difficult situations + - the way you look at Justice + I have learned a lot from you. You have occupied a special place in my heart over the time. +
+``` + +保存并刷新浏览器。 + + + +哇！这里发生了什么，我们的列表在哪里？ + +如果你仔细观察，你会发现没有显示换行符。在代码中我们在新的一行中编写列表项，但这些项在浏览器中显示在一行中。 + +如果你想在 HTML（新行）中插入换行符，你必须使用 ``。让我们来使用 `
`，看看它长什么样： + +``` +
+ After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you. +
+
+ You complete my darkness with your light. I love:
+ - the way you see good in the worse
+ - the way you handle emotionally difficult situations
+ - the way you look at Justice
+ I have learned a lot from you. You have occupied a special place in my heart over the time.
+
`，但第二个段落仍然是从一个新行开始，这是因为 `
` 元素会自动插入换行符。 + +我们使用纯文本编写列表，但是有两个标签可以供我们使用来达到相同的目的：`
- ` and `
- `。
+
+让我们解释一下名字的意思：ul 代表无序列表，li 代表列表项目。让我们使用它们来展示我们的列表：
+
+```
+
+ After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you. +
+``` + +``` ++ You complete my darkness with your light. I love: +
-
+
- the way you see good in the worse +
- the way you handle emotionally difficult situations +
- the way you look at Justice +
`，因为每个 ` - ` 会自动显示在新行中 +* 我们将每个列表项包含在 `
- ` 和 ` ` 之间 +* 我们将所有列表项的集合包裹在 `
- the way you see good in the worse +
- the way you handle emotionally difficult situations +
- the way you look at Justice +
- the way you see good in the worse +
- the way you handle emotionally difficult situations +
- the way you look at Justice +
- the way you see good in the worse +
- the way you handle emotionally difficult situations +
- the way you look at Justice +
- the way you see good in the worse +
- the way you handle emotionally difficult situations +
- the way you look at Justice +
- the way you see good in the worse +
- the way you handle emotionally difficult situations +
- the way you look at Justice +
- the way you see good in the worse +
- the way you handle emotionally difficult situations +
- the way you look at Justice +
- the way you see good in the worse +
- the way you handle emotionally difficult situations +
- the way you look at Justice +
- the way you see good in the worse +
- the way you handle emotionally difficult situations +
- the way you look at Justice +
- the way you see good in the worse +
- the way you handle emotionally difficult situations +
- the way you look at Justice +
- the way you see good in the worse +
- the way you handle emotionally difficult situations +
- the way you look at Justice +
- the way you see good in the worse +
- the way you handle emotionally difficult situations +
- the way you look at Justice +
- the way you see good in the worse +
- the way you handle emotionally difficult situations +
- the way you look at Justice +
- `：显示列表
+ * ``：用于分组我们信件的元素 + * `
`、`
`：用于标题和子标题 + * `
`：用于插入图像 + * ``、``：用于粗体和斜体文字样式 + * `. - -* Linked stylesheet: We write styles of all the elements in a separate file with .css extension. This file is called Stylesheet. - -Let’s have a look at how we defined the inline style of the “div” until now: - -``` -
-``` - -We can write this same style inside `` like this: - -``` -div{ - width:550px; -} -``` - -In embedded styling, the styles we write are separate from the elements. So we need a way to relate the element and its style. The first word “div” does exactly that. It lets the browser know that whatever style is inside the curly braces `{…}` belongs to the “div” element. Since this phrase determines which element to apply the style to, it’s called a selector. - -The way we write style remains same: property(width) and value(550px) separated by a colon(:) and ended by a semicolon(;). - -Let’s remove inline style from our “div” and “img” element and write it inside the ` -``` - -``` ---``` - -Save and refresh, and the result should remain the same. - -There is one big problem though — what if there is more than one “div” and “img” element in our HTML file? The styles that we defined for div and img inside the “style” element will apply to every div and img on the page. - -If you add another div in your code in the future, then that div will also become 550px wide. We don’t want that. - -We want to apply our styles to the specific div and img that we are using right now. To do this, we need to give our div and img element unique ids. Here’s how you can give an id to an element using its “id” attribute: - -``` -Bat Letter
-
- - After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you. -
-``` - -``` -You are the light of my life
-- You complete my darkness with your light. I love: -
--
-
- the way you see good in the worse -
- the way you handle emotionally difficult situations -
- the way you look at Justice -
- I have learned a lot from you. You have occupied a special place in my heart over the time. -
-I have a confession to make
-- It feels like my chest does have a heart. You make my heart beat. Your smile brings smile on my face, your pain brings pain to my heart. -
-- I don't show my emotions, but I think this man behind the mask is falling for you. -
-I love you Superman.
-- Your not-so-secret-lover,
-
- Batman --``` - -and here’s how to use th diff --git a/sources/tech/20180202 Tips for success when getting started with Ansible.md b/sources/tech/20180202 Tips for success when getting started with Ansible.md deleted file mode 100644 index 539db2ac86..0000000000 --- a/sources/tech/20180202 Tips for success when getting started with Ansible.md +++ /dev/null @@ -1,73 +0,0 @@ -Tips for success when getting started with Ansible -====== - - - -Ansible is an open source automation tool used to configure servers, install software, and perform a wide variety of IT tasks from one central location. It is a one-to-many agentless mechanism where all instructions are run from a control machine that communicates with remote clients over SSH, although other protocols are also supported. - -While targeted for system administrators with privileged access who routinely perform tasks such as installing and configuring applications, Ansible can also be used by non-privileged users. For example, a database administrator using the `mysql` login ID could use Ansible to create databases, add users, and define access-level controls. - -Let's go over a very simple example where a system administrator provisions 100 servers each day and must run a series of Bash commands on each one before handing it off to users. - - - -This is a simple example, but should illustrate how easily commands can be specified in yaml files and executed on remote servers. In a heterogeneous environment, conditional statements can be added so that certain commands are only executed in certain servers (e.g., "only execute `yum` commands in systems that are not Ubuntu or Debian"). - -One important feature in Ansible is that a playbook describes a desired state in a computer system, so a playbook can be run multiple times against a server without impacting its state. If a certain task has already been implemented (e.g., "user `sysman` already exists"), then Ansible simply ignores it and moves on. - -### Definitions - - * **Tasks:**``A task is the smallest unit of work. It can be an action like "Install a database," "Install a web server," "Create a firewall rule," or "Copy this configuration file to that server." - * **Plays:**``A play is made up of tasks. For example, the play: "Prepare a database to be used by a web server" is made up of tasks: 1) Install the database package; 2) Set a password for the database administrator; 3) Create a database; and 4) Set access to the database. - * **Playbook:**``A playbook is made up of plays. A playbook could be: "Prepare my website with a database backend," and the plays would be 1) Set up the database server; and 2) Set up the web server. - * **Roles:**``Roles are used to save and organize playbooks and allow sharing and reuse of playbooks. Following the previous examples, if you need to fully configure a web server, you can use a role that others have written and shared to do just that. Since roles are highly configurable (if written correctly), they can be easily reused to suit any given deployment requirements. - * **Ansible Galaxy:**``Ansible [Galaxy][1] is an online repository where roles are uploaded so they can be shared with others. It is integrated with GitHub, so roles can be organized into Git repositories and then shared via Ansible Galaxy. - - - -These definitions and their relationships are depicted here: - - - -Please note this is just one way to organize the tasks that need to be executed. We could have split up the installation of the database and the web server into separate playbooks and into different roles. Most roles in Ansible Galaxy install and configure individual applications. You can see examples for installing [mysql][2] and installing [httpd][3]. - -### Tips for writing playbooks - -The best source for learning Ansible is the official [documentation][4] site. And, as usual, online search is your friend. I recommend starting with simple tasks, like installing applications or creating users. Once you are ready, follow these guidelines: - - * When testing, use a small subset of servers so that your plays execute faster. If they are successful in one server, they will be successful in others. - * Always do a dry run to make sure all commands are working (run with `--check-mode` flag). - * Test as often as you need to without fear of breaking things. Tasks describe a desired state, so if a desired state is already achieved, it will simply be ignored. - * Be sure all host names defined in `/etc/ansible/hosts` are resolvable. - * Because communication to remote hosts is done using SSH, keys have to be accepted by the control machine, so either 1) exchange keys with remote hosts prior to starting; or 2) be ready to type in "Yes" to accept SSH key exchange requests for each remote host you want to manage. - * Although you can combine tasks for different Linux distributions in one playbook, it's cleaner to write a separate playbook for each distro. - - - -### In the final analysis - -Ansible is a great choice for implementing automation in your data center: - - * It's agentless, so it is simpler to install than other automation tools. - * Instructions are in YAML (though JSON is also supported) so it's easier than writing shell scripts. - * It's open source software, so contribute back to it and make it even better! - - - -How have you used Ansible to automate your data center? Share your experience in the comments. - --------------------------------------------------------------------------------- - -via: https://opensource.com/article/18/2/tips-success-when-getting-started-ansible - -作者：[Jose Delarosa][a] -译者：[译者ID](https://github.com/译者ID) -校对：[校对者ID](https://github.com/校对者ID) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 - -[a]:https://opensource.com/users/jdelaros1 -[1]:https://galaxy.ansible.com/ -[2]:https://galaxy.ansible.com/bennojoy/mysql/ -[3]:https://galaxy.ansible.com/xcezx/httpd/ -[4]:http://docs.ansible.com/ diff --git a/sources/tech/20180205 Rancher - Container Management Application.md b/sources/tech/20180205 Rancher - Container Management Application.md deleted file mode 100644 index f1900aff9d..0000000000 --- a/sources/tech/20180205 Rancher - Container Management Application.md +++ /dev/null @@ -1,221 +0,0 @@ -Rancher - Container Management Application -====== -Docker is a cutting-edge software used for containerization, that is used in most of IT companies to reduce infrastructure cost. - -By default docker comes without any GUI, which is easy for Linux administrator to manage it and it’s very difficult for developers to manage. When it’s come to production then it’s very difficult for Linux admin too. So, what would be the best solution to manage the docker without any trouble. - -The only way is GUI. The Docker API has allowed third party applications to interfacing with Docker. There are many docker GUI applications available in the market. We already wrote an article about Portainer application. Today we are going to discuss about Rancher. - -Containers make software development easier, enabling you to write code faster and run it better. However, running containers in production can be hard. - -**Suggested Read :** [Portainer – A Simple Docker Management GUI][1] - -### What is Rancher - -[Rancher][2] is a complete container management platform that makes it easy to deploy and run containers in production on any infrastructure. It provides infrastructure services such as multi-host networking, global and local load balancing, and volume snapshots. It integrates native Docker management capabilities such as Docker Machine and Docker Swarm. It offers a rich user experience that enables devops admins to operate Docker in production at large scale. - -Navigate to following article for docker installation on Linux. - -**Suggested Read :** -**(#)** [How to install Docker in Linux][3] -**(#)** [How to play with Docker images on Linux][4] -**(#)** [How to play with Docker containers on Linux][5] -**(#)** [How to Install, Run Applications inside Docker Containers][6] - -### Rancher Features - - * Set up Kubernetes in two minutes - * Launch apps with single click (90 popular Docker applications) - * Deploy and manage Docker easily - * complete container management platform for production environment - * Quickly deploy containers in production - * Automate container deployment and operations with a robust technology - * Modular infrastructure services - * Rich set of orchestration tools - * Rancher supports multiple authentication mechanisms - - - -### How to install Rancher - -Rancher installation is very simple since it’s runs as a lightweight Docker containers. Rancher is deployed as a set of Docker containers. Running Rancher is as simple as launching two containers. One container as the management server and another container on a node as an agent. Simple run the following command to deploy rancher on Linux. - -Rancher server offers two different package tags like `stable` & `latest`. The below commands will pull appropriate build rancher image and install on your system. It will only take a couple of minutes for Rancher server to start up. - - * `stable` : This tag will be their latest development builds. These builds will have been validated through rancher CI automation framework which is not advisable for deployment in production. - * `latest` : It’s a latest stable release version which is recommend for production environment. - - - -Rancher installation comes with many varieties. In this tutorial we are going to discuss about two variants. - - * Install rancher server in a single container (Inbuilt Rancher Database) - * Install rancher server in a single container (External Database) - - - -### Method-1 - -Run the following commands to install rancher server in a single container (Inbuilt Rancher Database). -``` -$ sudo docker run -d --restart=unless-stopped -p 8080:8080 rancher/server:stable - -$ sudo docker run -d --restart=unless-stopped -p 8080:8080 rancher/server:latest - -``` - -### Method-2 - -Instead of using the internal database that comes with Rancher server, you can start Rancher server pointing to an external database. First create required database, database user for the same. -``` -> CREATE DATABASE IF NOT EXISTS cattle COLLATE = 'utf8_general_ci' CHARACTER SET = 'utf8'; -> GRANT ALL ON cattle.* TO 'cattle'@'%' IDENTIFIED BY 'cattle'; -> GRANT ALL ON cattle.* TO 'cattle'@'localhost' IDENTIFIED BY 'cattle'; - -``` - -Run the following command to start Rancher connecting to an external database. -``` -$ sudo docker run -d --restart=unless-stopped -p 8080:8080 rancher/server \ - --db-host myhost.example.com --db-port 3306 --db-user username --db-pass password --db-name cattle - -``` - -If you want to test Rancher 2.0 use the following command to start. -``` -$ sudo docker run -d --restart=unless-stopped -p 80:80 -p 443:443 rancher/server:preview - -``` - -### Access & Setup Rancher Through GUI - -Navigate to the following URL `http://hostname:8080` or `http://server_ip:8080` to access rancher GUI. -[![][7]![][7]][8] - -### How To Register the Host - -Register your host URL which allow hosts to connect to the Rancher API. It’s one time setup. - -To do, Click “Add a Host” link under the main menu or Go to >> Infrastructure >> Add Hosts then hit `save` button. -[![][7]![][7]][9] - -By default access control authentication is disabled in rancher so first we have to enable the access control authentication through available method, otherwise anyone can access the GUI. - -Go to >> Admin >> Access Control and input the following values and finally hit `Enable Authentication` button to enable it. In my case i’m enabling via `local authentication` - - * **`Login UserName`** Input your descried login username - * **`Full Name`** Input your full name - * **`Password`** Input your descried password - * **`Confirm Password`**Confirm the password once again - - - -[![][7]![][7]][10] - -Logout and login back with your new login credential. -[![][7]![][7]][11] - -Now, i can see the local authentication is enabled. -[![][7]![][7]][12] - -### How To Add Hosts - -After register your host, it will take you to next page where you can choose Linux machines from varies cloud providers. We are going to add the host that is running Rancher server, so select the `custom` option and input the required information. - -Enter your server public IP address in the 4th step and run the command which is displaying in the 5th step into your terminal then finally hit `close` button. -``` -$ sudo docker run -e CATTLE_AGENT_IP="192.168.1.112" --rm --privileged -v /var/run/docker.sock:/var/run/docker.sock -v /var/lib/rancher:/var/lib/rancher rancher/agent:v1.2.9 http://192.168.1.112:8080/v1/scripts/3F8217A1DCF01A7B7F8A:1514678400000:D7WeLUcEUnqZOt8rWjrvoaUE - -INFO: Running Agent Registration Process, CATTLE_URL=http://192.168.1.112:8080/v1 -INFO: Attempting to connect to: http://66.70.189.137:8080/v1 -INFO: http://192.168.1.112:8080/v1 is accessible -INFO: Inspecting host capabilities -INFO: Boot2Docker: false -INFO: Host writable: true -INFO: Token: xxxxxxxx -INFO: Running registration -INFO: Printing Environment -INFO: ENV: CATTLE_ACCESS_KEY=A35151AB87C15633DFB4 -INFO: ENV: CATTLE_AGENT_IP=192.168.1.112 -INFO: ENV: CATTLE_HOME=/var/lib/cattle -INFO: ENV: CATTLE_REGISTRATION_ACCESS_KEY=registrationToken -INFO: ENV: CATTLE_REGISTRATION_SECRET_KEY=xxxxxxx -INFO: ENV: CATTLE_SECRET_KEY=xxxxxxx -INFO: ENV: CATTLE_URL=http://192.168.1.112:8080/v1 -INFO: ENV: DETECTED_CATTLE_AGENT_IP=172.17.0.1 -INFO: ENV: RANCHER_AGENT_IMAGE=rancher/agent:v1.2.9 -INFO: Deleting container rancher-agent -INFO: Launched Rancher Agent: 3415a1fd101f3c57d9cff6aef373c0ce66a3e20772122d2ca832039dcefd92fd - -``` - -[![][7]![][7]][13] - -Wait few seconds then the newly added host will be visible. To bring this Go to Infrastructure >> Hosts page. -[![][7]![][7]][14] - -### How To View Containers - -Just navigate the following location to view a list of running containers. Go to >> Infrastructure >> Containers. -[![][7]![][7]][15] - -### How To Create Container - -It’s very simple, just navigate the following location to create a container. - -Go to >> Infrastructure >> Containers >> “Add Container” and input the required information as per your requirement. To test this, i’m going to create Centos container with latest OS. -[![][7]![][7]][16] - -The same has been listed here. Infrastructure >> Containers -[![][7]![][7]][17] - -Hit on the `Container` name to view the container performances information like CPU, memory, network and storage. -[![][7]![][7]][18] - -To manage the container such as stop, start, clone, restart, etc. Choose the particular container then hit `Three dot's` button in the left side of the container or `Actions` button to perform. -[![][7]![][7]][19] - -If you want console access of the container, just hit `Execute Shell` option in the action button. -[![][7]![][7]][20] - -### How To Deploy Container From Application Catalog - -Rancher provides a catalog of application templates that make it easy to deploy in single click. It’s maintain popular applications (nearly 90) contributed by the Rancher community. -[![][7]![][7]][21] - -Go to >> Catalog >> All >> Choose the required application >> Finally hit “Launch” button to deploy. -[![][7]![][7]][22] - --------------------------------------------------------------------------------- - -via: https://www.2daygeek.com/rancher-a-complete-container-management-platform-for-production-environment/ - -作者：[Magesh Maruthamuthu][a] -译者：[译者ID](https://github.com/译者ID) -校对：[校对者ID](https://github.com/校对者ID) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 - -[a]:https://www.2daygeek.com/author/magesh/ -[1]:https://www.2daygeek.com/portainer-a-simple-docker-management-gui/ -[2]:http://rancher.com/ -[3]:https://www.2daygeek.com/install-docker-on-centos-rhel-fedora-ubuntu-debian-oracle-archi-scentific-linux-mint-opensuse/ -[4]:https://www.2daygeek.com/list-search-pull-download-remove-docker-images-on-linux/ -[5]:https://www.2daygeek.com/create-run-list-start-stop-attach-delete-interactive-daemonized-docker-containers-on-linux/ -[6]:https://www.2daygeek.com/install-run-applications-inside-docker-containers/ -[7]:data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7 -[8]:https://www.2daygeek.com/wp-content/uploads/2018/02/Install-rancher-container-management-application-in-linux-1.png -[9]:https://www.2daygeek.com/wp-content/uploads/2018/02/Install-rancher-container-management-application-in-linux-2.png -[10]:https://www.2daygeek.com/wp-content/uploads/2018/02/Install-rancher-container-management-application-in-linux-3.png -[11]:https://www.2daygeek.com/wp-content/uploads/2018/02/Install-rancher-container-management-application-in-linux-3a.png -[12]:https://www.2daygeek.com/wp-content/uploads/2018/02/Install-rancher-container-management-application-in-linux-4.png -[13]:https://www.2daygeek.com/wp-content/uploads/2018/02/Install-rancher-container-management-application-in-linux-5.png -[14]:https://www.2daygeek.com/wp-content/uploads/2018/02/Install-rancher-container-management-application-in-linux-6.png -[15]:https://www.2daygeek.com/wp-content/uploads/2018/02/Install-rancher-container-management-application-in-linux-7.png -[16]:https://www.2daygeek.com/wp-content/uploads/2018/02/Install-rancher-container-management-application-in-linux-8.png -[17]:https://www.2daygeek.com/wp-content/uploads/2018/02/Install-rancher-container-management-application-in-linux-9.png -[18]:https://www.2daygeek.com/wp-content/uploads/2018/02/Install-rancher-container-management-application-in-linux-10.png -[19]:https://www.2daygeek.com/wp-content/uploads/2018/02/Install-rancher-container-management-application-in-linux-11.png -[20]:https://www.2daygeek.com/wp-content/uploads/2018/02/Install-rancher-container-management-application-in-linux-12.png -[21]:https://www.2daygeek.com/wp-content/uploads/2018/02/Install-rancher-container-management-application-in-linux-13.png -[22]:https://www.2daygeek.com/wp-content/uploads/2018/02/Install-rancher-container-management-application-in-linux-14.png diff --git a/sources/tech/20180206 Power(Shell) to the people.md b/sources/tech/20180206 Power(Shell) to the people.md deleted file mode 100644 index 941dceffe5..0000000000 --- a/sources/tech/20180206 Power(Shell) to the people.md +++ /dev/null @@ -1,156 +0,0 @@ -Power(Shell) to the people -====== - - - -Earlier this year, [PowerShell Core][1] [became generally available][2] under an Open Source ([MIT][3]) license. PowerShell is hardly a new technology. From its first release for Windows in 2006, PowerShell's creators [sought][4] to incorporate the power and flexibility of Unix shells while remedying their perceived deficiencies, particularly the need for text manipulation to derive value from combining commands. - -Five major releases later, PowerShell Core allows the same innovative shell and command environment to run natively on all major operating systems, including OS X and Linux. Some (read: almost everyone) may still scoff at the audacity and/or the temerity of this Windows-born interloper to offer itself to platforms that have had strong shell environments since time immemorial (at least as defined by a millennial). In this post, I hope to make the case that PowerShell can provide advantages to even seasoned users. - -### Consistency across platforms - -If you plan to port your scripts from one execution environment to another, you need to make sure you use only the commands and syntaxes that work. For example, on GNU systems, you would obtain yesterday's date as follows: -``` -date --date="1 day ago" - -``` - -On BSD systems (such as OS X), the above syntax wouldn't work, as the BSD date utility requires the following syntax: -``` -date -v -1d - -``` - -Because PowerShell is licensed under a permissive license and built for all platforms, you can ship it with your application. Thus, when your scripts run in the target environment, they'll be running on the same shell using the same command implementations as the environment in which you tested your scripts. - -### Objects and structured data - -*nix commands and utilities rely on your ability to consume and manipulate unstructured data. Those who have lived for years with `sed` `grep` and `awk` may be unbothered by this statement, but there is a better way. - -Let's redo the yesterday's date example in PowerShell. To get the current date, run the `Get-Date` cmdlet (pronounced "commandlet"): -``` -> Get-Date - - - -Sunday, January 21, 2018 8:12:41 PM - -``` - -The output you see isn't really a string of text. Rather, it is a string representation of a .Net Core object. Just like any other object in any other OOP environment, it has a type and most often, methods you can call. - -Let's prove this: -``` -> $(Get-Date).GetType().FullName - -System.DateTime - -``` - -The `$(...)` syntax behaves exactly as you'd expect from POSIX shells—the result of the evaluation of the command in parentheses is substituted for the entire expression. In PowerShell, however, the $ is strictly optional in such expressions. And, most importantly, the result is a .Net object, not text. So we can call the `GetType()` method on that object to get its type object (similar to `Class` object in Java), and the `FullName` [property][5] to get the full name of the type. - -So, how does this object-orientedness make your life easier? - -First, you can pipe any object to the `Get-Member` cmdlet to see all the methods and properties it has to offer. -``` -> (Get-Date) | Get-Member -PS /home/yevster/Documents/ArticlesInProgress> $(Get-Date) | Get-Member - - - TypeName: System.DateTime - - -Name MemberType Definition ----- ---------- ---------- -Add Method datetime Add(timespan value) -AddDays Method datetime AddDays(double value) -AddHours Method datetime AddHours(double value) -AddMilliseconds Method datetime AddMilliseconds(double value) -AddMinutes Method datetime AddMinutes(double value) -AddMonths Method datetime AddMonths(int months) -AddSeconds Method datetime AddSeconds(double value) -AddTicks Method datetime AddTicks(long value) -AddYears Method datetime AddYears(int value) -CompareTo Method int CompareTo(System.Object value), int ... -``` - -You can quickly see that the DateTime object has an `AddDays` that you can quickly use to get yesterday's date: -``` -> (Get-Date).AddDays(-1) - - -Saturday, January 20, 2018 8:24:42 PM -``` - -To do something slightly more exciting, let's call Yahoo's weather service (because it doesn't require an API token) and get your local weather. -``` -$city="Boston" -$state="MA" -$url="https://query.yahooapis.com/v1/public/yql?q=select%20*%20from%20weather.forecast%20where%20woeid%20in%20(select%20woeid%20from%20geo.places(1)%20where%20text%3D%22${city}%2C%20${state}%22)&format=json&env=store%3A%2F%2Fdatatables.org%2Falltableswithkeys" -``` - -Now, we could do things the old-fashioned way and just run `curl $url` to get a giant blob of JSON, or... -``` -$weather=(Invoke-RestMethod $url) -``` - -If you look at the type of `$weather` (by running `echo $weather.GetType().FullName`), you will see that it's a `PSCustomObject`. It's a dynamic object that reflects the structure of the JSON. - -And PowerShell will be thrilled to help you navigate through it with its tab completion. Just type `$weather.` (making sure to include the ".") and press Tab. You will see all the root-level JSON keys. Type one, followed by a "`.`", press Tab again, and you'll see its children (if any). - -Thus, you can easily navigate to the data you want: -``` -> echo $weather.query.results.channel.atmosphere.pressure -1019.0 - - -> echo $weather.query.results.channel.wind.chill -41 -``` - -And if you have JSON or CSV lying around (or returned by an outside command) as unstructured data, just pipe it into the `ConvertFrom-Json` or `ConvertFrom-CSV` cmdlet, respectively, and you can have your data in nice clean objects. - -### Computing vs. automation - -We use shells for two purposes. One is for computing, to run individual commands and to manually respond to their output. The other is automation, to write scripts that execute multiple commands and respond to their output programmatically. - -A problem that most of us have learned to overlook is that these two purposes place different and conflicting requirements on the shell. Computing requires the shell to be laconic. The fewer keystrokes a user can get away with, the better. It's unimportant if what the user has typed is barely legible to another human being. Scripts, on the other hand, are code. Readability and maintainability are key. And here, POSIX utilities often fail us. While some commands do offer both laconic and readable syntaxes (e.g. `-f` and `--force`) for some of their parameters, the command names themselves err on the side of brevity, not readability. - -PowerShell includes several mechanisms to eliminate that Faustian tradeoff. - -First, tab completion eliminates typing of argument names. For instance, type `Get-Random -Mi`, press Tab and PowerShell will complete the argument for you: `Get-Random -Minimum`. But if you really want to be laconic, you don't even need to press Tab. For instance, PowerShell will understand -``` -Get-Random -Mi 1 -Ma 10 -``` - -because `Mi` and `Ma` each have unique completions. - -You may have noticed that all PowerShell cmdlet names have a verb-noun structure. This can help script readability, but you probably don't want to keep typing `Get-` over and over in the command line. So don't! If you type a noun without a verb, PowerShell will look for a `Get-` command with that noun. - -Caution: although PowerShell is not case-sensitive, it's a good practice to capitalize the first letter of the noun when you intend to use a PowerShell command. For example, typing `date` will call your system's `date` utility. Typing `Date` will call PowerShell's `Get-Date` cmdlet. - -And if that's not enough, PowerShell has aliases to create simple names. For example, if you type `alias -name cd`, you will discover the `cd` command in PowerShell is itself an alias for the `Set-Location` command. - -So to review—you get powerful tab completion, aliases, and noun completions to keep your command names short, automatic and consistent parameter name truncation, while still enjoying a rich, readable syntax for scripting. - -### So... friends? - -There are just some of the advantages of PowerShell. There are more features and cmdlets I haven't discussed (check out [Where-Object][6] or its alias `?` if you want to make `grep` cry). And hey, if you really feel homesick, PowerShell will be happy to launch your old native utilities for you. But give yourself enough time to get acclimated in PowerShell's object-oriented cmdlet world, and you may find yourself choosing to forget the way back. - --------------------------------------------------------------------------------- - -via: https://opensource.com/article/18/2/powershell-people - -作者：[Yev Bronshteyn][a] -译者：[译者ID](https://github.com/译者ID) -校对：[校对者ID](https://github.com/校对者ID) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 - -[a]:https://opensource.com/users/yevster -[1]:https://github.com/PowerShell/PowerShell/blob/master/README.md -[2]:https://blogs.msdn.microsoft.com/powershell/2018/01/10/powershell-core-6-0-generally-available-ga-and-supported/ -[3]:https://spdx.org/licenses/MIT -[4]:http://www.jsnover.com/Docs/MonadManifesto.pdf -[5]:https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/classes-and-structs/properties -[6]:https://docs.microsoft.com/en-us/powershell/module/microsoft.powershell.core/where-object?view=powershell-6 diff --git a/sources/tech/20180217 Louis-Philippe Véronneau .md b/sources/tech/20180217 Louis-Philippe Véronneau .md deleted file mode 100644 index bab2f4c169..0000000000 --- a/sources/tech/20180217 Louis-Philippe Véronneau .md +++ /dev/null @@ -1,59 +0,0 @@ -Louis-Philippe Véronneau - -====== -I've been watching [Critical Role][1]1 for a while now and since I've started my master's degree I haven't had much time to sit down and watch the show on YouTube as I used to do. - -I thus started listening to the podcasts instead; that way, I can listen to the show while I'm doing other productive tasks. Pretty quickly, I grew tired of manually downloading every episode each time I finished the last one. To make things worst, the podcast is hosted on PodBean and they won't let you download episodes on a mobile device without their app. Grrr. - -After the 10th time opening the terminal on my phone to download the podcast using some `wget` magic I decided enough was enough: I was going to write a dumb script to download them all in one batch. - -I'm a little ashamed to say it took me more time than I had intended... The PodBean website uses semi-randomized URLs, so I could not figure out a way to guess the paths to the hosted audio files. I considered using `youtube-dl` to get the DASH version of the show on YouTube, but Google has been heavily throttling DASH streams recently. Not cool Google. - -I then had the idea to use iTune's RSS feed to get the audio files. Surely they would somehow be included there? Of course Apple doesn't give you a simple RSS feed link on the iTunes podcast page, so I had to rummage around and eventually found out this is the link you have to use: -``` -https://itunes.apple.com/lookup?id=1243705452&entity=podcast - -``` - -Surprise surprise, from the json file this links points to, I found out the main Critical Role podcast page [has a proper RSS feed][2]. To my defense, the RSS button on the main podcast page brings you to some PodBean crap page. - -Anyway, once you have the RSS feed, it's only a matter of using `grep` and `sed` until you get what you want. - -Around 20 minutes later, I had downloaded all the episodes, for a total of 22Gb! Victory dance! - -Video clip loop of the Critical Role doing a victory dance. - -### Script - -Here's the bash script I wrote. You will need `recode` to run it, as the RSS feed includes some HTML entities. -``` -# Get the whole RSS feed -wget -qO /tmp/criticalrole.rss http://criticalrolepodcast.geekandsundry.com/feed/ - -# Extract the URLS and the episode titles -mp3s=( $(grep -o "http.\+mp3" /tmp/criticalrole.rss) ) -titles=( $(tail -n +45 /tmp/criticalrole.rss | grep -o ".\+ " \ - | sed -r 's@@@g; s@ @\\@g' | recode html..utf8) ) - -# Download all the episodes under their titles -for i in ${!titles[*]} -do - wget -qO "$(sed -e "s@\\\@\\ @g" <<< "${titles[$i]}").mp3" ${mp3s[$i]} -done - -``` - -1 - For those of you not familiar with Critical Role, it's web series where a group of voice actresses and actors from LA play Dungeons & Dragons. It's so good even people like me who never played D&D can enjoy it.. - --------------------------------------------------------------------------------- - -via: https://veronneau.org/downloading-all-the-critical-role-podcasts-in-one-batch.html - -作者：[Louis-Philippe Véronneau][a] -译者：[译者ID](https://github.com/译者ID) -校对：[校对者ID](https://github.com/校对者ID) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 - -[a]:https://veronneau.org/ -[1]:https://en.wikipedia.org/wiki/Critical_Role -[2]:http://criticalrolepodcast.geekandsundry.com/feed/ diff --git a/sources/tech/20180226 -Getting to Done- on the Linux command line.md b/sources/tech/20180226 -Getting to Done- on the Linux command line.md deleted file mode 100644 index c325a0d884..0000000000 --- a/sources/tech/20180226 -Getting to Done- on the Linux command line.md +++ /dev/null @@ -1,126 +0,0 @@ -'Getting to Done' on the Linux command line -====== - - -There is a lot of talk about getting things done at the command line. How many articles are there about using obscure flags with `ls`, nifty regular expressions with Sed and Awk, and how to parse out lots of text with Perl? That isn't what this is about. - -This is about [Getting _to_ Done][1], making sure that the stuff we have to do actually gets tracked and done using tools that don't require a graphical desktop, a web browser, or an internet connection. To do this, we'll look at four ways of tracking your to-do list: plaintext files, Todo.txt, TaskWarrior, and Org-mode. - -### Plain (and simple) text - - -![plaintext][3] - -I like to use Vim, but you can use Nano too. - -The most straightforward way to manage your to-do list is using a plaintext file in your editor of choice. Just open an empty file and add tasks, one per line. When you are done, delete the line. Simple, effective, and it doesn't matter what you use to do it. There are a couple of drawbacks to this method, though. Once you delete a line and save the file, it is gone forever. That can be a problem if you have to report on what you have done this week or last week. And while using a simple file is flexible, it can also get cluttered really easily. - -### Todo.txt: Plaintext leveled up - - -![todo.txt screen][5] - -Neat, organized, and easy to use - -That leads us to the [Todo.txt][6] file format and application. Installation is simple—[download][7] the latest release from GitHub and run `sudo make install` from the unpacked archive. - - -![Installing todo.txt][9] - -It works from a Git clone as well. - -Todo.txt makes it very easy to add tasks, list tasks, and mark them as done: - -| `todo.sh add "Some Task"` | add "Some Task" to my todo list | -| `todo.sh ls` | list all my tasks | -| `todo.sh ls due:2018-02-15` | list all tasks due on February 15, 2018 | -| `todo.sh do 3` | mark task number 3 as "done" | - -The actual list is still in plaintext, and you can edit it with your favorite text editor as long as you follow the [correct format][10]. - -There is also a very robust help built into the application. - - -![Syntax highlighting in todo.txt][12] - -You can even get syntax highlighting. - -There is also a large selection of add-ons, as well as specifications for writing your own. There are even browser extensions, mobile apps, and desktop apps that support the Todo.txt format. - - -![GNOME extensions in todo.txt][14] - -Even GNOME extensions. - -The biggest drawback to Todo.txt is the lack of an automatic or built-in synchronization mechanism. Most (if not all) of the browser extensions and mobile apps require Dropbox to perform synchronization between the app and the copy on your desktop. If you would like something with sync built-in, we have... - -### Taskwarrior: Now we're cooking with Python - -[Taskwarrior][15] is a Python application with many of the same features as Todo.txt. However, it stores the data in a database and has built-in synchronization capabilities. It also keeps track of what is next, notes how old tasks are, and will warn you if you have something more important to do than what you just did. - -[Installation][16] of Taskwarrior can be done either with your distribution's package manager, through Python's `pip` utility, or built from source. Using it is also pretty straightforward, with commands similar to Todo.txt: - -| `task add "Some Task"` | Add "Some Task" to the list | -| `task list` | List all tasks | -| `task list due ``:today` | List all tasks due on today's date | -| `task do 3` | Complete task number 3 | - -Taskwarrior also has some pretty nice text user interfaces. - -![Taskwarrior in Vit][18] - -I like Vit, which was inspired by Vim. - -Unlike Todo.txt, Taskwarrior can synchronize with a local or remote server. A very basic synchronization server called `taskd` is available if you wish to run your own, and there are several services available if you do not. - -Taskwarrior also has a thriving and extensive ecosystem of add-ons and extensions, as well as mobile and desktop apps. - -![Taskwarrior on GNOME][20] - -Taskwarrior looks really nice on GNOME. - -The only disadvantage to Taskwarrior is that, unlike the other programs listed here, you cannot directly modify the to-do list itself. You can export the task list to various formats, modify the export, and then re-import the files, but it is a lot clunkier than just opening the file directly in a text editor. - -Which brings us to the most powerful of them all... - -### Emacs Org-mode: Hulk smash tasks - -![Org-mode][22] - -Emacs has everything. - -Emacs [Org-mode][23] is by far the most powerful, most flexible open source to-do list manager out there. It supports multiple files, uses plaintext, is almost infinitely customizable, and understands calendars, due dates, and schedules. It is also significantly more complicated to set up than the other applications listed here. But once it is set up, it does everything the other applications do and more. If you are familiar with or a fan of [Bullet Journals][24], Org-mode is possibly the closest you can get on a computer. - -Org-mode will run anywhere Emacs runs, and there are a few mobile applications that can interact with it as well. Unfortunately, there are no desktop apps or browser extensions that support Org. Despite all that, Org-mode is still one of the best applications for tracking your to-do list, since it is so very powerful. - -### Choose your tool - -In the end, the goal of all these programs is to help you track what you need to do and make sure you don't forget to do something. While they all have the same basic functions, choosing which one is right for you depends on a lot of factors. Do you want synchronization built-in or not? Do you need a mobile app? Do any of the add-ons include a "must have" feature? Whatever your choice, remember that the program alone cannot make you more organized, but it can help. - --------------------------------------------------------------------------------- - -via: https://opensource.com/article/18/2/getting-to-done-agile-linux-command-line - -作者：[Kevin Sonney][a] -译者：[译者ID](https://github.com/译者ID) -校对：[校对者ID](https://github.com/校对者ID) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 - -[a]: -[1]:https://www.scruminc.com/getting-done/ -[3]:https://opensource.com/sites/default/files/u128651/plain-text.png (plaintext) -[5]:https://opensource.com/sites/default/files/u128651/todo-txt.png (todo.txt screen) -[6]:http://todotxt.org/ -[7]:https://github.com/todotxt/todo.txt-cli/releases -[9]:https://opensource.com/sites/default/files/u128651/todo-txt-install.png (Installing todo.txt) -[10]:https://github.com/todotxt/todo.txt -[12]:https://opensource.com/sites/default/files/u128651/todo-txt-vim.png (Syntax highlighting in todo.txt) -[14]:https://opensource.com/sites/default/files/u128651/tod-txt-gnome.png (GNOME extensions in todo.txt) -[15]:https://taskwarrior.org/ -[16]:https://taskwarrior.org/download/ -[18]:https://opensource.com/sites/default/files/u128651/taskwarrior-vit.png (Taskwarrior in Vit) -[20]:https://opensource.com/sites/default/files/u128651/taskwarrior-gnome.png (Taskwarrior on GNOME) -[22]:https://opensource.com/sites/default/files/u128651/emacs-org-mode.png (Org-mode) -[23]:https://orgmode.org/ -[24]:http://bulletjournal.com/ diff --git a/sources/tech/20180302 How to manage your workstation configuration with Ansible.md b/sources/tech/20180302 How to manage your workstation configuration with Ansible.md deleted file mode 100644 index fd24cd48ed..0000000000 --- a/sources/tech/20180302 How to manage your workstation configuration with Ansible.md +++ /dev/null @@ -1,170 +0,0 @@ -How to manage your workstation configuration with Ansible -====== - - - -Configuration management is a very important aspect of both server administration and DevOps. The "infrastructure as code" methodology makes it easy to deploy servers in various configurations and dynamically scale an organization's resources to keep up with user demands. But less attention is paid to individual administrators who want to automate the setup of their own laptops and desktops (workstations). - -In this series, I'll show you how to automate your workstation setup via [Ansible][1] , which will allow you to easily restore your entire configuration if you want or need to reload your machine. In addition, if you have multiple workstations, you can use this same approach to make the configuration identical on each. In this first article, we'll set up basic configuration management for our personal or work computers and set the foundation for the rest of the series. By the end of this article, you'll have a working setup to benefit from right away. Each article will automate more things and grow in complexity. - -### Why Ansible? - -Many configuration management solutions are available, including Salt Stack, Chef, and Puppet. I prefer Ansible because it's lighter in terms of resource utilization, its syntax is easier to read, and when harnessed properly it can revolutionize your configuration management. Ansible's lightweight nature is especially relevant to the topic at hand, because we may not want to run an entire server just to automate the setup of our laptops and desktops. Ideally, we want something fast; something we can use to get up and running quickly should we need to restore our workstations or synchronize our configuration between multiple machines. My specific method for Ansible (which I'll demonstrate in this article) is perfect for this—there's no server to maintain. You just download your configuration and run it. - -### My approach - -Typically, Ansible is run from a central server. It utilizes an inventory file, which is a text file that contains a list of all the hosts and their IP addresses or domain names we want Ansible to manage. This is great for static environments, but it is not ideal for workstations. The reason being we really don't know what the status of our workstations will be at any one moment. Perhaps I powered down my desktop or my laptop may be suspended and stowed in my bag. In either case, the Ansible server would complain, as it can't reach my machines if they are offline. We need something that's more of an on-demand approach, and the way we'll accomplish that is by utilizing `ansible-pull`. The `ansible-pull` command, which is part of Ansible, allows you to download your configuration from a Git repository and apply it immediately. You won't need to maintain a server or an inventory list; you simply run the `ansible-pull` command, feed it a Git repository URL, and it will do the rest for you. - -### Getting started - -First, install Ansible on the computer you want it to manage. One problem is that a lot of distributions ship with an older version. I can tell you from experience you'll definitely want the latest version available. New features are introduced into Ansible quite frequently, and if you're running an older version, example syntax you find online may not be functional because it's using features that aren't implemented in the version you have installed. Even point releases have quite a few new features. One example of this is the `dconf` module, which is new to Ansible as of 2.4. If you try to utilize syntax that makes use of this module, unless you have 2.4 or newer it will fail. In Ubuntu and its derivatives, we can easily install the latest version of Ansible with the official personal package archive ([PPA][2]). The following commands will do the trick: -``` -sudo apt-get install software-properties-common - -sudo apt-add-repository ppa:ansible/ansible - -sudo apt-get update - -sudo apt-get install ansible - -``` - -If you're not using Ubuntu, [consult Ansible's documentation][3] on how to obtain it for your platform. - -Next, we'll need a Git repository to hold our configuration. The easiest way to satisfy this requirement is to create an empty repository on GitHub, or you can utilize your own Git server if you have one. To keep things simple, I'll assume you're using GitHub, so adjust the commands if you're using something else. Create a repository in GitHub; you'll end up with a repository URL that will be similar to this: -``` -git@github.com:/ansible.git - -``` - -Clone that repository to your local working directory (ignore any message that complains that the repository is empty): -``` -git clone git@github.com: /ansible.git - -``` - -Now we have an empty repository we can work with. Change your working directory to be inside the repository (`cd ./ansible` for example) and create a file named `local.yml` in your favorite text editor. Place the following configuration in that file: -``` -- hosts: localhost - - become: true - - tasks: - - - name: Install htop - - apt: name=htop - -``` - -The file you just created is known as a **playbook** , and the instruction to install `htop` (a package I arbitrarily picked to serve as an example) is known as a **play**. The playbook itself is a file in the YAML format, which is a simple to read markup language. A full walkthrough of YAML is beyond the scope of this article, but you don't need to have an expert understanding of it to be proficient with Ansible. The configuration is easy to read; by simply looking at this file, you can easily glean that we're installing the `htop` package. Pay special attention to the `apt` module on the last line, which will only work on Debian-based systems. You can change this to `yum` instead of `apt` if you're using a Red Hat platform or change it to `dnf` if you're using Fedora. The `name` line simply gives information regarding our task and will be shown in the output. Therefore, you'll want to make sure the name is descriptive so it's easy to find if you need to troubleshoot multiple plays. - -Next, let's commit our new file to our repository: -``` -git add local.yml - -git commit -m "initial commit" - -git push origin master - -``` - -Now our new playbook should be present in our repository on GitHub. We can apply the playbook we created with the following command: -``` -sudo ansible-pull -U https://github.com/ /ansible.git - -``` - -If executed properly, the `htop` package should be installed on your system. You might've seen some warnings near the beginning that complain about the lack of an inventory file. This is fine, as we're not using an inventory file (nor do we need to for this use). At the end of the output, it will give you an overview of what it did. If `htop` was installed properly, you should see `changed=1` on the last line of the output. - -How did this work? The `ansible-pull` command uses the `-U` option, which expects a repository URL. I gave it the `https` version of the repository URL for security purposes because I don't want any hosts to have write access back to the repository (`https` is read-only by default). The `local.yml` playbook name is assumed, so we didn't need to provide a filename for the playbook—it will automatically run a playbook named `local.yml` if it finds it in the repository's root. Next, we used `sudo` in front of the command since we are modifying the system. - -Let's go ahead and add additional packages to our playbook. I'll add two additional packages so that it looks like this: -``` -- hosts: localhost - - become: true - - tasks: - - - name: Install htop - - apt: name=htop - - - - - name: Install mc - - apt: name=mc - - - - - name: Install tmux - - apt: name=tmux - -``` - -I added additional plays (tasks) for installing two other packages, `mc` and `tmux`. It doesn't matter what packages you choose to have this playbook install; I just picked these arbitrarily. You should install whichever packages you want all your systems to have. The only caveat is that you have to know that the packages exist in the repository for your distribution ahead of time. - -Before we commit and apply this updated playbook, we should clean it up. It will work fine as it is, but (to be honest) it looks kind of messy. Let's try installing all three packages in just one play. Replace the contents of your `local.yml` with this: -``` -- hosts: localhost - - become: true - - tasks: - - - name: Install packages - - apt: name={{item}} - - with_items: - - - htop - - - mc - - - tmux - -``` - -Now that looks cleaner and more efficient. We used `with_items` to consolidate our package list into one play. If we want to add additional packages, we simply add another line with a hyphen and a package name. Consider `with_items` to be similar to a `for` loop. Every package we list will be installed. - -Commit our new changes back to the repository: -``` -git add local.yml - -git commit -m "added additional packages, cleaned up formatting" - -git push origin master - -``` - -Now we can run our playbook to benefit from the new configuration: -``` -sudo ansible-pull -U https://github.com/ /ansible.git - -``` - -Admittedly, this example doesn't do much yet; all it does is install a few packages. You could've installed these packages much faster just using your package manager. However, as this series continues, these examples will become more complex and we'll automate more things. By the end, the Ansible configuration you'll create will automate more and more tasks. For example, the one I use automates the installation of hundreds of packages, sets up `cron` jobs, handles desktop configuration, and more. - -From what we've accomplished so far, you can probably already see the big picture. All we had to do was create a repository, put a playbook in that repository, then utilize the `ansible-pull` command to pull down that repository and apply it to our machine. We didn't need to set up a server. In the future, if we want to change our config, we can pull down the repo, update it, then push it back to our repository and apply it. If we're setting up a new machine, we only need to install Ansible and apply the configuration. - -In the next article, we'll automate this even further via `cron` and some additional items. In the meantime, I've copied the code for this article into [my GitHub repository][4] so you can check your syntax against mine. I'll update the code as we go along. - --------------------------------------------------------------------------------- - -via: https://opensource.com/article/18/3/manage-workstation-ansible - -作者：[Jay LaCroix][a] -译者：[译者ID](https://github.com/译者ID) -校对：[校对者ID](https://github.com/校对者ID) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 - -[a]:https://opensource.com/users/jlacroix -[1]:https://www.ansible.com/ -[2]:https://launchpad.net/ubuntu/+ppas -[3]:http://docs.ansible.com/ansible/latest/intro_installation.html -[4]:https://github.com/jlacroix82/ansible_article diff --git a/sources/tech/20180307 3 open source tools for scientific publishing.md b/sources/tech/20180307 3 open source tools for scientific publishing.md deleted file mode 100644 index 0bbc3578e9..0000000000 --- a/sources/tech/20180307 3 open source tools for scientific publishing.md +++ /dev/null @@ -1,78 +0,0 @@ -3 open source tools for scientific publishing -====== - - -One industry that lags behind others in the adoption of digital or open source tools is the competitive and lucrative world of scientific publishing. Worth over £19B ($26B) annually, according to figures published by Stephen Buranyi in [The Guardian][1] last year, the system for selecting, publishing, and sharing even the most important scientific research today still bears many of the constraints of print media. New digital-era technologies present a huge opportunity to accelerate discovery, make science collaborative instead of competitive, and redirect investments from infrastructure development into research that benefits society. - -The non-profit [eLife initiative][2] was established by the funders of research, in part to encourage the use of these technologies to this end. In addition to publishing an open-access journal for important advances in life science and biomedical research, eLife has made itself into a platform for experimentation and showcasing innovation in research communication—with most of this experimentation based around the open source ethos. - -Working on open publishing infrastructure projects gives us the opportunity to accelerate the reach and adoption of the types of technology and user experience (UX) best practices that we consider important to the advancement of the academic publishing industry. Speaking very generally, the UX of open source products is often left undeveloped, which can in some cases dissuade people from using it. As part of our investment in OSS development, we place a strong emphasis on UX in order to encourage users to adopt these products. - -All of our code is open source, and we actively encourage community involvement in our projects, which to us means faster iteration, more experimentation, greater transparency, and increased reach for our work. - -The projects that we are involved in, such as the development of Libero (formerly known as [eLife Continuum][3]) and the [Reproducible Document Stack][4], along with our recent collaboration with [Hypothesis][5], show how OSS can be used to bring about positive changes in the assessment, publication, and communication of new discoveries. - -### Libero - -Libero is a suite of services and applications available to publishers that includes a post-production publishing system, a full front-end user interface pattern suite, Libero's Lens Reader, an open API, and search and recommendation engines. - -Last year, we took a user-driven approach to redesigning the front end of Libero, resulting in less distracting site “furniture” and a greater focus on research articles. We tested and iterated all the key functional areas of the site with members of the eLife community to ensure the best possible reading experience for everyone. The site’s new API also provides simpler access to content for machine readability, including text mining, machine learning, and online application development. - -The content on our website and the patterns that drive the new design are all open source to encourage future product development for both eLife and other publishers that wish to use it. - -### The Reproducible Document Stack - -In collaboration with [Substance][6] and [Stencila][7], eLife is also engaged in a project to create a Reproducible Document Stack (RDS)—an open stack of tools for authoring, compiling, and publishing computationally reproducible manuscripts online. - -Today, an increasing number of researchers are able to document their computational experiments through languages such as [R Markdown][8] and [Python][9]. These can serve as important parts of the experimental record, and while they can be shared independently from or alongside the resulting research article, traditional publishing workflows tend to relegate these assets as a secondary class of content. To publish papers, researchers using these languages often have little option but to submit their computational results as “flattened” outputs in the form of figures, losing much of the value and reusability of the code and data references used in the computation. And while electronic notebook solutions such as [Jupyter][10] can enable researchers to publish their code in an easily reusable and executable form, that’s still in addition to, rather than as an integral part of, the published manuscript. - -The [Reproducible Document Stack][11] project aims to address these challenges through development and publication of a working prototype of a reproducible manuscript that treats code and data as integral parts of the document, demonstrating a complete end-to-end technology stack from authoring through to publication. It will ultimately allow authors to submit their manuscripts in a format that includes embedded code blocks and computed outputs (statistical results, tables, or graphs), and have those assets remain both visible and executable throughout the publication process. Publishers will then be able to preserve these assets directly as integral parts of the published online article. - -### Open annotation with Hypothesis - -Most recently, we introduced open annotation in collaboration with [Hypothesis][12] to enable users of our website to make comments, highlight important sections of articles, and engage with the reading public online. - -Through this collaboration, the open source Hypothesis software was customized with new moderation features, single sign-on authentication, and user-interface customization options, giving publishers more control over its implementation on their sites. These enhancements are already driving higher-quality discussions around published scholarly content. - -The tool can be integrated seamlessly into publishers’ websites, with the scholarly publishing platform [PubFactory][13] and content solutions provider [Ingenta][14] already taking advantage of its improved feature set. [HighWire][15] and [Silverchair][16] are also offering their publishers the opportunity to implement the service. - -### Other industries and open source - -Over time, we hope to see more publishers adopt Hypothesis, Libero, and other projects to help them foster the discovery and reuse of important scientific research. But the opportunities for innovation eLife has been able to leverage because of these and other OSS technologies are also prevalent in other industries. - -The world of data science would be nowhere without the high-quality, well-supported open source software and the communities built around it; [TensorFlow][17] is a leading example of this. Thanks to OSS and its communities, all areas of AI and machine learning have seen rapid acceleration and advancement compared to other areas of computing. Similar is the explosion in usage of Linux as a cloud web host, followed by containerization with Docker, and now the growth of Kubernetes, one of the most popular open source projects on GitHub. - -All of these technologies enable organizations to do more with less and focus on innovation instead of reinventing the wheel. And in the end, that’s the real benefit of OSS: It lets us all learn from each other’s failures while building on each other's successes. - -We are always on the lookout for opportunities to engage with the best emerging talent and ideas at the interface of research and technology. Find out more about some of these engagements on [eLife Labs][18], or contact [innovation@elifesciences.org][19] for more information. - --------------------------------------------------------------------------------- - -via: https://opensource.com/article/18/3/scientific-publishing-software - -作者：[Paul Shanno][a] -译者：[译者ID](https://github.com/译者ID) -校对：[校对者ID](https://github.com/校对者ID) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 - -[a]:https://opensource.com/users/pshannon -[1]:https://www.theguardian.com/science/2017/jun/27/profitable-business-scientific-publishing-bad-for-science -[2]:https://elifesciences.org/about -[3]:https://elifesciences.org/inside-elife/33e4127f/elife-introduces-continuum-a-new-open-source-tool-for-publishing -[4]:https://elifesciences.org/for-the-press/e6038800/elife-supports-development-of-open-technology-stack-for-publishing-reproducible-manuscripts-online -[5]:https://elifesciences.org/for-the-press/81d42f7d/elife-enhances-open-annotation-with-hypothesis-to-promote-scientific-discussion-online -[6]:https://github.com/substance -[7]:https://github.com/stencila/stencila -[8]:https://rmarkdown.rstudio.com/ -[9]:https://www.python.org/ -[10]:http://jupyter.org/ -[11]:https://elifesciences.org/labs/7dbeb390/reproducible-document-stack-supporting-the-next-generation-research-article -[12]:https://github.com/hypothesis -[13]:http://www.pubfactory.com/ -[14]:http://www.ingenta.com/ -[15]:https://github.com/highwire -[16]:https://www.silverchair.com/community/silverchair-universe/hypothesis/ -[17]:https://www.tensorflow.org/ -[18]:https://elifesciences.org/labs -[19]:mailto:innovation@elifesciences.org diff --git a/sources/tech/20180307 Protecting Code Integrity with PGP - Part 4- Moving Your Master Key to Offline Storage.md b/sources/tech/20180307 Protecting Code Integrity with PGP - Part 4- Moving Your Master Key to Offline Storage.md deleted file mode 100644 index df00e7e05e..0000000000 --- a/sources/tech/20180307 Protecting Code Integrity with PGP - Part 4- Moving Your Master Key to Offline Storage.md +++ /dev/null @@ -1,167 +0,0 @@ -Protecting Code Integrity with PGP — Part 4: Moving Your Master Key to Offline Storage -====== - - -In this tutorial series, we're providing practical guidelines for using PGP. You can catch up on previous articles here: - -[Part 1: Basic Concepts and Tools][1] - -[Part 2: Generating Your Master Key][2] - -[Part 3: Generating PGP Subkeys][3] - -Here in part 4, we continue the series with a look at how and why to move your master key from your home directory to offline storage. Let's get started. - -### Checklist - - * Prepare encrypted detachable storage (ESSENTIAL) - - * Back up your GnuPG directory (ESSENTIAL) - - * Remove the master key from your home directory (NICE) - - * Remove the revocation certificate from your home directory (NICE) - - - - -#### Considerations - -Why would you want to remove your master [C] key from your home directory? This is generally done to prevent your master key from being stolen or accidentally leaked. Private keys are tasty targets for malicious actors -- we know this from several successful malware attacks that scanned users' home directories and uploaded any private key content found there. - -It would be very damaging for any developer to have their PGP keys stolen -- in the Free Software world, this is often tantamount to identity theft. Removing private keys from your home directory helps protect you from such events. - -##### Back up your GnuPG directory - -**!!!Do not skip this step!!!** - -It is important to have a readily available backup of your PGP keys should you need to recover them (this is different from the disaster-level preparedness we did with paperkey). - -##### Prepare detachable encrypted storage - -Start by getting a small USB "thumb" drive (preferably two!) that you will use for backup purposes. You will first need to encrypt them: - -For the encryption passphrase, you can use the same one as on your master key. - -##### Back up your GnuPG directory - -Once the encryption process is over, re-insert the USB drive and make sure it gets properly mounted. Find out the full mount point of the device, for example by running the mount command (under Linux, external media usually gets mounted under /media/disk, under Mac it's /Volumes). - -Once you know the full mount path, copy your entire GnuPG directory there: -``` -$ cp -rp ~/.gnupg [/media/disk/name]/gnupg-backup - -``` - -(Note: If you get any Operation not supported on socket errors, those are benign and you can ignore them.) - -You should now test to make sure everything still works: -``` -$ gpg --homedir=[/media/disk/name]/gnupg-backup --list-key [fpr] - -``` - -If you don't get any errors, then you should be good to go. Unmount the USB drive and distinctly label it, so you don't blow it away next time you need to use a random USB drive. Then, put in a safe place -- but not too far away, because you'll need to use it every now and again for things like editing identities, adding or revoking subkeys, or signing other people's keys. - -##### Remove the master key - -The files in our home directory are not as well protected as we like to think. They can be leaked or stolen via many different means: - - * By accident when making quick homedir copies to set up a new workstation - - * By systems administrator negligence or malice - - * Via poorly secured backups - - * Via malware in desktop apps (browsers, pdf viewers, etc) - - * Via coercion when crossing international borders - - - - -Protecting your key with a good passphrase greatly helps reduce the risk of any of the above, but passphrases can be discovered via keyloggers, shoulder-surfing, or any number of other means. For this reason, the recommended setup is to remove your master key from your home directory and store it on offline storage. - -###### Removing your master key - -Please see the previous section and make sure you have backed up your GnuPG directory in its entirety. What we are about to do will render your key useless if you do not have a usable backup! - -First, identify the keygrip of your master key: -``` -$ gpg --with-keygrip --list-key [fpr] - -``` - -The output will be something like this: -``` -pub rsa4096 2017-12-06 [C] [expires: 2019-12-06] - 111122223333444455556666AAAABBBBCCCCDDDD - Keygrip = AAAA999988887777666655554444333322221111 -uid [ultimate] Alice Engineer /ansible.git - -``` - -If you recall, the `ansible-pull` command pulls down a Git repository and applies the configuration it contains. - -Now that our foundation is in place, we can expand upon our Ansible config and add features. Specifically, we'll add configuration to automate the deployment of future changes to our workstations. To support this goal, the first thing we should do is to create a user specifically to apply our Ansible configuration. This isn't required—we can continue to run our Ansible configuration under our own user. But using a separate user segregates this to a system process that will run in the background, without our involvement. - -We could create this user with the normal method, but since we're using Ansible, we should shy away from manual changes. Instead, we'll create a taskbook to handle user creation. This taskbook will create just one user for now, but you can always add additional plays to this taskbook to add additional users. I'll call this user `ansible`, but you can name it something else if you wish (if you do, make sure to update all occurrences). Let's create a taskbook named `users.yml` and place this code inside of it: -``` -- name: create ansible user - - user: name=ansible uid=900 - -``` - -Next, we need to edit our `local.yml` file and append this new taskbook to the file, so it will look like this: -``` -- hosts: localhost - - become: true - - pre_tasks: - - - name: update repositories - - apt: update_cache=yes - - changed_when: False - - - - tasks: - - - include: tasks/users.yml - - - include: tasks/packages.yml - -``` - -Now when we run our `ansible-pull` command, a user named `ansible` will be created on the system. Note that I specifically declared `User ID 900` for this user by using the `UID` option. This isn't required, but it's recommended. The reason is that UIDs under 1,000 are typically not shown on the login screen, which is great because there's no reason we would need to log into a desktop session as our `ansible` user. UID 900 is arbitrary; it should be any number under 1,000 that's not already in use. You can find out if UID 900 is in use on your system with the following command: -``` -cat /etc/passwd |grep 900 - -``` - -However, you shouldn't run into a problem with this UID because I've never seen it used by default in any distribution I've used so far. - -Now, we have an `ansible` user that will later be used to apply our Ansible configuration automatically. Next, we can create the actual cron job that will be used to automate this. Rather than place this in the `users.yml` taskbook we just created, we should separate this into its own file. Create a taskbook named `cron.yml` in the tasks directory and place the following code inside: -``` -- name: install cron job (ansible-pull) - - cron: user="ansible" name="ansible provision" minute="*/10" job="/usr/bin/ansible-pull -o -U https://github.com/ /ansible.git > /dev/null" - -``` - -The syntax for the cron module should be fairly self-explanatory. With this play, we're creating a cron job to be run as the `ansible` user. The job will execute every 10 minutes, and the command it will execute is this: -``` -/usr/bin/ansible-pull -o -U https://github.com/ /ansible.git > /dev/null - -``` - -Also, we can put additional cron jobs we want all our workstations to have into this one file. We just need to add additional plays to add new cron jobs. However, simply adding a new taskbook for cron isn't enough—we'll also need to add it to our `local.yml` file so it will be called. Place the following line with the other includes: -``` -- include: tasks/cron.yml - -``` - -Now when `ansible-pull` is run, it will set up a new cron job that will be run as the `ansible` user every 10 minutes. But, having an Ansible job running every 10 minutes isn't ideal because it will take considerable CPU power. It really doesn't make sense for Ansible to run every 10 minutes unless we've changed something in the Git repository. - -However, we've already solved this problem. Notice the `-o` option I added to the `ansible-pull` command in the cron job that we've never used before. This option tells Ansible to run only if the repository has changed since the last time `ansible-pull` was called. If the repository hasn't changed, it won't do anything. This way, you're not wasting valuable CPU for no reason. Sure, some CPU will be used when it pulls down the repository, but not nearly as much as it would use if it were applying your entire configuration all over again. When `ansible-pull` does run, it will go through all the tasks in the Playbook and taskbooks, but at least it won't run for no purpose. - -Although we've added all the required components to automate `ansible-pull`, it actually won't work properly yet. The `ansible-pull` command will run with `sudo`, which would give it access to perform system-level commands. However, our `ansible` user is not set up to perform tasks as `sudo`. Therefore, when the cron job triggers, it will fail. Normally we could just use `visudo` and manually set the `ansible` user up to have this access. However, we should do things the Ansible way from now on, and this is a great opportunity to show you how the `copy` module works. The `copy` module allows you to copy a file from your Ansible repository to somewhere else in the filesystem. In our case, we'll copy a config file for `sudo` to `/etc/sudoers.d/` so that the `ansible` user can perform administrative tasks. - -Open up the `users.yml` taskbook, and add the following play to the bottom: -``` -- name: copy sudoers_ansible - - copy: src=files/sudoers_ansible dest=/etc/sudoers.d/ansible owner=root group=root mode=0440 - -``` - -The `copy` module, as we can see, copies a file from our repository to somewhere else. In this case, we're grabbing a file named `sudoers_ansible` (which we will create shortly) and copying it to `/etc/sudoers.d/ansible` with `root` as the owner. - -Next, we need to create the file that we'll be copying. In the root of your Ansible repository, create a `files` directory: -``` -mkdir files - -``` - -Then, in the `files` directory we just created, create the `sudoers_ansible` file with the following content: -``` -ansible ALL=(ALL) NOPASSWD: ALL - -``` - -Creating a file in `/etc/sudoers.d`, like we're doing here, allows us to configure `sudo` for a specific user. Here we're allowing the `ansible` user full access to the system via `sudo` without a password prompt. This will allow `ansible-pull` to run as a background task without us needing to run it manually. - -Now, you can run `ansible-pull` again to pull down the latest changes: -``` -sudo ansible-pull -U https://github.com/ /ansible.git - -``` - -From this point forward, the cron job for `ansible-pull` will run every 10 minutes in the background and check your repository for changes. If it finds changes, it will run your playbook and apply your taskbooks. - -So now we have a fully working solution. When you first set up a new laptop or desktop, you'll run the `ansible-pull` command manually, but only the first time. From that point forward, the `ansible` user will take care of subsequent runs in the background. When you want to make a change to your workstation machines, you simply pull down your Git repository, make the changes, then push those changes back to the repository. Then, the next time the cron job fires on each machine, it will pull down those changes and apply them. You now only have to make changes once, and all your workstations will follow suit. This method may be a bit unconventional though. Normally, you'd have an `inventory` file with your machines listed and several roles each machine could be a member of. However, the `ansible-pull` method, as described in this article, is a very efficient way of managing workstation configuration. - -I have updated the code in my [GitHub repository][2] for this article, so feel free to browse the code there and check your syntax against mine. Also, I moved the code from the previous article into its own directory in that repository. - -In part 3, we'll close out the series by using Ansible to configure GNOME desktop settings. I'll show you how to set your wallpaper and lock screen, apply a desktop theme, and more. - -In the meantime, it's time for a little homework assignment. Most of us have configuration files we like to maintain for various applications we use. This could be configuration files for Bash, Vim, or whatever tools you use. I challenge you now to automate copying these configuration files to your machines via the Ansible repository we've been working on. In this article, I've shown you how to copy a file, so take a look at that and see if you can apply that knowledge to your personal files. - --------------------------------------------------------------------------------- - -via: https://opensource.com/article/18/3/manage-your-workstation-configuration-ansible-part-2 - -作者：[Jay LaCroix][a] -译者：[译者ID](https://github.com/译者ID) -校对：[校对者ID](https://github.com/校对者ID) -选题：[lujun9972](https://github.com/lujun9972) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 - -[a]:https://opensource.com/users/jlacroix -[1]:https://opensource.com/article/18/3/manage-workstation-ansible -[2]:https://github.com/jlacroix82/ansible_article.git diff --git a/sources/tech/20180328 What NASA Has Been Doing About Open Science.md b/sources/tech/20180328 What NASA Has Been Doing About Open Science.md deleted file mode 100644 index 96d3aaa4a0..0000000000 --- a/sources/tech/20180328 What NASA Has Been Doing About Open Science.md +++ /dev/null @@ -1,114 +0,0 @@ -What NASA Has Been Doing About Open Science -====== -![][1] - -We have recently started a new [Science category][2] on It’s FOSS. We covered [how open source approach is impacting Science][3] in the last article. In this open science article, we discuss [NASA][4]‘s actively growing efforts that involve their dynamic role in boosting scientific research by encouraging open source practices. - -### How NASA is using Open Source approach to improve science - -It was a great [initiative][5] by NASA that they made their entire research library freely available on the public domain. - -Yes! Entire research library for everyone to access and get benefit from it in their research. - -Their open science resources can now be mainly classified into these three categories as follows: - - * Open Source NASA - * Open API - * Open Data - - - -#### 1\. Open Source NASA - -Here’s an interesting interview of [Chris Wanstrath][6], co-founder and CEO of [GitHub][7], about how it all began to form many years ago: - -Uniquely named “[code.nasa.gov][8]“, NASA now has precisely 365 scientific software available as [open source via GitHub][9] as of the time of this post. So if you are a developer who loves coding, you can study each one of them every day for a year’s time! - -Even if you are not a developer, you can still browse through the fantastic collection of open source packages enlisted on the portal! - -One of the interesting open source packages listed here is the source code of [Apollo 11][10]‘s guidance computer. The Apollo 11 spaceflight took [the first two humans to the Moon][11], namely, [Neil Armstrong][12] and [Edwin Aldrin][13] ! If you want to know more about Edwin Aldrin, you might want to pay a visit [here][14]. - -##### Licenses being used by NASA’s Open Source Initiative: - -Here are the different [open source licenses][15] categorized as under: - -#### 2\. Open API - -An Open [Application Programming Interface][16] or API plays a significant role in practicing Open Science. Just like [The Open Source Initiative][17], there is also one for API, called [The Open API Initiative][18]. Here is a simple illustration of how an API bridges an application with its developer: - -![][19] - -Do check out the link in the caption in the image above. The API has been explained in a straightforward manner. It concludes with five exciting takeaways in the end. - -![][20] - -Makes one wonder how different [an open vs a proprietary API][21] would be. - -![][22] - -Targeted towards application developers, [NASA’s open API][23] is an initiative to significantly improve the accessibility of data that could also contain image content. The site has a live editor, allowing you check out the [API][16] behind [Astronomy Picture of the Day (APOD)][24]. - -#### 3\. Open Data - -![][25] - -In [our first science article][3], we shared with you the various open data models of three countries mentioned under the “Open Science” section, namely, France, India and the U.S. NASA also has a similar approach towards the same idea. This is a very important ideology that is being adopted by [many countries][26]. - -[NASA’s Open Data Portal][27] focuses on openness by having an ever-growing catalog of data, available for anyone to access freely. The inclusion of datasets within this collection is an essential and radical step towards the development of research of any kind. NASA have even taken a fantastic initiative to ask for dataset suggestions for submission on their portal and that’s really very innovative, considering the growing trends of [data science][28], [AI and deep learning][29]. - -The following video shows students and scientists coming up with their own definitions of Data Science based on their personal experience and research. That is really encouraging! [Dr. Murtaza Haider][30], Ted Rogers School of Management, Ryerson University, mentions the difference Open Source is making in the field of Data Science before the video ends. He explains in very simple terms, how development models transitioned from a closed source approach to an open one. The vision has proved to be sufficiently true enough in today’s time. - -![][31] - -Now anyone can suggest a dataset of any kind on NASA. Coming back to the video above, NASA’s initiative can be related so much with submitting datasets and working on analyzing them for better Data Science! - -![][32] - -You just need to signup for free. This initiative will have a very positive effect in the future, considering open discussions on the public forum and the significance of datasets in every type of analytical field that could exist. Statistical studies will also significantly improve for sure. We will talk about these concepts in detail in a future article and also about their relativeness to an open source model. - -So thus concludes an exploration into NASA’s open science model. See you soon in another open science article! - --------------------------------------------------------------------------------- - -via: https://itsfoss.com/nasa-open-science/ - -作者：[Avimanyu Bandyopadhyay][a] -译者：[译者ID](https://github.com/译者ID) -校对：[校对者ID](https://github.com/校对者ID) -选题：[lujun9972](https://github.com/lujun9972) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 - -[a]: https://itsfoss.com/author/avimanyu/ -[1]:https://itsfoss.com/wp-content/uploads/2018/03/tux-in-space.jpg -[2]:https://itsfoss.com/category/science/ -[3]:https://itsfoss.com/open-source-impact-on-science/ -[4]:https://www.nasa.gov/ -[5]:https://futurism.com/free-science-nasa-just-opened-its-entire-research-library-to-the-public/ -[6]:http://chriswanstrath.com/ -[7]:https://github.com/ -[8]:http://code.nasa.gov -[9]:https://github.com/open-source -[10]:https://www.nasa.gov/mission_pages/apollo/missions/apollo11.html -[11]:https://www.space.com/16758-apollo-11-first-moon-landing.html -[12]:https://www.jsc.nasa.gov/Bios/htmlbios/armstrong-na.html -[13]:https://www.jsc.nasa.gov/Bios/htmlbios/aldrin-b.html -[14]:https://buzzaldrin.com/the-man/ -[15]:https://itsfoss.com/open-source-licenses-explained/ -[16]:https://en.wikipedia.org/wiki/Application_programming_interface -[17]:https://opensource.org/ -[18]:https://www.openapis.org/ -[19]:https://itsfoss.com/wp-content/uploads/2018/03/api-bridge.jpeg -[20]:https://itsfoss.com/wp-content/uploads/2018/03/open-api-diagram.jpg -[21]:http://www.apiacademy.co/resources/api-strategy-lesson-201-private-apis-vs-open-apis/ -[22]:https://itsfoss.com/wp-content/uploads/2018/03/nasa-open-api-live-example.jpg -[23]:https://api.nasa.gov/ -[24]:https://apod.nasa.gov/apod/astropix.html -[25]:https://itsfoss.com/wp-content/uploads/2018/03/nasa-open-data-portal.jpg -[26]:https://www.xbrl.org/the-standard/why/ten-countries-with-open-data/ -[27]:https://data.nasa.gov/ -[28]:https://en.wikipedia.org/wiki/Data_science -[29]:https://www.kdnuggets.com/2017/07/ai-deep-learning-explained-simply.html -[30]:https://www.ryerson.ca/tedrogersschool/bm/programs/real-estate-management/murtaza-haider/ -[31]:https://itsfoss.com/wp-content/uploads/2018/03/suggest-dataset-nasa-1.jpg -[32]:https://itsfoss.com/wp-content/uploads/2018/03/suggest-dataset-nasa-2-1.jpg diff --git a/sources/tech/20180329 Python ChatOps libraries- Opsdroid and Errbot.md b/sources/tech/20180329 Python ChatOps libraries- Opsdroid and Errbot.md deleted file mode 100644 index 5f409956f7..0000000000 --- a/sources/tech/20180329 Python ChatOps libraries- Opsdroid and Errbot.md +++ /dev/null @@ -1,241 +0,0 @@ -Python ChatOps libraries: Opsdroid and Errbot -====== - - -This article was co-written with [Lacey Williams Henschel][1]. - -ChatOps is conversation-driven development. The idea is you can write code that is executed in response to something typed in a chat window. As a developer, you could use ChatOps to merge pull requests from Slack, automatically assign a support ticket to someone from a received Facebook message, or check the status of a deployment through IRC. - -In the Python world, the most widely used ChatOps libraries are Opsdroid and Errbot. In this month's Python column, let's chat about what it's like to use them, what each does well, and how to get started with them. - -### Opsdroid - -[Opsdroid][2] is a relatively young (since 2016) open source chatbot library written in Python. It has good documentation, a great tutorial, and includes plugins to help you connect to popular chat services. - -#### What's built in - -The library itself doesn't ship with everything you need to get started, but this is by design. The lightweight framework encourages you to enable its existing connectors (what Opsdroid calls the plugins that help you connect to chat services) or write your own, but it doesn't weigh itself down by shipping with connectors you may not need. You can easily enable existing Opsdroid connectors for: - - -+ The command line -+ Cisco Spark -+ Facebook -+ GitHub -+ Matrix -+ Slack -+ Telegram -+ Twitter -+ Websockets - - -Opsdroid calls the functions the chatbot performs "skills." Skills are `async` Python functions and use Opsdroid's matching decorators, called "matchers." You can configure your Opsdroid project to use skills from the same codebase your configuration file is in or import skills from outside public or private repositories. - -You can enable some existing Opsdroid skills as well, including [seen][3], which tells you when a specific user was last seen by the bot, and [weather][4], which will report the weather to the user. - -Finally, Opdroid allows you to configure databases using its existing database modules. Current databases with Opsdroid support include: - - -+ Mongo -+ Redis -+ SQLite - - -You configure databases, skills, and connectors in the `configuration.yaml` file in your Opsdroid project. - -#### Opsdroid pros - -**Docker support:** Opsdroid is meant to work well in Docker from the get-go. Docker instructions are part of its [installation documentation][5]. Using Opsdroid with Docker Compose is also simple: Set up Opsdroid as a service and when you run `docker-compose up`, your Opsdroid service will start and your chatbot will be ready to chat. -``` -version: "3" - - - -services: - - opsdroid: - - container_name: opsdroid - - build: - - context: . - - dockerfile: Dockerfile - -``` - -**Lots of connectors:** Opsdroid supports nine connectors to services like Slack and GitHub out of the box; all you need to do is enable those connectors in your configuration file and pass necessary tokens or API keys. For example, to enable Opsdroid to post in a Slack channel named `#updates`, add this to the `connectors` section of your configuration file: -``` - - name: slack - - api-token: "this-is-my-token" - - default-room: "#updates" - -``` - -You will have to [add a bot user][6] to your Slack workspace before configuring Opsdroid to connect to Slack. - -If you need to connect to a service that Opsdroid does not support, there are instructions for adding your own connectors in the [docs][7]. - -**Pretty good docs.** Especially for a young-ish library in active development, Opsdroid's docs are very helpful. The docs include a [tutorial][8] that leads you through creating a couple of different basic skills. The Opsdroid documentation on [skills][9], [connectors][7], [databases][10], and [matchers][11] is also clear. - -The repositories for its supported skills and connectors provide helpful example code for when you start writing your own custom skills and connectors. - -**Natural language processing:** Opsdroid supports regular expressions for its skills, but also several NLP APIs, including [Dialogflow][12], [luis.ai][13], [Recast.AI][14], and [wit.ai][15]. - -#### Possible Opsdroid concern - -Opsdroid doesn't yet enable the full features of some of its connectors. For example, the Slack API allows you to add color bars, images, and other "attachments" to your message. The Opsdroid Slack connector doesn't enable the "attachments" feature, so you would need to write a custom Slack connector if those features were important to you. If a connector is missing a feature you need, though, Opsdroid would welcome your [contribution][16]. The docs could use some more examples, especially of expected use cases. - -#### Example usage - -`hello/__init__.py` -``` -from opsdroid.matchers import match_regex - -import random - - - - - -@match_regex(r'hi|hello|hey|hallo') - -async def hello(opsdroid, config, message): - - text = random.choice(["Hi {}", "Hello {}", "Hey {}"]).format(message.user) - - await message.respond(text) - -``` - -`configuration.yaml` -``` -connectors: - - - name: websocket - - - -skills: - - - - - name: hello - - repo: "https://github.com/ /hello-skill" - -``` - -### Errbot - -[Errbot][17] is a batteries-included open source chatbot. Errbot was released in 2012 and has everything anyone would expect from a mature project, including good documentation, a great tutorial, and plenty of plugins to help you connect to existing popular chat services. - -#### What's built in - -Unlike Opsdroid, which takes a more lightweight approach, Errbot ships with everything you need to build a customized bot safely. - -Errbot includes support for XMPP, IRC, Slack, Hipchat, and Telegram services natively. It lists support for 10 other services through community-supplied backends. - -#### Errbot pros - -**Good docs:** Errbot's docs are mature and easy to use. - -**Dynamic plugin architecture:** Errbot allow you to securely install, uninstall, update, enable, and disable plugins by chatting with the bot. This makes development and adding features easy. For the security conscious, this can all be locked down thanks to Errbot's granular permission system. - -Errbot uses your plugin docstrings to generate documentation for available commands when someone types `!help`, which makes it easier to know what each command does. - -**Built-in administration and security:** Errbot allows you to restrict lists of users who have administrative rights and even has fine-grained access controls. For example, you can restrict which commands may be called by specific users and/or specific rooms. - -**Extensive plugin framework:** Errbot supports hooks, callbacks, subcommands, webhooks, polling, and many [more features][18]. If those aren't enough, you can even write [Dynamic plugins][19]. This feature is useful if you want to enable chat commands based on what commands are available on a remote server. - -**Ships with a testing framework:** Errbot supports [pytest][20] and ships with some useful utilities that make testing your plugins easy and possible. Its "[testing your plugins][21]" docs are well thought out and provide enough to get started. - -#### Possible Errbot concerns - -**Initial !:** By default, Errbot commands are issued starting with an exclamation mark (`!help` and `!hello`). Some people may like this, but others may find it annoying. Thankfully, this is easy to turn off. - -**Plugin metadata:** At first, Errbot's [Hello World][22] plugin example seems easy to use. However, I couldn't get my plugin to load until I read further into the tutorial and discovered that I also needed a `.plug` file, a file Errbot uses to load plugins. This is a pretty minor nitpick, but it wasn't obvious to me until I dug further into the docs. - -#### Example usage - -`hello.py` -``` -import random - -from errbot import BotPlugin, botcmd - - - -class Hello(BotPlugin): - - - - @botcmd - - def hello(self, msg, args): - - text = random.choice(["Hi {}", "Hello {}", "Hey {}"]).format(message.user) - - return text - -``` - -`hello.plug` -``` -[Core] - -Name = Hello - -Module = hello - - - -[Python] - -Version = 2+ - - - -[Documentation] - -Description = Example "Hello" plugin - -``` - -Have you used Errbot or Opsdroid? If so, please leave a comment with your impressions on these tools. - --------------------------------------------------------------------------------- - -via: https://opensource.com/article/18/3/python-chatops-libraries-opsdroid-and-errbot - -作者：[Jeff Triplett][a] -译者：[译者ID](https://github.com/译者ID) -校对：[校对者ID](https://github.com/校对者ID) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 - -[a]:https://opensource.com/users/laceynwilliams -[1]:https://opensource.com/users/laceynwilliams -[2]:https://opsdroid.github.io/ -[3]:https://github.com/opsdroid/skill-seen -[4]:https://github.com/opsdroid/skill-weather -[5]:https://opsdroid.readthedocs.io/en/stable/#docker -[6]:https://api.slack.com/bot-users -[7]:https://opsdroid.readthedocs.io/en/stable/extending/connectors/ -[8]:https://opsdroid.readthedocs.io/en/stable/tutorials/introduction/ -[9]:https://opsdroid.readthedocs.io/en/stable/extending/skills/ -[10]:https://opsdroid.readthedocs.io/en/stable/extending/databases/ -[11]:https://opsdroid.readthedocs.io/en/stable/matchers/overview/ -[12]:https://opsdroid.readthedocs.io/en/stable/matchers/dialogflow/ -[13]:https://opsdroid.readthedocs.io/en/stable/matchers/luis.ai/ -[14]:https://opsdroid.readthedocs.io/en/stable/matchers/recast.ai/ -[15]:https://opsdroid.readthedocs.io/en/stable/matchers/wit.ai/ -[16]:https://opsdroid.readthedocs.io/en/stable/contributing/ -[17]:http://errbot.io/en/latest/ -[18]:http://errbot.io/en/latest/features.html#extensive-plugin-framework -[19]:http://errbot.io/en/latest/user_guide/plugin_development/dynaplugs.html -[20]:http://pytest.org/ -[21]:http://errbot.io/en/latest/user_guide/plugin_development/testing.html -[22]:http://errbot.io/en/latest/index.html#simple-to-build-upon diff --git a/sources/tech/20180331 Emacs -4- Automated emails to org-mode and org-mode syncing.md b/sources/tech/20180331 Emacs -4- Automated emails to org-mode and org-mode syncing.md deleted file mode 100644 index 4efe606f51..0000000000 --- a/sources/tech/20180331 Emacs -4- Automated emails to org-mode and org-mode syncing.md +++ /dev/null @@ -1,72 +0,0 @@ -Emacs #4: Automated emails to org-mode and org-mode syncing -====== -This is fourth in [a series on Emacs and org-mode][1]. - -Hopefully by now you’ve started to see how powerful and useful org-mode is. If you’re like me, you’re thinking: - -“I’d really like to have this in sync across all my devices.” - -and, perhaps: - -“Can I forward emails into org-mode?” - -This being Emacs, the answers, of course, are “Yes.” - -### Syncing - -Since org-mode just uses text files, syncing is pretty easily accomplished using any number of tools. I use git with git-remote-gcrypt. Due to some limitations of git-remote-gcrypt, each machine tends to push to its own branch, and to master on command. Each machine merges from all the other branches and pushes the result to master after a merge. A cron job causes pushes to the machine’s branch to happen, and a bit of elisp coordinates it all — making sure to save buffers before a sync, refresh them from disk after, etc. - -The code for this post is somewhat more extended, so I will be linking to it on github rather than posting inline. - -I have a directory $HOME/org where all my org-stuff lives. In ~/org lives [a Makefile][2] that handles the syncing. It defines these targets: - - * push: adds, commits, and pushes to a branch named after the machine’s hostname - * fetch: does a simple git fetch - * sync: adds, commits, pulls remote changes, merges, and (assuming the merge was successful) pushes to the branch named after the machine’s hostname plus master - - - -Now, in my user’s crontab, I have this: -``` -*/15 * * * * make -C $HOME/org push fetch 2>&1 | logger --tag 'orgsync' - -``` - -The [accompanying elisp code][3] defines a shortcut (C-c s) to cause a sync to occur. Thanks to the cronjob, as long as files were saved — even if I didn’t explicitly sync on the other boxen — they’ll be pulled in. - -I have found this setup to work really well. - -### Emailing to org-mode - -Before going down this path, one should ask the question: do you really need it? I use org-mode with mu4e, and the integration is excellent; any org task can link to an email by message-id, and this is ideal — it lets a person do things like make a reminder to reply to a message in a week. - -However, org is not just about reminders. It’s also a knowledge base, authoring system, etc. And, not all of my mail clients use mu4e. (Note: things like MobileOrg exist for mobile devices). I don’t actually use this as much as I thought I would, but it has its uses and I thought I’d document it here too. - -Now I didn’t want to just be able to accept plain text email. I wanted to be able to handle attachments, HTML mail, etc. This quickly starts to sound problematic — but with tools like ripmime and pandoc, it’s not too bad. - -The first step is to set up some way to get mail into a specific folder. A plus-extension, special user, whatever. I then use a [fetchmail configuration][4] to pull it down and run my [insorgmail][5] script. - -This script is where all the interesting bits happen. It starts with ripmime to process the message. HTML bits are converted from HTML to org format using pandoc. an org hierarchy is made to represent the structure of the email as best as possible. emails can get pretty complicated, with HTML and the rest, but I have found this does an acceptable job with my use cases. - -### Up next… - -My last post on org-mode will talk about using it to write documents and prepare slides — a use for which I found myself surprisingly pleased with it, but which needed a bit of tweaking. - - - --------------------------------------------------------------------------------- - -via: http://changelog.complete.org/archives/9898-emacs-4-automated-emails-to-org-mode-and-org-mode-syncing - -作者：[John Goerzen][a] -译者：[译者ID](https://github.com/译者ID) -校对：[校对者ID](https://github.com/校对者ID) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 - -[a]:http://changelog.complete.org/ -[1]:https://changelog.complete.org/archives/tag/emacs2018 -[2]:https://github.com/jgoerzen/public-snippets/blob/master/emacs/org-tools/Makefile -[3]:https://github.com/jgoerzen/public-snippets/blob/master/emacs/org-tools/emacs-config.org -[4]:https://github.com/jgoerzen/public-snippets/blob/master/emacs/org-tools/fetchmailrc.orgmail -[5]:https://github.com/jgoerzen/public-snippets/blob/master/emacs/org-tools/insorgmail diff --git a/sources/tech/20180402 An introduction to the Flask Python web app framework.md b/sources/tech/20180402 An introduction to the Flask Python web app framework.md new file mode 100644 index 0000000000..4b07338bc5 --- /dev/null +++ b/sources/tech/20180402 An introduction to the Flask Python web app framework.md @@ -0,0 +1,451 @@ +[#]: collector: (lujun9972) +[#]: translator: ( ) +[#]: reviewer: ( ) +[#]: publisher: ( ) +[#]: subject: (An introduction to the Flask Python web app framework) +[#]: via: (https://opensource.com/article/18/4/flask) +[#]: author: (Nicholas Hunt-Walker https://opensource.com/users/nhuntwalker) +[#]: url: ( ) + +An introduction to the Flask Python web app framework +====== +In the first part in a series comparing Python frameworks, learn about Flask. + + +If you're developing a web app in Python, chances are you're leveraging a framework. A [framework][1] "is a code library that makes a developer's life easier when building reliable, scalable, and maintainable web applications" by providing reusable code or extensions for common operations. There are a number of frameworks for Python, including [Flask][2], [Tornado][3], [Pyramid][4], and [Django][5]. New Python developers often ask: Which framework should I use? + + * New visitors to the site should be able to register new accounts. + * Registered users can log in, log out, see information for their profiles, and edit their information. + * Registered users can create new task items, see their existing tasks, and edit existing tasks. + + + +This series is designed to help developers answer that question by comparing those four frameworks. To compare their features and operations, I'll take each one through the process of constructing an API for a simple To-Do List web application. The API is itself fairly straightforward: + +All this rounds out to a compact set of API endpoints that each backend must implement, along with the allowed HTTP methods: + + * `GET /` + * `POST /accounts` + * `POST /accounts/login` + * `GET /accounts/logout` + * `GET, PUT, DELETE /accounts/ ` + * `GET, POST /accounts/ /tasks` + * `GET, PUT, DELETE /accounts/ /tasks/ ` + + + +Each framework has a different way to put together its routes, models, views, database interaction, and overall application configuration. I'll describe those aspects of each framework in this series, which will begin with Flask. + +### Flask startup and configuration + +Like most widely used Python libraries, the Flask package is installable from the [Python Package Index][6] (PPI). First create a directory to work in (something like `flask_todo` is a fine directory name) then install the `flask` package. You'll also want to install `flask-sqlalchemy` so your Flask application has a simple way to talk to a SQL database. + +I like to do this type of work within a Python 3 virtual environment. To get there, enter the following on the command line: + +``` +$ mkdir flask_todo +$ cd flask_todo +$ pipenv install --python 3.6 +$ pipenv shell +(flask-someHash) $ pipenv install flask flask-sqlalchemy +``` + +If you want to turn this into a Git repository, this is a good place to run `git init`. It'll be the root of the project, and if you want to export the codebase to a different machine, it will help to have all the necessary setup files here. + +A good way to get moving is to turn the codebase into an installable Python distribution. At the project's root, create `setup.py` and a directory called `todo` to hold the source code. + +The `setup.py` should look something like this: + +``` +from setuptools import setup, find_packages + +requires = [ + 'flask', + 'flask-sqlalchemy', + 'psycopg2', +] + +setup( + name='flask_todo', + version='0.0', + description='A To-Do List built with Flask', + author=' ', + author_email=' ', + keywords='web flask', + packages=find_packages(), + include_package_data=True, + install_requires=requires +) +``` + +This way, whenever you want to install or deploy your project, you'll have all the necessary packages in the `requires` list. You'll also have everything you need to set up and install the package in `site-packages`. For more information on how to write an installable Python distribution, check out [the docs on setup.py][7]. + +Within the `todo` directory containing your source code, create an `app.py` file and a blank `__init__.py` file. The `__init__.py` file allows you to import from `todo` as if it were an installed package. The `app.py` file will be the application's root. This is where all the `Flask` application goodness will go, and you'll create an environment variable that points to that file. If you're using `pipenv` (like I am), you can locate your virtual environment with `pipenv --venv` and set up that environment variable in your environment's `activate` script. + +``` +# in your activate script, probably at the bottom (but anywhere will do) + +export FLASK_APP=$VIRTUAL_ENV/../todo/app.py +export DEBUG='True' +``` + +When you installed `Flask`, you also installed the `flask` command-line script. Typing `flask run` will prompt the virtual environment's Flask package to run an HTTP server using the `app` object in whatever script the `FLASK_APP` environment variable points to. The script above also includes an environment variable named `DEBUG` that will be used a bit later. + +Let's talk about this `app` object. + +In `todo/app.py`, you'll create an `app` object, which is an instance of the `Flask` object. It'll act as the central configuration object for the entire application. It's used to set up pieces of the application required for extended functionality, e.g., a database connection and help with authentication. + +It's regularly used to set up the routes that will become the application's points of interaction. To explain what this means, let's look at the code it corresponds to. + +``` +from flask import Flask + +app = Flask(__name__) + +@app.route('/') +def hello_world(): + """Print 'Hello, world!' as the response body.""" + return 'Hello, world!' +``` + +This is the most basic complete Flask application. `app` is an instance of `Flask`, taking in the `__name__` of the script file. This lets Python know how to import from files relative to this one. The `app.route` decorator decorates the first **view** function; it can specify one of the routes used to access the application. (We'll look at this later.) + +Any view you specify must be decorated by `app.route` to be a functional part of the application. You can have as many functions as you want scattered across the application, but in order for that functionality to be accessible from anything external to the application, you must decorate that function and specify a route to make it into a view. + +In the example above, when the app is running and accessed at `http://domainname/`, a user will receive `"Hello, World!"` as a response. + +### Connecting the database in Flask + +While the code example above represents a complete Flask application, it doesn't do anything interesting. One interesting thing a web application can do is persist user data, but it needs the help of and connection to a database. + +Flask is very much a "do it yourself" web framework. This means there's no built-in database interaction, but the `flask-sqlalchemy` package will connect a SQL database to a Flask application. The `flask-sqlalchemy` package needs just one thing to connect to a SQL database: The database URL. + +Note that a wide variety of SQL database management systems can be used with `flask-sqlalchemy`, as long as the DBMS has an intermediary that follows the [DBAPI-2 standard][8]. In this example, I'll use PostgreSQL (mainly because I've used it a lot), so the intermediary to talk to the Postgres database is the `psycopg2` package. Make sure `psycopg2` is installed in your environment and include it in the list of required packages in `setup.py`. You don't have to do anything else with it; `flask-sqlalchemy` will recognize Postgres from the database URL. + +Flask needs the database URL to be part of its central configuration through the `SQLALCHEMY_DATABASE_URI` attribute. A quick and dirty solution is to hardcode a database URL into the application. + +``` +# top of app.py +from flask import Flask +from flask_sqlalchemy import SQLAlchemy + +app = Flask(__name__) +app.config['SQLALCHEMY_DATABASE_URI'] = 'postgres://localhost:5432/flask_todo' +db = SQLAlchemy(app) +``` + +However, this is not a sustainable solution. If you change databases or don't want your database URL visible in source control, you'll have to take extra steps to ensure your information is appropriate for the environment. + +You can make things simpler by using environment variables. They will ensure that, no matter what machine the code runs on, it always points at the right stuff if that stuff is configured in the running environment. It also ensures that, even though you need that information to run the application, it never shows up as a hardcoded value in source control. + +In the same place you declared `FLASK_APP`, declare a `DATABASE_URL` pointing to the location of your Postgres database. Development tends to work locally, so just point to your local database. + +``` +# also in your activate script + +export DATABASE_URL='postgres://localhost:5432/flask_todo' +``` + +Now in `app.py`, include the database URL in your app configuration. + +``` +app.config['SQLALCHEMY_DATABASE_URI'] = os.environ.get('DATABASE_URL', '') +db = SQLAlchemy(app) +``` + +And just like that, your application has a database connection! + +### Defining objects in Flask + +Having a database to talk to is a good first step. Now it's time to define some objects to fill that database. + +In application development, a "model" refers to the data representation of some real or conceptual object. For example, if you're building an application for a car dealership, you may define a `Car` model that encapsulates all of a car's attributes and behavior. + +In this case, you're building a To-Do List with Tasks, and each Task belongs to a User. Before you think too deeply about how they're related to each other, start by defining objects for Tasks and Users. + +The `flask-sqlalchemy` package leverages [SQLAlchemy][9] to set up and inform the database structure. You'll define a model that will live in the database by inheriting from the `db.Model` object and define the attributes of those models as `db.Column` instances. For each column, you must specify a data type, so you'll pass that data type into the call to `db.Column` as the first argument. + +Because the model definition occupies a different conceptual space than the application configuration, make `models.py` to hold model definitions separate from `app.py`. The Task model should be constructed to have the following attributes: + + * `id`: a value that's a unique identifier to pull from the database + * `name`: the name or title of the task that the user will see when the task is listed + * `note`: any extra comments that a person might want to leave with their task + * `creation_date`: the date and time the task was created + * `due_date`: the date and time the task is due to be completed (if at all) + * `completed`: a way to indicate whether or not the task has been completed + + + +Given this attribute list for Task objects, the application's `Task` object can be defined like so: + +``` +from .app import db +from datetime import datetime + +class Task(db.Model): + """Tasks for the To Do list.""" + id = db.Column(db.Integer, primary_key=True) + name = db.Column(db.Unicode, nullable=False) + note = db.Column(db.Unicode) + creation_date = db.Column(db.DateTime, nullable=False) + due_date = db.Column(db.DateTime) + completed = db.Column(db.Boolean, default=False) + + def __init__(self, *args, **kwargs): + """On construction, set date of creation.""" + super().__init__(*args, **kwargs) + self.creation_date = datetime.now() +``` + +Note the extension of the class constructor method. At the end of the day, any model you construct is still a Python object and therefore must go through construction in order to be instantiated. It's important to ensure that the creation date of the model instance reflects its actual date of creation. You can explicitly set that relationship by effectively saying, "when an instance of this model is constructed, record the date and time and set it as the creation date." + +### Model relationships + +In a given web application, you may want to be able to express relationships between objects. In the To-Do List example, users own multiple tasks, and each task is owned by only one user. This is an example of a "many-to-one" relationship, also known as a foreign key relationship, where the tasks are the "many" and the user owning those tasks is the "one." + +In Flask, a many-to-one relationship can be specified using the `db.relationship` function. First, build the User object. + +``` +class User(db.Model): + """The User object that owns tasks.""" + id = db.Column(db.Integer, primary_key=True) + username = db.Column(db.Unicode, nullable=False) + email = db.Column(db.Unicode, nullable=False) + password = db.Column(db.Unicode, nullable=False) + date_joined = db.Column(db.DateTime, nullable=False) + token = db.Column(db.Unicode, nullable=False) + + def __init__(self, *args, **kwargs): + """On construction, set date of creation.""" + super().__init__(*args, **kwargs) + self.date_joined = datetime.now() + self.token = secrets.token_urlsafe(64) +``` + +It looks very similar to the Task object; you'll find that most objects have the same basic format of class attributes as table columns. Every once in a while, you'll run into something a little different, including some multiple-inheritance magic, but this is the norm. + +Now that the `User` model is created, you can set up the foreign key relationship. For the "many," set fields for the `user_id` of the `User` that owns this task, as well as the `user` object with that ID. Also make sure to include a keyword argument (`back_populates`) that updates the User model when the task gets a user as an owner. + +For the "one," set a field for the `tasks` the specific user owns. Similar to maintaining the two-way relationship on the Task object, set a keyword argument on the User's relationship field to update the Task when it is assigned to a user. + +``` +# on the Task object +user_id = db.Column(db.Integer, db.ForeignKey('user.id'), nullable=False) +user = db.relationship("user", back_populates="tasks") + +# on the User object +tasks = db.relationship("Task", back_populates="user") +``` + +### Initializing the database + +Now that the models and model relationships are set, start setting up your database. Flask doesn't come with its own database-management utility, so you'll have to write your own (to some degree). You don't have to get fancy with it; you just need something to recognize what tables are to be created and some code to create them (or drop them should the need arise). If you need something more complex, like handling updates to database tables (i.e., database migrations), you'll want to look into a tool like [Flask-Migrate][10] or [Flask-Alembic][11]. + +Create a script called `initializedb.py` next to `setup.py` for managing the database. (Of course, it doesn't need to be called this, but why not give names that are appropriate to a file's function?) Within `initializedb.py`, import the `db` object from `app.py` and use it to create or drop tables. `initializedb.py` should end up looking something like this: + +``` +from todo.app import db +import os + +if bool(os.environ.get('DEBUG', '')): + db.drop_all() +db.create_all() +``` + +If a `DEBUG` environment variable is set, drop tables and rebuild. Otherwise, just create the tables once and you're good to go. + +### Views and URL config + +The last bits needed to connect the entire application are the views and routes. In web development, a "view" (in concept) is functionality that runs when a specific access point (a "route") in your application is hit. These access points appear as URLs: paths to functionality in an application that return some data or handle some data that has been provided. The views will be logical structures that handle specific HTTP requests from a given client and return some HTTP response to that client. + +In Flask, views appear as functions; for example, see the `hello_world` view above. For simplicity, here it is again: + +``` +@app.route('/') +def hello_world(): + """Print 'Hello, world!' as the response body.""" + return 'Hello, world!' +``` + +When the route of `http://domainname/` is accessed, the client receives the response, "Hello, world!" + +With Flask, a function is marked as a view when it is decorated by `app.route`. In turn, `app.route` adds to the application's central configuration a map from the specified route to the function that runs when that route is accessed. You can use this to start building out the rest of the API. + +Start with a view that handles only `GET` requests, and respond with the JSON representing all the routes that will be accessible and the methods that can be used to access them. + +``` +from flask import jsonify + +@app.route('/api/v1', methods=["GET"]) +def info_view(): + """List of routes for this API.""" + output = { + 'info': 'GET /api/v1', + 'register': 'POST /api/v1/accounts', + 'single profile detail': 'GET /api/v1/accounts/ ', + 'edit profile': 'PUT /api/v1/accounts/ ', + 'delete profile': 'DELETE /api/v1/accounts/ ', + 'login': 'POST /api/v1/accounts/login', + 'logout': 'GET /api/v1/accounts/logout', + "user's tasks": 'GET /api/v1/accounts/ /tasks', + "create task": 'POST /api/v1/accounts/ /tasks', + "task detail": 'GET /api/v1/accounts/ /tasks/ ', + "task update": 'PUT /api/v1/accounts/ /tasks/ ', + "delete task": 'DELETE /api/v1/accounts/ /tasks/ ' + } + return jsonify(output) +``` + +Since you want your view to handle one specific type of HTTP request, use `app.route` to add that restriction. The `methods` keyword argument will take a list of strings as a value, with each string a type of possible HTTP method. In practice, you can use `app.route` to restrict to one or more types of HTTP request or accept any by leaving the `methods` keyword argument alone. + +Whatever you intend to return from your view function **must** be a string or an object that Flask turns into a string when constructing a properly formatted HTTP response. The exceptions to this rule are when you're trying to handle redirects and exceptions thrown by your application. What this means for you, the developer, is that you need to be able to encapsulate whatever response you're trying to send back to the client into something that can be interpreted as a string. + +A good structure that contains complexity but can still be stringified is a Python dictionary. Therefore, I recommend that, whenever you want to send some data to the client, you choose a Python `dict` with whatever key-value pairs you need to convey information. To turn that dictionary into a properly formatted JSON response, headers and all, pass it as an argument to Flask's `jsonify` function (`from flask import jsonify`). + +The view function above takes what is effectively a listing of every route that this API intends to handle and sends it to the client whenever the `http://domainname/api/v1` route is accessed. Note that, on its own, Flask supports routing to exactly matching URIs, so accessing that same route with a trailing `/` would create a 404 error. If you wanted to handle both with the same view function, you'd need stack decorators like so: + +``` +@app.route('/api/v1', methods=["GET"]) +@app.route('/api/v1/', methods=["GET"]) +def info_view(): + # blah blah blah more code +``` + +An interesting case is that if the defined route had a trailing slash and the client asked for the route without the slash, you wouldn't need to double up on decorators. Flask would redirect the client's request appropriately. It's odd that it doesn't work both ways. + +### Flask requests and the DB + +At its base, a web framework's job is to handle incoming HTTP requests and return HTTP responses. The previously written view doesn't really have much to do with HTTP requests aside from the URI that was accessed. It doesn't process any data. Let's look at how Flask behaves when data needs handling. + +The first thing to know is that Flask doesn't provide a separate `request` object to each view function. It has **one** global request object that every view function can use, and that object is conveniently named `request` and is importable from the Flask package. + +The next thing is that Flask's route patterns can have a bit more nuance. One scenario is a hardcoded route that must be matched perfectly to activate a view function. Another scenario is a route pattern that can handle a range of routes, all mapping to one view by allowing a part of that route to be variable. If the route in question has a variable, the corresponding value can be accessed from the same-named variable in the view's parameter list. + +``` +@app.route('/a/sample/ /route) +def some_view(variable): + # some code blah blah blah +``` + +To communicate with the database within a view, you must use the `db` object that was populated toward the top of the script. Its `session` attribute is your connection to the database when you want to make changes. If you just want to query for objects, the objects built from `db.Model` have their own database interaction layer through the `query` attribute. + +Finally, any response you want from a view that's more complex than a string must be built deliberately. Previously you built a response using a "jsonified" dictionary, but certain assumptions were made (e.g., 200 status code, status message "OK," Content-Type of "text/plain"). Any special sauce you want in your HTTP response must be added deliberately. + +Knowing these facts about working with Flask views allows you to construct a view whose job is to create new `Task` objects. Let's look at the code (below) and address it piece by piece. + +``` +from datetime import datetime +from flask import request, Response +from flask_sqlalchemy import SQLAlchemy +import json + +from .models import Task, User + +app = Flask(__name__) +app.config['SQLALCHEMY_DATABASE_URI'] = os.environ.get('DATABASE_URL', '') +db = SQLAlchemy(app) + +INCOMING_DATE_FMT = '%d/%m/%Y %H:%M:%S' + +@app.route('/api/v1/accounts/ /tasks', methods=['POST']) +def create_task(username): + """Create a task for one user.""" + user = User.query.filter_by(username=username).first() + if user: + task = Task( + name=request.form['name'], + note=request.form['note'], + creation_date=datetime.now(), + due_date=datetime.strptime(due_date, INCOMING_DATE_FMT) if due_date else None, + completed=bool(request.form['completed']), + user_id=user.id, + ) + db.session.add(task) + db.session.commit() + output = {'msg': 'posted'} + response = Response( + mimetype="application/json", + response=json.dumps(output), + status=201 + ) + return response +``` + +Let's start with the `@app.route` decorator. The route is `'/api/v1/accounts/ /tasks'`, where ` ` is a route variable. Put angle brackets around any part of the route you want to be variable, then include that part of the route on the next line in the parameter list **with the same name**. The only parameters that should be in the parameter list should be the variables in your route. + +Next comes the query: + +``` +user = User.query.filter_by(username=username).first() +``` + +To look for one user by username, conceptually you need to look at all the User objects stored in the database and find the users with the username matching the one that was requested. With Flask, you can ask the `User` object directly through the `query` attribute for the instance matching your criteria. This type of query would provide a list of objects (even if it's only one object or none at all), so to get the object you want, just call `first()`. + +``` +task = Task( + name=request.form['name'], + note=request.form['note'], + creation_date=datetime.now(), + due_date=datetime.strptime(due_date, INCOMING_DATE_FMT) if due_date else None, + completed=bool(request.form['completed']), + user_id=user.id, +) +``` + +Whenever data is sent to the application, regardless of the HTTP method used, that data is stored on the `form` attribute of the `request` object. The name of the field on the frontend will be the name of the key mapped to that data in the `form` dictionary. It'll always come in the form of a string, so if you want your data to be a specific data type, you'll have to make it explicit by casting it as the appropriate type. + +The other thing to note is the assignment of the current user's user ID to the newly instantiated `Task`. This is how that foreign key relationship is maintained. + +``` +db.session.add(task) +db.session.commit() +``` + +Creating a new `Task` instance is great, but its construction has no inherent connection to tables in the database. In order to insert a new row into the corresponding SQL table, you must use the `session` attached to the `db` object. The `db.session.add(task)` stages the new `Task` instance to be added to the table, but doesn't add it yet. While it's done only once here, you can add as many things as you want before committing. The `db.session.commit()` takes all the staged changes, or "commits," and applies them to the corresponding tables in the database. + +``` +output = {'msg': 'posted'} +response = Response( + mimetype="application/json", + response=json.dumps(output), + status=201 +) +``` + +The response is an actual instance of a `Response` object with its `mimetype`, body, and `status` set deliberately. The goal for this view is to alert the user they created something new. Seeing how this view is supposed to be part of a backend API that sends and receives JSON, the response body must be JSON serializable. A dictionary with a simple string message should suffice. Ensure that it's ready for transmission by calling `json.dumps` on your dictionary, which will turn your Python object into valid JSON. This is used instead of `jsonify`, as `jsonify` constructs an actual response object using its input as the response body. In contrast, `json.dumps` just takes a given Python object and converts it into a valid JSON string if possible. + +By default, the status code of any response sent with Flask will be `200`. That will work for most circumstances, where you're not trying to send back a specific redirection-level or error-level message. Since this case explicitly lets the frontend know when a new item has been created, set the status code to be `201`, which corresponds to creating a new thing. + +And that's it! That's a basic view for creating a new `Task` object in Flask given the current setup of your To-Do List application. Similar views could be constructed for listing, editing, and deleting tasks, but this example offers an idea of how it could be done. + +### The bigger picture + +There is much more that goes into an application than one view for creating new things. While I haven't discussed anything about authorization/authentication systems, testing, database migration management, cross-origin resource sharing, etc., the details above should give you more than enough to start digging into building your own Flask applications. + +Learn more Python at [PyCon Cleveland 2018][12]. + +-------------------------------------------------------------------------------- + +via: https://opensource.com/article/18/4/flask + +作者：[Nicholas Hunt-Walker][a] +选题：[lujun9972][b] +译者：[译者ID](https://github.com/译者ID) +校对：[校对者ID](https://github.com/校对者ID) + +本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 + +[a]: https://opensource.com/users/nhuntwalker +[b]: https://github.com/lujun9972 +[1]: https://www.fullstackpython.com/web-frameworks.html +[2]: http://flask.pocoo.org/ +[3]: http://www.tornadoweb.org/en/stable/ +[4]: https://trypyramid.com/ +[5]: https://www.djangoproject.com/ +[6]: https://pypi.python.org +[7]: https://docs.python.org/3/distutils/setupscript.html +[8]: https://www.python.org/dev/peps/pep-0249/ +[9]: https://www.sqlalchemy.org/ +[10]: https://flask-migrate.readthedocs.io/en/latest/ +[11]: https://flask-alembic.readthedocs.io/en/stable/ +[12]: https://us.pycon.org/2018/ diff --git a/sources/tech/20180404 Emacs -5- Documents and Presentations with org-mode.md b/sources/tech/20180404 Emacs -5- Documents and Presentations with org-mode.md deleted file mode 100644 index 06c8dc8856..0000000000 --- a/sources/tech/20180404 Emacs -5- Documents and Presentations with org-mode.md +++ /dev/null @@ -1,177 +0,0 @@ -Emacs #5: Documents and Presentations with org-mode -====== - -### 1 About org-mode exporting - -#### 1.1 Background - -org-mode isn't just an agenda-making program. It can also export to lots of formats: LaTeX, PDF, Beamer, iCalendar (agendas), HTML, Markdown, ODT, plain text, man pages, and more complicated formats such as a set of web pages. - -This isn't just some afterthought either; it's a core part of the system and integrates very well. - -One file can be source code, automatically-generated output, task list, documentation, and presentation, all at once. - -Some use org-mode as their preferred markup format, even for things like LaTeX documents. The org-mode manual has an extensive [section on exporting][13]. - -#### 1.2 Getting started - -From any org-mode document, just hit C-c C-e. From there will come up a menu, letting you choose various export formats and options. These are generally single-key options so it's easy to set and execute. For instance, to export a document to a PDF, use C-c C-e l p or for HTML export, C-c C-e h h. - -There are lots of settings available for all of these export options; see the manual. It is, in fact, quite possible to use LaTeX-format equations in both LaTeX and HTML modes, to insert arbitrary preambles and settings for different modes, etc. - -#### 1.3 Add-on packages - -ELPA containts many addition exporters for org-mode as well. Check there for details. - -### 2 Beamer slides with org-mode - -#### 2.1 About Beamer - -[Beamer][14] is a LaTeX environment for making presentations. Its features include: - -* Automated generating of structural elements in the presentation (see, for example, [the Marburg theme][1]). This provides a visual reference for the audience of where they are in the presentation. - -* Strong help for structuring the presentation - -* Themes - -* Full LaTeX available - -#### 2.2 Benefits of Beamer in org-mode - -org-mode has a lot of benefits for working with Beamer. Among them: - -* org-mode's very easy and strong support for visualizing and changing the structure makes it very quick to reorganize your material. - -* Combined with org-babel, live source code (with syntax highlighting) and results can be embedded. - -* The syntax is often easier to work with. - -I have completely replaced my usage of LibreOffice/Powerpoint/GoogleDocs with org-mode and beamer. It is, in fact, rather frustrating when I have to use one of those tools, as they are nowhere near as strong as org-mode for visualizing a presentation structure. - -#### 2.3 Headline Levels - -org-mode's Beamer export will convert sections of your document (defined by headings) into slides. The question, of course, is: which sections? This is governed by the H [export setting][15] (org-export-headline-levels). - -There are many ways to go, which suit people. I like to have my presentation like this: - -``` -#+OPTIONS: H:2 -#+BEAMER_HEADER: \AtBeginSection{\frame{\sectionpage}} -``` - -This gives a standalone section slide for each major topic, to highlight major transitions, and then takes the level 2 (two asterisks) headings to set the slide. Many Beamer themes expect a third level of indirection, so you would set H:3 for them. - -#### 2.4 Themes and settings - -You can configure many Beamer and LaTeX settings in your document by inserting lines at the top of your org file. This document, for instance, defines: - -``` -#+TITLE: Documents and presentations with org-mode -#+AUTHOR: John Goerzen -#+BEAMER_HEADER: \institute{The Changelog} -#+PROPERTY: comments yes -#+PROPERTY: header-args :exports both :eval never-export -#+OPTIONS: H:2 -#+BEAMER_THEME: CambridgeUS -#+BEAMER_COLOR_THEME: default -``` - -#### 2.5 Advanced settings - -I like to change some colors, bullet formatting, and the like. I round out my document with: - -``` -# We can't just +BEAMER_INNER_THEME: default because that picks the theme default. -# Override per https://tex.stackexchange.com/questions/11168/change-bullet-style-formatting-in-beamer -#+BEAMER_INNER_THEME: default -#+LaTeX_CLASS_OPTIONS: [aspectratio=169] -#+BEAMER_HEADER: \definecolor{links}{HTML}{0000A0} -#+BEAMER_HEADER: \hypersetup{colorlinks=,linkcolor=,urlcolor=links} -#+BEAMER_HEADER: \setbeamertemplate{itemize items}[default] -#+BEAMER_HEADER: \setbeamertemplate{enumerate items}[default] -#+BEAMER_HEADER: \setbeamertemplate{items}[default] -#+BEAMER_HEADER: \setbeamercolor*{local structure}{fg=darkred} -#+BEAMER_HEADER: \setbeamercolor{section in toc}{fg=darkred} -#+BEAMER_HEADER: \setlength{\parskip}{\smallskipamount} -``` - -Here, aspectratio=169 sets a 16:9 aspect ratio, and the remaining are standard LaTeX/Beamer configuration bits. - -#### 2.6 Shrink (to fit) - -Sometimes you've got some really large code examples and you might prefer to just shrink the slide to fit. - -Just type C-c C-x p, set the BEAMER_opt property to shrink=15\. - -(Or a larger value of shrink). The previous slide uses this here. - -#### 2.7 Result - -Here's the end result: - - [][16] - -### 3 Interactive Slides - -#### 3.1 Interactive Emacs Slideshows - -With the [org-tree-slide package][17], you can display your slideshow from right within Emacs. Just run M-x org-tree-slide-mode. Then, use C-> and C-< to move between slides. - -You might find C-c C-x C-v (which is org-toggle-inline-images) helpful to cause the system to display embedded images. - -#### 3.2 HTML Slideshows - -There are a lot of ways to export org-mode presentations to HTML, with various levels of JavaScript integration. See the [non-beamer presentations section][18] of the org-mode wiki for details. - -### 4 Miscellaneous - -#### 4.1 Additional resources to accompany this post - -* [orgmode.org beamer tutorial][2] - -* [LaTeX wiki][3] - -* [Generating section title slides][4] - -* [Shrinking content to fit on slide][5] - -* A great resource: refcard-org-beamer See its [Github repo][6] Make sure to check out both the PDF and the .org file - -* A nice [Theme matrix][7] - -#### 4.2 Up next in my Emacs series… - -mu4e for email! - - --------------------------------------------------------------------------------- - -via: http://changelog.complete.org/archives/9900-emacs-5-documents-and-presentations-with-org-mode - -作者：[John Goerzen][a] -译者：[译者ID](https://github.com/译者ID) -校对：[校对者ID](https://github.com/校对者ID) -选题：[lujun9972](https://github.com/lujun9972) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 - -[a]:http://changelog.complete.org/archives/author/jgoerzen -[1]:https://hartwork.org/beamer-theme-matrix/all/beamer-albatross-Marburg-1.png -[2]:https://orgmode.org/worg/exporters/beamer/tutorial.html -[3]:https://en.wikibooks.org/wiki/LaTeX/Presentations -[4]:https://tex.stackexchange.com/questions/117658/automatically-generate-section-title-slides-in-beamer/117661 -[5]:https://tex.stackexchange.com/questions/78514/content-doesnt-fit-in-one-slide -[6]:https://github.com/fniessen/refcard-org-beamer -[7]:https://hartwork.org/beamer-theme-matrix/ -[8]:https://changelog.complete.org/archives/tag/emacs2018 -[9]:https://github.com/jgoerzen/public-snippets/blob/master/emacs/emacs-org-beamer/emacs-org-beamer.org -[10]:http://changelog.complete.org/archives/9900-emacs-5-documents-and-presentations-with-org-mode -[11]:https://github.com/jgoerzen/public-snippets/raw/master/emacs/emacs-org-beamer/emacs-org-beamer.pdf -[12]:https://github.com/jgoerzen/public-snippets/raw/master/emacs/emacs-org-beamer/emacs-org-beamer-document.pdf -[13]:https://orgmode.org/manual/Exporting.html#Exporting -[14]:https://en.wikipedia.org/wiki/Beamer_(LaTeX) -[15]:https://orgmode.org/manual/Export-settings.html#Export-settings -[16]:https://www.flickr.com/photos/jgoerzen/26366340577/in/dateposted/ -[17]:https://orgmode.org/worg/org-tutorials/non-beamer-presentations.html#org-tree-slide -[18]:https://orgmode.org/worg/org-tutorials/non-beamer-presentations.html diff --git a/sources/tech/20180407 12 Best GTK Themes for Ubuntu and other Linux Distributions.md b/sources/tech/20180407 12 Best GTK Themes for Ubuntu and other Linux Distributions.md deleted file mode 100644 index 1bd3f8d0d7..0000000000 --- a/sources/tech/20180407 12 Best GTK Themes for Ubuntu and other Linux Distributions.md +++ /dev/null @@ -1,172 +0,0 @@ -12 Best GTK Themes for Ubuntu and other Linux Distributions -====== -**Brief: Let’s have a look at some of the beautiful GTK themes that you can use not only in Ubuntu but other Linux distributions that use GNOME.** - -For those of us that use Ubuntu proper, the move from Unity to Gnome as the default desktop environment has made theming and customizing easier than ever. Gnome has a fairly large tweaking community, and there is no shortage of fantastic GTK themes for users to choose from. With that in mind, I went ahead and found some of my favorite themes that I have come across in recent months. These are what I believe offer some of the best experiences that you can find. - -### Best themes for Ubuntu and other Linux distributions - -This is not an exhaustive list and may exclude some of the themes you already use and love, but hopefully, you find at least one theme that you enjoy that you did not already know about. All themes present should work on any Gnome 3 setup, Ubuntu or not. I lost some screenshots so I have taken images from the official websites. - -The themes listed here are in no particular order. - -But before you see the best GNOME themes, you should learn [how to install themes in Ubuntu GNOME][1]. - -#### 1\. Arc-Ambiance - -![][2] - -Arc and Arc variant themes have been around for quite some time now, and are widely regarded as some of the best themes you can find. In this example, I have selected Arc-Ambiance because of its modern take on the default Ambiance theme in Ubuntu. - -I am a fan of both the Arc theme and the default Ambiance theme, so needless to say, I was pumped when I came across a theme that merged the best of both worlds. If you are a fan of the arc themes but not a fan of this one in particular, Gnome look has plenty of other options that will most certainly suit your taste. - -[Arc-Ambiance Theme][3] - -#### 2\. Adapta Colorpack - -![][4] - -The Adapta theme has been one of my favorite flat themes I have ever found. Like Arc, Adapata is widely adopted by many-a-linux user. I have selected this color pack because in one download you have several options to choose from. In fact, there are 19 to choose from. Yep. You read that correctly. 19! - -So, if you are a fan of the flat/material design language that we see a lot of today, then there is most likely a variant in this theme pack that will satisfy you. - -[Adapta Colorpack Theme][5] - -#### 3\. Numix Collection - -![][6] - -Ah, Numix! Oh, the years we have spent together! For those of us that have been theming our DE for the last couple of years, you must have come across the Numix themes or icon packs at some point in time. Numix was probably the first modern theme for Linux that I fell in love with, and I am still in love with it today. And after all these years, it still hasn’t lost its charm. - -The gray tone throughout the theme, especially with the default pinkish-red highlight color, makes for a genuinely clean and complete experience. You would be hard pressed to find a theme pack as polished as Numix. And in this offering, you have plenty of options to choose from, so go crazy! - -[Numix Collection Theme][7] - -#### 4\. Hooli - -![][8] - -Hooli is a theme that has been out for some time now, but only recently came across my radar. I am a fan of most flat themes but have usually strayed away from themes that come to close to the material design language. Hooli, like Adapta, takes notes from that design language, but does it in a way that I think sets it apart from the rest. The green highlight color is one of my favorite parts about the theme, and it does a good job at not overpowering the entire theme. - -[Hooli Theme][9] - -#### 5\. Arrongin/Telinkrin - -![][10] - -Bonus: Two themes in one! And they are relatively new contenders in the theming realm. They both take notes from Ubuntu’s soon to be finished “[communitheme][11]” and bring it to your desktop today. The only real difference I can find between the offerings are the colors. Arrongin is centered around an Ubuntu-esq orange color, while Telinkrin uses a slightly more KDE Breeze-esq blue. I personally prefer the blue, but both are great options! - -[Arrongin/Telinkrin Themes][12] - -#### 6\. Gnome-osx - -![][13] - -I have to admit, usually, when I see that a theme has “osx” or something similar in the title, I don’t expect much. Most Apple inspired themes seem to have so much in common that I can’t really find a reason to use them. There are two themes I can think of that break this mold: the Arc-osc them and the Gnome-osx theme that we have here. - -The reason I like the Gnome-osx theme is because it truly does look at home on the Gnome desktop. It does a great job at blending into the DE without being too flat. So for those of you that enjoy a slightly less flat theme, and you like the red, yellow, and green button scheme for the close, minimize, and maximize buttons, than this theme is perfect for you. - -[Gnome-osx Theme][14] - -#### 7\. Ultimate Maia - -![][15] - -There was a time when I used Manjaro Gnome. Since then I have reverted back to Ubuntu, but one thing I wish I could have brought with me was the Manjaro theme. If you feel the same about the Manjaro theme as I do, then you are in luck because you can bring it to ANY distro you want that is running Gnome! - -The rich green color, the Breeze-esq close, minimize, maximize buttons, and the over-all polish of the theme makes for one compelling option. It even offers some other color variants of you are not a fan of the green. But let’s be honest…who isn’t a fan of that Manjaro green color? - -[Ultimate Maia Theme][16] - -#### 8\. Vimix - -![][17] - -This was a theme I easily got excited about. It is modern, pulls from the macOS red, yellow, green buttons without directly copying them, and tones down the vibrancy of the theme, making for one unique alternative to most other themes. It comes with three dark variants and several colors to choose from so most of us will find something we like. - -[Vimix Theme][18] - -#### 9\. Ant - -![][19] - -Like Vimix, Ant pulls inspiration from macOS for the button colors without directly copying the style. Where Vimix tones down the color options, Ant adds a richness to the colors that looks fantastic on my System 76 Galago Pro screen. The variation between the three theme options is pretty dramatic, and though it may not be to everyone’s taste, it is most certainly to mine. - -[Ant Theme][20] - -#### 10\. Flat Remix - -![][21] - -If you haven’t noticed by this point, I am a sucker for someone who pays attention to the details in the close, minimize, maximize buttons. The color theme that Flat Remix uses is one I have not seen anywhere else, with a red, blue, and orange color way. Add that on top of a theme that looks almost like a mix between Arc and Adapta, and you have Flat Remix. - -I am personally a fan of the dark option, but the light alternative is very nice as well. So if you like subtle transparencies, a cohesive dark theme, and a touch of color here and there, Flat Remix is for you. - -[Flat Remix Theme][22] - -#### 11\. Paper - -![][23] - -[Paper][24] has been around for some time now. I remember using it for the first back in 2014. I would say, at this point, Paper is more known for its icon pack than for its GTK theme, but that doesn’t mean that the theme isn’t a wonderful option in and of its self. Even though I adored the Paper icons from the beginning, I can’t say that I was a huge fan of the Paper theme when I first tried it out. - -I felt like the bright colors and fun approach to a theme made for an “immature” experience. Now, years later, Paper has grown on me, to say the least, and the light hearted approach that the theme takes is one I greatly appreciate. - -[Paper Theme][25] - -#### 12\. Pop - -![][26] - -Pop is one of the newer offerings on this list. Created by the folks over at [System 76][27], the Pop GTK theme is a fork of the Adapta theme listed earlier and comes with a matching icon pack, which is a fork of the previously mentioned Paper icon pack. - -The theme was released soon after System 76 announced that they were releasing [their own distribution,][28] Pop!_OS. You can read my [Pop!_OS review][29] to know more about it. Needless to say, I think Pop is a fantastic theme with a superb amount of polish and offers a fresh feel to any Gnome desktop. - -[Pop Theme][30] - -#### Conclusion - -Obviously, there way more themes to choose from than we could feature in one article, but these are some of the most complete and polished themes I have used in recent months. If you think we missed any that you really like or you just really dislike one that I featured above, then feel free to let me know in the comment section below and share why you think your favorite themes are better! - --------------------------------------------------------------------------------- - -via: https://itsfoss.com/best-gtk-themes/ - -作者：[Phillip Prado][a] -译者：[译者ID](https://github.com/译者ID) -校对：[校对者ID](https://github.com/校对者ID) -选题：[lujun9972](https://github.com/lujun9972) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 - -[a]:https://itsfoss.com/author/phillip/ -[1]:https://itsfoss.com/install-themes-ubuntu/ -[2]:https://itsfoss.com/wp-content/uploads/2018/03/arcambaince-300x225.png -[3]:https://www.gnome-look.org/p/1193861/ -[4]:https://itsfoss.com/wp-content/uploads/2018/03/adapta-300x169.jpg -[5]:https://www.gnome-look.org/p/1190851/ -[6]:https://itsfoss.com/wp-content/uploads/2018/03/numix-300x169.png -[7]:https://www.gnome-look.org/p/1170667/ -[8]:https://itsfoss.com/wp-content/uploads/2018/03/hooli2-800x500.jpg -[9]:https://www.gnome-look.org/p/1102901/ -[10]:https://itsfoss.com/wp-content/uploads/2018/03/AT-800x590.jpg -[11]:https://itsfoss.com/ubuntu-community-theme/ -[12]:https://www.gnome-look.org/p/1215199/ -[13]:https://itsfoss.com/wp-content/uploads/2018/03/gosx-800x473.jpg -[14]:https://www.opendesktop.org/s/Gnome/p/1171688/ -[15]:https://itsfoss.com/wp-content/uploads/2018/03/ultimatemaia-800x450.jpg -[16]:https://www.opendesktop.org/s/Gnome/p/1193879/ -[17]:https://itsfoss.com/wp-content/uploads/2018/03/vimix-800x450.jpg -[18]:https://www.gnome-look.org/p/1013698/ -[19]:https://itsfoss.com/wp-content/uploads/2018/03/ant-800x533.png -[20]:https://www.opendesktop.org/p/1099856/ -[21]:https://itsfoss.com/wp-content/uploads/2018/03/flatremix-800x450.png -[22]:https://www.opendesktop.org/p/1214931/ -[23]:https://itsfoss.com/wp-content/uploads/2018/04/paper-800x450.jpg -[24]:https://itsfoss.com/install-paper-theme-linux/ -[25]:https://snwh.org/paper/download -[26]:https://itsfoss.com/wp-content/uploads/2018/04/pop-800x449.jpg -[27]:https://system76.com/ -[28]:https://itsfoss.com/system76-popos-linux/ -[29]:https://itsfoss.com/pop-os-linux-review/ -[30]:https://github.com/pop-os/gtk-theme/blob/master/README.md diff --git a/sources/tech/20180409 How to create LaTeX documents with Emacs.md b/sources/tech/20180409 How to create LaTeX documents with Emacs.md deleted file mode 100644 index 7dc16bcf10..0000000000 --- a/sources/tech/20180409 How to create LaTeX documents with Emacs.md +++ /dev/null @@ -1,281 +0,0 @@ -How to create LaTeX documents with Emacs -====== - - -In his excellent article, [An introduction to creating documents in LaTeX][1], author [Aaron Cocker][2] introduces the [LaTeX typesetting system][3] and explains how to create a LaTeX document using [TeXstudio][4]. He also lists a few LaTeX editors that many users find helpful in creating LaTeX documents. - -This comment on the article by [Greg Pittman][5] caught my attention: "LaTeX seems like an awful lot of typing when you first start...". This is true. LaTeX involves a lot of typing and debugging, if you missed a special character like an exclamation mark, which can discourage many users, especially beginners. In this article, I will introduce you to [GNU Emacs][6] and describe how to use it to create LaTeX documents. - -### Creating your first document - -Launch Emacs by typing: -``` -emacs -q --no-splash helloworld.org - -``` - -The `-q` flag ensures that no Emacs initializations will load. The `--no-splash-screen` flag prevents splash screens to ensure that only one window is open, with the file `helloworld.org`. - -![Emacs startup screen][8] - -GNU Emacs with the helloworld.org file opened in a buffer window - -Let's add some LaTeX headers the Emacs way: Go to **Org** in the menu bar and select **Export/Publish**. - -![template_flow.png][10] - -Inserting a default template - -In the next window, Emacs offers options to either export or insert a template. Insert the template by entering **#** ([#] Insert template). This will move a cursor to a mini-buffer, where the prompt reads **Options category:**. At this time you may not know the category names; press Tab to see possible completions. Type "default" and press Enter. The following content will be inserted: -``` -#+TITLE: helloworld - -#+DATE: <2018-03-12 Mon> - -#+AUTHOR: - -#+EMAIL: makerpm@nubia - -#+OPTIONS: ':nil *:t -:t ::t <:t H:3 \n:nil ^:t arch:headline - -#+OPTIONS: author:t c:nil creator:comment d:(not "LOGBOOK") date:t - -#+OPTIONS: e:t email:nil f:t inline:t num:t p:nil pri:nil stat:t - -#+OPTIONS: tags:t tasks:t tex:t timestamp:t toc:t todo:t |:t - -#+CREATOR: Emacs 25.3.1 (Org mode 8.2.10) - -#+DESCRIPTION: - -#+EXCLUDE_TAGS: noexport - -#+KEYWORDS: - -#+LANGUAGE: en - -#+SELECT_TAGS: export - -``` - -Change the title, date, author, and email as you wish. Mine looks like this: -``` -#+TITLE: Hello World! My first LaTeX document - -#+DATE: \today - -#+AUTHOR: Sachin Patil - -#+EMAIL: psachin@redhat.com - -``` - -We don't want to create a Table of Contents yet, so change the value of `toc` from `t` to `nil` inline, as shown below: -``` -#+OPTIONS: tags:t tasks:t tex:t timestamp:t toc:nil todo:t |:t - -``` - -Let's add a section and paragraphs. A section starts with an asterisk (*). We'll copy the content of some paragraphs from Aaron's post (from the [Lipsum Lorem Ipsum generator][11]): -``` -* Introduction - - - - \paragraph{} - - Lorem ipsum dolor sit amet, consectetur adipiscing elit. Cras lorem - - nisi, tincidunt tempus sem nec, elementum feugiat ipsum. Nulla in - - diam libero. Nunc tristique ex a nibh egestas sollicitudin. - - - - \paragraph{} - - Mauris efficitur vitae ex id egestas. Vestibulum ligula felis, - - pulvinar a posuere id, luctus vitae leo. Sed ac imperdiet orci, non - - elementum leo. Nullam molestie congue placerat. Phasellus tempor et - - libero maximus commodo. - -``` - - -![helloworld_file.png][13] - -The helloworld.org file - -With the content in place, we'll export the content as a PDF. Select **Export/Publish** from the **Org** menu again, but this time, type **l** (export to LaTeX), followed by **o** (as PDF file and open). This not only opens PDF file for you to view, but also saves the file as `helloworld.pdf` in the same path as `helloworld.org`. - -![org_to_pdf.png][15] - -Exporting helloworld.org to helloworld.pdf - -![org_and_pdf_file.png][17] - -Opening the helloworld.pdf file - -You can also export org to PDF by pressing `Alt + x`, then typing "org-latex-export-to-pdf". Use Tab to auto-complete. - -Emacs also creates the `helloworld.tex` file to give you control over the content. - -![org_tex_pdf.png][19] - -Emacs with LaTeX, org, and PDF files open in three different windows - -You can compile the `.tex` file to `.pdf` using the command: -``` -pdflatex helloworld.tex - -``` - -You can also export the `.org` file to HTML or as a simple text file. What I like about .org files is they can be pushed to [GitHub][20], where they are rendered just like any other markdown formats. - -### Creating a LaTeX Beamer presentation - -Let's go a step further and create a LaTeX [Beamer][21] presentation using the same file with some modifications as shown below: -``` -#+TITLE: LaTeX Beamer presentation - -#+DATE: \today - -#+AUTHOR: Sachin Patil - -#+EMAIL: psachin@redhat.com - -#+OPTIONS: ':nil *:t -:t ::t <:t H:3 \n:nil ^:t arch:headline - -#+OPTIONS: author:t c:nil creator:comment d:(not "LOGBOOK") date:t - -#+OPTIONS: e:t email:nil f:t inline:t num:t p:nil pri:nil stat:t - -#+OPTIONS: tags:t tasks:t tex:t timestamp:t toc:nil todo:t |:t - -#+CREATOR: Emacs 25.3.1 (Org mode 8.2.10) - -#+DESCRIPTION: - -#+EXCLUDE_TAGS: noexport - -#+KEYWORDS: - -#+LANGUAGE: en - -#+SELECT_TAGS: export - -#+LATEX_CLASS: beamer - -#+BEAMER_THEME: Frankfurt - -#+BEAMER_INNER_THEME: rounded - - - - - -* Introduction - -*** Programming - - - Python - - - Ruby - - - -*** Paragraph one - - - - Lorem ipsum dolor sit amet, consectetur adipiscing - - elit. Cras lorem nisi, tincidunt tempus sem nec, elementum feugiat - - ipsum. Nulla in diam libero. Nunc tristique ex a nibh egestas - - sollicitudin. - - - -*** Paragraph two - - - - Mauris efficitur vitae ex id egestas. Vestibulum - - ligula felis, pulvinar a posuere id, luctus vitae leo. Sed ac - - imperdiet orci, non elementum leo. Nullam molestie congue - - placerat. Phasellus tempor et libero maximus commodo. - - - -* Thanks - -*** Links - - - Link one - - - Link two - -``` - -We have added three more lines to the header: -``` -#+LATEX_CLASS: beamer - -#+BEAMER_THEME: Frankfurt - -#+BEAMER_INNER_THEME: rounded - -``` - -To export to PDF, press `Alt + x` and type "org-beamer-export-to-pdf". - -![latex_beamer_presentation.png][23] - -The Latex Beamer presentation, created using Emacs and Org mode - -I hope you enjoyed creating this LaTeX and Beamer document using Emacs (note that it's faster to use keyboard shortcuts than a mouse). Emacs Org-mode offers much more than I can cover in this post; you can learn more at [orgmode.org][24]. - --------------------------------------------------------------------------------- - -via: https://opensource.com/article/18/4/how-create-latex-documents-emacs - -作者：[Sachin Patil][a] -译者：[译者ID](https://github.com/译者ID) -校对：[校对者ID](https://github.com/校对者ID) -选题：[lujun9972](https://github.com/lujun9972) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 - -[a]:https://opensource.com/users/psachin -[1]:https://opensource.com/article/17/6/introduction-latex -[2]:https://opensource.com/users/aaroncocker -[3]:https://www.latex-project.org -[4]:http://www.texstudio.org/ -[5]:https://opensource.com/users/greg-p -[6]:https://www.gnu.org/software/emacs/ -[7]:/file/392261 -[8]:https://opensource.com/sites/default/files/styles/panopoly_image_original/public/images/life-uploads/emacs_startup.png?itok=UnT4PgK5 (Emacs startup screen) -[9]:/file/392266 -[10]:https://opensource.com/sites/default/files/styles/panopoly_image_original/public/images/life-uploads/insert_template_flow.png?itok=V_c2KipO (template_flow.png) -[11]:https://www.lipsum.com/feed/html -[12]:/file/392271 -[13]:https://opensource.com/sites/default/files/styles/panopoly_image_original/public/images/life-uploads/helloworld_file.png?itok=o8IX0TsJ (helloworld_file.png) -[14]:/file/392276 -[15]:https://opensource.com/sites/default/files/styles/panopoly_image_original/public/images/life-uploads/org_to_pdf.png?itok=fNnC1Y-L (org_to_pdf.png) -[16]:/file/392281 -[17]:https://opensource.com/sites/default/files/styles/panopoly_image_original/public/images/life-uploads/org_and_pdf_file.png?itok=HEhtw-cu (org_and_pdf_file.png) -[18]:/file/392286 -[19]:https://opensource.com/sites/default/files/styles/panopoly_image_original/public/images/life-uploads/org_tex_pdf.png?itok=poZZV_tj (org_tex_pdf.png) -[20]:https://github.com -[21]:https://www.sharelatex.com/learn/Beamer -[22]:/file/392291 -[23]:https://opensource.com/sites/default/files/styles/panopoly_image_original/public/images/life-uploads/latex_beamer_presentation.png?itok=rsPSeIuM (latex_beamer_presentation.png) -[24]:https://orgmode.org/worg/org-tutorials/org-latex-export.html diff --git a/sources/tech/20180411 How To Setup Static File Server Instantly.md b/sources/tech/20180411 How To Setup Static File Server Instantly.md deleted file mode 100644 index b388b389fa..0000000000 --- a/sources/tech/20180411 How To Setup Static File Server Instantly.md +++ /dev/null @@ -1,171 +0,0 @@ -How To Setup Static File Server Instantly -====== - - -Ever wanted to share your files or project over network, but don’t know how to do? No worries! Here is a simple utility named **“serve”** to share your files instantly over network. This simple utility will instantly turn your system into a static file server, allowing you to serve your files over network. You can access the files from any devices regardless of their operating system. All you need is a web browser. This utility also can be used to serve static websites. It is formerly known as “list” and “micro-list”, but now the name has been changed to “serve”, which is much more suitable for the purpose of this utility. - -### Setup Static File Server Using Serve - -To install “serve”, you need to install NodeJS and NPM first. Refer the following link to install NodeJS and NPM in your Linux box. - -Once NodeJS and NPM installed, run the following command to install “serve”. -``` -$ npm install -g serve - -``` - -Done! Now is the time to serve the files or folders. - -The typical syntax to use “serve” is: -``` -$ serve [options] - -``` - -### Serve Specific files or folders - -For example, let us share the contents of the **Documents** directory. To do so, run: -``` -$ serve Documents/ - -``` - -Sample output would be: - -![][2] - -As you can see in the above screenshot, the contents of the given directory have been served over network via two URLs. - -To access the contents from the local system itself, all you have to do is open your web browser and navigate to ** - -``` - -For example, I am going to search for how to create tgz archive. -``` -$ how2 create archive tgz - -``` - -Oops! I get the following error. -``` -/home/sk/.nvm/versions/node/v9.11.1/lib/node_modules/how2/node_modules/devnull/transports/transport.js:59 -Transport.prototype.__proto__ = EventEmitter.prototype; - ^ - - TypeError: Cannot read property 'prototype' of undefined - at Object. (/home/sk/.nvm/versions/node/v9.11.1/lib/node_modules/how2/node_modules/devnull/transports/transport.js:59:46) - at Module._compile (internal/modules/cjs/loader.js:654:30) - at Object.Module._extensions..js (internal/modules/cjs/loader.js:665:10) - at Module.load (internal/modules/cjs/loader.js:566:32) - at tryModuleLoad (internal/modules/cjs/loader.js:506:12) - at Function.Module._load (internal/modules/cjs/loader.js:498:3) - at Module.require (internal/modules/cjs/loader.js:598:17) - at require (internal/modules/cjs/helpers.js:11:18) - at Object. (/home/sk/.nvm/versions/node/v9.11.1/lib/node_modules/how2/node_modules/devnull/transports/stream.js:8:17) - at Module._compile (internal/modules/cjs/loader.js:654:30) - -``` - -I may be a bug. I hope it gets fixed in the future versions. However, I find a workaround posted [**here**][3]. - -To fix this error temporarily, you need to edit the **transport.js** file using command: -``` -$ vi /home/sk/.nvm/versions/node/v9.11.1/lib/node_modules/how2/node_modules/devnull/transports/transport.js - -``` - -The actual path of this file will be displayed in your error output. Replace the above file path with your own. Then find the following line: -``` -var EventEmitter = process.EventEmitter; - -``` - -and replace it with following line: -``` -var EventEmitter = require('events'); - -``` - -Press ESC and type **:wq** to save and quit the file. - -Now search again the query. -``` -$ how2 create archive tgz - -``` - -Here is the sample output from my Ubuntu system. - -[![][4]][5] - -If the answer you’re looking for is not displayed in the above output, press **SPACE BAR** key to start the interactive search where you can go through all suggested questions and answers from the Stack Overflow site. - -[![][4]][6] - -Use UP/DOWN arrows to move between the results. Once you got the right answer/question, hit SPACE BAR or ENTER key to open it in the Terminal. - -[![][4]][7] - -To go back and exit, press **ESC**. - -**Search answers for specific language** - -If you don’t specify a language it **defaults to Bash** unix command line and give you immediately the most likely answer as above. You can also narrow the results to a specific language, for example perl, python, c, Java etc. - -For instance, to search for queries related to “Python” language only using **-l** flag as shown below. -``` -$ how2 -l python linked list - -``` - -[![][4]][8] - -To get a quick help, type: -``` -$ how2 -h - -``` - -### Conclusion - -The how2 utility is a basic command line program to quickly search for questions and answers from Stack Overflow without leaving your Terminal and it does this job pretty well. However, it is just CLI browser for Stack overflow. For some advanced features such as searching most voted questions, searching queries using multiple tags, colored interface, submitting a new question and viewing questions stats etc., **SoCLI** is good to go. - -And, that’s all for now. Hope this was useful. I will be soon here with another useful guide. Until then, stay tuned with OSTechNix! - -Cheers! - - - --------------------------------------------------------------------------------- - -via: https://www.ostechnix.com/how-to-browse-stack-overflow-from-terminal/ - -作者：[SK][a] -译者：[译者ID](https://github.com/译者ID) -校对：[校对者ID](https://github.com/校对者ID) -选题：[lujun9972](https://github.com/lujun9972) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 - -[a]:https://www.ostechnix.com/author/sk/ -[1]:https://www.ostechnix.com/search-browse-stack-overflow-website-commandline/ -[2]:https://www.ostechnix.com/google-search-navigator-enhance-keyboard-navigation-in-google-search/ -[3]:https://github.com/santinic/how2/issues/79 -[4]:data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7 -[5]:http://www.ostechnix.com/wp-content/uploads/2018/04/stack-overflow-1.png -[6]:http://www.ostechnix.com/wp-content/uploads/2018/04/stack-overflow-2.png -[7]:http://www.ostechnix.com/wp-content/uploads/2018/04/stack-overflow-3.png -[8]:http://www.ostechnix.com/wp-content/uploads/2018/04/stack-overflow-4.png diff --git a/sources/tech/20180419 Migrating to Linux- Network and System Settings.md b/sources/tech/20180419 Migrating to Linux- Network and System Settings.md deleted file mode 100644 index f3930f1777..0000000000 --- a/sources/tech/20180419 Migrating to Linux- Network and System Settings.md +++ /dev/null @@ -1,116 +0,0 @@ -Migrating to Linux: Network and System Settings -====== - - -In this series, we provide an overview of fundamentals to help you successfully make the transition to Linux from another operating system. If you missed the earlier articles in the series, you can find them here: - -[Part 1 - An Introduction][1] - -[Part 2 - Disks, Files, and Filesystems][2] - -[Part 3 - Graphical Environments][3] - -[Part 4 - The Command Line][4] - -[Part 5 - Using sudo][5] - -[Part 6 - Installing Software][6] - -Linux gives you a lot of control over network and system settings. On your desktop, Linux lets you tweak just about anything on the system. Most of these settings are exposed in plain text files under the /etc directory. Here I describe some of the most common settings you’ll use on your desktop Linux system. - -A lot of settings can be found in the Settings program, and the available options will vary by Linux distribution. Usually, you can change the background, tweak sound volume, connect to printers, set up displays, and more. While I won't talk about all of the settings here, you can certainly explore what's in there. - -### Connect to the Internet - -Connecting to the Internet in Linux is often fairly straightforward. If you are wired through an Ethernet cable, Linux will usually get an IP address and connect automatically when the cable is plugged in or at startup if the cable is already connected. - -If you are using wireless, in most distributions there is a menu, either in the indicator panel or in settings (depending on your distribution), where you can select the SSID for your wireless network. If the network is password protected, it will usually prompt you for the password. Afterward, it connects, and the process is fairly smooth. - -You can adjust network settings in the graphical environment by going into settings. Sometimes this is called System Settings or just Settings. Often you can easily spot the settings program because its icon is a gear or a picture of tools (Figure 1). - - -![Network Settings][8] - -Figure 1: Gnome Desktop Network Settings Indicator Icon. - -[Used with permission][9] - -### Network Interface Names - -Under Linux, network devices have names. Historically, these are given names like eth0 and wlan0 -- or Ethernet and wireless, respectively. Newer Linux systems have been using different names that appear more esoteric, like enp4s0 and wlp5s0. If the name starts with en, it's a wired Ethernet interface. If it starts with wl, it's a wireless interface. The rest of the letters and numbers reflect how the device is connected to hardware. - -### Network Management from the Command Line - -If you want more control over your network settings, or if you are managing network connections without a graphical desktop, you can also manage the network from the command line. - -Note that the most common service used to manage networks in a graphical desktop is the Network Manager, and Network Manager will often override setting changes made on the command line. If you are using the Network Manager, it's best to change your settings in its interface so it doesn't undo the changes you make from the command line or someplace else. - -Changing settings in the graphical environment is very likely to be interacting with the Network Manager, and you can also change Network Manager settings from the command line using the tool called nmtui. The nmtui tool provides all the settings that you find in the graphical environment but gives it in a text-based semi-graphical interface that works on the command line (Figure 2). - - - -On the command line, there is an older tool called ifconfig to manage networks and a newer one called ip. On some distributions, ifconfig is considered to be deprecated and is not even installed by default. On other distributions, ifconfig is still in use. - -Here are some commands that will allow you to display and change network settings: - - - -### Process and System Information - -In Windows, you can go into the Task Manager to see a list of the all the programs and services that are running. You can also stop programs from running. And you can view system performance in some of the tabs displayed there. - -You can do similar things in Linux both from the command line and from graphical tools. In Linux, there are a few graphical tools available depending on your distribution. The most common ones are System Monitor or KSysGuard. In these tools, you can see system performance, see a list of processes, and even kill processes (Figure 3). - - - -In these tools, you can also view global network traffic on your system (Figure 4). - - -![System Monitor][11] - -Figure 4: Screenshot of Gnome System Monitor. - -[Used with permission][9] - -### Managing Process and System Usage - -There are also quite a few tools you can use from the command line. The command ps can be used to list processes on your system. By default, it will list processes running in your current terminal session. But you can list other processes by giving it various command line options. You can get more help on ps with the commands info ps, or man ps. - -Most folks though want to get a list of processes because they would like to stop the one that is using up too much memory or CPU time. In this case, there are two commands that make this task much easier. These are top and htop (Figure 5). - - - -The top and htop tools work very similarly to each other. These commands update their list every second or two and re-sort the list so that the task using the most CPU is at the top. You can also change the sorting to sort by other resources as well such as memory usage. - -In either of these programs (top and htop), you can type '?' to get help, and 'q' to quit. With top, you can press 'k' to kill a process and then type in the unique PID number for the process to kill it. - -With htop, you can highlight a task by pressing down arrow or up arrow to move the highlight bar, and then press F9 to kill the task followed by Enter to confirm. - -The information and tools provided in this series will help you get started with Linux. With a little time and patience, you'll feel right at home. - -Learn more about Linux through the free ["Introduction to Linux" ][12]course from The Linux Foundation and edX. - --------------------------------------------------------------------------------- - -via: https://www.linux.com/blog/learn/2018/4/migrating-linux-network-and-system-settings - -作者：[John Bonesio][a] -选题：[lujun9972](https://github.com/lujun9972) -译者：[译者ID](https://github.com/译者ID) -校对：[校对者ID](https://github.com/校对者ID) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 - -[a]:https://www.linux.com/users/johnbonesio -[1]:https://www.linux.com/blog/learn/intro-to-linux/2017/10/migrating-linux-introduction -[2]:https://www.linux.com/blog/learn/intro-to-linux/2017/11/migrating-linux-disks-files-and-filesystems -[3]:https://www.linux.com/blog/learn/2017/12/migrating-linux-graphical-environments -[4]:https://www.linux.com/blog/learn/2018/1/migrating-linux-command-line -[5]:https://www.linux.com/blog/learn/2018/3/migrating-linux-using-sudo -[6]:https://www.linux.com/blog/learn/2018/3/migrating-linux-installing-software -[7]:https://www.linux.com/files/images/figure-1png-2 -[8]:https://www.linux.com/sites/lcom/files/styles/rendered_file/public/figure-1_2.png?itok=J-C6q-t5 (Network Settings) -[9]:https://www.linux.com/licenses/category/used-permission -[10]:https://www.linux.com/files/images/figure-4png-1 -[11]:https://www.linux.com/sites/lcom/files/styles/rendered_file/public/figure-4_1.png?itok=boI-L1mF (System Monitor) -[12]:https://training.linuxfoundation.org/linux-courses/system-administration-training/introduction-to-linux diff --git a/sources/tech/20180420 How To Remove Password From A PDF File in Linux.md b/sources/tech/20180420 How To Remove Password From A PDF File in Linux.md deleted file mode 100644 index 0e4318c858..0000000000 --- a/sources/tech/20180420 How To Remove Password From A PDF File in Linux.md +++ /dev/null @@ -1,220 +0,0 @@ -How To Remove Password From A PDF File in Linux -====== - - -Today I happen to share a password protected PDF file to one of my friend. I knew the password of that PDF file, but I didn’t want to disclose it. Instead, I just wanted to remove the password and send the file to him. I started to looking for some easy ways to remove the password protection from the pdf files on Internet. After a quick google search, I came up with four methods to remove password from a PDF file in Linux. The funny thing is I had already done it few years ago and I almost forgot it. If you’re wondering how to remove password from a PDF file in Linux, read on! It is not that difficult. - -### Remove Password From A PDF File in Linux - -**Method 1 – Using Qpdf** - -The **Qpdf** is a PDF transformation software which is used to encrypt and decrypt PDF files, convert PDF files to another equivalent pdf files. Qpdf is available in the default repositories of most Linux distributions, so you can install it using the default package manager. - -For example, Qpdf can be installed on Arch Linux and its variants using [**pacman**][1] as shown below. -``` -$ sudo pacman -S qpdf - -``` - -On Debian, Ubuntu, Linux Mint: -``` -$ sudo apt-get install qpdf - -``` - -Now let us remove the password from a pdf file using qpdf. - -I have a password-protected PDF file named **“secure.pdf”**. Whenever I open this file, it prompts me to enter the password to display its contents. - -![][3] - -I know the password of the above pdf file. However, I don’t want to share the password with anyone. So what I am going to do is to simply remove the password of the PDF file using Qpdf utility with following command. -``` -$ qpdf --password='123456' --decrypt secure.pdf output.pdf - -``` - -Quite easy, isn’t it? Yes, it is! Here, **123456** is the password of the **secure.pdf** file. Replace the password with your own. - -**Method 2 – Using Pdftk** - -**Pdftk** is yet another great software for manipulating pdf documents. Pdftk can do almost all sort of pdf operations, such as; - - * Encrypt and decrypt pdf files. - * Merge PDF documents. - * Collate PDF page Scans. - * Split PDF pages. - * Rotate PDF files or pages. - * Fill PDF forms with X/FDF data and/or flatten forms. - * Generate FDF data stencils from PDF forms. - * Apply a background watermark or a foreground stamp. - * Report PDF metrics, bookmarks and metadata. - * Add/update PDF bookmarks or metadata. - * Attach files to PDF pages or the PDF document. - * Unpack PDF attachments. - * Burst a PDF file into single pages. - * Compress and decompress page streams. - * Repair corrupted PDF file. - - - -Pddftk is available in AUR, so you can install it using any AUR helper programs on Arch Linux its derivatives. - -Using [**Pacaur**][4]: -``` -$ pacaur -S pdftk - -``` - -Using [**Packer**][5]: -``` -$ packer -S pdftk - -``` - -Using [**Trizen**][6]: -``` -$ trizen -S pdftk - -``` - -Using [**Yay**][7]: -``` -$ yay -S pdftk - -``` - -Using [**Yaourt**][8]: -``` -$ yaourt -S pdftk - -``` - -On Debian, Ubuntu, Linux Mint, run: -``` -$ sudo apt-get instal pdftk - -``` - -On CentOS, Fedora, Red Hat: - -First, Install EPEL repository: -``` -$ sudo yum install epel-release - -``` - -Or -``` -$ sudo dnf install epel-release - -``` - -Then install PDFtk application using command: -``` -$ sudo yum install pdftk - -``` - -Or -``` -$ sudo dnf install pdftk - -``` - -Once pdftk installed, you can remove the password from a pdf document using command: -``` -$ pdftk secure.pdf input_pw 123456 output output.pdf - -``` - -Replace ‘123456’ with your correct password. This command decrypts the “secure.pdf” file and create an equivalent non-password protected file named “output.pdf”. - -**Also read:** - -**Method 3 – Using Poppler** - -**Poppler** is a PDF rendering library based on the xpdf-3.0 code base. It contains the following set of command line utilities for manipulating PDF documents. - - * **pdfdetach** – lists or extracts embedded files. - * **pdffonts** – font analyzer. - * **pdfimages** – image extractor. - * **pdfinfo** – document information. - * **pdfseparate** – page extraction tool. - * **pdfsig** – verifies digital signatures. - * **pdftocairo** – PDF to PNG/JPEG/PDF/PS/EPS/SVG converter using Cairo. - * **pdftohtml** – PDF to HTML converter. - * **pdftoppm** – PDF to PPM/PNG/JPEG image converter. - * **pdftops** – PDF to PostScript (PS) converter. - * **pdftotext** – text extraction. - * **pdfunite** – document merging tool. - - - -For the purpose of this guide, we only use the “pdftops” utility. - -To install Poppler on Arch Linux based distributions, run: -``` -$ sudo pacman -S poppler - -``` - -On Debian, Ubuntu, Linux Mint: -``` -$ sudo apt-get install poppler-utils - -``` - -On RHEL, CentOS, Fedora: -``` -$ sudo yum install poppler-utils - -``` - -Once Poppler installed, run the following command to decrypt the password protected pdf file and create a new equivalent file named output.pdf. -``` -$ pdftops -upw 123456 secure.pdf output.pdf - -``` - -Again, replace ‘123456’ with your pdf password. - -As you might noticed in all above methods, we just converted the password protected pdf file named “secure.pdf” to another equivalent pdf file named “output.pdf”. Technically speaking, we really didn’t remove the password from the source file, instead we decrypted it and saved it as another equivalent pdf file without password protection. - -**Method 4 – Print to a file -** - -This is the easiest method in all of the above methods. You can use your existing PDF viewer such as Atril document viewer, Evince etc., and print the password protected pdf file to another file. - -Open the password protected file in your PDF viewer application. Go to **File - > Print**. And save the pdf file in any location of your choice. - -![][9] - -And, that’s all. Hope this was useful. Do you know/use any other methods to remove the password protection from PDF files? Let us know in the comment section below. - -More good stuffs to come. Stay tuned! - -Cheers! - - - --------------------------------------------------------------------------------- - -via: https://www.ostechnix.com/how-to-remove-password-from-a-pdf-file-in-linux/ - -作者：[SK][a] -选题：[lujun9972](https://github.com/lujun9972) -译者：[译者ID](https://github.com/译者ID) -校对：[校对者ID](https://github.com/校对者ID) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 - -[a]:https://www.ostechnix.com/author/sk/ -[1]:https://www.ostechnix.com/getting-started-pacman/ -[2]:data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7 -[3]:http://www.ostechnix.com/wp-content/uploads/2018/04/Remove-Password-From-A-PDF-File-1.png -[4]:https://www.ostechnix.com/install-pacaur-arch-linux/ -[5]:https://www.ostechnix.com/install-packer-arch-linux-2/ -[6]:https://www.ostechnix.com/trizen-lightweight-aur-package-manager-arch-based-systems/ -[7]:https://www.ostechnix.com/yay-found-yet-another-reliable-aur-helper/ -[8]:https://www.ostechnix.com/install-yaourt-arch-linux/ diff --git a/sources/tech/20180422 Command Line Tricks For Data Scientists - kade killary.md b/sources/tech/20180422 Command Line Tricks For Data Scientists - kade killary.md deleted file mode 100644 index aea3b6b035..0000000000 --- a/sources/tech/20180422 Command Line Tricks For Data Scientists - kade killary.md +++ /dev/null @@ -1,526 +0,0 @@ -Command Line Tricks For Data Scientists • kade killary -====== - - - -For many data scientists, data manipulation begins and ends with Pandas or the Tidyverse. In theory, there is nothing wrong with this notion. It is, after all, why these tools exist in the first place. Yet, these options can often be overkill for simple tasks like delimiter conversion. - -Aspiring to master the command line should be on every developer’s list, especially data scientists. Learning the ins and outs of your shell will undeniably make you more productive. Beyond that, the command line serves as a great history lesson in computing. For instance, awk - a data-driven scripting language. Awk first appeared in 1977 with the help of [Brian Kernighan][1], the K in the legendary [K&R book][2]. Today, some near 50 years later, awk remains relevant with [new books][3] still appearing every year! Thus, it’s safe to assume that an investment in command line wizardry won’t depreciate any time soon. - -### What We’ll Cover - - * ICONV - * HEAD - * TR - * WC - * SPLIT - * SORT & UNIQ - * CUT - * PASTE - * JOIN - * GREP - * SED - * AWK - - - -### ICONV - -File encodings can be tricky. For the most part files these days are all UTF-8 encoded. To understand some of the magic behind UTF-8, check out this [excellent video][4]. Nonetheless, there are times where we receive a file that isn’t in this format. This can lead to some wonky attempts at swapping the encoding schema. Here, `iconv` is a life saver. Iconv is a simple program that will take text in one encoding and output the text in another. -``` -# Converting -f (from) latin1 (ISO-8859-1) -# -t (to) standard UTF_8 - -iconv -f ISO-8859-1 -t UTF-8 < input.txt > output.txt - -``` - - * Useful options: - - * `iconv -l` list all known encodings - * `iconv -c` silently discard characters that cannot be converted - - - -### HEAD - -If you are a frequent Pandas user then `head` will be familiar. Often when dealing with new data the first thing we want to do is get a sense of what exists. This leads to firing up Pandas, reading in the data and then calling `df.head()` \- strenuous, to say the least. Head, without any flags, will print out the first 10 lines of a file. The true power of `head` lies in testing out cleaning operations. For instance, if we wanted to change the delimiter of a file from commas to pipes. One quick test would be: `head mydata.csv | sed 's/,/|/g'`. -``` -# Prints out first 10 lines - -head filename.csv - -# Print first 3 lines - -head -n 3 filename.csv - -``` - - * Useful options: - - * `head -n` print a specific number of lines - * `head -c` print a specific number of bytes - - - -### TR - -Tr is analogous to translate. This powerful utility is a workhorse for basic file cleaning. An ideal use case is for swapping out the delimiters within a file. -``` -# Converting a tab delimited file into commas - -cat tab_delimited.txt | tr "\t" "," comma_delimited.csv - -``` - -Another feature of `tr` is all the built in `[:class:]` variables at your disposal. These include: -``` -[:alnum:] all letters and digits -[:alpha:] all letters -[:blank:] all horizontal whitespace -[:cntrl:] all control characters -[:digit:] all digits -[:graph:] all printable characters, not including space -[:lower:] all lower case letters -[:print:] all printable characters, including space -[:punct:] all punctuation characters -[:space:] all horizontal or vertical whitespace -[:upper:] all upper case letters -[:xdigit:] all hexadecimal digits - -``` - -You can chain a variety of these together to compose powerful programs. The following is a basic word count program you could use to check your READMEs for overuse. -``` -cat README.md | tr "[:punct:][:space:]" "\n" | tr "[:upper:]" "[:lower:]" | grep . | sort | uniq -c | sort -nr - -``` - -Another example using basic regex: -``` -# Converting all upper case letters to lower case - -cat filename.csv | tr '[A-Z]' '[a-z]' - -``` - - * Useful options: - - * `tr -d` delete characters - * `tr -s` squeeze characters - * `\b` backspace - * `\f` form feed - * `\v` vertical tab - * `\NNN` character with octal value NNN - - - -### WC - -Word count. Its value is primarily derived from the `-l` flag, which will give you the line count. -``` -# Will return number of lines in CSV - -wc -l gigantic_comma.csv - -``` - -This tool comes in handy to confirm the output of various commands. So, if we were to convert the delimiters within a file and then run `wc -l` we would expect the total lines to be the same. If not, then we know something went wrong. - - * Useful options: - - * `wc -c` print the byte counts - * `wc -m` print the character counts - * `wc -L` print length of longest line - * `wc -w` print word counts - - - -### SPLIT - -File sizes can range dramatically. And depending on the job, it could be beneficial to split up the file - thus `split`. The basic syntax for split is: -``` -# We will split our CSV into new_filename every 500 lines - -split -l 500 filename.csv new_filename_ - -# filename.csv -# ls output -# new_filename_aaa -# new_filename_aab -# new_filename_aac - -``` - -Two quirks are the naming convention and lack of file extensions. The suffix convention can be numeric via the `-d` flag. To add file extensions, you’ll need to run the following `find` command. It will change the names of ALL files within the current directory by appending `.csv`, so be careful. -``` -find . -type f -exec mv '{}' '{}'.csv \; - -# ls output -# filename.csv.csv -# new_filename_aaa.csv -# new_filename_aab.csv -# new_filename_aac.csv - -``` - - * Useful options: - - * `split -b` split by certain byte size - * `split -a` generate suffixes of length N - * `split -x` split using hex suffixes - - - -### SORT & UNIQ - -The preceding commands are obvious: they do what they say they do. These two provide the most punch in tandem (i.e. unique word counts). This is due to `uniq`, which only operates on duplicate adjacent lines. Thus, the reason to `sort` before piping the output through. One interesting note is that `sort -u` will achieve the same results as the typical `sort file.txt | uniq` pattern. - -Sort does have a sneakily useful ability for data scientists: the ability to sort an entire CSV based on a particular column. -``` -# Sorting a CSV file by the second column alphabetically - -sort -t"," -k2,2 filename.csv - -# Numerically - -sort -t"," -k2n,2 filename.csv - -# Reverse order - -sort -t"," -k2nr,2 filename.csv - -``` - -The `-t` option here is to specify the comma as our delimiter. More often than not spaces or tabs are assumed. Furthermore, the `-k` flag is for specifying our key. The syntax for this is `-km,n`, with `m` being the starting field and `n` being the last. - - * Useful options: - - * `sort -f` ignore case - * `sort -r` reverse sort order - * `sort -R` scramble order - * `uniq -c` count number of occurrences - * `uniq -d` only print duplicate lines - - - -### CUT - -Cut is for removing columns. To illustrate, if we only wanted the first and third columns. -``` -cut -d, -f 1,3 filename.csv - -``` - -To select every column other than the first. -``` -cut -d, -f 2- filename.csv - -``` - -In combination with other commands, `cut` serves as a filter. -``` -# Print first 10 lines of column 1 and 3, where "some_string_value" is present - -head filename.csv | grep "some_string_value" | cut -d, -f 1,3 - -``` - -Finding out the number of unique values within the second column. -``` -cat filename.csv | cut -d, -f 2 | sort | uniq | wc -l - -# Count occurences of unique values, limiting to first 10 results - -cat filename.csv | cut -d, -f 2 | sort | uniq -c | head - -``` - -### PASTE - -Paste is a niche command with an interesting function. If you have two files that you need merged, and they are already sorted, `paste` has you covered. -``` -# names.txt -adam -john -zach - -# jobs.txt -lawyer -youtuber -developer - -# Join the two into a CSV - -paste -d ',' names.txt jobs.txt > person_data.txt - -# Output -adam,lawyer -john,youtuber -zach,developer - -``` - -For a more SQL_-esque variant, see below. - -### JOIN - -Join is a simplistic, quasi-tangential, SQL. The largest differences being that `join` will return all columns and matches can only be on one field. By default, `join` will try and use the first column as the match key. For a different result, the following syntax is necessary: -``` -# Join the first file (-1) by the second column -# and the second file (-2) by the first - -join -t"," -1 2 -2 1 first_file.txt second_file.txt - -``` - -The standard join is an inner join. However, an outer join is also viable through the `-a` flag. Another noteworthy quirk is the `-e` flag, which can be used to substitute a value if a missing field is found. -``` -# Outer join, replace blanks with NULL in columns 1 and 2 -# -o which fields to substitute - 0 is key, 1.1 is first column, etc... - -join -t"," -1 2 -a 1 -a2 -e ' NULL' -o '0,1.1,2.2' first_file.txt second_file.txt - -``` - -Not the most user-friendly command, but desperate times, desperate measures. - - * Useful options: - - * `join -a` print unpairable lines - * `join -e` replace missing input fields - * `join -j` equivalent to `-1 FIELD -2 FIELD` - - - -### GREP - -Global search for a regular expression and print, or `grep`; likely, the most well known command, and with good reason. Grep has a lot of power, especially for finding your way around large codebases. Within the realm of data science, it acts as a refining mechanism for other commands. Although its standard usage is valuable as well. -``` -# Recursively search and list all files in directory containing 'word' - -grep -lr 'word' . - -# List number of files containing word - -grep -lr 'word' . | wc -l - -``` - -Count total number of lines containing word / pattern. -``` -grep -c 'some_value' filename.csv - -# Same thing, but in all files in current directory by file name - -grep -c 'some_value' * - -``` - -Grep for multiple values using the or operator - `\|`. -``` -grep "first_value\|second_value" filename.csv - -``` - - * Useful options - - * `alias grep="grep --color=auto"` make grep colorful - * `grep -E` use extended regexps - * `grep -w` only match whole words - * `grep -l` print name of files with match - * `grep -v` inverted matching - - - -### THE BIG GUNS - -Sed and Awk are the two most powerful commands in this article. For brevity, I’m not going to go into exhausting detail about either. Instead, I will cover a variety of commands that prove their impressive might. If you want to know more, [there is a book][5] just for that. - -### SED - -At its core `sed` is a stream editor. It excels at substitutions, but can also be leveraged for all out refactoring. - -The most basic `sed` command consists of `s/old/new/g`. This translates to search for old value, replace with new globally. Without the `/g` our command would terminate after the first occurrence. - -To get a quick taste of the power lets dive into an example. In this scenario you’ve been given the following file: -``` -balance,name -$1,000,john -$2,000,jack - -``` - -The first thing we may want to do is remove the dollar signs. The `-i` flag indicates in-place. The `''` is to indicate a zero-length file extension, thus overwriting our initial file. Ideally, you would test each of these individually and then output to a new file. -``` -sed -i '' 's/\$//g' data.txt - -# balance,name -# 1,000,john -# 2,000,jack - -``` - -Next up, the commas in our `balance` column values. -``` -sed -i '' 's/\([0-9]\),\([0-9]\)/\1\2/g' data.txt - -# balance,name -# 1000,john -# 2000,jack - -``` - -Lastly, Jack up and decided to quit one day. So, au revoir, mon ami. -``` -sed -i '' '/jack/d' data.txt - -# balance,name -# 1000,john - -``` - -As you can see, `sed` packs quite a punch, but the fun doesn’t stop there. - -### AWK - -The best for last. Awk is much more than a simple command: it is a full-blown language. Of everything covered in this article, `awk` is by far the coolest. If you find yourself impressed there are loads of great resources - see [here][6], [here][7] and [here][8]. - -Common use cases for `awk` include: - - * Text processing - * Formatted text reports - * Performing arithmetic operations - * Performing string operations - - - -Awk can parallel `grep` in its most nascent form. -``` -awk '/word/' filename.csv - -``` - -Or with a little more magic the combination of `grep` and `cut`. Here, `awk` prints the third and fourth column, tab separated, for all lines with our word. `-F,` merely changes our delimiter to a comma. -``` -awk -F, '/word/ { print $3 "\t" $4 }' filename.csv - -``` - -Awk comes with a lot of nifty variables built-in. For instance, `NF` \- number of fields - and `NR` \- number of records. To get the fifty-third record in a file: -``` -awk -F, 'NR == 53' filename.csv - -``` - -An added wrinkle is the ability to filter based off of one or more values. The first example, below, will print the line number and columns for records where the first column equals string. -``` -awk -F, ' $1 == "string" { print NR, $0 } ' filename.csv - -# Filter based off of numerical value in second column - -awk -F, ' $2 == 1000 { print NR, $0 } ' filename.csv - -``` - -Multiple numerical expressions: -``` -# Print line number and columns where column three greater -# than 2005 and column five less than one thousand - -awk -F, ' $3 >= 2005 && $5 <= 1000 { print NR, $0 } ' filename.csv - -``` - -Sum the third column: -``` -awk -F, '{ x+=$3 } END { print x }' filename.csv - -``` - -The sum of the third column, for values where the first column equals “something”. -``` -awk -F, '$1 == "something" { x+=$3 } END { print x }' filename.csv - -``` - -Get the dimensions of a file: -``` -awk -F, 'END { print NF, NR }' filename.csv - -# Prettier version - -awk -F, 'BEGIN { print "COLUMNS", "ROWS" }; END { print NF, NR }' filename.csv - -``` - -Print lines appearing twice: -``` -awk -F, '++seen[$0] == 2' filename.csv - -``` - -Remove duplicate lines: -``` -# Consecutive lines -awk 'a !~ $0; {a=$0}'] - -# Nonconsecutive lines -awk '! a[$0]++' filename.csv - -# More efficient -awk '!($0 in a) {a[$0];print} - -``` - -Substitute multiple values using built-in function `gsub()`. -``` -awk '{gsub(/scarlet|ruby|puce/, "red"); print}' - -``` - -This `awk` command will combine multiple CSV files, ignoring the header and then append it at the end. -``` -awk 'FNR==1 && NR!=1{next;}{print}' *.csv > final_file.csv - -``` - -Need to downsize a massive file? Welp, `awk` can handle that with help from `sed`. Specifically, this command breaks one big file into multiple smaller ones based on a line count. This one-liner will also add an extension. -``` -sed '1d;$d' filename.csv | awk 'NR%NUMBER_OF_LINES==1{x="filename-"++i".csv";}{print > x}' - -# Example: splitting big_data.csv into data_(n).csv every 100,000 lines - -sed '1d;$d' big_data.csv | awk 'NR%100000==1{x="data_"++i".csv";}{print > x}' - -``` - -### CLOSING - -The command line boasts endless power. The commands covered in this article are enough to elevate you from zero to hero in no time. Beyond those covered, there are many utilities to consider for daily data operations. [Csvkit][9], [xsv][10] and [q][11] are three of note. If you’re looking to take an even deeper dive into command line data science, then look no further than [this book][12]. It’s also available online [for free][13]! - --------------------------------------------------------------------------------- - -via: http://kadekillary.work/post/cli-4-ds/ - -作者：[Kade Killary][a] -选题：[lujun9972](https://github.com/lujun9972) -译者：[译者ID](https://github.com/译者ID) -校对：[校对者ID](https://github.com/校对者ID) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 - -[a]:http://kadekillary.work/authors/kadekillary -[1]:https://en.wikipedia.org/wiki/Brian_Kernighan -[2]:https://en.wikipedia.org/wiki/The_C_Programming_Language -[3]:https://www.amazon.com/Learning-AWK-Programming-cutting-edge-text-processing-ebook/dp/B07BT98HDS -[4]:https://www.youtube.com/watch?v=MijmeoH9LT4 -[5]:https://www.amazon.com/sed-awk-Dale-Dougherty/dp/1565922255/ref=sr_1_1?ie=UTF8&qid=1524381457&sr=8-1&keywords=sed+and+awk -[6]:https://www.amazon.com/AWK-Programming-Language-Alfred-Aho/dp/020107981X/ref=sr_1_1?ie=UTF8&qid=1524388936&sr=8-1&keywords=awk -[7]:http://www.grymoire.com/Unix/Awk.html -[8]:https://www.tutorialspoint.com/awk/index.htm -[9]:http://csvkit.readthedocs.io/en/1.0.3/ -[10]:https://github.com/BurntSushi/xsv -[11]:https://github.com/harelba/q -[12]:https://www.amazon.com/Data-Science-Command-Line-Time-Tested/dp/1491947853/ref=sr_1_1?ie=UTF8&qid=1524390894&sr=8-1&keywords=data+science+at+the+command+line -[13]:https://www.datascienceatthecommandline.com/ diff --git a/sources/tech/20180425 Things to do After Installing Ubuntu 18.04.md b/sources/tech/20180425 Things to do After Installing Ubuntu 18.04.md deleted file mode 100644 index 4e69d04837..0000000000 --- a/sources/tech/20180425 Things to do After Installing Ubuntu 18.04.md +++ /dev/null @@ -1,294 +0,0 @@ -Things to do After Installing Ubuntu 18.04 -====== -**Brief: This list of things to do after installing Ubuntu 18.04 helps you get started with Bionic Beaver for a smoother desktop experience.** - -[Ubuntu][1] 18.04 Bionic Beaver releases today. You are perhaps already aware of the [new features in Ubuntu 18.04 LTS][2] release. If not, here’s the video review of Ubuntu 18.04 LTS: - -[Subscribe to YouTube Channel for more Ubuntu Videos][3] - -If you opted to install Ubuntu 18.04, I have listed out a few recommended steps that you can follow to get started with it. - -### Things to do after installing Ubuntu 18.04 Bionic Beaver - -![Things to do after installing Ubuntu 18.04][4] - -I should mention that the list of things to do after installing Ubuntu 18.04 depends a lot on you and your interests and needs. If you are a programmer, you’ll focus on installing programming tools. If you are a graphic designer, you’ll focus on installing graphics tools. - -Still, there are a few things that should be applicable to most Ubuntu users. This list is composed of those things plus a few of my of my favorites. - -Also, this list is for the default [GNOME desktop][5]. If you are using some other flavor like [Kubuntu][6], Lubuntu etc then the GNOME-specific stuff won’t be applicable to your system. - -You don’t have to follow each and every point on the list blindly. You should see if the recommended action suits your requirements or not. - -With that said, let’s get started with this list of things to do after installing Ubuntu 18.04. - -#### 1\. Update the system - -This is the first thing you should do after installing Ubuntu. Update the system without fail. It may sound strange because you just installed a fresh OS but still, you must check for the updates. - -In my experience, if you don’t update the system right after installing Ubuntu, you might face issues while trying to install a new program. - -To update Ubuntu 18.04, press Super Key (Windows Key) to launch the Activity Overview and look for Software Updater. Run it to check for updates. - -![Software Updater in Ubuntu 17.10][7] - -**Alternatively** , you can use these famous commands in the terminal ( Use Ctrl+Alt+T): -``` -sudo apt update && sudo apt upgrade - -``` - -#### 2\. Enable additional repositories for more software - -[Ubuntu has several repositories][8] from where it provides software for your system. These repositories are: - - * Main – Free and open-source software supported by Ubuntu team - * Universe – Free and open-source software maintained by the community - * Restricted – Proprietary drivers for devices. - * Multiverse – Software restricted by copyright or legal issues. - * Canonical Partners – Software packaged by Ubuntu for their partners - - - -Enabling all these repositories will give you access to more software and proprietary drivers. - -Go to Activity Overview by pressing Super Key (Windows key), and search for Software & Updates: - -![Software and Updates in Ubuntu 17.10][9] - -Under the Ubuntu Software tab, make sure you have checked all of the Main, Universe, Restricted and Multiverse repository checked. - -![Setting repositories in Ubuntu 18.04][10] - -Now move to the **Other Software** tab, check the option of **Canonical Partners**. - -![Enable Canonical Partners repository in Ubuntu 17.10][11] - -You’ll have to enter your password in order to update the software sources. Once it completes, you’ll find more applications to install in the Software Center. - -#### 3\. Install media codecs - -In order to play media files like MP#, MPEG4, AVI etc, you’ll need to install media codecs. Ubuntu has them in their repository but doesn’t install it by default because of copyright issues in various countries. - -As an individual, you can install these media codecs easily using the Ubuntu Restricted Extra package. Click on the link below to install it from the Software Center. - -[Install Ubuntu Restricted Extras][12] - -Or alternatively, use the command below to install it: -``` -sudo apt install ubuntu-restricted-extras - -``` - -#### 4\. Install software from the Software Center - -Now that you have setup the repositories and installed the codecs, it is time to get software. If you are absolutely new to Ubuntu, please follow this [guide to installing software in Ubuntu][13]. - -There are several ways to install software. The most convenient way is to use the Software Center that has thousands of software available in various categories. You can install them in a few clicks from the software center. - -![Software Center in Ubuntu 17.10 ][14] - -It depends on you what kind of software you would like to install. I’ll suggest some of my favorites here. - - * **VLC** – media player for videos - * **GIMP** – Photoshop alternative for Linux - * **Pinta** – Paint alternative in Linux - * **Calibre** – eBook management tool - * **Chromium** – Open Source web browser - * **Kazam** – Screen recorder tool - * [**Gdebi**][15] – Lightweight package installer for .deb packages - * **Spotify** – For streaming music - * **Skype** – For video messaging - * **Kdenlive** – [Video editor for Linux][16] - * **Atom** – [Code editor][17] for programming - - - -You may also refer to this list of [must-have Linux applications][18] for more software recommendations. - -#### 5\. Install software from the Web - -Though Ubuntu has thousands of applications in the software center, you may not find some of your favorite applications despite the fact that they support Linux. - -Many software vendors provide ready to install .deb packages. You can download these .deb files from their website and install it by double-clicking on it. - -[Google Chrome][19] is one such software that you can download from the web and install it. - -#### 6\. Opt out of data collection in Ubuntu 18.04 (optional) - -Ubuntu 18.04 collects some harmless statistics about your system hardware and your system installation preference. It also collects crash reports. - -You’ll be given the option to not send this data to Ubuntu servers when you log in to Ubuntu 18.04 for the first time. - -![Opt out of data collection in Ubuntu 18.04][20] - -If you miss it that time, you can disable it by going to System Settings -> Privacy and then set the Problem Reporting to Manual. - -![Privacy settings in Ubuntu 18.04][21] - -#### 7\. Customize the GNOME desktop (Dock, themes, extensions and more) - -The GNOME desktop looks good in Ubuntu 18.04 but doesn’t mean you cannot change it. - -You can do a few visual changes from the System Settings. You can change the wallpaper of the desktop and the lock screen, you can change the position of the dock (launcher on the left side), change power settings, Bluetooth etc. In short, you can find many settings that you can change as per your need. - -![Ubuntu 17.10 System Settings][22] - -Changing themes and icons are the major way to change the looks of your system. I advise going through the list of [best GNOME themes][23] and [icons for Ubuntu][24]. Once you have found the theme and icon of your choice, you can use them with GNOME Tweaks tool. - -You can install GNOME Tweaks via the Software Center or you can use the command below to install it: -``` -sudo apt install gnome-tweak-tool - -``` - -Once it is installed, you can easily [install new themes and icons][25]. - -![Change theme is one of the must to do things after installing Ubuntu 17.10][26] - -You should also have a look at [use GNOME extensions][27] to further enhance the looks and capabilities of your system. I made this video about using GNOME extensions in 17.10 and you can follow the same for Ubuntu 18.04. - -If you are wondering which extension to use, do take a look at this list of [best GNOME extensions][28]. - -I also recommend reading this article on [GNOME customization in Ubuntu][29] so that you can know the GNOME desktop in detail. - -#### 8\. Prolong your battery and prevent overheating - -Let’s move on to [prevent overheating in Linux laptops][30]. TLP is a wonderful tool that controls CPU temperature and extends your laptops’ battery life in the long run. - -Make sure that you haven’t installed any other power saving application such as [Laptop Mode Tools][31]. You can install it using the command below in a terminal: -``` -sudo apt install tlp tlp-rdw - -``` - -Once installed, run the command below to start it: -``` -sudo tlp start - -``` - -#### 9\. Save your eyes with Nightlight - -Nightlight is my favorite feature in GNOME desktop. Keeping [your eyes safe at night][32] from the computer screen is very important. Reducing blue light helps reducing eye strain at night. - -![flux effect][33] - -GNOME provides a built-in Night Light option, which you can activate in the System Settings. - -Just go to System Settings-> Devices-> Displays and turn on the Night Light option. - -![Enabling night light is a must to do in Ubuntu 17.10][34] - -#### 9\. Disable automatic suspend for laptops - -Ubuntu 18.04 comes with a new automatic suspend feature for laptops. If the system is running on battery and is inactive for 20 minutes, it will go in suspend mode. - -I understand that the intention is to save battery life but it is an inconvenience as well. You can’t keep the power plugged in all the time because it’s not good for the battery life. And you may need the system to be running even when you are not using it. - -Thankfully, you can change this behavior. Go to System Settings -> Power. Under Suspend & Power Button section, either turn off the Automatic Suspend option or extend its time period. - -![Disable automatic suspend in Ubuntu 18.04][35] - -You can also change the screen dimming behavior in here. - -#### 10\. System cleaning - -I have written in detail about [how to clean up your Ubuntu system][36]. I recommend reading that article to know various ways to keep your system free of junk. - -Normally, you can use this little command to free up space from your system: -``` -sudo apt autoremove - -``` - -It’s a good idea to run this command every once a while. If you don’t like the command line, you can use a GUI tool like [Stacer][37] or [Bleach Bit][38]. - -#### 11\. Going back to Unity or Vanilla GNOME (not recommended) - -If you have been using Unity or GNOME in the past, you may not like the new customized GNOME desktop in Ubuntu 18.04. Ubuntu has customized GNOME so that it resembles Unity but at the end of the day, it is neither completely Unity nor completely GNOME. - -So if you are a hardcore Unity or GNOMEfan, you may want to use your favorite desktop in its ‘real’ form. I wouldn’t recommend but if you insist here are some tutorials for you: - -#### 12\. Can’t log in to Ubuntu 18.04 after incorrect password? Here’s a workaround - -I noticed a [little bug in Ubuntu 18.04][39] while trying to change the desktop session to Ubuntu Community theme. It seems if you try to change the sessions at the login screen, it rejects your password first and at the second attempt, the login gets stuck. You can wait for 5-10 minutes to get it back or force power it off. - -The workaround here is that after it displays the incorrect password message, click Cancel, then click your name, then enter your password again. - -#### 13\. Experience the Community theme (optional) - -Ubuntu 18.04 was supposed to have a dashing new theme developed by the community. The theme could not be completed so it could not become the default look of Bionic Beaver release. I am guessing that it will be the default theme in Ubuntu 18.10. - -![Ubuntu 18.04 Communitheme][40] - -You can try out the aesthetic theme even today. [Installing Ubuntu Community Theme][41] is very easy. Just look for it in the software center, install it, restart your system and then at the login choose the Communitheme session. - -#### 14\. Get Windows 10 in Virtual Box (if you need it) - -In a situation where you must use Windows for some reasons, you can [install Windows in virtual box inside Linux][42]. It will run as a regular Ubuntu application. - -It’s not the best way but it still gives you an option. You can also [use WINE to run Windows software on Linux][43]. In both cases, I suggest trying the alternative native Linux application first before jumping to virtual machine or WINE. - -#### What do you do after installing Ubuntu? - -Those were my suggestions for getting started with Ubuntu. There are many more tutorials that you can find under [Ubuntu 18.04][44] tag. You may go through them as well to see if there is something useful for you. - -Enough from myside. Your turn now. What are the items on your list of **things to do after installing Ubuntu 18.04**? The comment section is all yours. - --------------------------------------------------------------------------------- - -via: https://itsfoss.com/things-to-do-after-installing-ubuntu-18-04/ - -作者：[Abhishek Prakash][a] -选题：[lujun9972](https://github.com/lujun9972) -译者：[译者ID](https://github.com/译者ID) -校对：[校对者ID](https://github.com/校对者ID) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 - -[a]:http://itsfoss.com/author/abhishek/ -[1]:https://www.ubuntu.com/ -[2]:https://itsfoss.com/ubuntu-18-04-release-features/ -[3]:https://www.youtube.com/c/itsfoss?sub_confirmation=1 -[4]:https://4bds6hergc-flywheel.netdna-ssl.com/wp-content/uploads/2018/04/things-to-after-installing-ubuntu-18-04-featured-800x450.jpeg -[5]:https://www.gnome.org/ -[6]:https://kubuntu.org/ -[7]:https://4bds6hergc-flywheel.netdna-ssl.com/wp-content/uploads/2017/10/software-update-ubuntu-17-10.jpg -[8]:https://help.ubuntu.com/community/Repositories/Ubuntu -[9]:https://4bds6hergc-flywheel.netdna-ssl.com/wp-content/uploads/2017/10/software-updates-ubuntu-17-10.jpg -[10]:https://4bds6hergc-flywheel.netdna-ssl.com/wp-content/uploads/2018/04/repositories-ubuntu-18.png -[11]:https://4bds6hergc-flywheel.netdna-ssl.com/wp-content/uploads/2017/10/software-repository-ubuntu-17-10.jpeg -[12]:apt://ubuntu-restricted-extras -[13]:https://itsfoss.com/remove-install-software-ubuntu/ -[14]:https://4bds6hergc-flywheel.netdna-ssl.com/wp-content/uploads/2017/10/Ubuntu-software-center-17-10-800x551.jpeg -[15]:https://itsfoss.com/gdebi-default-ubuntu-software-center/ -[16]:https://itsfoss.com/best-video-editing-software-linux/ -[17]:https://itsfoss.com/best-modern-open-source-code-editors-for-linux/ -[18]:https://itsfoss.com/essential-linux-applications/ -[19]:https://www.google.com/chrome/ -[20]:https://4bds6hergc-flywheel.netdna-ssl.com/wp-content/uploads/2018/04/opt-out-of-data-collection-ubuntu-18-800x492.jpeg -[21]:https://4bds6hergc-flywheel.netdna-ssl.com/wp-content/uploads/2018/04/privacy-ubuntu-18-04-800x417.png -[22]:https://4bds6hergc-flywheel.netdna-ssl.com/wp-content/uploads/2017/10/System-Settings-Ubuntu-17-10-800x573.jpeg -[23]:https://itsfoss.com/best-gtk-themes/ -[24]:https://itsfoss.com/best-icon-themes-ubuntu-16-04/ -[25]:https://itsfoss.com/install-themes-ubuntu/ -[26]:https://4bds6hergc-flywheel.netdna-ssl.com/wp-content/uploads/2017/10/GNOME-Tweak-Tool-Ubuntu-17-10.jpeg -[27]:https://itsfoss.com/gnome-shell-extensions/ -[28]:https://itsfoss.com/best-gnome-extensions/ -[29]:https://itsfoss.com/gnome-tricks-ubuntu/ -[30]:https://itsfoss.com/reduce-overheating-laptops-linux/ -[31]:https://wiki.archlinux.org/index.php/Laptop_Mode_Tools -[32]:https://itsfoss.com/night-shift-flux-ubuntu-linux/ -[33]:https://4bds6hergc-flywheel.netdna-ssl.com/wp-content/uploads/2016/03/flux-eyes-strain.jpg -[34]:https://4bds6hergc-flywheel.netdna-ssl.com/wp-content/uploads/2017/10/Enable-Night-Light-Feature-Ubuntu-17-10-800x396.jpeg -[35]:https://4bds6hergc-flywheel.netdna-ssl.com/wp-content/uploads/2018/04/disable-automatic-suspend-ubuntu-18-800x586.jpeg -[36]:https://itsfoss.com/free-up-space-ubuntu-linux/ -[37]:https://itsfoss.com/optimize-ubuntu-stacer/ -[38]:https://itsfoss.com/bleachbit-2-release/ -[39]:https://gitlab.gnome.org/GNOME/gnome-shell/issues/227 -[40]:https://4bds6hergc-flywheel.netdna-ssl.com/wp-content/uploads/2018/04/ubunt-18-theme.jpeg -[41]:https://itsfoss.com/ubuntu-community-theme/ -[42]:https://itsfoss.com/install-windows-10-virtualbox-linux/ -[43]:https://itsfoss.com/use-windows-applications-linux/ -[44]:https://itsfoss.com/tag/ubuntu-18-04/ diff --git a/sources/tech/20180428 A Beginners Guide To Flatpak.md b/sources/tech/20180428 A Beginners Guide To Flatpak.md deleted file mode 100644 index db1dfa8181..0000000000 --- a/sources/tech/20180428 A Beginners Guide To Flatpak.md +++ /dev/null @@ -1,311 +0,0 @@ -A Beginners Guide To Flatpak -====== - - - -A while, we have written about [**Ubuntu’s Snaps**][1]. Snaps are introduced by Canonical for Ubuntu operating system, and later it was adopted by other Linux distributions such as Arch, Gentoo, and Fedora etc. A snap is a single binary package bundled with all required libraries and dependencies, and you can install it on any Linux distribution, regardless of its version and architecture. Similar to Snaps, there is also another tool called **Flatpak**. As you may already know, packaging distributed applications for different Linux distributions are quite time consuming and difficult process. Each distributed application has different set of libraries and dependencies for various Linux distributions. But, Flatpak, the new framework for desktop applications that completely reduces this burden. Now, you can build a single Flatpak app and install it on various operating systems. How cool, isn’t it? - -Also, the users don’t have to worry about the libraries and dependencies, everything is bundled within the app itself. Most importantly, Flaptpak apps are sandboxed and isolated from the rest of the host operating system, and other applications. Another notable feature is we can install multiple versions of the same application at the same time in the same system. For example, you can install VLC player version 2.1, 2.2, and 2.3 on the same system. So, the developers can test different versions of same application at a time. - -In this tutorial, we will see how to install Flatpak in GNU/Linux. - -### Install Flatpak - -Flatpak is available for many popular Linux distributions such as Arch Linux, Debian, Fedora, Gentoo, Red Hat, Linux Mint, openSUSE, Solus, Mageia and Ubuntu distributions. - -To install Flatpak on Arch Linux, run: -``` -$ sudo pacman -S flatpak - -``` - -Flatpak is available in the default repositories of Debian Stretch and newer. To install it, run: -``` -$ sudo apt install flatpak - -``` - -On Fedora, Flatpak is installed by default. All you have to do is enable enable Flathub as described in the next section. - -Just in case, it is not installed for any reason, run: -``` -$ sudo dnf install flatpak - -``` - -On RHEL 7, run: -``` -$ sudo yum install flatpak - -``` - -On Linux Mint 18.3, flatpak is installed by default. So, no setup required. - -On openSUSE Tumbleweed, Flatpak can also be installed using Zypper: -``` -$ sudo zypper install flatpak - -``` - -On Ubuntu, add the following repository and install Flatpak as shown below. -``` -$ sudo add-apt-repository ppa:alexlarsson/flatpak - -$ sudo apt update - -$ sudo apt install flatpak - -``` - -The Flatpak plugin for the Software app makes it possible to install apps without needing the command line. To install this plugin, run: -``` -$ sudo apt install gnome-software-plugin-flatpak - -``` - -For other Linux distributions, refer the official installation [**link**][2]. - -### Getting Started With Flatpak - -There are many popular applications such as Gimp, Kdenlive, Steam, Spotify, Visual studio code etc., available as flatpaks. - -Let us now see the basic usage of flatpak command. - -First of all, we need to add remote repositories. - -#### Adding Remote Repositories** - -**Enable Flathub Repository:** - -**Flathub** is nothing but a central repository where all flatpak applications available to users. To enable it, just run: -``` -$ sudo flatpak remote-add --if-not-exists flathub https://flathub.org/repo/flathub.flatpakrepo - -``` - -Flathub is enough to install most popular apps. Just in case you wanted to try some GNOME apps, add the GNOME repository. - -**Enable GNOME Repository:** - -The GNOME repository contains all GNOME core applications. GNOME flatpak repository itself is available as two versions, **stable** and **nightly**. - -To add GNOME stable repository, run the following commands: -``` -$ wget https://sdk.gnome.org/keys/gnome-sdk.gpg - -$ sudo flatpak remote-add --gpg-import=gnome-sdk.gpg --if-not-exists gnome-apps https://sdk.gnome.org/repo-apps/ - -``` - -Applications in this repository require the **3.20 version of the org.gnome.Platform runtime**. - -To install the stable runtimes, run: -``` -$ sudo flatpak remote-add --gpg-import=gnome-sdk.gpg gnome https://sdk.gnome.org/repo/ - -``` - -To add the GNOME nightly apps repository, run: -``` -$ wget https://sdk.gnome.org/nightly/keys/nightly.gpg - -$ sudo flatpak remote-add --gpg-import=nightly.gpg --if-not-exists gnome-nightly-apps https://sdk.gnome.org/nightly/repo-apps/ - -``` - -Applications in this repository require the **nightly version of the org.gnome.Platform runtime**. - -To install the nightly runtimes, run: -``` -$ sudo flatpak remote-add --gpg-import=nightly.gpg gnome-nightly https://sdk.gnome.org/nightly/repo/ - -``` - -#### Listing Remotes - -To list all configured remote repositories, run: -``` -$ flatpak remotes -Name Options -flathub system -gnome system -gnome-apps system -gnome-nightly system -gnome-nightly-apps system - -``` - -As you can see, the above command lists the remotes that you have added in your system. It also lists whether the remote has been added per-user or system-wide. - -#### Removing Remotes - -To remove a remote, for example flathub, simply do; -``` -$ sudo flatpak remote-delete flathub - -``` - -Here **flathub** is remote name. - -#### Installing Flatpak Applications - -In this section, we will see how to install flatpak apps. To install a flatpak application - -To install an application, simply do: -``` -$ sudo flatpak install flathub com.spotify.Client - -``` - -All the apps in the GNOME stable repository uses the version name of “stable”. - -To install any Stable GNOME applications, for example **Evince** , run: -``` -$ sudo flatpak install gnome-apps org.gnome.Evince stable - -``` - -All the apps in the GNOME nightly repository uses the version name of “master”. - -For example, to install gedit, run: -``` -$ sudo flatpak install gnome-nightly-apps org.gnome.gedit master - -``` - -If you don’t want to install apps system-wide, you also can install flatpak apps per-user like below. -``` -$ flatpak install --user - -``` - -All installed apps will be stored in **$HOME/.var/app/** location. -``` -$ ls $HOME/.var/app/ -com.spotify.Client - -``` - -#### Running Flatpak Applications - -You can launch the installed applications at any time from the application launcher. From command line, you can run it, for example Spotify, using command: -``` -$ flatpak run com.spotify.Client - -``` - -#### Listing Applications - -To view the installed applications and runtimes, run: -``` -$ flatpak list - -``` - -To view only the applications, not run times, use this command instead. -``` -$ flatpak list --app - -``` - -You can also view the list of available applications and runtimes from all remotes using command: -``` -$ flatpak remote-ls - -``` - -To list only applications not runtimes, run: -``` -$ flatpak remote-ls --app - -``` - -To list applications and runtimes from a specific repository, for example **gnome-apps** , run: -``` -$ flatpak remote-ls gnome-apps - -``` - -To list only the applications from a remote repository, run: -``` -$ flatpak remote-ls flathub --app - -``` - -#### Updating Applications - -To update all your flatpak applications, run: -``` -$ flatpak update - -``` - -To update a specific application, we do: -``` -$ flatpak update com.spotify.Client - -``` - -#### Getting Details Of Applications - -To display the details of a installed application, run: -``` -$ flatpak info io.github.mmstick.FontFinder - -``` - -Sample output: -``` -Ref: app/io.github.mmstick.FontFinder/x86_64/stable -ID: io.github.mmstick.FontFinder -Arch: x86_64 -Branch: stable -Origin: flathub -Date: 2018-04-11 15:10:31 +0000 -Subject: Workaround appstream issues (391ef7f5) -Commit: 07164e84148c9fc8b0a2a263c8a468a5355b89061b43e32d95008fc5dc4988f4 -Parent: dbff9150fce9fdfbc53d27e82965010805f16491ec7aa1aa76bf24ec1882d683 -Location: /var/lib/flatpak/app/io.github.mmstick.FontFinder/x86_64/stable/07164e84148c9fc8b0a2a263c8a468a5355b89061b43e32d95008fc5dc4988f4 -Installed size: 2.5 MB -Runtime: org.gnome.Platform/x86_64/3.28 - -``` - -#### Removing Applications - -To remove a flatpak application, run: -``` -$ sudo flatpak uninstall com.spotify.Client - -``` - -For details, refer flatpak help section. -``` -$ flatpak --help - -``` - -And, that’s all for now. Hope you had basic idea about Flatpak. - -If you find this guide useful, please share it on your social, professional networks and support OSTechNix. - -More good stuffs to come. Stay tuned! - -Cheers! - - - --------------------------------------------------------------------------------- - -via: https://www.ostechnix.com/flatpak-new-framework-desktop-applications-linux/ - -作者：[SK][a] -选题：[lujun9972](https://github.com/lujun9972) -译者：[译者ID](https://github.com/译者ID) -校对：[校对者ID](https://github.com/校对者ID) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 - -[a]:https://www.ostechnix.com/author/sk/ -[1]:http://www.ostechnix.com/introduction-ubuntus-snap-packages/ -[2]:https://flatpak.org/setup/ diff --git a/sources/tech/20180429 The Easiest PDO Tutorial (Basics).md b/sources/tech/20180429 The Easiest PDO Tutorial (Basics).md deleted file mode 100644 index 9bda5fa335..0000000000 --- a/sources/tech/20180429 The Easiest PDO Tutorial (Basics).md +++ /dev/null @@ -1,170 +0,0 @@ -The Easiest PDO Tutorial (Basics) -====== - - - -Approximately 80% of the web is powered by PHP. And similarly, high number goes for SQL as well. Up until PHP version 5.5, we had the **mysql_** commands for accessing mysql databases but they were eventually deprecated due to insufficient security. - -This happened with PHP 5.5 in 2013 and as I write this article, the year is 2018 and we are on PHP 7.2. The deprecation of mysql**_** brought 2 major ways of accessing the database, the **mysqli** and the **PDO** libraries. - -Now though the mysqli library was the official successor, PDO gained more fame due to a simple reason that mysqli could only support mysql databases whereas PDO could support 12 different types of database drivers. Also, PDO had several more features that made it the better choice for most developers. You can see some of the feature comparisons in the table below; - -| | PDO | MySQLi | -| Database support** | 12 drivers | Only MySQL | -| Paradigm | OOP | Procedural + OOP | -| Prepared Statements Client Side) | Yes | No | -| Named Parameters | Yes | No | - -Now I guess it is pretty clear why PDO is the choice for most developers, so let’s dig into it and hopefully we will try to cover most of the PDO you need in this article itself. - -### Connection - -The first step is connecting to the database and since PDO is completely Object Oriented, we will be using the instance of a PDO class. - -The first thing we do is we define the host, database name, user, password and the database charset. - -`$host = 'localhost';` - -`$db = 'theitstuff';` - -`$user = 'root';` - -`$pass = 'root';` - -`$charset = 'utf8mb4';` - -`$dsn = "mysql:host=$host;dbname=$db;charset=$charset";` - -`$conn = new PDO($dsn, $user, $pass);` - -After that, as you can see in the code above we have created the **DSN** variable, the DSN variable is simply a variable that holds the information about the database. For some people running mysql on external servers, you could also adjust your port number by simply supplying a **port=$port_number**. - -Finally, you can create an instance of the PDO class, I have used the **$conn** variable and I have supplied the **$dsn, $user, $pass** parameters. If you have followed this, you should now have an object named $conn that is an instance of the PDO connection class. Now it’s time to get into the database and run some queries. - -### A simple SQL Query - -Let us now run a simple SQL query. - -`$tis = $conn->query('SELECT name, age FROM students');` - -`while ($row = $tis->fetch())` - -`{` - -`echo $row['name']."\t";` - -`echo $row['age'];` - -`echo "
";` - -`}` - -This is the simplest form of running a query with PDO. We first created a variable called **tis( **short for TheITStuff** )** and then you can see the syntax as we used the query function from the $conn object that we had created. - -We then ran a while loop and created a **$row** variable to fetch the contents from the **$tis** object and finally echoed out each row by calling out the column name. - -Easy wasn’t it ?. Now let’s get to the prepared statement. - -### Prepared Statements - -Prepared statements were one of the major reasons people started using PDO as it had prepared statements that could prevent SQL injections. - -There are 2 basic methods available, you could either use positional or named parameters. - -#### Position parameters - -Let us see an example of a query using positional parameters. - -`$tis = $conn->prepare("INSERT INTO STUDENTS(name, age) values(?, ?)");` - -`$tis->bindValue(1,'mike');` - -`$tis->bindValue(2,22);` - -`$tis->execute();` - -In the above example, we have placed 2 question marks and later used the **bindValue()** function to map the values into the query. The values are bound to the position of the question mark in the statement. - -I could also use variables instead of directly supplying values by using the **bindParam()** function and example for the same would be this. - -`$name='Rishabh'; $age=20;` - -`$tis = $conn->prepare("INSERT INTO STUDENTS(name, age) values(?, ?)");` - -`$tis->bindParam(1,$name);` - -`$tis->bindParam(2,$age);` - -`$tis->execute();` - -### Named Parameters - -Named parameters are also prepared statements that map values/variables to a named position in the query. Since there is no positional binding, it is very efficient in queries that use the same variable multiple time. - -`$name='Rishabh'; $age=20;` - -`$tis = $conn->prepare("INSERT INTO STUDENTS(name, age) values(:name, :age)");` - -`$tis->bindParam(':name', $name);` - -`$tis->bindParam(':age', $age);` - -`$tis->execute();` - -The only change you can notice is that I used **:name** and **:age** as placeholders and then mapped variables to them. The colon is used before the parameter and it is of extreme importance to let PDO know that the position is for a variable. - -You can similarly use **bindValue()** to directly map values using Named parameters as well. - -### Fetching the Data - -PDO is very rich when it comes to fetching data and it actually offers a number of formats in which you can get the data from your database. - -You can use the **PDO::FETCH_ASSOC** to fetch associative arrays, **PDO::FETCH_NUM** to fetch numeric arrays and **PDO::FETCH_OBJ** to fetch object arrays. - -`$tis = $conn->prepare("SELECT * FROM STUDENTS");` - -`$tis->execute();` - -`$result = $tis->fetchAll(PDO::FETCH_ASSOC);` - -You can see that I have used **fetchAll** since I wanted all matching records. If only one row is expected or desired, you can simply use **fetch.** - -Now that we have fetched the data it is time to loop through it and that is extremely easy. - -`foreach($result as $lnu){` - -`echo $lnu['name'];` - -`echo $lnu['age']."
";` - -`}` - -You can see that since I had requested associative arrays, I am accessing individual members by their names. - -Though there is absolutely no problem in defining how you want your data delivered, you could actually set one as default when defining the connection variable itself. - -All you need to do is create an options array where you put in all your default configs and simply pass the array in the connection variable. - -`$options = [` - -` PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,` - -`];` - -`$conn = new PDO($dsn, $user, $pass, $options);` - -This was a very brief and quick intro to PDO we will be making an advanced tutorial soon. If you had any difficulties understanding any part of the tutorial, do let me know in the comment section and I’ll be there for you. - - --------------------------------------------------------------------------------- - -via: http://www.theitstuff.com/easiest-pdo-tutorial-basics - -作者：[Rishabh Kandari][a] -选题：[lujun9972](https://github.com/lujun9972) -译者：[译者ID](https://github.com/译者ID) -校对：[校对者ID](https://github.com/校对者ID) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 - -[a]:http://www.theitstuff.com/author/reevkandari diff --git a/sources/tech/20180503 11 Methods To Find System-Server Uptime In Linux.md b/sources/tech/20180503 11 Methods To Find System-Server Uptime In Linux.md deleted file mode 100644 index 7a30127b07..0000000000 --- a/sources/tech/20180503 11 Methods To Find System-Server Uptime In Linux.md +++ /dev/null @@ -1,193 +0,0 @@ -11 Methods To Find System/Server Uptime In Linux -====== -Do you want to know, how long your Linux system has been running without downtime? when the system is up and what date. - -There are multiple commands is available in Linux to check server/system uptime and most of users prefer the standard and very famous command called `uptime` to get this details. - -Server uptime is not important for some people but it’s very important for server administrators when the server running with mission-critical applications such as online shopping portal, netbanking portal, etc,. - -It must be zero downtime because if there is a down time then it will impact badly to million users. - -As i told, many commands are available to check server uptime in Linux. In this tutorial we are going teach you how to check this using below 11 methods. - -Uptime means how long the server has been up since its last shutdown or reboot. - -The uptime command the fetch the details from `/proc` files and print the server uptime, the `/proc` file is not directly readable by humans. - -The below commands will print how long the system has been running and up. It also shows some additional information. - -### Method-1 : Using uptime Command - -uptime command will tell how long the system has been running. It gives a one line display of the following information. - -The current time, how long the system has been running, how many users are currently logged on, and the system load averages for the past 1, 5, and 15 minutes. -``` -# uptime - - 08:34:29 up 21 days, 5:46, 1 user, load average: 0.06, 0.04, 0.00 - -``` - -### Method-2 : Using w Command - -w command provides a quick summary of every user logged into a computer, what each user is currently doing, -and what load all the activity is imposing on the computer itself. The command is a one-command combination of several other Unix programs: who, uptime, and ps -a. -``` -# w - - 08:35:14 up 21 days, 5:47, 1 user, load average: 0.26, 0.09, 0.02 -USER TTY FROM [email protected] IDLE JCPU PCPU WHAT -root pts/1 103.5.134.167 08:34 0.00s 0.01s 0.00s w - -``` - -### Method-3 : Using top Command - -Top command is one of the basic command to monitor real-time system processes in Linux. It display system information and running processes information like uptime, average load, tasks running, number of users logged in, number of CPUs & cpu utilization, Memory & swap information. Run top command then hit E to bring the memory utilization in MB. - -**Suggested Read :** [TOP Command Examples to Monitor Server Performance][1] -``` -# top -c - -top - 08:36:01 up 21 days, 5:48, 1 user, load average: 0.12, 0.08, 0.02 -Tasks: 98 total, 1 running, 97 sleeping, 0 stopped, 0 zombie -Cpu(s): 0.0%us, 0.3%sy, 0.0%ni, 99.7%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st -Mem: 1872888k total, 1454644k used, 418244k free, 175804k buffers -Swap: 2097148k total, 0k used, 2097148k free, 1098140k cached - - PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND - 1 root 20 0 19340 1492 1172 S 0.0 0.1 0:01.04 /sbin/init - 2 root 20 0 0 0 0 S 0.0 0.0 0:00.00 [kthreadd] - 3 root RT 0 0 0 0 S 0.0 0.0 0:00.00 [migration/0] - 4 root 20 0 0 0 0 S 0.0 0.0 0:34.32 [ksoftirqd/0] - 5 root RT 0 0 0 0 S 0.0 0.0 0:00.00 [stopper/0] - -``` - -### Method-4 : Using who Command - -who command displays a list of users who are currently logged into the computer. The who command is related to the command w, which provides the same information but also displays additional data and statistics. -``` -# who -b - -system boot 2018-04-12 02:48 - -``` - -### Method-5 : Using last Command - -The last command displays a list of last logged in users. Last searches back through the file /var/log/wtmp and displays a list of all users logged in (and out) since that file was created. -``` -# last reboot -F | head -1 | awk '{print $5,$6,$7,$8,$9}' - -Thu Apr 12 02:48:04 2018 - -``` - -### Method-6 : Using /proc/uptime File - -This file contains information detailing how long the system has been on since its last restart. The output of `/proc/uptime` is quite minimal. - -The first number is the total number of seconds the system has been up. The second number is how much of that time the machine has spent idle, in seconds. -``` -# cat /proc/uptime - -1835457.68 1809207.16 - -``` - -# date -d “$(Method-7 : Using tuptime Command - -Tuptime is a tool for report the historical and statistical running time of the system, keeping it between restarts. Like uptime command but with more interesting output. -``` -$ tuptime - -``` - -### Method-8 : Using htop Command - -htop is an interactive process viewer for Linux which was developed by Hisham using ncurses library. Htop have many of features and options compared to top command. - -**Suggested Read :** [Monitor system resources using Htop command][2] -``` -# htop - - CPU[| 0.5%] Tasks: 48, 5 thr; 1 running - Mem[||||||||||||||||||||||||||||||||||||||||||||||||||| 165/1828MB] Load average: 0.10 0.05 0.01 - Swp[ 0/2047MB] Uptime: 21 days, 05:52:35 - - PID USER PRI NI VIRT RES SHR S CPU% MEM% TIME+ Command -29166 root 20 0 110M 2484 1240 R 0.0 0.1 0:00.03 htop -29580 root 20 0 11464 3500 1032 S 0.0 0.2 55:15.97 /bin/sh ./OSWatcher.sh 10 1 - 1 root 20 0 19340 1492 1172 S 0.0 0.1 0:01.04 /sbin/init - 486 root 16 -4 10780 900 348 S 0.0 0.0 0:00.07 /sbin/udevd -d - 748 root 18 -2 10780 932 360 S 0.0 0.0 0:00.00 /sbin/udevd -d - -``` - -### Method-9 : Using glances Command - -Glances is a cross-platform curses-based system monitoring tool written in Python. We can say all in one place, like maximum of information in a minimum of space. It uses psutil library to get information from your system. - -Glances capable to monitor CPU, Memory, Load, Process list, Network interface, Disk I/O, Raid, Sensors, Filesystem (and folders), Docker, Monitor, Alert, System info, Uptime, Quicklook (CPU, MEM, LOAD), etc,. - -**Suggested Read :** [Glances (All in one Place)– An Advanced Real Time System Performance Monitoring Tool for Linux][3] -``` -glances - -ubuntu (Ubuntu 17.10 64bit / Linux 4.13.0-37-generic) - IP 192.168.1.6/24 Uptime: 21 days, 05:55:15 - -CPU [|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||| 90.6%] CPU - 90.6% nice: 0.0% ctx_sw: 4K MEM \ 78.4% active: 942M SWAP - 5.9% LOAD 2-core -MEM [||||||||||||||||||||||||||||||||||||||||||||||||||||||||| 78.0%] user: 55.1% irq: 0.0% inter: 1797 total: 1.95G inactive: 562M total: 12.4G 1 min: 4.35 -SWAP [|||| 5.9%] system: 32.4% iowait: 1.8% sw_int: 897 used: 1.53G buffers: 14.8M used: 749M 5 min: 4.38 - idle: 7.6% steal: 0.0% free: 431M cached: 273M free: 11.7G 15 min: 3.38 - -NETWORK Rx/s Tx/s TASKS 211 (735 thr), 4 run, 207 slp, 0 oth sorted automatically by memory_percent, flat view -docker0 0b 232b -enp0s3 12Kb 4Kb Systemd 7 Services loaded: 197 active: 196 failed: 1 -lo 616b 616b -_h478e48e 0b 232b CPU% MEM% VIRT RES PID USER NI S TIME+ R/s W/s Command - 63.8 18.9 2.33G 377M 2536 daygeek 0 R 5:57.78 0 0 /usr/lib/firefox/firefox -contentproc -childID 1 -isForBrowser -intPrefs 6:50|7:-1|19:0|34:1000|42:20|43:5|44:10|51 -DefaultGateway 83ms 78.5 10.9 3.46G 217M 2039 daygeek 0 S 21:07.46 0 0 /usr/bin/gnome-shell - 8.5 10.1 2.32G 201M 2464 daygeek 0 S 8:45.69 0 0 /usr/lib/firefox/firefox -new-window -DISK I/O R/s W/s 1.1 8.5 2.19G 170M 2653 daygeek 0 S 2:56.29 0 0 /usr/lib/firefox/firefox -contentproc -childID 4 -isForBrowser -intPrefs 6:50|7:-1|19:0|34:1000|42:20|43:5|44:10|51 -dm-0 0 0 1.7 7.2 2.15G 143M 2880 daygeek 0 S 7:10.46 0 0 /usr/lib/firefox/firefox -contentproc -childID 6 -isForBrowser -intPrefs 6:50|7:-1|19:0|34:1000|42:20|43:5|44:10|51 -sda1 9.46M 12K 0.0 4.9 1.78G 97.2M 6125 daygeek 0 S 1:36.57 0 0 /usr/lib/firefox/firefox -contentproc -childID 7 -isForBrowser -intPrefs 6:50|7:-1|19:0|34:1000|42:20|43:5|44:10|51 - -``` - -### Method-10 : Using stat Command - -stat command displays the detailed status of a particular file or a file system. -``` -# stat /var/log/dmesg | grep Modify - -Modify: 2018-04-12 02:48:04.027999943 -0400 - -``` - -### Method-11 : Using procinfo Command - -procinfo gathers some system data from the /proc directory and prints it nicely formatted on the standard output device. -``` -# procinfo | grep Bootup - -Bootup: Fri Apr 20 19:40:14 2018 Load average: 0.16 0.05 0.06 1/138 16615 - -``` - --------------------------------------------------------------------------------- - -via: https://www.2daygeek.com/11-methods-to-find-check-system-server-uptime-in-linux/ - -作者：[Magesh Maruthamuthu][a] -选题：[lujun9972](https://github.com/lujun9972) -译者：[译者ID](https://github.com/译者ID) -校对：[校对者ID](https://github.com/校对者ID) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 - -[a]:https://www.2daygeek.com/author/magesh/ -[1]:https://www.2daygeek.com/top-command-examples-to-monitor-server-performance/ -[2]:https://www.2daygeek.com/htop-command-examples-to-monitor-system-resources/ -[3]:https://www.2daygeek.com/install-glances-advanced-real-time-linux-system-performance-monitoring-tool-on-centos-fedora-ubuntu-debian-opensuse-arch-linux/ diff --git a/sources/tech/20180507 Modularity in Fedora 28 Server Edition.md b/sources/tech/20180507 Modularity in Fedora 28 Server Edition.md new file mode 100644 index 0000000000..0b5fb0415b --- /dev/null +++ b/sources/tech/20180507 Modularity in Fedora 28 Server Edition.md @@ -0,0 +1,76 @@ +[#]: collector: (lujun9972) +[#]: translator: ( ) +[#]: reviewer: ( ) +[#]: publisher: ( ) +[#]: url: ( ) +[#]: subject: (Modularity in Fedora 28 Server Edition) +[#]: via: (https://fedoramagazine.org/wp-content/uploads/2018/05/f28-server-modularity-816x345.jpg) +[#]: author: (Stephen Gallagher https://fedoramagazine.org/author/sgallagh/) + +Modularity in Fedora 28 Server Edition +====== + + + +### What is Modularity? + +A classic conundrum that all open-source distributions have faced is the “too fast/too slow” problem. Users install an operating system in order to enable the use of their applications. A comprehensive distribution like Fedora has an advantage and a disadvantage to the large amount of available software. While the package the user wants may be available, it might not be available in the version needed. Here’s how Modularity can help solve that problem. + +Fedora sometimes moves too fast for some users. Its rapid release cycle and desire to carry the latest stable software can result in breaking compatibility with applications. If a user can’t run a web application because Fedora upgraded a web framework to an incompatible version, it can be very frustrating. The classic answer to the “too fast” problem has been “Fedora should have an LTS release.” However, this approach only solves half the problem and makes the flip side of this conundrum worse. + +There are also times when Fedora moves too slowly for some of its users. For example, a Fedora release may be poorly-timed alongside the release of other desirable software. Once a Fedora release is declared stable, packagers must abide by the [Stable Updates Policy][1] and not introduce incompatible changes into the system. + +Fedora Modularity addresses both sides of this problem. Fedora will still ship a standard release under its traditional policy. However, it will also ship a set of modules that define alternative versions of popular software. Those in the “too fast” camp still have the benefit of Fedora’s newer kernel and other general platform enhancements. In addition, they still have access to older frameworks or toolchains that support their applications. + +In addition, those users who like to live closer to the edge can access newer software than was available at release time. + +### What is Modularity not? + +Modularity is not a drop-in replacement for [Software Collections][2]. These two technologies try to solve many of the same problems, but have distinct differences. + +Software Collections install different versions of packages in parallel on the system. However, their downside is that each installation exists in its own namespaced portion of the filesystem. Furthermore, each application that relies on them needs to be told where to find them. + +With Modularity, only one version of a package exists on the system, but the user can choose which one. The advantage is that this version lives in a standard location on the system. The package requires no special changes to applications that rely on it. Feedback from user studies shows most users don’t actually rely on parallel installation. Containerization and virtualization solve that problem. + +### Why not just use containers? + +This is another common question. Why would a user want modules when they could just use containers? The answer is, someone still has to maintain the software in the containers. Modules provide pre-packaged content for those containers that users don’t need to maintain, update and patch on their own. This is how Fedora takes the traditional value of a distribution and moves it into the new, containerized world. + +Here’s an example of how Modularity solves problems for users of Node.js and Review Board. + +### Node.js + +Many readers may be familiar with Node.js, a popular server-side JavaScript runtime. Node.js has an even/odd release policy. Its community supports even-numbered releases (6.x, 8.x, 10.x, etc.) for around 30 months. Meanwhile, they support odd-numbered releases that are essentially developer previews for 9 months. + +Due to this cycle, Fedora carried only the most recent even-numbered version of Node.js in its stable repositories. It avoided the odd-numbered versions entirely since their lifecycle was shorter than Fedora, and generally not aligned with a Fedora release. This didn’t sit well with some Fedora users, who wanted access to the latest and greatest enhancements. + +Thanks to Modularity, Fedora 28 shipped with not just one, but three versions of Node.js to satisfy both developers and stable deployments. Fedora 28’s traditional repository shipped with Node.js 8.x. This version was the most recent long-term stable version at release time. The Modular repositories (available by default on Fedora 28 Server edition) also made the older Node.js 6.x release and the newer Node.js 9.x development release available. + +Additionally, Node.js released 10.x upstream just days after Fedora 28\. In the past, users who wanted to deploy that version had to wait until Fedora 29, or use sources from outside Fedora. However, thanks again to Modularity, Node.js 10.x is already [available][3] in the Modular Updates-Testing repository for Fedora 28. + +### Review Board + +Review Board is a popular Django application for performing code reviews. Fedora included Review Board from Fedora 13 all the way until Fedora 21\. At that point, Fedora moved to Django 1.7\. Review Board was unable to keep up, due to backwards-incompatible changes in Django’s database support. It remained alive in EPEL for RHEL/CentOS 7, simply because those releases had fortunately frozen on Django 1.6\. Nevertheless, its time in Fedora was apparently over. + +However, with the advent of Modularity, Fedora could again ship the older Django as a non-default module stream. As a result, Review Board has been restored to Fedora as a module. Fedora carries both supported releases from upstream: 2.5.x and 3.0.x. + +### Putting the pieces together + +Fedora has always provided users with a wide range of software to use. Fedora Modularity now provides them with deeper choices for which versions of the software they need. The next few years will be very exciting for Fedora, as developers and users start putting together their software in new and exciting (or old and exciting) ways. + +-------------------------------------------------------------------------------- + +via: https://fedoramagazine.org/wp-content/uploads/2018/05/f28-server-modularity-816x345.jpg + +作者：[Stephen Gallagher][a] +选题：[lujun9972][b] +译者：[译者ID](https://github.com/译者ID) +校对：[校对者ID](https://github.com/校对者ID) + +本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 + +[a]: https://fedoramagazine.org/author/sgallagh/ +[b]: https://github.com/lujun9972 +[1]: https://fedoraproject.org/wiki/Updates_Policy#Stable_Releases +[2]: https://www.softwarecollections.org +[3]: https://bodhi.fedoraproject.org/updates/FEDORA-MODULAR-2018-2b0846cb86 diff --git a/sources/tech/20180514 An introduction to the Pyramid web framework for Python.md b/sources/tech/20180514 An introduction to the Pyramid web framework for Python.md new file mode 100644 index 0000000000..a16e604774 --- /dev/null +++ b/sources/tech/20180514 An introduction to the Pyramid web framework for Python.md @@ -0,0 +1,617 @@ +[#]: collector: (lujun9972) +[#]: translator: ( ) +[#]: reviewer: ( ) +[#]: publisher: ( ) +[#]: subject: (An introduction to the Pyramid web framework for Python) +[#]: via: (https://opensource.com/article/18/5/pyramid-framework) +[#]: author: (Nicholas Hunt-Walker https://opensource.com/users/nhuntwalker) +[#]: url: ( ) + +An introduction to the Pyramid web framework for Python +====== +In the second part in a series comparing Python frameworks, learn about Pyramid. + + +In the [first article][1] in this four-part series comparing different Python web frameworks, I explained how to create a To-Do List web application in the [Flask][2] web framework. In this second article, I'll do the same task with the [Pyramid][3] web framework. Future articles will look at [Tornado][4] and [Django][5]; as I go along, I'll explore more of the differences among them. + +### Installing, starting up, and doing configuration + +Self-described as "the start small, finish big, stay finished framework," Pyramid is much like Flask in that it takes very little effort to get it up and running. In fact, you'll recognize many of the same patterns as you build out this application. The major difference between the two, however, is that Pyramid comes with several useful utilities, which I'll describe shortly. + +To get started, create a virtual environment and install the package. + +``` +$ mkdir pyramid_todo +$ cd pyramid_todo +$ pipenv install --python 3.6 +$ pipenv shell +(pyramid-someHash) $ pipenv install pyramid +``` + +As with Flask, it's smart to create a `setup.py` file to make the app you build an easily installable Python distribution. + +``` +# setup.py +from setuptools import setup, find_packages + +requires = [ + 'pyramid', + 'paster_pastedeploy', + 'pyramid-ipython', + 'waitress' +] + +setup( + name='pyramid_todo', + version='0.0', + description='A To-Do List build with Pyramid', + author='', + author_email=' ', + keywords='web pyramid pylons', + packages=find_packages(), + include_package_data=True, + install_requires=requires, + entry_points={ + 'paste.app_factory': [ + 'main = todo:main', + ] + } +) +``` + +`entry_points` section near the end sets up entry points into the application that other services can use. This allows the `plaster_pastedeploy` package to access what will be the `main` function in the application for building an application object and serving it. (I'll circle back to this in a bit.) + +Thesection near the end sets up entry points into the application that other services can use. This allows thepackage to access what will be thefunction in the application for building an application object and serving it. (I'll circle back to this in a bit.) + +When you installed `pyramid`, you also gained a few Pyramid-specific shell commands; the main ones to pay attention to are `pserve` and `pshell`. `pserve` will take an INI-style configuration file specified as an argument and serve the application locally. `pshell` will also take a configuration file as an argument, but instead of serving the application, it'll open up a Python shell that is aware of the application and its internal configuration. + +The configuration file is pretty important, so it's worth a closer look. Pyramid can take its configuration from environment variables or a configuration file. To avoid too much confusion around what is where, in this tutorial you'll write most of your configuration in the configuration file, with only a select few, sensitive configuration parameters set in the virtual environment. + +Create a file called `config.ini` + +``` +[app:main] +use = egg:todo +pyramid.default_locale_name = en + +[server:main] +use = egg:waitress#main +listen = localhost:6543 +``` + +This says a couple of things: + + * The actual application will come from the `main` function located in the `todo` package installed in the environment + * To serve this app, use the `waitress` package installed in the environment and serve on localhost port 6543 + + + +When serving an application and working in development, it helps to set up logging so you can see what's going on. The following configuration will handle logging for the application: + +``` +# continuing on... +[loggers] +keys = root, todo + +[handlers] +keys = console + +[formatters] +keys = generic + +[logger_root] +level = INFO +handlers = console + +[logger_todo] +level = DEBUG +handlers = +qualname = todo + +[handler_console] +class = StreamHandler +args = (sys.stderr,) +level = NOTSET +formatter = generic + +[formatter_generic] +format = %(asctime)s %(levelname)-5.5s [%(name)s:%(lineno)s][%(threadName)s] %(message)s +``` + +In short, this configuration asks to log everything to do with the application to the console. If you want less output, set the logging level to `WARN` so a message will fire only if there's a problem. + +Because Pyramid is meant for an application that grows, plan out a file structure that could support that growth. Web applications can, of course, be built however you want. In general, the conceptual blocks you'll want to cover will contain: + + * **Models** for containing the code and logic for dealing with data representations + * **Views** for code and logic pertaining to the request-response cycle + * **Routes** for the paths for access to the functionality of your application + * **Scripts** for any code that might be used in configuration or management of the application itself + + + +Given the above, the file structure can look like so: + +``` +setup.py +config.ini +todo/ + __init__.py + models.py + routes.py + views.py + scripts/ +``` + +Much like Flask's `app` object, Pyramid has its own central configuration. It comes from its `config` module and is known as the `Configurator` object. This object will handle everything from route configuration to pointing to where models and views exist. All this is done in an inner directory called `todo` within an `__init__.py` file. + +``` +# todo/__init__.py + +from pyramid.config import Configurator + +def main(global_config, **settings): + """Returns a Pyramid WSGI application.""" + config = Configurator(settings=settings) + config.scan() + return config.make_wsgi_app() +``` + +The `main` function looks for some global configuration from your environment as well as any settings that came through the particular configuration file you provide when you run the application. It takes those settings and uses them to build an instance of the `Configurator` object, which (for all intents and purposes) is the factory for your application. Finally, `config.scan()` looks for any views you'd like to attach to your application that are marked as Pyramid views. + +Wow, that was a lot to configure. + +### Using routes and views + +Now that a chunk of the configuration is done, you can start adding functionality to the application. Functionality comes in the form of URL routes that external clients can hit, which then map to functions that Python can run. + +With Pyramid, all functionality must be added to the `Configurator` in some way, shape, or form. For example, say you want to build the same simple `hello_world` view that you built with Flask, mapping to the route of `/`. With Pyramid, you can register the `/` route with the `Configurator` using the `.add_route()` method. This method takes as arguments the name of the route that you want to add as well as the actual pattern that must be matched to access that route. For this case, add the following to your `Configurator`: + +``` +config.add_route('home', '/') +``` + +Until you create a view and attach it to that route, that path into your application sits open and alone. When you add the view, make sure to include the `request` object in the parameter list. Every Pyramid view must have the `request` object as its first parameter, as that's what's being passed as the first argument to the view when it's called by Pyramid. + +One similarity that Pyramid views share with Flask is that you can mark a function as a view with a decorator. Specifically, the `@view_config` decorator from `pyramid.view`. + +In `views.py`, build the view that you want to see in the world. + +``` +from pyramid.view import view_config + +@view_config(route_name="hello", renderer="string") +def hello_world(request): + """Print 'Hello, world!' as the response body.""" + return 'Hello, world!' +``` + +With the `@view_config` decorator, you have to at least specify the name of the route that will map to this particular view. You can stack `view_config` decorators on top of one another to map to multiple routes if you want, but you have to have at least one to connect view the view at all, and each one must include the name of a route. **[NOTE: Is "to connect view the view" phrased correctly?]** + +The other argument, `renderer`, is optional but not really. If you don't specify a renderer, you have to deliberately construct the HTTP response you want to send back to the client using the `Response` object from `pyramid.response`. By specifying the `renderer` as a string, Pyramid knows to take whatever is returned by this function and wrap it in that same `Response` object with the MIME type of `text/plain`. By default, Pyramid allows you to use `string` and `json` as renderers. If you've attached a templating engine to your application because you want to have Pyramid generate your HTML as well, you can point directly to your HTML template as your renderer. + +The first view is done. Here's what `__init__.py` looks like now with the attached route. + +``` +# in __init__.py +from pyramid.config import Configurator + +def main(global_config, **settings): + """Returns a Pyramid WSGI application.""" + config = Configurator(settings=settings) + config.add_route('hello', '/') + config.scan() + return config.make_wsgi_app() +``` + +Spectacular! Getting here was no easy feat, but now that you're set up, you can add functionality with significantly less difficulty. + +### Smoothing a rough edge + +Right now the application only has one route, but it's easy to see that a large application can have many dozens or even hundreds of routes. Containing them all in the same `main` function with your central configuration isn't really the best idea, because it would become cluttered. Thankfully, it's fairly easy to include routes with a few tweaks to the application. + +**One** : In the `routes.py` file, create a function called `includeme` (yes, it must actually be named this) that takes a configurator object as an argument. + +``` +# in routes.py +def includeme(config): + """Include these routes within the application.""" +``` + +**Two** : Move the `config.add_route` method call from `__init__.py` into the `includeme` function: + +``` +def includeme(config): + """Include these routes within the application.""" + config.add_route('hello', '/') +``` + +**Three** : Alert the Configurator that you need to include this `routes.py` file as part of its configuration. Because it's in the same directory as `__init__.py`, you can get away with specifying the import path to this file as `.routes`. + +``` +# in __init__.py +from pyramid.config import Configurator + +def main(global_config, **settings): + """Returns a Pyramid WSGI application.""" + config = Configurator(settings=settings) + config.include('.routes') + config.scan() + return config.make_wsgi_app() +``` + +### Connecting the database + +As with Flask, you'll want to persist data by connecting a database. Pyramid will leverage [SQLAlchemy][6] directly instead of using a specially tailored package. + +First get the easy part out of the way. `psycopg2` and `sqlalchemy` are required to talk to the Postgres database and manage the models, so add them to `setup.py`. + +``` +# in setup.py +requires = [ + 'pyramid', + 'pyramid-ipython', + 'waitress', + 'sqlalchemy', + 'psycopg2' +] +# blah blah other code +``` + +Now, you have a decision to make about how you'll include the database's URL. There's no wrong answer here; what you do will depend on the application you're building and how public your codebase needs to be. + +The first option will keep as much configuration in one place as possible by hard-coding the database URL into the `config.ini` file. One drawback is this creates a security risk for applications with a public codebase. Anyone who can view the codebase will be able to see the full database URL, including username, password, database name, and port. Another is maintainability; if you needed to change environments or the application's database location, you'd have to modify the `config.ini` file directly. Either that or you'll have to maintain one configuration file for each new environment, which adds the potential for discontinuity and errors in the application. **If you choose this option** , modify the `config.ini` file under the `[app:main]` heading to include this key-value pair: + +``` +sqlalchemy.url = postgres://localhost:5432/pyramid_todo +``` + +The second option specifies the location of the database URL when you create the `Configurator`, pointing to an environment variable whose value can be set depending on the environment where you're working. One drawback is that you're further splintering the configuration, with some in the `config.ini` file and some directly in the Python codebase. Another drawback is that when you need to use the database URL anywhere else in the application (e.g., in a database management script), you have to code in a second reference to that same environment variable (or set up the variable in one place and import from that location). **If you choose this option** , add the following: + +``` +# in __init__.py +import os +from pyramid.config import Configurator + +SQLALCHEMY_URL = os.environ.get('DATABASE_URL', '') + +def main(global_config, **settings): + """Returns a Pyramid WSGI application.""" + settings['sqlalchemy.url'] = SQLALCHEMY_URL # <-- important! + config = Configurator(settings=settings) + config.include('.routes') + config.scan() + return config.make_wsgi_app() +``` + +### Defining objects + +OK, so now you have a database. Now you need `Task` and `User` objects. + +Because it uses SQLAlchemy directly, Pyramid differs somewhat from Flash on how objects are built. First, every object you want to construct must inherit from SQLAlchemy's [declarative base class][7]. It'll keep track of everything that inherits from it, enabling simpler management of the database. + +``` +# in models.py +from sqlalchemy.ext.declarative import declarative_base + +Base = declarative_base() + +class Task(Base): + pass + +class User(Base): + pass +``` + +The columns, data types for those columns, and model relationships will be declared in much the same way as with Flask, although they'll be imported directly from SQLAlchemy instead of some pre-constructed `db` object. Everything else is the same. + +``` +# in models.py +from datetime import datetime +import secrets + +from sqlalchemy import ( + Column, Unicode, Integer, DateTime, Boolean, relationship +) +from sqlalchemy.ext.declarative import declarative_base + +Base = declarative_base() + +class Task(Base): + """Tasks for the To Do list.""" + id = Column(Integer, primary_key=True) + name = Column(Unicode, nullable=False) + note = Column(Unicode) + creation_date = Column(DateTime, nullable=False) + due_date = Column(DateTime) + completed = Column(Boolean, default=False) + user_id = Column(Integer, ForeignKey('user.id'), nullable=False) + user = relationship("user", back_populates="tasks") + + def __init__(self, *args, **kwargs): + """On construction, set date of creation.""" + super().__init__(*args, **kwargs) + self.creation_date = datetime.now() + +class User(Base): + """The User object that owns tasks.""" + id = Column(Integer, primary_key=True) + username = Column(Unicode, nullable=False) + email = Column(Unicode, nullable=False) + password = Column(Unicode, nullable=False) + date_joined = Column(DateTime, nullable=False) + token = Column(Unicode, nullable=False) + tasks = relationship("Task", back_populates="user") + + def __init__(self, *args, **kwargs): + """On construction, set date of creation.""" + super().__init__(*args, **kwargs) + self.date_joined = datetime.now() + self.token = secrets.token_urlsafe(64) +``` + +Note that there's no `config.include` line for `models.py` anywhere because it's not needed. A `config.include` line is needed only if some part of the application's configuration needs to be changed. This has only created two objects, inheriting from some `Base` class that SQLAlchemy gave us. + +### Initializing the database + +Now that the models are done, you can write a script to talk to and initialize the database. In the `scripts` directory, create two files: `__init__.py` and `initializedb.py`. The first is simply to turn the `scripts` directory into a Python package. The second is the script needed for database management. + +`initializedb.py` needs a function to set up the necessary tables in the database. Like with Flask, this script must be aware of the `Base` object, whose metadata keeps track of every class that inherits from it. The database URL is required to point to and modify its tables. + +As such, this database initialization script will work: + +``` +# initializedb.py +from sqlalchemy import engine_from_config +from todo import SQLALCHEMY_URL +from todo.models import Base + +def main(): + settings = {'sqlalchemy.url': SQLALCHEMY_URL} + engine = engine_from_config(settings, prefix='sqlalchemy.') + if bool(os.environ.get('DEBUG', '')): + Base.metadata.drop_all(engine) + Base.metadata.create_all(engine) +``` + +**Important note:** This will work only if you include the database URL as an environment variable in `todo/__init__.py` (the second option above). If the database URL was stored in the configuration file, you'll have to include a few lines to read that file. It will look something like this: + +``` +# alternate initializedb.py +from pyramid.paster import get_appsettings +from pyramid.scripts.common import parse_vars +from sqlalchemy import engine_from_config +import sys +from todo.models import Base + +def main(): + config_uri = sys.argv[1] + options = parse_vars(sys.argv[2:]) + settings = get_appsettings(config_uri, options=options) + engine = engine_from_config(settings, prefix='sqlalchemy.') + if bool(os.environ.get('DEBUG', '')): + Base.metadata.drop_all(engine) + Base.metadata.create_all(engine) +``` + +Either way, in `setup.py`, add a console script that will access and run this function. + +``` +# bottom of setup.py +setup( + # ... other stuff + entry_points={ + 'paste.app_factory': [ + 'main = todo:main', + ], + 'console_scripts': [ + 'initdb = todo.scripts.initializedb:main', + ], + } +) +``` + +When this package is installed, you'll have access to a new console script called `initdb`, which will construct the tables in your database. If the database URL is stored in the configuration file, you'll have to include the path to that file when you invoke the command. It'll look like `$ initdb /path/to/config.ini`. + +### Handling requests and the database + +Ok, here's where it gets a little deep. Let's talk about **transactions**. A "transaction," in an abstract sense, is any change made to an existing database. As with Flask, transactions are persisted no sooner than when they are committed. If changes have been made that haven't yet been committed, and you don't want those to occur (maybe there's an error thrown in the process), you can **rollback** a transaction and abort those changes. + +In Python, the [transaction package][8] allows you to interact with transactions as objects, which can roll together multiple changes into one single commit. `transaction` provides **transaction managers** , which give applications a straightforward, thread-aware way of handling transactions so all you need to think about is what to change. The `pyramid_tm` package will take the transaction manager from `transaction` and wire it up in a way that's appropriate for Pyramid's request-response cycle, attaching a transaction manager to every incoming request. + +Normally, with Pyramid the `request` object is populated when the route mapping to a view is accessed and the view function is called. Every view function will have a `request` object to work with**.** However, Pyramid allows you to modify its configuration to add whatever you might need to the `request` object. You can use the transaction manager that you'll be adding to the `request` to create a session with every request and add that session to the request. + +Yay, so why is this important? + +By attaching a transaction-managed session to the `request` object, when the view finishes processing the request, any changes made to the database session will be committed without you needing to explicitly commit**.** Here's what all these concepts look like in code. + +``` +# __init__.py +import os +from pyramid.config import Configurator +from sqlalchemy import engine_from_config +from sqlalchemy.orm import sessionmaker +import zope.sqlalchemy + +SQLALCHEMY_URL = os.environ.get('DATABASE_URL', '') + +def get_session_factory(engine): + """Return a generator of database session objects.""" + factory = sessionmaker() + factory.configure(bind=engine) + return factory + +def get_tm_session(session_factory, transaction_manager): + """Build a session and register it as a transaction-managed session.""" + dbsession = session_factory() + zope.sqlalchemy.register(dbsession, transaction_manager=transaction_manager) + return dbsession + +def main(global_config, **settings): + """Returns a Pyramid WSGI application.""" + settings['sqlalchemy.url'] = SQLALCHEMY_URL + settings['tm.manager_hook'] = 'pyramid_tm.explicit_manager' + config = Configurator(settings=settings) + config.include('.routes') + config.include('pyramid_tm') + session_factory = get_session_factory(engine_from_config(settings, prefix='sqlalchemy.')) + config.registry['dbsession_factory'] = session_factory + config.add_request_method( + lambda request: get_tm_session(session_factory, request.tm), + 'dbsession', + reify=True + ) + + config.scan() + return config.make_wsgi_app() +``` + +That looks like a lot, but it only did was what was explained above, plus it added an attribute to the `request` object called `request.dbsession`. + +A few new packages were included here, so update `setup.py` with those packages. + +``` +# in setup.py +requires = [ + 'pyramid', + 'pyramid-ipython', + 'waitress', + 'sqlalchemy', + 'psycopg2', + 'pyramid_tm', + 'transaction', + 'zope.sqlalchemy' +] +# blah blah other stuff +``` + +### Revisiting routes and views + +You need to make some real views that handle the data within the database and the routes that map to them. + +Start with the routes. You created the `routes.py` file to handle your routes but didn't do much beyond the basic `/` route. Let's fix that. + +``` +# routes.py +def includeme(config): + config.add_route('info', '/api/v1/') + config.add_route('register', '/api/v1/accounts') + config.add_route('profile_detail', '/api/v1/accounts/{username}') + config.add_route('login', '/api/v1/accounts/login') + config.add_route('logout', '/api/v1/accounts/logout') + config.add_route('tasks', '/api/v1/accounts/{username}/tasks') + config.add_route('task_detail', '/api/v1/accounts/{username}/tasks/{id}') +``` + +Now, it not only has static URLs like `/api/v1/accounts`, but it can handle some variable URLs like `/api/v1/accounts/{username}/tasks/{id}` where any variable in a URL will be surrounded by curly braces. + +To create the view to create an individual task in your application (like in the Flash example), you can use the `@view_config` decorator to ensure that it only takes incoming `POST` requests and check out how Pyramid handles data from the client. + +Take a look at the code, then check out how it differs from Flask's version. + +``` +# in views.py +from datetime import datetime +from pyramid.view import view_config +from todo.models import Task, User + +INCOMING_DATE_FMT = '%d/%m/%Y %H:%M:%S' + +@view_config(route_name="tasks", request_method="POST", renderer='json') +def create_task(request): + """Create a task for one user.""" + response = request.response + response.headers.extend({'Content-Type': 'application/json'}) + user = request.dbsession.query(User).filter_by(username=request.matchdict['username']).first() + if user: + due_date = request.json['due_date'] + task = Task( + name=request.json['name'], + note=request.json['note'], + due_date=datetime.strptime(due_date, INCOMING_DATE_FMT) if due_date else None, + completed=bool(request.json['completed']), + user_id=user.id + ) + request.dbsession.add(task) + response.status_code = 201 + return {'msg': 'posted'} +``` + +To start, note on the `@view_config` decorator that the only type of request you want this view to handle is a "POST" request. If you want to specify one type of request or one set of requests, provide either the string noting the request or a tuple/list of such strings. + +``` +response = request.response +response.headers.extend({'Content-Type': 'application/json'}) +# ...other code... +response.status_code = 201 +``` + +The HTTP response sent to the client is generated based on `request.response`. Normally, you wouldn't have to worry about that object. It would just produce a properly formatted HTTP response and you'd never know the difference. However, because you want to do something specific, like modify the response's status code and headers, you need to access that response and its methods/attributes. + +Unlike with Flask, you don't need to modify the view function parameter list just because you have variables in the route URL. Instead, any time a variable exists in the route URL, it is collected in the `matchdict` attribute of the `request`. It will exist there as a key-value pair, where the key will be the variable (e.g., "username") and the value will be whatever value was specified in the route (e.g., "bobdobson"). Regardless of what value is passed in through the route URL, it'll always show up as a string in the `matchdict`. So, when you want to pull the username from the incoming request URL, access it with `request.matchdict['username']` + +``` +user = request.dbsession.query(User).filter_by(username=request.matchdict['username']).first() +``` + +Querying for objects when using `sqlalchemy` directly differs significantly from what the `flask-sqlalchemy` package allows. Recall that when you used `flask-sqlalchemy` to build your models, the models inherited from the `db.Model` object. That `db` object already contained a connection to the database, so that connection could perform a straightforward operation like `User.query.all()`. + +That simple interface isn't present here, as the models in the Pyramid app inherit from `Base`, which is generated from `declarative_base()`, coming directly from the `sqlalchemy` package. It has no direct awareness of the database it'll be accessing. That awareness was attached to the `request` object via the app's central configuration as the `dbsession` attribute. Here's the code from above that did that: + +``` +config.add_request_method( + lambda request: get_tm_session(session_factory, request.tm), + 'dbsession', + reify=True +) +``` + +With all that said, whenever you want to query OR modify the database, you must work through `request.dbsession`. In the case, you want to query your "users" table for a specific user by using their username as their identifier. As such, the `User` object is provided as an argument to the `.query` method, then the normal SQLAlchemy operations are done from there. + +An interesting thing about this way of querying the database is that you can query for more than just one object or list of one type of object. You can query for: + + * Object attributes on their own, e.g., `request.dbsession.query(User.username)` would query for usernames + * Tuples of object attributes, e.g., `request.dbsession.query(User.username, User.date_joined)` + * Tuples of multiple objects, e.g., `request.dbsession.query(User, Task)` + + + +The data sent along with the incoming request will be found within the `request.json` dictionary. + +The last major difference is, because of all the machinations necessary to attach the committing of a session's activity to Pyramid's request-response cycle, you don't have to call `request.dbsession.commit()` at the end of your view. It's convenient, but there is one thing to be aware of moving forward. If instead of a new add to the database, you wanted to edit a pre-existing object in the database, you couldn't use `request.dbsession.commit()`. Pyramid will throw an error, saying something along the lines of "commit behavior is being handled by the transaction manager, so you can't call it on your own." And if you don't do something that resembles committing your changes, your changes won't stick. + +The solution here is to use `request.dbsession.flush()`. The job of `.flush()` is to signal to the database that some changes have been made and need to be included with the next commit. + +### Planning for the future + +At this point, you've set up most of the important parts of Pyramid, analogous to what you constructed with Flask in part one. There's much more that goes into an application, but much of the meat is handled here. Other view functions will follow similar formatting, and of course, there's always the question of security (which Pyramid has built in!). + +One of the major differences I see in the setup of a Pyramid application is that it has a much more intense configuration step than there is with Flask. I broke down those configuration steps to explain more about what's going on when a Pyramid application is constructed. However, it'd be disingenuous to act like I've known all of this since I started programming. My first experience with the Pyramid framework was with Pyramid 1.7 and its scaffolding system of `pcreate`, which builds out most of the necessary configuration, so all you need to do is think about the functionality you want to build. + +As of Pyramid 1.8, `pcreate` has been deprecated in favor of [cookiecutter][9], which effectively does the same thing. The difference is that it's maintained by someone else, and there are cookiecutter templates for more than just Pyramid projects. Now that we've gone through the components of a Pyramid project, I'd never endorse building a Pyramid project from scratch again when a cookiecutter template is available. Why do the hard work if you don't have to? In fact, the [pyramid-cookiecutter-alchemy][10] template would accomplish much of what I've written here (and a little bit more). It's actually similar to the `pcreate` scaffold I used when I first learned Pyramid. + +Learn more Python at [PyCon Cleveland 2018][11]. + +-------------------------------------------------------------------------------- + +via: https://opensource.com/article/18/5/pyramid-framework + +作者：[Nicholas Hunt-Walker][a] +选题：[lujun9972][b] +译者：[译者ID](https://github.com/译者ID) +校对：[校对者ID](https://github.com/校对者ID) + +本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 + +[a]: https://opensource.com/users/nhuntwalker +[b]: https://github.com/lujun9972 +[1]: https://opensource.com/article/18/4/flask +[2]: http://flask.pocoo.org/ +[3]: https://trypyramid.com/ +[4]: http://www.tornadoweb.org/en/stable/ +[5]: https://www.djangoproject.com/ +[6]: https://www.sqlalchemy.org/ +[7]: http://docs.sqlalchemy.org/en/latest/orm/extensions/declarative/api.html#api-reference +[8]: http://zodb.readthedocs.io/en/latest/transactions.html +[9]: https://cookiecutter.readthedocs.io/en/latest/ +[10]: https://github.com/Pylons/pyramid-cookiecutter-alchemy +[11]: https://us.pycon.org/2018/ diff --git a/sources/tech/20180518 How to Manage Fonts in Linux.md b/sources/tech/20180518 How to Manage Fonts in Linux.md deleted file mode 100644 index 0faca7fa17..0000000000 --- a/sources/tech/20180518 How to Manage Fonts in Linux.md +++ /dev/null @@ -1,145 +0,0 @@ -How to Manage Fonts in Linux -====== - - - -Not only do I write technical documentation, I write novels. And because I’m comfortable with tools like GIMP, I also create my own book covers (and do graphic design for a few clients). That artistic endeavor depends upon a lot of pieces falling into place, including fonts. - -Although font rendering has come a long way over the past few years, it continues to be an issue in Linux. If you compare the look of the same fonts on Linux vs. macOS, the difference is stark. This is especially true when you’re staring at a screen all day. But even though the rendering of fonts has yet to find perfection in Linux, one thing that the open source platform does well is allow users to easily manage their fonts. From selecting, adding, scaling, and adjusting, you can work with fonts fairly easily in Linux. - -Here, I’ll share some of the tips I’ve depended on over the years to help extend my “font-ability” in Linux. These tips will especially help those who undertake artistic endeavors on the open source platform. Because there are so many desktop interfaces available for Linux (each of which deal with fonts in a different way), when a desktop environment becomes central to the management of fonts, I’ll be focusing primarily on GNOME and KDE. - -With that said, let’s get to work. - -### Adding new fonts - -For the longest time, I have been a collector of fonts. Some might say I have a bit of an obsession. And since my early days of using Linux, I’ve always used the same process for adding fonts to my desktops. There are two ways to do this: - - * Make the fonts available on a per-user basis. - - * Make the fonts available system-wide. - - - - -Because my desktops never have other users (besides myself), I only ever work with fonts on a per-user basis. However, I will show you how to do both. First, let’s see how to add fonts on a per-user basis. The first thing you must do is find fonts. Both True Type Fonts (TTF) and Open Type Fonts (OTF) can be added. I add fonts manually. Do this is, I create a new hidden directory in ~/ called ~/.fonts. This can be done with the command: -``` -mkdir ~/.fonts - -``` - -With that folder created, I then move all of my TTF and OTF files into the directory. That’s it. Every font you add into that directory will now be available for use to your installed apps. But remember, those fonts will only be available to that one user. - -If you want to make that collection of fonts available to all, here’s what you do: - - 1. Open up a terminal window. - - 2. Change into the directory housing all of your fonts. - - 3. Copy all of those fonts with the commands sudo cp *.ttf *.TTF /usr/share/fonts/truetype/ and sudo cp *.otf *.OTF /usr/share/fonts/opentype - - - - -The next time a user logs in, they’ll have access to all those glorious fonts. - -### GUI Font Managers - -There are a few ways to manage your fonts in Linux, via GUI. How it’s done will depend on your desktop environment. Let’s examine KDE first. With the KDE that ships with Kubuntu 18.04, you’ll find a Font Management tool pre-installed. Open that tool and you can easily add, remove, enable, and disable fonts (as well as get information about all of the installed fonts. This tool also makes it easy for you to add and remove fonts for personal and system-wide use. Let’s say you want to add a particular font for personal usage. To do this, download your font and then open up the Font Management tool. In this tool (Figure 1), click on Personal Fonts and then click the + Add button. - - -![adding fonts][2] - -Figure 1: Adding personal fonts in KDE. - -[Used with permission][3] - -Navigate to the location of your fonts, select them, and click Open. Your fonts will then be added to the Personal section and are immediately available for you to use (Figure 2). - - -![KDE Font Manager][5] - -Figure 2: Fonts added with the KDE Font Manager. - -[Used with permission][3] - -To do the same thing in GNOME requires the installation of an application. Open up either GNOME Software or Ubuntu Software (depending upon the distribution you’re using) and search for Font Manager. Select Font Manager and then click the Install button. Once the software is installed, launch it from the desktop menu. With the tool open, let’s install fonts on a per-user basis. Here’s how: - - 1. Select User from the left pane (Figure 3). - - 2. Click the + button at the top of the window. - - 3. Navigate to and select the downloaded fonts. - - 4. Click Open. - - - - -![Adding fonts ][7] - -Figure 3: Adding fonts in GNOME. - -[Used with permission][3] - -### Tweaking fonts - -There are three concepts you must first understand: - - * **Font Hinting:** The use of mathematical instructions to adjust the display of a font outline so that it lines up with a rasterized grid. - - * **Anti-aliasing:** The technique used to add greater realism to a digital image by smoothing jagged edges on curved lines and diagonals. - - * **Scaling factor:** **** A scalable unit that allows you to multiple the point size of a font. So if you’re font is 12pt and you have an scaling factor of 1, the font size will be 12pt. If your scaling factor is 2, the font size will be 24pt. - - - - -Let’s say you’ve installed your fonts, but they don’t look quite as good as you’d like. How do you tweak the appearance of fonts? In both the KDE and GNOME desktops, you can make a few adjustments. One thing to consider with the tweaking of fonts is that taste is very much subjective. You might find yourself having to continually tweak until you get the fonts looking exactly how you like (dictated by your needs and particular taste). Let’s first look at KDE. - -Open up the System Settings tool and clock on Fonts. In this section, you can not only change various fonts, you can also enable and configure both anti-aliasing and enable font scaling factor (Figure 4). - - -![Configuring fonts][9] - -Figure 4: Configuring fonts in KDE. - -[Used with permission][3] - -To configure anti-aliasing, select Enabled from the drop-down and then click Configure. In the resulting window (Figure 5), you can configure an exclude range, sub-pixel rendering type, and hinting style. - -Once you’ve made your changes, click Apply. Restart any running applications and the new settings will take effect. - -To do this in GNOME, you have to have either use Font Manager or GNOME Tweaks installed. For this, GNOME Tweaks is the better tool. If you open the GNOME Dash and cannot find Tweaks installed, open GNOME Software (or Ubuntu Software), and install GNOME Tweaks. Once installed, open it and click on the Fonts section. Here you can configure hinting, anti-aliasing, and scaling factor (Figure 6). - -![Tweaking fonts][11] - -Figure 6: Tweaking fonts in GNOME. - -[Used with permission][3] - -### Make your fonts beautiful - -And that’s the gist of making your fonts look as beautiful as possible in Linux. You may not see a macOS-like rendering of fonts, but you can certainly improve the look. Finally, the fonts you choose will have a large impact on how things look. Make sure you’re installing clean, well-designed fonts; otherwise, you’re fighting a losing battle. - -Learn more about Linux through the free ["Introduction to Linux" ][12] course from The Linux Foundation and edX. - --------------------------------------------------------------------------------- - -via: https://www.linux.com/learn/intro-to-linux/2018/5/how-manage-fonts-linux - -作者：[Jack Wallen][a] -选题：[lujun9972](https://github.com/lujun9972) -译者：[译者ID](https://github.com/译者ID) -校对：[校对者ID](https://github.com/校对者ID) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 - -[a]:https://www.linux.com/users/jlwallen -[2]:https://www.linux.com/sites/lcom/files/styles/rendered_file/public/fonts_1.jpg?itok=7yTTe6o3 (adding fonts) -[3]:https://www.linux.com/licenses/category/used-permission -[5]:https://www.linux.com/sites/lcom/files/styles/rendered_file/public/fonts_2.jpg?itok=_g0dyVYq (KDE Font Manager) -[7]:https://www.linux.com/sites/lcom/files/styles/rendered_file/public/fonts_3.jpg?itok=8o884QKs (Adding fonts ) -[9]:https://www.linux.com/sites/lcom/files/styles/rendered_file/public/fonts_4.jpg?itok=QJpPzFED (Configuring fonts) -[11]:https://www.linux.com/sites/lcom/files/styles/rendered_file/public/fonts_6.jpg?itok=4cQeIW9C (Tweaking fonts) -[12]:https://training.linuxfoundation.org/linux-courses/system-administration-training/introduction-to-linux diff --git a/sources/tech/20180518 What-s a hero without a villain- How to add one to your Python game.md b/sources/tech/20180518 What-s a hero without a villain- How to add one to your Python game.md deleted file mode 100644 index 3ca8fba288..0000000000 --- a/sources/tech/20180518 What-s a hero without a villain- How to add one to your Python game.md +++ /dev/null @@ -1,275 +0,0 @@ -What's a hero without a villain? How to add one to your Python game -====== - - -In the previous articles in this series (see [part 1][1], [part 2][2], [part 3][3], and [part 4][4]), you learned how to use Pygame and Python to spawn a playable character in an as-yet empty video game world. But, what's a hero without a villain? - -It would make for a pretty boring game if you had no enemies, so in this article, you'll add an enemy to your game and construct a framework for building levels. - -It might seem strange to jump ahead to enemies when there's still more to be done to make the player sprite fully functional, but you've learned a lot already, and creating villains is very similar to creating a player sprite. So relax, use the knowledge you already have, and see what it takes to stir up some trouble. - -For this exercise, you can download some pre-built assets from [Open Game Art][5]. Here are some of the assets I use: - - -+ Inca tileset -+ Some invaders -+ Sprites, characters, objects, and effects - - -### Creating the enemy sprite - -Yes, whether you realize it or not, you basically already know how to implement enemies. The process is very similar to creating a player sprite: - - 1. Make a class so enemies can spawn. - 2. Create an `update` function so enemies can detect collisions. - 3. Create a `move` function so your enemy can roam around. - - - -Start with the class. Conceptually, it's mostly the same as your Player class. You set an image or series of images, and you set the sprite's starting position. - -Before continuing, make sure you have a graphic for your enemy, even if it's just a temporary one. Place the graphic in your game project's `images` directory (the same directory where you placed your player image). - -A game looks a lot better if everything alive is animated. Animating an enemy sprite is done the same way as animating a player sprite. For now, though, keep it simple, and use a non-animated sprite. - -At the top of the `objects` section of your code, create a class called Enemy with this code: -``` -class Enemy(pygame.sprite.Sprite): - - ''' - - Spawn an enemy - - ''' - - def __init__(self,x,y,img): - - pygame.sprite.Sprite.__init__(self) - - self.image = pygame.image.load(os.path.join('images',img)) - - self.image.convert_alpha() - - self.image.set_colorkey(ALPHA) - - self.rect = self.image.get_rect() - - self.rect.x = x - - self.rect.y = y - -``` - -If you want to animate your enemy, do it the [same way][4] you animated your player. - -### Spawning an enemy - -You can make the class useful for spawning more than just one enemy by allowing yourself to tell the class which image to use for the sprite and where in the world the sprite should appear. This means you can use this same enemy class to generate any number of enemy sprites anywhere in the game world. All you have to do is make a call to the class, and tell it which image to use and the X and Y coordinates of your desired spawn point. - -Again, this is similar in principle to spawning a player sprite. In the `setup` section of your script, add this code: -``` -enemy = Enemy(20,200,'yeti.png')# spawn enemy - -enemy_list = pygame.sprite.Group() # create enemy group - -enemy_list.add(enemy) # add enemy to group - -``` - -In that sample code, `20` is the X position and `200` is the Y position. You might need to adjust these numbers, depending on how big your enemy sprite is, but try to get it to spawn in a place so that you can reach it with your player sprite. `Yeti.png` is the image used for the enemy. - -Next, draw all enemies in the enemy group to the screen. Right now, you have only one enemy, but you can add more later if you want. As long as you add an enemy to the enemies group, it will be drawn to the screen during the main loop. The middle line is the new line you need to add: -``` - player_list.draw(world) - - enemy_list.draw(world) # refresh enemies - - pygame.display.flip() - -``` - -Launch your game. Your enemy appears in the game world at whatever X and Y coordinate you chose. - -### Level one - -Your game is in its infancy, but you will probably want to add another level. It's important to plan ahead when you program so your game can grow as you learn more about programming. Even though you don't even have one complete level yet, you should code as if you plan on having many levels. - -Think about what a "level" is. How do you know you are at a certain level in a game? - -You can think of a level as a collection of items. In a platformer, such as the one you are building here, a level consists of a specific arrangement of platforms, placement of enemies and loot, and so on. You can build a class that builds a level around your player. Eventually, when you create more than one level, you can use this class to generate the next level when your player reaches a specific goal. - -Move the code you wrote to create an enemy and its group into a new function that will be called along with each new level. It requires some modification so that each time you create a new level, you can create several enemies: -``` -class Level(): - - def bad(lvl,eloc): - - if lvl == 1: - - enemy = Enemy(eloc[0],eloc[1],'yeti.png') # spawn enemy - - enemy_list = pygame.sprite.Group() # create enemy group - - enemy_list.add(enemy) # add enemy to group - - if lvl == 2: - - print("Level " + str(lvl) ) - - - - return enemy_list - -``` - -The `return` statement ensures that when you use the `Level.bad` function, you're left with an `enemy_list` containing each enemy you defined. - -Since you are creating enemies as part of each level now, your `setup` section needs to change, too. Instead of creating an enemy, you must define where the enemy will spawn and what level it belongs to. -``` -eloc = [] - -eloc = [200,20] - -enemy_list = Level.bad( 1, eloc ) - -``` - -Run the game again to confirm your level is generating correctly. You should see your player, as usual, and the enemy you added in this chapter. - -### Hitting the enemy - -An enemy isn't much of an enemy if it has no effect on the player. It's common for enemies to cause damage when a player collides with them. - -Since you probably want to track the player's health, the collision check happens in the Player class rather than in the Enemy class. You can track the enemy's health, too, if you want. The logic and code are pretty much the same, but, for now, just track the player's health. - -To track player health, you must first establish a variable for the player's health. The first line in this code sample is for context, so add the second line to your Player class: -``` - self.frame = 0 - - self.health = 10 - -``` - -In the `update` function of your Player class, add this code block: -``` - hit_list = pygame.sprite.spritecollide(self, enemy_list, False) - - for enemy in hit_list: - - self.health -= 1 - - print(self.health) - -``` - -This code establishes a collision detector using the Pygame function `sprite.spritecollide`, called `enemy_hit`. This collision detector sends out a signal any time the hitbox of its parent sprite (the player sprite, where this detector has been created) touches the hitbox of any sprite in `enemy_list`. The `for` loop is triggered when such a signal is received and deducts a point from the player's health. - -Since this code appears in the `update` function of your player class and `update` is called in your main loop, Pygame checks for this collision once every clock tick. - -### Moving the enemy - -An enemy that stands still is useful if you want, for instance, spikes or traps that can harm your player, but the game is more of a challenge if the enemies move around a little. - -Unlike a player sprite, the enemy sprite is not controlled by the user. Its movements must be automated. - -Eventually, your game world will scroll, so how do you get an enemy to move back and forth within the game world when the game world itself is moving? - -You tell your enemy sprite to take, for example, 10 paces to the right, then 10 paces to the left. An enemy sprite can't count, so you have to create a variable to keep track of how many paces your enemy has moved and program your enemy to move either right or left depending on the value of your counting variable. - -First, create the counter variable in your Enemy class. Add the last line in this code sample: -``` - self.rect = self.image.get_rect() - - self.rect.x = x - - self.rect.y = y - - self.counter = 0 # counter variable - -``` - -Next, create a `move` function in your Enemy class. Use an if-else loop to create what is called an infinite loop: - - * Move right if the counter is on any number from 0 to 100. - * Move left if the counter is on any number from 100 to 200. - * Reset the counter back to 0 if the counter is greater than 200. - - - -An infinite loop has no end; it loops forever because nothing in the loop is ever untrue. The counter, in this case, is always either between 0 and 100 or 100 and 200, so the enemy sprite walks right to left and right to left forever. - -The actual numbers you use for how far the enemy will move in either direction depending on your screen size, and possibly, eventually, the size of the platform your enemy is walking on. Start small and work your way up as you get used to the results. Try this first: -``` - def move(self): - - ''' - - enemy movement - - ''' - - distance = 80 - - speed = 8 - - - - if self.counter >= 0 and self.counter <= distance: - - self.rect.x += speed - - elif self.counter >= distance and self.counter <= distance*2: - - self.rect.x -= speed - - else: - - self.counter = 0 - - - - self.counter += 1 - -``` - -You can adjust the distance and speed as needed. - -Will this code work if you launch your game now? - -Of course not, and you probably know why. You must call the `move` function in your main loop. The first line in this sample code is for context, so add the last two lines: -``` - enemy_list.draw(world) #refresh enemy - - for e in enemy_list: - - e.move() - -``` - -Launch your game and see what happens when you hit your enemy. You might have to adjust where the sprites spawn so that your player and your enemy sprite can collide. When they do collide, look in the console of [IDLE][6] or [Ninja-IDE][7] to see the health points being deducted. - - - -You may notice that health is deducted for every moment your player and enemy are touching. That's a problem, but it's a problem you'll solve later, after you've had more practice with Python. - -For now, try adding some more enemies. Remember to add each enemy to the `enemy_list`. As an exercise, see if you can think of how you can change how far different enemy sprites move. - --------------------------------------------------------------------------------- - -via: https://opensource.com/article/18/5/pygame-enemy - -作者：[Seth Kenlon][a] -选题：[lujun9972](https://github.com/lujun9972) -译者：[译者ID](https://github.com/译者ID) -校对：[校对者ID](https://github.com/校对者ID) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 - -[a]: https://opensource.com/users/seth -[1]:https://opensource.com/article/17/10/python-101 -[2]:https://opensource.com/article/17/12/game-framework-python -[3]:https://opensource.com/article/17/12/game-python-add-a-player -[4]:https://opensource.com/article/17/12/game-python-moving-player -[5]:https://opengameart.org -[6]:https://docs.python.org/3/library/idle.html -[7]:http://ninja-ide.org/ diff --git a/sources/tech/20180523 How to dual-boot Linux and Windows.md b/sources/tech/20180523 How to dual-boot Linux and Windows.md deleted file mode 100644 index 372097c866..0000000000 --- a/sources/tech/20180523 How to dual-boot Linux and Windows.md +++ /dev/null @@ -1,224 +0,0 @@ -translating by Auk7F7 -How to dual-boot Linux and Windows -====== - - - -Even though Linux is a great operating system with widespread hardware and software support, the reality is that sometimes you have to use Windows, perhaps due to key apps that won't run under Linux. Thankfully, dual-booting Windows and Linux is very straightforward—and I'll show you how to set it up, with Windows 10 and Ubuntu 18.04, in this article. - -Before you get started, make sure you've backed up your computer. Although the dual-boot setup process is not very involved, accidents can still happen. So take the time to back up your important files in case chaos theory comes into play. In addition to backing up your files, consider taking an image backup of the disk as well, though that's not required and can be a more advanced process. - -### Prerequisites - -To get started, you will need the following five items: - -#### 1\. Two USB flash drives (or DVD-Rs) - -I recommend installing Windows and Ubuntu via flash drives since they're faster than DVDs. It probably goes without saying, but creating bootable media erases everything on the flash drive. Therefore, make sure the flash drives are empty or contain data you don't care about losing. - -If your machine doesn't support booting from USB, you can create DVD media instead. Unfortunately, because no two computers seem to have the same DVD-burning software, I can't walk you through that process. However, if your DVD-burning application has an option to burn from an ISO image, that's the option you need. - -#### 2\. A Windows 10 license - -If Windows 10 came with your PC, the license will be built into the computer, so you don't need to worry about entering it during installation. If you bought the retail edition, you should have a product key, which you will need to enter during the installation process. - -#### 3\. Windows 10 Media Creation Tool - -Download and launch the Windows 10 [Media Creation Tool][1]. Once you launch the tool, it will walk you through the steps required to create the Windows media on a USB or DVD-R. Note: Even if you already have Windows 10 installed, it's a good idea to create bootable media anyway, just in case something goes wrong and you need to reinstall it. - -#### 4\. Ubuntu 18.04 installation media - -Download the [Ubuntu 18.04][2] ISO image. - -#### 5\. Etcher software (for making a bootable Ubuntu USB drive) - -For creating bootable media for any Linux distribution, I recommend [Etcher][3]. Etcher works on all three major operating systems (Linux, MacOS, and Windows) and is careful not to let you overwrite your current operating system partition. - -Once you have downloaded and launched Etcher, click Select image, and point it to the Ubuntu ISO you downloaded in step 4. Next, click Select drive to choose your flash drive, and click Flash! to start the process of turning a flash drive into an Ubuntu installer. (If you're using a DVD-R, use your computer's DVD-burning software instead.) - -### Install Windows and Ubuntu - -You should be ready to begin. At this point, you should have accomplished the following: - - * Backed up your important files - * Created Windows installation media - * Created Ubuntu installation media - - - -There are two ways of going about the installation. First, if you already have Windows 10 installed, you can have the Ubuntu installer resize the partition, and the installation will proceed in the empty space. Or, if you haven't installed Windows 10, install it on a smaller partition you can set up during the installation process. (I'll describe how to do that below.) The second way is preferred and less error-prone. There's a good chance you won't have any issues either way, but installing Windows manually and giving it a smaller partition, then installing Ubuntu, is the easiest way to go. - -If you already have Windows 10 on your computer, skip the following Windows installation instructions and proceed to Installing Ubuntu. - -#### Installing Windows - -Insert the Windows installation media you created into your computer and boot from it. How you do this depends on your computer, but most have a key you can press to initiate the boot menu. On a Dell PC for example, that key is F12. If the flash drive doesn't show up as an option, you may need to restart the computer. Sometimes it will show up only if you've inserted the media before turning on the computer. If you see a message like, "press any key to boot from the installation media," press a key. You should see the following screen. Select your language and keyboard style and click Next. - -![Windows setup][5] - -Click on Install now to start the Windows installer. - -On the next screen, it will ask for your product key. If you don't have one because Windows 10 came with your PC, select "I don't have a product key." It should automatically activate after the installation once it catches up with updates. If you do have a product key, type that in and click Next. - - -![Enter product key][7] - - -Select which version of Windows you want to install. If you have a retail copy, the label will tell you what version you have. Otherwise, it is typically located with the documentation that came with your computer. In most cases, it's going to be either Windows 10 Home or Windows 10 Pro. Most PCs that come with the Home edition have a label that simply reads "Windows 10," while Pro is clearly marked. - - -![Select Windows version][10] - - -Accept the license agreement by checking the box, then click Next. - - -![Accept license terms][12] - - -After accepting the agreement, you have two installation options available. Choose the second option, Custom: Install Windows only (advanced). - - -![Select type of Windows installation][14] - - -The next screen should show your current hard disk configuration. - - -![Hard drive configuration][16] - - -Your results will probably look different than mine. I have never used this hard disk before, so it's completely unallocated. You will probably see one or more partitions for your current operating system. Highlight each partition and remove it. - -At this point, your screen will show your entire disk as unallocated. To continue, create a new partition. - - -![Create a new partition][18] - - -Here you can see that I divided the drive in half (or close enough) by creating a partition of 81,920MB (which is close to half of 160GB). Give Windows at least 40GB, preferably 64GB or more. Leave the rest of the drive unallocated, as that's where you'll install Ubuntu later. - -Your results will look similar to this: - - -![Leaving a partition with unallocated space][20] - - -Confirm the partitioning looks good to you and click Next. Windows will begin installing. - - -![Installing Windows][22] - - -If your computer successfully boots into Windows, you're all set to move on to the next step. - -![Windows desktop][24] - - -#### Installing Ubuntu - -Whether it was already there or you worked through the steps above, at this point you should have Windows installed. Now use the Ubuntu installation media you created earlier to boot into Ubuntu. Go ahead and insert the media and boot your computer from it. Again, the exact sequence of keys to access the boot menu varies from one computer to another, so check your documentation if you're not sure. If all goes well, you see the following screen once the media finishes loading: - - -![Ubuntu installation welcome screen][26] - - -Here, you can select between Try Ubuntu or Install Ubuntu. Don't install just yet; instead, click Try Ubuntu. After it finishes loading, you should see the Ubuntu desktop. - - -![Ubuntu desktop][28] - -By clicking Try Ubuntu, you have opted to try out Ubuntu before you install it. Here, in Live mode, you can play around with Ubuntu and make sure everything works before you commit to the installation. Ubuntu works with most PC hardware, but it's always better to test it out beforehand. Make sure you can access the internet and get audio and video playback. Going to YouTube and playing a video is a good way of doing all of that at once. If you need to connect to a wireless network, click on the networking icon at the top-right of the screen. There, you can find a list of wireless networks and connect to yours. - -Once you're ready to go, double-click on the Install Ubuntu 18.04 LTS icon on the desktop to launch the installer. - -Choose the language you want to use for the installation process, then click Continue. - - -![Select language in Ubuntu][30] - - -Next, choose the keyboard layout. Once you've made your selection, click Continue. - - -![Select keyboard in Ubuntu][32] - -You have a few options on the screen below. One, you can choose a Normal or a Minimal installation. For most people, the Normal installation is ideal. Advanced users may want to do a Minimal install instead, which has fewer software applications installed by default. In addition, you can choose to download updates and whether or not to include third-party software and drivers. I recommend checking both of those boxes. When done, click Continue. - - -![Choose Ubuntu installation options][34] - -The next screen asks whether you want to erase the disk or set up a dual-boot. Since you're dual-booting, choose Install Ubuntu alongside Windows 10. Click Install Now. - - -![install Ubuntu alongside Windows][36] - - -The following screen may appear. If you installed Windows from scratch and left unallocated space on the disk, Ubuntu will automatically set itself up in the empty space, so you won't see this screen. If you already had Windows 10 installed and it's taking up the entire drive, this screen will appear and give you an option to select a disk at the top. If you have just one disk, you can choose how much space to steal from Windows and apply to Ubuntu. You can drag the vertical line in the middle left and right with your mouse to take space away from one and gives it to the other. Adjust this exactly the way you want it, then click Install Now. - - -![Allocate drive space][38] - - -You should see a confirmation screen indicating what Ubuntu plans on doing. If everything looks right, click Continue. - -Ubuntu is now installing in the background. You still have some configuration to do, though. While Ubuntu tries its best to figure out your location, you can click on the map to narrow it down to ensure your time zone and other things are set correctly. - -Next, fill in the user account information: your name, computer name, username, and password. Click Continue when you're done. - -There you have it! The installation is complete. Go ahead and reboot the PC. - -If all went according to plan, you should see a screen similar to this when your computer restarts. Choose Ubuntu or Windows 10; the other options are for troubleshooting, so I won't go into them. - -Try booting into both Ubuntu and Windows to test them out and make sure everything works as expected. If it does, you now have both Windows and Ubuntu installed on your computer. - --------------------------------------------------------------------------------- - -via: https://opensource.com/article/18/5/dual-boot-linux - -作者：[Jay LaCroix][a] -选题：[lujun9972](https://github.com/lujun9972) -译者：[译者ID](https://github.com/译者ID) -校对：[校对者ID](https://github.com/校对者ID) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 - -[a]:https://opensource.com/users/jlacroix -[1]:https://www.microsoft.com/en-us/software-download/windows10 -[2]:https://www.ubuntu.com/download/desktop -[3]:http://www.etcher.io -[4]:/file/397066 -[5]:https://opensource.com/sites/default/files/uploads/linux-dual-boot_01.png (Windows setup) -[6]:/file/397076 -[7]:https://opensource.com/sites/default/files/uploads/linux-dual-boot_03.png (Enter product key) -[8]:data:image/gif;base64,R0lGODlhAQABAPABAP///wAAACH5BAEKAAAALAAAAAABAAEAAAICRAEAOw== (Click and drag to move) -[9]:/file/397081 -[10]:https://opensource.com/sites/default/files/uploads/linux-dual-boot_04.png (Select Windows version) -[11]:/file/397086 -[12]:https://opensource.com/sites/default/files/uploads/linux-dual-boot_05.png (Accept license terms) -[13]:/file/397091 -[14]:https://opensource.com/sites/default/files/uploads/linux-dual-boot_06.png (Select type of Windows installation) -[15]:/file/397096 -[16]:https://opensource.com/sites/default/files/uploads/linux-dual-boot_07.png (Hard drive configuration) -[17]:/file/397101 -[18]:https://opensource.com/sites/default/files/uploads/linux-dual-boot_08.png (Create a new partition) -[19]:/file/397106 -[20]:https://opensource.com/sites/default/files/uploads/linux-dual-boot_09.png (Leaving a partition with unallocated space) -[21]:/file/397111 -[22]:https://opensource.com/sites/default/files/uploads/linux-dual-boot_10.png (Installing Windows) -[23]:/file/397116 -[24]:https://opensource.com/sites/default/files/uploads/linux-dual-boot_11.png (Windows desktop) -[25]:/file/397121 -[26]:https://opensource.com/sites/default/files/uploads/linux-dual-boot_12.png (Ubuntu installation welcome screen) -[27]:/file/397126 -[28]:https://opensource.com/sites/default/files/uploads/linux-dual-boot_13.png (Ubuntu desktop) -[29]:/file/397131 -[30]:https://opensource.com/sites/default/files/uploads/linux-dual-boot_15.png (Select language in Ubuntu) -[31]:/file/397136 -[32]:https://opensource.com/sites/default/files/uploads/linux-dual-boot_16.png (Select keyboard in Ubuntu) -[33]:/file/397141 -[34]:https://opensource.com/sites/default/files/uploads/linux-dual-boot_17.png (Choose Ubuntu installation options) -[35]:/file/397146 -[36]:https://opensource.com/sites/default/files/uploads/linux-dual-boot_18.png (Install Ubuntu alongside Windows) -[37]:/file/397151 -[38]:https://opensource.com/sites/default/files/uploads/linux-dual-boot_18b.png (Allocate drive space) diff --git a/sources/tech/20180525 How to Set Different Wallpaper for Each Monitor in Linux.md b/sources/tech/20180525 How to Set Different Wallpaper for Each Monitor in Linux.md deleted file mode 100644 index 386149400c..0000000000 --- a/sources/tech/20180525 How to Set Different Wallpaper for Each Monitor in Linux.md +++ /dev/null @@ -1,89 +0,0 @@ -How to Set Different Wallpaper for Each Monitor in Linux -====== -**Brief: If you want to display different wallpapers on multiple monitors on Ubuntu 18.04 or any other Linux distribution with GNOME, MATE or Budgie desktop environment, this nifty tool will help you achieve this.** - -Multi-monitor setup often leads to multiple issues on Linux but I am not going to discuss those issues in this article. I have rather a positive article on multiple monitor support on Linux. - -If you are using multiple monitor, perhaps you would like to setup a different wallpaper for each monitor. I am not sure about other Linux distributions and desktop environments, but Ubuntu with [GNOME desktop][1] doesn’t provide this functionality on its own. - -Fret not! In this quick tutorial, I’ll show you how to set a different wallpaper for each monitor on Linux distributions with GNOME desktop environment. - -### Setting up different wallpaper for each monitor on Ubuntu 18.04 and other Linux distributions - -![Different wallaper on each monitor in Ubuntu][2] - -I am going to use a nifty tool called [HydraPaper][3] for setting different backgrounds on different monitors. HydraPaper is a [GTK][4] based application to set different backgrounds for each monitor in [GNOME desktop environment][5]. - -It also supports on [MATE][6] and [Budgie][7] desktop environments. Which means Ubuntu MATE and [Ubuntu Budgie][8] users can also benefit from this application. - -#### Install HydraPaper on Linux using FlatPak - -HydraPaper can be installed easily using [FlatPak][9]. Ubuntu 18.04 already provides support for FlatPaks so all you need to do is to download the application file and double click on it to open it with the GNOME Software Center. - -You can refer to this article to learn [how to enable FlatPak support][10] on your distribution. Once you have the FlatPak support enabled, just download it from [FlatHub][11] and install it. - -[Download HydraPaper][12] - -#### Using HydraPaper for setting different background on different monitors - -Once installed, just look for HydraPaper in application menu and start the application. You’ll see images from your Pictures folder here because by default the application takes images from the Pictures folder of the user. - -You can add your own folder(s) where you keep your wallpapers. Do note that it doesn’t find images recursively. If you have nested folders, it will only show images from the top folder. - -![Setting up different wallpaper for each monitor on Linux][13] - -Using HydraPaper is absolutely simple. Just select the wallpapers for each monitor and click on the apply button at the top. You can easily identify external monitor(s) termed with HDMI. - -![Setting up different wallpaper for each monitor on Linux][14] - -You can also add selected wallpapers to ‘Favorites’ for quick access. Doing this will move the ‘favorite wallpapers’ from Wallpapers tab to Favorites tab. - -![Setting up different wallpaper for each monitor on Linux][15] - -You don’t need to start HydraPaper at each boot. Once you set different wallpaper for different monitor, the settings are saved and you’ll see your chosen wallpapers even after restart. This would be expected behavior of course but I thought I would mention the obvious. - -One big downside of HydraPaper is in the way it is designed to work. You see, HydraPaper combines your selected wallpapers into one single image and stretches it across the screens giving an impression of having different background on each display. And this becomes an issue when you remove the external display. - -For example, when I tried using my laptop without the external display, it showed me an background image like this. - -![Dual Monitor wallpaper HydraPaper][16] - -Quite obviously, this is not what I would expect. - -#### Did you like it? - -HydraPaper makes setting up different backgrounds on different monitors a painless task. It supports more than two monitors and monitors with different orientation. Simple interface with only the required features makes it an ideal application for those who always use dual monitors. - -How do you set different wallpaper for different monitor on Linux? Do you think HydraPaper is an application worth installing? - -Do share your views and if you find this article, please share it on various social media channels such as Twitter and [Reddit][17]. - --------------------------------------------------------------------------------- - -via: https://itsfoss.com/wallpaper-multi-monitor/ - -作者：[Abhishek Prakash][a] -选题：[lujun9972](https://github.com/lujun9972) -译者：[译者ID](https://github.com/译者ID) -校对：[校对者ID](https://github.com/校对者ID) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 - -[a]: https://itsfoss.com/author/abhishek/ -[1]:https://www.gnome.org/ -[2]:https://4bds6hergc-flywheel.netdna-ssl.com/wp-content/uploads/2018/05/multi-monitor-wallpaper-setup-800x450.jpeg -[3]:https://github.com/GabMus/HydraPaper -[4]:https://www.gtk.org/ -[5]:https://itsfoss.com/gnome-tricks-ubuntu/ -[6]:https://mate-desktop.org/ -[7]:https://budgie-desktop.org/home/ -[8]:https://itsfoss.com/ubuntu-budgie-18-review/ -[9]:https://flatpak.org -[10]:https://flatpak.org/setup/ -[11]:https://flathub.org -[12]:https://flathub.org/apps/details/org.gabmus.hydrapaper -[13]:https://4bds6hergc-flywheel.netdna-ssl.com/wp-content/uploads/2018/05/different-wallpaper-each-monitor-hydrapaper-2-800x631.jpeg -[14]:https://4bds6hergc-flywheel.netdna-ssl.com/wp-content/uploads/2018/05/different-wallpaper-each-monitor-hydrapaper-1.jpeg -[15]:https://4bds6hergc-flywheel.netdna-ssl.com/wp-content/uploads/2018/05/different-wallpaper-each-monitor-hydrapaper-3.jpeg -[16]:https://4bds6hergc-flywheel.netdna-ssl.com/wp-content/uploads/2018/05/hydra-paper-dual-monitor-800x450.jpeg -[17]:https://www.reddit.com/r/LinuxUsersGroup/ diff --git a/sources/tech/20180527 Streaming Australian TV Channels to a Raspberry Pi.md b/sources/tech/20180527 Streaming Australian TV Channels to a Raspberry Pi.md new file mode 100644 index 0000000000..ac756223f1 --- /dev/null +++ b/sources/tech/20180527 Streaming Australian TV Channels to a Raspberry Pi.md @@ -0,0 +1,209 @@ +[#]: collector: (lujun9972) +[#]: translator: ( ) +[#]: reviewer: ( ) +[#]: publisher: ( ) +[#]: url: ( ) +[#]: subject: (Streaming Australian TV Channels to a Raspberry Pi) +[#]: via: (https://blog.dxmtechsupport.com.au/streaming-australian-tv-channels-to-a-raspberry-pi/) +[#]: author: (James Mawson https://blog.dxmtechsupport.com.au/author/james-mawson/) + +Streaming Australian TV Channels to a Raspberry Pi +====== + +If you’re anything like me, it’s been years since you’ve even thought about hooking an antenna to your television. With so much of the good stuff available by streaming and download, it’s easy go a very long time without even thinking about free-to-air TV. + +But every now and again, something comes up – perhaps the cricket, news and current affairs shows, the FIFA World Cup – where the easiest thing would be to just chuck on the telly. + +When I first started tinkering with the Raspberry Pi as a gaming and media centre platform, the standard advice for watching broadcast TV always seemed to involve an antenna and a USB TV tuner. + +Which I guess is fine if you can be arsed. + +But what if you utterly can’t? + +What if you bitterly resent the idea of more clutter, more cords to add to the mess, more stuff to buy? What if every USB port is precious and jealously guarded for your keyboard, mouse, game controllers and removable storage? What if the wall port for your roof antenna is in a different room? + +That’s all a bit of a hassle for a thing you might use only a few times a year. + +In 2018, shouldn’t we just be able to stream free TV from the internet? + +It turns out that, yes, we can access legal and high quality TV streams from any Australian IP using [Freeview][1]. And thanks to a cool Kodi Add-on by [Matt Huisman][2], it’s now really easy to access this service from a Raspberry Pi. + +I’ve tested this to work on a Model 3 B+ running Retropie 4.4 and Kodi 17.6. But it should work similarly for other models and operating systems, so long as you’re using a reasonably up-to-date version of Kodi. + +Let’s jump right in. + +### If You Already Have Kodi Installed + +If you’re already using your Raspberry Pi to watch movies and TV shows, there’s a good chance you’ve already installed Kodi. + +Most Raspberry Pi operating systems intended for media centre use – such as OSMC or Xbian – come with Kodi installed by default. + +It’s fairly easy to get running on other Linux operating systems, and you might have already installed it there too. + +If your version of Kodi is more than a year or so old, it might be an idea to update it. The following instructions are written for the interface on Kodi 17 (Krypton). + +You can do that by typing the following commands at the command line: + +``` +sudo apt-get update +sudo apt-get upgrade +``` + +And now you can skip ahead to the next section. + +### Installing Kodi + +Installing Kodi on Retropie and other versions of Raspbian is fairly simple. Other Linux operating systems should be able to run it, perhaps with a bit of coaxing. + +You will need to be connected to the internet to install it. + +If you’re using something, such as Risc OS – you probably can’t install kodi. You will need to either swap in another SD card, or use a boot loader to boot into a media centre OS for your TV viewing. + +#### Installing Kodi on Retropie + +It’s really easy to install Kodi using the Retropie menu system. + +Here’s how: + + 1. Navigate to the Retropie main screen – that’s that horizontal menu where you can scroll left and right through all your different consoles + 2. Select “Retropie” + 3. Select “Retropie setup” + 4. Select “Manage Packages” + 5. Select “Manage Optional Packages” + 6. Scroll down and select “Kodi” + 7. Select “Install from Binary” + + + +This will take a minute or two to install. Once it’s installed, you can exit out of the Retropie Setup screen. When you next restart Retropie, you will see Kodi under the “Ports” section of the Retropie main screen. + +#### Installing Kodi on Raspbian + +If you’re running Raspbian without Retropie. But that’s okay, because it’s pretty easy to do it from the command line + +Just type: + +``` +sudo apt-get update +sudo apt-get install kodi +``` + +At this point you have a vanilla installation of Kodi. You can run it by typing: + +``` +kodi +``` + +It’s possible to delve a lot further into setting up Kodi from the command line. Check out [this guide][3] if you’re interested. + +If not, what you’ve just installed will work just fine. + +#### Installing Kodi on Other Versions of Linux + +If you’re using a different flavour of Linux, such as Pidora or Arch Linux ARM, then the above might or might not work – I’m not really sure, because I don’t really use these operating systems. + +If you get stuck, it might be worth a look at the [how-to guide][4] on the Kodi wiki. + +#### Dual Booting a Media Centre OS + +If your operating system of choice isn’t suitable for Kodi – or is just too confusing and difficult to figure out – it might be easiest to use a boot loader for multiple operating systems on the one SD card. + +You can set this up using an OS installer like [PINN][5]. + +Using PINN, you can install a media centre OS like [OSMC][6] to use Kodi – it will be installed with the operating system – and then your preferred OS for your other uses. + +It’s even possible to [move your existing OS over][7]. + +### Adding Australian TV Channels to Kodi + +With Kodi installed and running, you’ve got a pretty good media player for the files on your network and hard drive. + +But we need to install an add-on if we want to use it to chuck on the telly. This only takes a minute or so. + +#### Installing Matt Huisman’s Kodi Repository + +Ready? Let’s get started. + + 1. Open Kodi + 2. Click the cog icon at the top left to enter the settings + 3. Click “System Settings” + 4. Select “Add-ons” + 5. Make sure that “Unknown Sources” is enabled + 6. Right click anywhere on the screen to navigate back to the settings menu + 7. Click “File Manager” + 8. Click “Add Source” + 9. Double-click “Add Source” + 10. Select “ ” + 11. Type in exactly ** -a -G photos -sudo usermod guest -a -G photos - -``` - -You may have to log out and log back in to see the changes, but, when you do, running `groups` will show _photos_ as one of the groups you belong to. - -A couple of things to point out about the `usermod` command shown above. First: Be careful not to use the `-g` option instead of `-G`. The `-g` option changes your primary group and could lock you out of your stuff if you use it by accident. `-G`, on the other hand, _adds_ you to the groups listed and doesn't mess with the primary group. If you want to add your user to more groups than one, list them one after another, separated by commas, no spaces, after `-G`: -``` -sudo usermod -a -G photos,pizza,spaceforce - -``` - -Second: Be careful not to forget the `-a` parameter. The `-a` parameter stands for _append_ and attaches the list of groups you pass to `-G` to the ones you already belong to. This means that, if you don't include `-a`, the list of groups you already belong to, will be overwritten, again locking you out from stuff you need. - -Neither of these are catastrophic problems, but it will mean you will have to add your user back manually to all the groups you belonged to, which can be a pain, especially if you have lost access to the _sudo_ and _wheel_ group. - -### Permits, Please! - -There is still one more thing to do before you can copy images to the _/photos_ directory. Notice how, when you did `ls -l /` above, permissions for that folder came back as _drwxr-xr-x_. - -If you read [the article I recommended at the beginning of this post][3], you'll know that the first _d_ indicates that the entry in the file system is a directory, and then you have three sets of three characters ( _rwx_ , _r-x_ , _r-x_ ) that indicate the permissions for the user owner ( _rwx_ ) of the directory, then the group owner ( _r-x_ ), and finally the rest of the users ( _r-x_ ). This means that the only person who has write permissions so far, that is, the only person who can copy or create files in the _/photos_ directory, is the _root_ user. - -But [that article I mentioned also tells you how to change the permissions for a directory or file][3]: -``` -sudo chmod g+w /photos - -``` - -Running `ls -l /` after that will give you _/photos_ permissions as _drwxrwxr-x_ which is what you want: group members can now write into the directory. - -Now you can try and copy an image or, indeed, any other file to the directory and it should go through without a problem: -``` -cp image.jpg /photos - -``` - -The _guest_ user will also be able to read and write from the directory. They will also be able to read and write to it, and even move or delete files created by other users within the shared directory. - -### Conclusion - -The permissions and privileges system in Linux has been honed over decades. inherited as it is from the old Unix systems of yore. As such, it works very well and is well thought out. Becoming familiar with it is essential for any Linux sysadmin. In fact, you can't do much admining at all unless you understand it. But, it's not that hard. - -Next time, we'll be dive into files and see the different ways of creating, manipulating, and destroying them in creative ways. Always fun, that last one. - -See you then! - -Learn more about Linux through the free ["Introduction to Linux" ][4]course from The Linux Foundation and edX. - --------------------------------------------------------------------------------- - -via: https://www.linux.com/blog/learn/intro-to-linux/2018/7/users-groups-and-other-linux-beasts-part-2 - -作者：[Paul Brown][a] -选题：[lujun9972](https://github.com/lujun9972) -译者：[译者ID](https://github.com/译者ID) -校对：[校对者ID](https://github.com/校对者ID) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 - -[a]:https://www.linux.com/users/bro66 -[1]:https://www.linux.com/blog/learn/2018/5/manipulating-directories-linux -[2]:https://www.linux.com/learn/intro-to-linux/2018/7/users-groups-and-other-linux-beasts -[3]:https://www.linux.com/learn/understanding-linux-file-permissions -[4]:https://training.linuxfoundation.org/linux-courses/system-administration-training/introduction-to-linux diff --git a/sources/tech/20180719 Building tiny container images.md b/sources/tech/20180719 Building tiny container images.md deleted file mode 100644 index bdaef5f08c..0000000000 --- a/sources/tech/20180719 Building tiny container images.md +++ /dev/null @@ -1,362 +0,0 @@ -Building tiny container images -====== - - - -When [Docker][1] exploded onto the scene a few years ago, it brought containers and container images to the masses. Although Linux containers existed before then, Docker made it easy to get started with a user-friendly command-line interface and an easy-to-understand way to build images using the Dockerfile format. But while it may be easy to jump in, there are still some nuances and tricks to building container images that are usable, even powerful, but still small in size. - -### First pass: Clean up after yourself - -Some of these examples involve the same kind of cleanup you would use with a traditional server, but more rigorously followed. Smaller image sizes are critical for quickly moving images around, and storing multiple copies of unnecessary data on disk is a waste of resources. Consequently, these techniques should be used more regularly than on a server with lots of dedicated storage. - -An example of this kind of cleanup is removing cached files from an image to recover space. Consider the difference in size between a base image with [Nginx][2] installed by `dnf` with and without the metadata and yum cache cleaned up: -``` -# Dockerfile with cache - -FROM fedora:28 - -LABEL maintainer Chris Collins - -ExecStart= /usr/bin/minetest --server -ExecStop= /bin/kill -2 $MAINPID - -[Install] -WantedBy= multi-user.targe - -``` - -The `Conflicts=` directive shown above makes sure _minetest.timer_ is stopped as soon as the _minetest.service_ is successfully started. - -Now enable and start _minetest.timer_ : -``` -systemctl enable minetest.timer -systemctl start minetest.timer - -``` - -And, if you boot the server at, say, 6 o'clock, _minetest.timer_ will start up and, as the time falls between 5 and 7, _minetest.timer_ will try and start _minetest.service_ every minute. But, as soon as _minetest.service_ is running, systemd will stop _minetest.timer_ because it "conflicts" with _minetest.service_ , thus avoiding the timer from trying to start the service over and over when it is already running. - -It is a bit counterintuitive that you use the service to kill the timer that started it up in the first place, but it works. - -### Conclusion - -You probably think that there are better ways of doing all of the above. I have heard the term "overengineered" in regard to these articles, especially when using systemd timers instead of cron. - -But, the purpose of this series of articles is not to provide the best solution to any particular problem. The aim is to show solutions that use systemd units as much as possible, even to a ridiculous length. The aim is to showcase plenty of examples of how the different types of units and the directives they contain can be leveraged. It is up to you, the reader, to find the real practical applications for all of this. - -Be that as it may, there is still one more thing to go: next time, we'll be looking at _sockets_ and _targets_ , and then we'll be done with systemd units. - -Learn more about Linux through the free ["Introduction to Linux" ][5]course from The Linux Foundation and edX. - --------------------------------------------------------------------------------- - -via: https://www.linux.com/blog/intro-to-linux/2018/8/systemd-timers-two-use-cases-0 - -作者：[Paul Brown][a] -选题：[lujun9972](https://github.com/lujun9972) -译者：[译者ID](https://github.com/译者ID) -校对：[校对者ID](https://github.com/校对者ID) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 - -[a]:https://www.linux.com/users/bro66 -[1]:https://www.linux.com/blog/learn/intro-to-linux/2018/7/setting-timer-systemd-linux -[2]:https://popcon.debian.org/ -[3]:https://www.linux.com/blog/intro-to-linux/2018/6/systemd-services-reacting-change -[4]:https://www.linux.com/blog/learn/intro-to-linux/2018/6/systemd-services-monitoring-files-and-directories -[5]:https://training.linuxfoundation.org/linux-courses/system-administration-training/introduction-to-linux diff --git a/sources/tech/20180807 5 reasons the i3 window manager makes Linux better.md b/sources/tech/20180807 5 reasons the i3 window manager makes Linux better.md deleted file mode 100644 index 8ad6a4ac7d..0000000000 --- a/sources/tech/20180807 5 reasons the i3 window manager makes Linux better.md +++ /dev/null @@ -1,111 +0,0 @@ -5 reasons the i3 window manager makes Linux better -====== - - - -One of the nicest things about Linux (and open source software in general) is the freedom to choose among different alternatives to address our needs. - -I've been using Linux for a long time, but I was never entirely happy with the desktop environment options available. Until last year, [Xfce][1] was the closest to what I consider a good compromise between features and performance. Then I found [i3][2], an amazing piece of software that changed my life. - -I3 is a tiling window manager. The goal of a window manager is to control the appearance and placement of windows in a windowing system. Window managers are often used as part a full-featured desktop environment (such as GNOME or Xfce), but some can also be used as standalone applications. - -A tiling window manager automatically arranges the windows to occupy the whole screen in a non-overlapping way. Other popular tiling window managers include [wmii][3] and [xmonad][4]. - -![i3 tiled window manager screenshot][6] - -Screenshot of i3 with three tiled windows - -Following are the top five reasons I use the i3 window manager and recommend it for a better Linux desktop experience. - -### 1\. Minimalism - -I3 is fast. It is neither bloated nor fancy. It is designed to be simple and efficient. As a developer, I value these features, as I can use the extra capacity to power my favorite development tools or test stuff locally using containers or virtual machines. - -In addition, i3 is a window manager and, unlike full-featured desktop environments, it does not dictate the applications you should use. Do you want to use Thunar from Xfce as your file manager? GNOME's gedit to edit text? I3 does not care. Pick the tools that make the most sense for your workflow, and i3 will manage them all in the same way. - -### 2\. Screen real estate - -As a tiling window manager, i3 will automatically "tile" or position the windows in a non-overlapping way, similar to laying tiles on a wall. Since you don't need to worry about window positioning, i3 generally makes better use of your screen real estate. It also allows you to get to what you need faster. - -There are many useful cases for this. For example, system administrators can open several terminals to monitor or work on different remote systems simultaneously; and developers can use their favorite IDE or editor and a few terminals to test their programs. - -In addition, i3 is flexible. If you need more space for a particular window, enable full-screen mode or switch to a different layout, such as stacked or tabbed. - -### 3\. Keyboard-driven workflow - -I3 makes extensive use of keyboard shortcuts to control different aspects of your environment. These include opening the terminal and other programs, resizing and positioning windows, changing layouts, and even exiting i3. When you start using i3, you need to memorize a few of those shortcuts to get around and, with time, you'll use more of them. - -The main benefit is that you don't often need to switch contexts from the keyboard to the mouse. With practice, it means you'll improve the speed and efficiency of your workflow. - -For example, to open a new terminal, press ` + `. Since the windows are automatically positioned, you can start typing your commands right away. Combine that with a nice terminal-driven text editor (e.g., Vim) and a keyboard-focused browser for a fully keyboard-driven workflow. - -In i3, you can define shortcuts for everything. Here are some examples: - - * Open terminal - * Open browser - * Change layouts - * Resize windows - * Control music player - * Switch workspaces - - - -Now that I am used to this workflow, I can't see myself going back to a regular desktop environment. - -### 4\. Flexibility - -I3 strives to be minimal and use few system resources, but that does not mean it can't be pretty. I3 is flexible and can be customized in several ways to improve the visual experience. Because i3 is a window manager, it doesn't provide tools to enable customizations; you need external tools for that. Some examples: - - * Use `feh` to define a background picture for your desktop. - * Use a compositor manager such as `compton` to enable effects like window fading and transparency. - * Use `dmenu` or `rofi` to enable customizable menus that can be launched from a keyboard shortcut. - * Use `dunst` for desktop notifications. - - - -I3 is fully configurable, and you can control every aspect of it by updating the default configuration file. From changing all keyboard shortcuts, to redefining the name of the workspaces, to modifying the status bar, you can make i3 behave in any way that makes the most sense for your needs. - -![i3 with rofi menu and dunst desktop notifications][8] - -i3 with `rofi` menu and `dunst` desktop notifications - -Finally, for more advanced users, i3 provides a full interprocess communication ([IPC][9]) interface that allows you to use your favorite language to develop scripts or programs for even more customization options. - -### 5\. Workspaces - -In i3, a workspace is an easy way to group windows. You can group them in different ways according to your workflow. For example, you can put the browser on one workspace, the terminal on another, an email client on a third, etc. You can even change i3's configuration to always assign specific applications to their own workspaces. - -Switching workspaces is quick and easy. As usual in i3, do it with a keyboard shortcut. Press ` +num` to switch to workspace `num`. If you get into the habit of always assigning applications/groups of windows to the same workspace, you can quickly switch between them, which makes workspaces a very useful feature. - -In addition, you can use workspaces to control multi-monitor setups, where each monitor gets an initial workspace. If you switch to that workspace, you switch to that monitor—without moving your hand off the keyboard. - -Finally, there is another, special type of workspace in i3: the scratchpad. It is an invisible workspace that shows up in the middle of the other workspaces by pressing a shortcut. This is a convenient way to access windows or programs that you frequently use, such as an email client or your music player. - -### Give it a try - -If you value simplicity and efficiency and are not afraid of working with the keyboard, i3 is the window manager for you. Some say it is for advanced users, but that is not necessarily the case. You need to learn a few basic shortcuts to get around at the beginning, but they'll soon feel natural and you'll start using them without thinking. - -This article just scratches the surface of what i3 can do. For more details, consult [i3's documentation][10]. - --------------------------------------------------------------------------------- - -via: https://opensource.com/article/18/8/i3-tiling-window-manager - -作者：[Ricardo Gerardi][a] -选题：[lujun9972](https://github.com/lujun9972) -译者：[译者ID](https://github.com/译者ID) -校对：[校对者ID](https://github.com/校对者ID) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 - -[a]:https://opensource.com/users/rgerardi -[1]:https://xfce.org/ -[2]:https://i3wm.org/ -[3]:https://code.google.com/archive/p/wmii/ -[4]:https://xmonad.org/ -[5]:/file/406476 -[6]:https://opensource.com/sites/default/files/uploads/i3_screenshot.png (i3 tiled window manager screenshot) -[7]:/file/405161 -[8]:https://opensource.com/sites/default/files/uploads/rofi_dunst.png (i3 with rofi menu and dunst desktop notifications) -[9]:https://i3wm.org/docs/ipc.html -[10]:https://i3wm.org/docs/userguide.html diff --git a/sources/tech/20180809 Perform robust unit tests with PyHamcrest.md b/sources/tech/20180809 Perform robust unit tests with PyHamcrest.md deleted file mode 100644 index 1c7d7e9226..0000000000 --- a/sources/tech/20180809 Perform robust unit tests with PyHamcrest.md +++ /dev/null @@ -1,176 +0,0 @@ -Perform robust unit tests with PyHamcrest -====== - - - -At the base of the [testing pyramid][1] are unit tests. Unit tests test one unit of code at a time—usually one function or method. - -Often, a single unit test is designed to test one particular flow through a function, or a specific branch choice. This enables easy mapping of a unit test that fails and the bug that made it fail. - -Ideally, unit tests use few or no external resources, isolating them and making them faster. - -_Good_ tests increase developer productivity by catching bugs early and making testing faster. _Bad_ tests decrease developer productivity. - -Unit test suites help maintain high-quality products by signaling problems early in the development process. An effective unit test catches bugs before the code has left the developer machine, or at least in a continuous integration environment on a dedicated branch. This marks the difference between good and bad unit tests:tests increase developer productivity by catching bugs early and making testing faster.tests decrease developer productivity. - -Productivity usually decreases when testing _incidental features_. The test fails when the code changes, even if it is still correct. This happens because the output is different, but in a way that is not part of the function's contract. - -A good unit test, therefore, is one that helps enforce the contract to which the function is committed. - -If a unit test breaks, the contract is violated and should be either explicitly amended (by changing the documentation and tests), or fixed (by fixing the code and leaving the tests as is). - -While limiting tests to enforce only the public contract is a complicated skill to learn, there are tools that can help. - -One of these tools is [Hamcrest][2], a framework for writing assertions. Originally invented for Java-based unit tests, today the Hamcrest framework supports several languages, including [Python][3]. - -Hamcrest is designed to make test assertions easier to write and more precise. -``` -def add(a, b): - - return a + b - - - -from hamcrest import assert_that, equal_to - - - -def test_add(): - - assert_that(add(2, 2), equal_to(4)) - -``` - -This is a simple assertion, for simple functionality. What if we wanted to assert something more complicated? -``` -def test_set_removal(): - - my_set = {1, 2, 3, 4} - - my_set.remove(3) - - assert_that(my_set, contains_inanyorder([1, 2, 4])) - - assert_that(my_set, is_not(has_item(3))) - -``` - -Note that we can succinctly assert that the result has `1`, `2`, and `4` in any order since sets do not guarantee order. - -We also easily negate assertions with `is_not`. This helps us write _precise assertions_ , which allow us to limit ourselves to enforcing public contracts of functions. - -Sometimes, however, none of the built-in functionality is _precisely_ what we need. In those cases, Hamcrest allows us to write our own matchers. - -Imagine the following function: -``` -def scale_one(a, b): - - scale = random.randint(0, 5) - - pick = random.choice([a,b]) - - return scale * pick - -``` - -We can confidently assert that the result divides into at least one of the inputs evenly. - -A matcher inherits from `hamcrest.core.base_matcher.BaseMatcher`, and overrides two methods: -``` -class DivisibleBy(hamcrest.core.base_matcher.BaseMatcher): - - - - def __init__(self, factor): - - self.factor = factor - - - - def _matches(self, item): - - return (item % self.factor) == 0 - - - - def describe_to(self, description): - - description.append_text('number divisible by') - - description.append_text(repr(self.factor)) - -``` - -Writing high-quality `describe_to` methods is important, since this is part of the message that will show up if the test fails. -``` -def divisible_by(num): - - return DivisibleBy(num) - -``` - -By convention, we wrap matchers in a function. Sometimes this gives us a chance to further process the inputs, but in this case, no further processing is needed. -``` -def test_scale(): - - result = scale_one(3, 7) - - assert_that(result, - - any_of(divisible_by(3), - - divisible_by(7))) - -``` - -Note that we combined our `divisible_by` matcher with the built-in `any_of` matcher to ensure that we test only what the contract commits to. - -While editing this article, I heard a rumor that the name "Hamcrest" was chosen as an anagram for "matches". Hrm... -``` ->>> assert_that("matches", contains_inanyorder(*"hamcrest") - -Traceback (most recent call last): - - File " ", line 1, in - - File "/home/moshez/src/devops-python/build/devops/lib/python3.6/site-packages/hamcrest/core/assert_that.py", line 43, in assert_that - - _assert_match(actual=arg1, matcher=arg2, reason=arg3) - - File "/home/moshez/src/devops-python/build/devops/lib/python3.6/site-packages/hamcrest/core/assert_that.py", line 57, in _assert_match - - raise AssertionError(description) - -AssertionError: - -Expected: a sequence over ['h', 'a', 'm', 'c', 'r', 'e', 's', 't'] in any order - - but: no item matches: 'r' in ['m', 'a', 't', 'c', 'h', 'e', 's'] - -``` - -Researching more, I found the source of the rumor: It is an anagram for "matchers". -``` ->>> assert_that("matchers", contains_inanyorder(*"hamcrest")) - ->>> - -``` - -If you are not yet writing unit tests for your Python code, now is a good time to start. If you are writing unit tests for your Python code, using Hamcrest will allow you to make your assertion _precise_ —neither more nor less than what you intend to test. This will lead to fewer false positives when modifying code and less time spent modifying tests for working code. - --------------------------------------------------------------------------------- - -via: https://opensource.com/article/18/8/robust-unit-tests-hamcrest - -作者：[Moshe Zadka][a] -选题：[lujun9972](https://github.com/lujun9972) -译者：[译者ID](https://github.com/译者ID) -校对：[校对者ID](https://github.com/校对者ID) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 - -[a]:https://opensource.com/users/moshez -[1]:https://martinfowler.com/bliki/TestPyramid.html -[2]:http://hamcrest.org/ -[3]:https://www.python.org/ diff --git a/sources/tech/20180814 5 open source strategy and simulation games for Linux.md b/sources/tech/20180814 5 open source strategy and simulation games for Linux.md deleted file mode 100644 index 1f7e94c22f..0000000000 --- a/sources/tech/20180814 5 open source strategy and simulation games for Linux.md +++ /dev/null @@ -1,111 +0,0 @@ -5 open source strategy and simulation games for Linux -====== - - - -Gaming has traditionally been one of Linux's weak points. That has changed somewhat in recent years thanks to Steam, GOG, and other efforts to bring commercial games to multiple operating systems, but those games are often not open source. Sure, the games can be played on an open source operating system, but that is not good enough for an open source purist. - -So, can someone who only uses free and open source software find games that are polished enough to present a solid gaming experience without compromising their open source ideals? Absolutely. While open source games are unlikely ever to rival some of the AAA commercial games developed with massive budgets, there are plenty of open source games, in many genres, that are fun to play and can be installed from the repositories of most major Linux distributions. Even if a particular game is not packaged for a particular distribution, it is usually easy to download the game from the project's website to install and play it. - -This article looks at strategy and simulation games. I have already written about [arcade-style games][1], [board & card games][2], [puzzle games][3], [racing & flying games][4], and [role-playing games][5]. - -### Freeciv - - - -[Freeciv][6] is an open source version of the [Civilization series][7] of computer games. Gameplay is most similar to the earlier games in the Civilization series, and Freeciv even has options to use Civilization 1 and Civilization 2 rule sets. Freeciv involves building cities, exploring the world map, developing technologies, and competing with other civilizations trying to do the same. Victory conditions include defeating all the other civilizations, developing a space colony, or hitting deadline if neither of the first two conditions are met. The game can be played against AI opponents or other human players. Different tile-sets are available to change the look of the game's map. - -To install Freeciv, run the following command: - - * On Fedora: `dnf install freeciv` - * On Debian/Ubuntu: `apt install freeciv` - - - -### MegaGlest - - - -[MegaGlest][8] is an open source real-time strategy game in the style of Blizzard Entertainment's [Warcraft][9] and [StarCraft][10] games. Players control one of several different factions, building structures and recruiting units to explore the map and battle their opponents. At the beginning of the match, a player can build only the most basic buildings and recruit the weakest units. To build and recruit better things, players must work their way up their factions technology tree by building structures and recruiting units that unlock more advanced options. Combat units will attack when enemy units come into range, but for optimal strategy, it is best to manage the battle directly by controlling the units. Simultaneously managing the construction of new structures, recruiting new units, and managing battles can be a challenge, but that is the point of a real-time strategy game. MegaGlest provides a nice variety of factions, so there are plenty of reasons to try new and different strategies. - -To install MegaGlest, run the following command: - - * On Fedora: `dnf install megaglest` - * On Debian/Ubuntu: `apt install megaglest` - - - -### OpenTTD - - - -[OpenTTD][11] (see also [our review][12]) is an open source implementation of [Transport Tycoon Deluxe][13]. The object of the game is to create a transportation network and earn money, which allows the player to build an even bigger transportation network. The network can include boats, buses, trains, trucks, and planes. By default, gameplay takes place between 1950 and 2050, with players aiming to get the highest performance rating possible before time runs out. The performance rating is based on things like the amount of cargo delivered, the number of vehicles they have, and how much money they earned. - -To install OpenTTD, run the following command: - - * On Fedora: `dnf install openttd` - * On Debian/Ubuntu: `apt install openttd` - - - -### The Battle for Wesnoth - - - -[The Battle for Wesnoth][14] is one of the most polished open source games available. This turn-based strategy game has a fantasy setting. Play takes place on a hexagonal grid, where individual units battle each other for control. Each type of unit has unique strengths and weaknesses, which requires players to plan their attacks accordingly. There are many different campaigns available for The Battle for Wesnoth, each with different objectives and storylines. The Battle for Wesnoth also comes with a map editor for players interested in creating their own maps or campaigns. - -To install The Battle for Wesnoth, run the following command: - - * On Fedora: `dnf install wesnoth` - * On Debian/Ubuntu: `apt install wesnoth` - - - -### UFO: Alien Invasion - - - -[UFO: Alien Invasion][15] is an open source tactical strategy game inspired by the [X-COM series][20]. There are two distinct gameplay modes: geoscape and tactical. In geoscape mode, the player takes control of the big picture and deals with managing their bases, researching new technologies, and controlling overall strategy. In tactical mode, the player controls a squad of soldiers and directly confronts the alien invaders in a turn-based battle. Both modes provide different gameplay styles, but both require complex strategy and tactics. - -To install UFO: Alien Invasion, run the following command: - - * On Debian/Ubuntu: `apt install ufoai` - - - -Unfortunately, UFO: Alien Invasion is not packaged for Fedora. - -Did I miss one of your favorite open source strategy or simulation games? Share it in the comments below. - --------------------------------------------------------------------------------- - -via: https://opensource.com/article/18/8/strategy-simulation-games-linux - -作者：[Joshua Allen Holm][a] -选题：[lujun9972](https://github.com/lujun9972) -译者：[译者ID](https://github.com/译者ID) -校对：[校对者ID](https://github.com/校对者ID) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 - -[a]:https://opensource.com/users/holmja -[1]:https://opensource.com/article/18/1/arcade-games-linux -[2]:https://opensource.com/article/18/3/card-board-games-linux -[3]:https://opensource.com/article/18/6/puzzle-games-linux -[4]:https://opensource.com/article/18/7/racing-flying-games-linux -[5]:https://opensource.com/article/18/8/role-playing-games-linux -[6]:http://www.freeciv.org/ -[7]:https://en.wikipedia.org/wiki/Civilization_(series) -[8]:https://megaglest.org/ -[9]:https://en.wikipedia.org/wiki/Warcraft -[10]:https://en.wikipedia.org/wiki/StarCraft -[11]:https://www.openttd.org/ -[12]:https://opensource.com/life/15/7/linux-game-review-openttd -[13]:https://en.wikipedia.org/wiki/Transport_Tycoon#Transport_Tycoon_Deluxe -[14]:https://www.wesnoth.org/ -[15]:https://ufoai.org/ -[16]:https://opensource.com/downloads/cheat-sheets?intcmp=7016000000127cYAAQ -[17]:https://opensource.com/alternatives?intcmp=7016000000127cYAAQ -[18]:https://opensource.com/tags/linux?intcmp=7016000000127cYAAQ -[19]:https://developers.redhat.com/cheat-sheets/advanced-linux-commands/?intcmp=7016000000127cYAAQ -[20]:https://en.wikipedia.org/wiki/X-COM diff --git a/sources/tech/20180814 HTTP request routing and validation with gorilla-mux.md b/sources/tech/20180814 HTTP request routing and validation with gorilla-mux.md deleted file mode 100644 index 410f692ad9..0000000000 --- a/sources/tech/20180814 HTTP request routing and validation with gorilla-mux.md +++ /dev/null @@ -1,674 +0,0 @@ -HTTP request routing and validation with gorilla/mux -====== - - - -The Go networking library includes the `http.ServeMux` structure type, which supports HTTP request multiplexing (routing): A web server routes an HTTP request for a hosted resource, with a URI such as /sales4today, to a code handler; the handler performs the appropriate logic before sending an HTTP response, typically an HTML page. Here’s a sketch of the architecture: -``` - +------------+ +--------+ +---------+ -HTTP request---->| web server |---->| router |---->| handler | - +------------+ +--------+ +---------+ -``` - -In a call to the `ListenAndServe` method to start an HTTP server -``` -http.ListenAndServe(":8888", nil) // args: port & router -``` - -a second argument of `nil` means that the `DefaultServeMux` is used for request routing. - -The `gorilla/mux` package has a `mux.Router` type as an alternative to either the `DefaultServeMux` or a customized request multiplexer. In the `ListenAndServe` call, a `mux.Router` instance would replace `nil` as the second argument. What makes the `mux.Router` so appealing is best shown through a code example: - -### 1\. A sample crud web app - -The crud web application (see below) supports the four CRUD (Create Read Update Delete) operations, which match four HTTP request methods: POST, GET, PUT, and DELETE, respectively. In the crud app, the hosted resource is a list of cliche pairs, each a cliche and a conflicting cliche such as this pair: -``` -Out of sight, out of mind. Absence makes the heart grow fonder. - -``` - -New cliche pairs can be added, and existing ones can be edited or deleted. - -**The crud web app** -``` -package main - -import ( - "gorilla/mux" - "net/http" - "fmt" - "strconv" -) - -const GETALL string = "GETALL" -const GETONE string = "GETONE" -const POST string = "POST" -const PUT string = "PUT" -const DELETE string = "DELETE" - -type clichePair struct { - Id int - Cliche string - Counter string -} - -// Message sent to goroutine that accesses the requested resource. -type crudRequest struct { - verb string - cp *clichePair - id int - cliche string - counter string - confirm chan string -} - -var clichesList = []*clichePair{} -var masterId = 1 -var crudRequests chan *crudRequest - -// GET / -// GET /cliches -func ClichesAll(res http.ResponseWriter, req *http.Request) { - cr := &crudRequest{verb: GETALL, confirm: make(chan string)} - completeRequest(cr, res, "read all") -} - -// GET /cliches/id -func ClichesOne(res http.ResponseWriter, req *http.Request) { - id := getIdFromRequest(req) - cr := &crudRequest{verb: GETONE, id: id, confirm: make(chan string)} - completeRequest(cr, res, "read one") -} - -// POST /cliches - -func ClichesCreate(res http.ResponseWriter, req *http.Request) { - - cliche, counter := getDataFromRequest(req) - - cp := new(clichePair) - - cp.Cliche = cliche - - cp.Counter = counter - - cr := &crudRequest{verb: POST, cp: cp, confirm: make(chan string)} - - completeRequest(cr, res, "create") - -} - - - -// PUT /cliches/id - -func ClichesEdit(res http.ResponseWriter, req *http.Request) { - - id := getIdFromRequest(req) - - cliche, counter := getDataFromRequest(req) - - cr := &crudRequest{verb: PUT, id: id, cliche: cliche, counter: counter, confirm: make(chan string)} - - completeRequest(cr, res, "edit") - -} - - - -// DELETE /cliches/id - -func ClichesDelete(res http.ResponseWriter, req *http.Request) { - - id := getIdFromRequest(req) - - cr := &crudRequest{verb: DELETE, id: id, confirm: make(chan string)} - - completeRequest(cr, res, "delete") - -} - - - -func completeRequest(cr *crudRequest, res http.ResponseWriter, logMsg string) { - - crudRequests<-cr - - msg := <-cr.confirm - - res.Write([]byte(msg)) - - logIt(logMsg) - -} - - - -func main() { - - populateClichesList() - - - - // From now on, this gorountine alone accesses the clichesList. - - crudRequests = make(chan *crudRequest, 8) - - go func() { // resource manager - - for { - - select { - - case req := <-crudRequests: - - if req.verb == GETALL { - - req.confirm<-readAll() - - } else if req.verb == GETONE { - - req.confirm<-readOne(req.id) - - } else if req.verb == POST { - - req.confirm<-addPair(req.cp) - - } else if req.verb == PUT { - - req.confirm<-editPair(req.id, req.cliche, req.counter) - - } else if req.verb == DELETE { - - req.confirm<-deletePair(req.id) - - } - - } - - }() - - startServer() - -} - - - -func startServer() { - - router := mux.NewRouter() - - - - // Dispatch map for CRUD operations. - - router.HandleFunc("/", ClichesAll).Methods("GET") - - router.HandleFunc("/cliches", ClichesAll).Methods("GET") - - router.HandleFunc("/cliches/{id:[0-9]+}", ClichesOne).Methods("GET") - - - - router.HandleFunc("/cliches", ClichesCreate).Methods("POST") - - router.HandleFunc("/cliches/{id:[0-9]+}", ClichesEdit).Methods("PUT") - - router.HandleFunc("/cliches/{id:[0-9]+}", ClichesDelete).Methods("DELETE") - - - - http.Handle("/", router) // enable the router - - - - // Start the server. - - port := ":8888" - - fmt.Println("\nListening on port " + port) - - http.ListenAndServe(port, router); // mux.Router now in play - -} - - - -// Return entire list to requester. - -func readAll() string { - - msg := "\n" - - for _, cliche := range clichesList { - - next := strconv.Itoa(cliche.Id) + ": " + cliche.Cliche + " " + cliche.Counter + "\n" - - msg += next - - } - - return msg - -} - - - -// Return specified clichePair to requester. - -func readOne(id int) string { - - msg := "\n" + "Bad Id: " + strconv.Itoa(id) + "\n" - - - - index := findCliche(id) - - if index >= 0 { - - cliche := clichesList[index] - - msg = "\n" + strconv.Itoa(id) + ": " + cliche.Cliche + " " + cliche.Counter + "\n" - - } - - return msg - -} - - - -// Create a new clichePair and add to list - -func addPair(cp *clichePair) string { - - cp.Id = masterId - - masterId++ - - clichesList = append(clichesList, cp) - - return "\nCreated: " + cp.Cliche + " " + cp.Counter + "\n" - -} - - - -// Edit an existing clichePair - -func editPair(id int, cliche string, counter string) string { - - msg := "\n" + "Bad Id: " + strconv.Itoa(id) + "\n" - - index := findCliche(id) - - if index >= 0 { - - clichesList[index].Cliche = cliche - - clichesList[index].Counter = counter - - msg = "\nCliche edited: " + cliche + " " + counter + "\n" - - } - - return msg - -} - - - -// Delete a clichePair - -func deletePair(id int) string { - - idStr := strconv.Itoa(id) - - msg := "\n" + "Bad Id: " + idStr + "\n" - - index := findCliche(id) - - if index >= 0 { - - clichesList = append(clichesList[:index], clichesList[index + 1:]...) - - msg = "\nCliche " + idStr + " deleted\n" - - } - - return msg - -} - - - -//*** utility functions - -func findCliche(id int) int { - - for i := 0; i < len(clichesList); i++ { - - if id == clichesList[i].Id { - - return i; - - } - - } - - return -1 // not found - -} - - - -func getIdFromRequest(req *http.Request) int { - - vars := mux.Vars(req) - - id, _ := strconv.Atoi(vars["id"]) - - return id - -} - - - -func getDataFromRequest(req *http.Request) (string, string) { - - // Extract the user-provided data for the new clichePair - - req.ParseForm() - - form := req.Form - - cliche := form["cliche"][0] // 1st and only member of a list - - counter := form["counter"][0] // ditto - - return cliche, counter - -} - - - -func logIt(msg string) { - - fmt.Println(msg) - -} - - - -func populateClichesList() { - - var cliches = []string { - - "Out of sight, out of mind.", - - "A penny saved is a penny earned.", - - "He who hesitates is lost.", - - } - - var counterCliches = []string { - - "Absence makes the heart grow fonder.", - - "Penny-wise and dollar-foolish.", - - "Look before you leap.", - - } - - - - for i := 0; i < len(cliches); i++ { - - cp := new(clichePair) - - cp.Id = masterId - - masterId++ - - cp.Cliche = cliches[i] - - cp.Counter = counterCliches[i] - - clichesList = append(clichesList, cp) - - } - -} - -``` - -To focus on request routing and validation, the crud app does not use HTML pages as responses to requests. Instead, requests result in plaintext response messages: A list of the cliche pairs is the response to a GET request, confirmation that a new cliche pair has been added to the list is a response to a POST request, and so on. This simplification makes it easy to test the app, in particular, the `gorilla/mux` components, with a command-line utility such as [curl][1]. - -The `gorilla/mux` package can be installed from [GitHub][2]. The crud app runs indefinitely; hence, it should be terminated with a Control-C or equivalent. The code for the crud app, together with a README and sample curl tests, is available on [my website][3]. - -### 2\. Request routing - -The `mux.Router` extends REST-style routing, which gives equal weight to the HTTP method (e.g., GET) and the URI or path at the end of a URL (e.g., /cliches). The URI serves as the noun for the HTTP verb (method). For example, in an HTTP request a startline such as -``` -GET /cliches - -``` - -means get all of the cliche pairs, whereas a startline such as -``` -POST /cliches - -``` - -means create a cliche pair from data in the HTTP body. - -In the crud web app, there are five functions that act as request handlers for five variations of an HTTP request: -``` -ClichesAll(...) # GET: get all of the cliche pairs - -ClichesOne(...) # GET: get a specified cliche pair - -ClichesCreate(...) # POST: create a new cliche pair - -ClichesEdit(...) # PUT: edit an existing cliche pair - -ClichesDelete(...) # DELETE: delete a specified cliche pair - -``` - -Each function takes two arguments: an `http.ResponseWriter` for sending a response back to the requester, and a pointer to an `http.Request`, which encapsulates information from the underlying HTTP request. The `gorilla/mux` package makes it easy to register these request handlers with the web server, and to perform regex-based validation. - -The `startServer` function in the crud app registers the request handlers. Consider this pair of registrations, with `router` as a `mux.Router` instance: -``` -router.HandleFunc("/", ClichesAll).Methods("GET") - -router.HandleFunc("/cliches", ClichesAll).Methods("GET") - -``` - -These statements mean that a GET request for either the single slash / or /cliches should be routed to the `ClichesAll` function, which then handles the request. For example, the curl request (with % as the command-line prompt) -``` -% curl --request GET localhost:8888/ - -``` - -produces this response: -``` -1: Out of sight, out of mind. Absence makes the heart grow fonder. - -2: A penny saved is a penny earned. Penny-wise and dollar-foolish. - -3: He who hesitates is lost. Look before you leap. - -``` - -The three cliche pairs are the initial data in the crud app. - -In this pair of registration statements -``` -router.HandleFunc("/cliches", ClichesAll).Methods("GET") - -router.HandleFunc("/cliches", ClichesCreate).Methods("POST") - -``` - -the URI is the same (/cliches) but the verbs differ: GET in the first case, and POST in the second. This registration exemplifies REST-style routing because the difference in the verbs alone suffices to dispatch the requests to two different handlers. - -More than one HTTP method is allowed in a registration, although this strains the spirit of REST-style routing: -``` -router.HandleFunc("/cliches", DoItAll).Methods("POST", "GET") - -``` - -HTTP requests can be routed on features besides the verb and the URI. For example, the registration -``` -router.HandleFunc("/cliches", ClichesCreate).Schemes("https").Methods("POST") - -``` - -requires HTTPS access for a POST request to create a new cliche pair. In similar fashion, a registration might require a request to have a specified HTTP header element (e.g., an authentication credential). - -### 3\. Request validation - -The `gorilla/mux` package takes an easy, intuitive approach to request validation through regular expressions. Consider this request handler for a get one operation: -``` -router.HandleFunc("/cliches/{id:[0-9]+}", ClichesOne).Methods("GET") - -``` - -This registration rules out HTTP requests such as -``` -% curl --request GET localhost:8888/cliches/foo - -``` - -because foo is not a decimal numeral. The request results in the familiar 404 (Not Found) status code. Including the regex pattern in this handler registration ensures that the `ClichesOne` function is called to handle a request only if the request URI ends with a decimal integer value: -``` -% curl --request GET localhost:8888/cliches/3 # ok - -``` - -As a second example, consider the request -``` -% curl --request PUT --data "..." localhost:8888/cliches - -``` - -This request results in a status code of 405 (Bad Method) because the /cliches URI is registered, in the crud app, only for GET and POST requests. A PUT request, like a GET one request, must include a numeric id at the end of the URI: -``` -router.HandleFunc("/cliches/{id:[0-9]+}", ClichesEdit).Methods("PUT") - -``` - -### 4\. Concurrency issues - -The `gorilla/mux` router executes each call to a registered request handler as a separate goroutine, which means that concurrency is baked into the package. For example, if there are ten simultaneous requests such as -``` -% curl --request POST --data "..." localhost:8888/cliches - -``` - -then the `mux.Router` launches ten goroutines to execute the `ClichesCreate` handler. - -Of the five request operations GET all, GET one, POST, PUT, and DELETE, the last three alter the requested resource, the shared `clichesList` that houses the cliche pairs. Accordingly, the crudapp needs to guarantee safe concurrency by coordinating access to the `clichesList`. In different but equivalent terms, the crud app must prevent a race condition on the `clichesList`. In a production environment, a database system might be used to store a resource such as the `clichesList`, and safe concurrency then could be managed through database transactions. - -The crud app takes the recommended Go approach to safe concurrency: - - * Only a single goroutine, the resource manager started in the crud app `startServer` function, has access to the `clichesList` once the web server starts listening for requests. - * The request handlers such as `ClichesCreate` and `ClichesAll` send a (pointer to) a `crudRequest` instance to a Go channel (thread-safe by default), and the resource manager alone reads from this channel. The resource manager then performs the requested operation on the `clichesList`. - - - -The safe-concurrency architecture can be sketched as follows: -``` - crudRequest read/write - -request handlers------------->resource manager------------>clichesList - -``` - -With this architecture, no explicit locking of the `clichesList` is needed because only one goroutine, the resource manager, accesses the `clichesList` once CRUD requests start coming in. - -To keep the crud app as concurrent as possible, it’s essential to have an efficient division of labor between the request handlers, on the one side, and the single resource manager, on the other side. Here, for review, is the `ClichesCreate` request handler: -``` -func ClichesCreate(res http.ResponseWriter, req *http.Request) { - - cliche, counter := getDataFromRequest(req) - - cp := new(clichePair) - - cp.Cliche = cliche - - cp.Counter = counter - - cr := &crudRequest{verb: POST, cp: cp, confirm: make(chan string)} - - completeRequest(cr, res, "create") - -}ClichesCreateres httpResponseWriterreqclichecountergetDataFromRequestreqcpclichePaircpClicheclichecpCountercountercr&crudRequestverbPOSTcpcpconfirmcompleteRequestcrres - -``` - -`ClichesCreate` calls the utility function `getDataFromRequest`, which extracts the new cliche and counter-cliche from the POST request. The `ClichesCreate` function then creates a new `ClichePair`, sets two fields, and creates a `crudRequest` to be sent to the single resource manager. This request includes a confirmation channel, which the resource manager uses to return information back to the request handler. All of the setup work can be done without involving the resource manager because the `clichesList` is not being accessed yet. - -The request handlercalls the utility function, which extracts the new cliche and counter-cliche from the POST request. Thefunction then creates a new, sets two fields, and creates ato be sent to the single resource manager. This request includes a confirmation channel, which the resource manager uses to return information back to the request handler. All of the setup work can be done without involving the resource manager because theis not being accessed yet. - -The `completeRequest` utility function called at the end of the `ClichesCreate` function and the other request handlers -``` -completeRequest(cr, res, "create") // shown above - -``` - -brings the resource manager into play by putting a `crudRequest` into the `crudRequests` channel: -``` -func completeRequest(cr *crudRequest, res http.ResponseWriter, logMsg string) { - - crudRequests<-cr // send request to resource manager - - msg := <-cr.confirm // await confirmation string - - res.Write([]byte(msg)) // send confirmation back to requester - - logIt(logMsg) // print to the standard output - -} - -``` - -For a POST request, the resource manager calls the utility function `addPair`, which changes the `clichesList` resource: -``` -func addPair(cp *clichePair) string { - - cp.Id = masterId // assign a unique ID - - masterId++ // update the ID counter - - clichesList = append(clichesList, cp) // update the list - - return "\nCreated: " + cp.Cliche + " " + cp.Counter + "\n" - -} - -``` - -The resource manager calls similar utility functions for the other CRUD operations. It’s worth repeating that the resource manager is the only goroutine to read or write the `clichesList` once the web server starts accepting requests. - -For web applications of any type, the `gorilla/mux` package provides request routing, request validation, and related services in a straightforward, intuitive API. The crud web app highlights the package’s main features. Give the package a test drive, and you’ll likely be a buyer. - --------------------------------------------------------------------------------- - -via: https://opensource.com/article/18/8/http-request-routing-validation-gorillamux - -作者：[Marty Kalin][a] -选题：[lujun9972](https://github.com/lujun9972) -译者：[译者ID](https://github.com/译者ID) -校对：[校对者ID](https://github.com/校对者ID) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 - -[a]:https://opensource.com/users/mkalindepauledu -[1]:https://curl.haxx.se/ -[2]:https://github.com/gorilla/mux -[3]:http://condor.depaul.edu/mkalin diff --git a/sources/tech/20180823 Getting started with Sensu monitoring.md b/sources/tech/20180823 Getting started with Sensu monitoring.md deleted file mode 100644 index 7d0a65e306..0000000000 --- a/sources/tech/20180823 Getting started with Sensu monitoring.md +++ /dev/null @@ -1,290 +0,0 @@ -Getting started with Sensu monitoring -====== - - -Sensu is an open source infrastructure and application monitoring solution that monitors servers, services, and application health, and sends alerts and notifications with third-party integration. Written in Ruby, Sensu can use either [RabbitMQ][1] or [Redis][2] to handle messages. It uses Redis to store data. - -If you want to monitor your cloud infrastructure in a simple and efficient manner, Sensu is a good option. It can be integrated with many of the modern DevOps stacks your organization may already be using, such as [Slack][3], [HipChat][4], or [IRC][5], and it can even send mobile/pager alerts with [PagerDuty][6]. - -Sensu's [modular architecture][7] means every component can be installed on the same server or on completely separate machines. - -### Architecture - -Sensu's main communication mechanism is the Transport. Every Sensu component must connect to the Transport in order to send messages to each other. Transport can use either RabbitMQ (recommended in production) or Redis. - -Sensu Server processes event data and takes action. It registers clients and processes check results and monitoring events using filters, mutators, and handlers. The server publishes check definitions to the clients and the Sensu API provides a RESTful API, providing access to monitoring data and core functionality. - -[Sensu Client][8] executes checks either scheduled by Sensu Server or local checks definitions. Sensu uses a data store (Redis) to keep all the persistent data. Finally, [Uchiwa][9] is the web interface to communicate with Sensu API. - -![sensu_system.png][11] - -### Installing Sensu - -#### Prerequisites - - * One Linux installation to act as the server node (I used CentOS 7 for this article) - - * One or more Linux machines to monitor (clients) - - - - -#### Server side - -Sensu requires Redis to be installed. To install Redis, enable the EPEL repository: -``` -$ sudo yum install epel-release -y - -``` - -Then install Redis: -``` -$ sudo yum install redis -y - -``` - -Modify `/etc/redis.conf` to disable protected mode, listen on every interface, and set a password: -``` -$ sudo sed -i 's/^protected-mode yes/protected-mode no/g' /etc/redis.conf - -$ sudo sed -i 's/^bind 127.0.0.1/bind 0.0.0.0/g' /etc/redis.conf - -$ sudo sed -i 's/^# requirepass foobared/requirepass password123/g' /etc/redis.conf - -``` - -Enable and start Redis service: -``` -$ sudo systemctl enable redis -$ sudo systemctl start redis -``` - -Redis is now installed and ready to be used by Sensu. - -Now let’s install Sensu. - -First, configure the Sensu repository and install the packages: -``` -$ sudo tee /etc/yum.repos.d/sensu.repo << EOF -[sensu] -name=sensu -baseurl=https://sensu.global.ssl.fastly.net/yum/\$releasever/\$basearch/ -gpgcheck=0 -enabled=1 -EOF - -$ sudo yum install sensu uchiwa -y -``` - -Let’s create the bare minimum configuration files for Sensu: -``` -$ sudo tee /etc/sensu/conf.d/api.json << EOF -{ - "api": { - "host": "127.0.0.1", - "port": 4567 - } -} -EOF -``` - -Next, configure `sensu-api` to listen on localhost, with Port 4567: -``` -$ sudo tee /etc/sensu/conf.d/redis.json << EOF -{ - "redis": { - "host": " ", - "port": 6379, - "password": "password123" - } -} -EOF - - -$ sudo tee /etc/sensu/conf.d/transport.json << EOF -{ - "transport": { - "name": "redis" - } -} -EOF -``` - -In these two files, we configure Sensu to use Redis as the transport mechanism and the address where Redis will listen. Clients need to connect directly to the transport mechanism. These two files will be required on each client machine. -``` -$ sudo tee /etc/sensu/uchiwa.json << EOF -{ - "sensu": [ - { - "name": "sensu", - "host": "127.0.0.1", - "port": 4567 - } - ], - "uchiwa": { - "host": "0.0.0.0", - "port": 3000 - } -} -EOF -``` - -In this file, we configure Uchiwa to listen on every interface (0.0.0.0) on Port 3000. We also configure Uchiwa to use `sensu-api` (already configured). - -For security reasons, change the owner of the configuration files you just created: -``` -$ sudo chown -R sensu:sensu /etc/sensu -``` - -Enable and start the Sensu services: -``` -$ sudo systemctl enable sensu-server sensu-api sensu-client -$ sudo systemctl start sensu-server sensu-api sensu-client -$ sudo systemctl enable uchiwa -$ sudo systemctl start uchiwa -``` - -Try accessing the Uchiwa website: http:// :3000 - -For production environments, it’s recommended to run a cluster of RabbitMQ as the Transport instead of Redis (a Redis cluster can be used in production too), and to run more than one instance of Sensu Server and API for load balancing and high availability. - -Sensu is now installed. Now let’s configure the clients. - -#### Client side - -To add a new client, you will need to enable Sensu repository on the client machines by creating the file `/etc/yum.repos.d/sensu.repo`. -``` -$ sudo tee /etc/yum.repos.d/sensu.repo << EOF -[sensu] -name=sensu -baseurl=https://sensu.global.ssl.fastly.net/yum/\$releasever/\$basearch/ -gpgcheck=0 -enabled=1 -EOF -``` - -With the repository enabled, install the package Sensu: -``` -$ sudo yum install sensu -y -``` - -To configure `sensu-client`, create the same `redis.json` and `transport.json` created in the server machine, as well as the `client.json` configuration file: -``` -$ sudo tee /etc/sensu/conf.d/client.json << EOF -{ - "client": { - "name": "rhel-client", - "environment": "development", - "subscriptions": [ - "frontend" - ] - } -} -EOF -``` - -In the name field, specify a name to identify this client (typically the hostname). The environment field can help you filter, and subscription defines which monitoring checks will be executed by the client. - -Finally, enable and start the services and check in Uchiwa, as the new client will register automatically: -``` -$ sudo systemctl enable sensu-client -$ sudo systemctl start sensu-client -``` - -### Sensu checks - -Sensu checks have two components: a plugin and a definition. - -Sensu is compatible with the [Nagios check plugin specification][12], so any check for Nagios can be used without modification. Checks are executable files and are run by the Sensu client. - -Check definitions let Sensu know how, where, and when to run the plugin. - -#### Client side - -Let’s install one check plugin on the client machine. Remember, this plugin will be executed on the clients. - -Enable EPEL and install `nagios-plugins-http` : -``` -$ sudo yum install -y epel-release -$ sudo yum install -y nagios-plugins-http -``` - -Now let’s explore the plugin by executing it manually. Try checking the status of a web server running on the client machine. It should fail as we don’t have a web server running: -``` -$ /usr/lib64/nagios/plugins/check_http -I 127.0.0.1 -connect to address 127.0.0.1 and port 80: Connection refused -HTTP CRITICAL - Unable to open TCP socket -``` - -It failed, as expected. Check the return code of the execution: -``` -$ echo $? -2 - -``` - -The Nagios check plugin specification defines four return codes for the plugin execution: - -| **Plugin return code** | **State** | -|------------------------|-----------| -| 0 | OK | -| 1 | WARNING | -| 2 | CRITICAL | -| 3 | UNKNOWN | - -With this information, we can now create the check definition on the server. - -#### Server side - -On the server machine, create the file `/etc/sensu/conf.d/check_http.json`: -``` -{ - "checks": { - "check_http": { - "command": "/usr/lib64/nagios/plugins/check_http -I 127.0.0.1", - "interval": 10, - "subscribers": [ - "frontend" - ] - } - } -} -``` - -In the command field, use the command we tested before. `Interval` will tell Sensu how frequently, in seconds, this check should be executed. Finally, `subscribers` will define the clients where the check will be executed. - -Restart both sensu-api and sensu-server and confirm that the new check is available in Uchiwa. -``` -$ sudo systemctl restart sensu-api sensu-server -``` - -### What’s next? - -Sensu is a powerful tool, and this article covers just a glimpse of what it can do. See the [documentation][13] to learn more, and visit the Sensu site to learn more about the [Sensu community][14]. - --------------------------------------------------------------------------------- - -via: https://opensource.com/article/18/8/getting-started-sensu-monitoring-solution - -作者：[Michael Zamot][a] -选题：[lujun9972](https://github.com/lujun9972) -译者：[译者ID](https://github.com/译者ID) -校对：[校对者ID](https://github.com/校对者ID) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 - -[a]:https://opensource.com/users/mzamot -[1]:https://www.rabbitmq.com/ -[2]:https://redis.io/topics/config -[3]:https://slack.com/ -[4]:https://en.wikipedia.org/wiki/HipChat -[5]:http://www.irc.org/ -[6]:https://www.pagerduty.com/ -[7]:https://docs.sensu.io/sensu-core/1.4/overview/architecture/ -[8]:https://docs.sensu.io/sensu-core/1.4/installation/install-sensu-client/ -[9]:https://uchiwa.io/#/ -[10]:/file/406576 -[11]:https://opensource.com/sites/default/files/uploads/sensu_system.png (sensu_system.png) -[12]:https://assets.nagios.com/downloads/nagioscore/docs/nagioscore/4/en/pluginapi.html -[13]:https://docs.sensu.io/ -[14]:https://sensu.io/community diff --git a/sources/tech/20180828 An Introduction to Quantum Computing with Open Source Cirq Framework.md b/sources/tech/20180828 An Introduction to Quantum Computing with Open Source Cirq Framework.md deleted file mode 100644 index 8cec20916d..0000000000 --- a/sources/tech/20180828 An Introduction to Quantum Computing with Open Source Cirq Framework.md +++ /dev/null @@ -1,228 +0,0 @@ -An Introduction to Quantum Computing with Open Source Cirq Framework -====== -As the title suggests what we are about to begin discussing, this article is an effort to understand how far we have come in Quantum Computing and where we are headed in the field in order to accelerate scientific and technological research, through an Open Source perspective with Cirq. - -First, we will introduce you to the world of Quantum Computing. We will try our best to explain the basic idea behind the same before we look into how Cirq would be playing a significant role in the future of Quantum Computing. Cirq, as you might have heard of recently, has been breaking news in the field and in this Open Science article, we will try to find out why. - - - -``` - -We went ahead and installed the Cirq library with Pip3 for Python3: -``` -pip3 install cirq - -``` - -#### Enabling Plot and PDF generation (optional) - -Optional system dependencies not install-able with pip can be installed with: -``` -sudo apt-get install python3-tk texlive-latex-base latexmk - -``` - - * python3-tk is Python’s own graphic library which enables plotting functionality. - * texlive-latex-base and latexmk enable PDF writing functionality. - - - -Later, we successfully tested Cirq with the following command and code: -``` -python3 -c 'import cirq; print(cirq.google.Foxtail)' - -``` - -We got the resulting output as: - -![][18] - -#### Configuring Pycharm IDE for Cirq - -We also configured a Python IDE [PyCharm on Ubuntu][19] to test the same results: - -Since we installed Cirq for Python3 on our Linux system, we set the path to the project interpreter in the IDE settings to be: -``` -/usr/bin/python3 - -``` - -![][20] - -In the output above, you can note that the path to the project interpreter that we just set, is shown along with the path to the test program file (test.py). An exit code of 0 shows that the program has finished executing successfully without errors. - -So, that’s a ready-to-use IDE environment where you can import the Cirq library to start programming with Python and simulate Quantum circuits. - -#### Get started with Cirq - -A good place to start are the [examples][21] that have been made available on Cirq’s Github page. - -The developers have included this [tutorial][22] on GitHub to get started with learning Cirq. If you are serious about learning Quantum Computing, they recommend an excellent book called [“Quantum Computation and Quantum Information” by Nielsen and Chuang][23]. - -#### OpenFermion-Cirq - -[OpenFermion][24] is an open source library for obtaining and manipulating representations of fermionic systems (including Quantum Chemistry) for simulation on Quantum Computers. Fermionic systems are related to the generation of [fermions][25], which according to [particle physics][26], follow [Fermi-Dirac statistics][27]. - -OpenFermion has been hailed as [a great practice tool][28] for chemists and researchers involved with [Quantum Chemistry][29]. The main focus of Quantum Chemistry is the application of [Quantum Mechanics][30] in physical models and experiments of chemical systems. Quantum Chemistry is also referred to as [Molecular Quantum Mechanics][31]. - -The advent of Cirq has now made it possible for OpenFermion to extend its functionality by providing routines and tools for using Cirq to compile and compose circuits for Quantum simulation algorithms. - -#### Google Bristlecone - -On March 5, 2018, Google presented [Bristlecone][32], their new Quantum processor, at the annual [American Physical Society meeting][33] in Los Angeles. The [gate-based superconducting system][34] provides a test platform for research into [system error rates][35] and [scalability][36] of Google’s [qubit technology][37], along-with applications in Quantum [simulation][38], [optimization][39], and [machine learning.][40] - -In the near future, Google wants to make its 72 qubit Bristlecone Quantum processor [cloud accessible][41]. Bristlecone will gradually become quite capable to perform a task that a Classical Supercomputer would not be able to complete in a reasonable amount of time. - -Cirq would make it easier for researchers to directly write programs for Bristlecone on the cloud, serving as a very convenient interface for real-time Quantum programming and testing. - -Cirq will allow us to: - - * Fine tune control over Quantum circuits, - * Specify [gate][42] behavior using native gates, - * Place gates appropriately on the device & - * Schedule the timing of these gates. - - - -### The Open Science Perspective on Cirq - -As we all know Cirq is Open Source on GitHub, its addition to the Open Source Scientific Communities, especially those which are focused on Quantum Research, can now efficiently collaborate to solve the current challenges in Quantum Computing today by developing new ways to reduce error rates and improve accuracy in the existing Quantum models. - -Had Cirq not followed an Open Source model, things would have definitely been a lot more challenging. A great initiative would have been missed out and we would not have been one step closer in the field of Quantum Computing. - -### Summary - -To summarize in the end, we first introduced you to the concept of Quantum Computing by comparing it to existing Classical Computing techniques followed by a very important video on recent developmental updates in Quantum Computing since last year. We then briefly discussed Noisy Intermediate Scale Quantum, which is what Cirq is specifically built for. - -We saw how we can install and test Cirq on an Ubuntu system. We also tested the installation for usability on an IDE environment with some resources to get started to learn the concept. - -Finally, we also saw two examples of how Cirq would be an essential advantage in the development of research in Quantum Computing, namely OpenFermion and Bristlecone. We concluded the discussion by highlighting some thoughts on Cirq with an Open Science Perspective. - -We hope we were able to introduce you to Quantum Computing with Cirq in an easy to understand manner. If you have any feedback related to the same, please let us know in the comments section. Thank you for reading and we look forward to see you in our next Open Science article. - --------------------------------------------------------------------------------- - -via: https://itsfoss.com/qunatum-computing-cirq-framework/ - -作者：[Avimanyu Bandyopadhyay][a] -选题：[lujun9972](https://github.com/lujun9972) -译者：[译者ID](https://github.com/译者ID) -校对：[校对者ID](https://github.com/校对者ID) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 - -[a]: https://itsfoss.com/author/avimanyu/ -[1]:https://en.wikipedia.org/wiki/Subatomic_particle -[2]:https://en.wikipedia.org/wiki/Quantum -[3]:https://www.clerro.com/guide/491/quantum-superposition-and-entanglement-explained -[4]:https://physics.stackexchange.com/questions/148131/can-quantum-entanglement-and-quantum-superposition-be-considered-the-same-phenom -[5]:https://4bds6hergc-flywheel.netdna-ssl.com/wp-content/uploads/2018/08/bit-vs-qubit.jpg -[6]:http://www.rfwireless-world.com/Terminology/Difference-between-Bit-and-Qubit.html -[7]:https://en.wikipedia.org/wiki/Proof_by_exhaustion -[8]:https://www.explainthatstuff.com/how-supercomputers-work.html -[9]:https://arxiv.org/abs/1801.00862 -[10]:https://www.xconomy.com/san-francisco/2018/07/19/google-partners-with-zapata-on-open-source-quantum-computing-effort/ -[11]:https://www.zapatacomputing.com/about/ -[12]:https://github.com/quantumlib/Cirq -[13]:https://itsfoss.com/python-setup-linux/ -[14]:https://virtualenv.pypa.io -[15]:https://cirq.readthedocs.io/en/latest/install.html#installing-on-linux -[16]:https://4bds6hergc-flywheel.netdna-ssl.com/wp-content/uploads/2018/08/cirq-framework-linux.jpeg -[17]:https://pypi.org/project/pip/ -[18]:https://4bds6hergc-flywheel.netdna-ssl.com/wp-content/uploads/2018/08/cirq-test-output.jpg -[19]:https://itsfoss.com/install-pycharm-ubuntu/ -[20]:https://4bds6hergc-flywheel.netdna-ssl.com/wp-content/uploads/2018/08/cirq-tested-on-pycharm.jpg -[21]:https://github.com/quantumlib/Cirq/tree/master/examples -[22]:https://github.com/quantumlib/Cirq/blob/master/docs/tutorial.md -[23]:http://mmrc.amss.cas.cn/tlb/201702/W020170224608149940643.pdf -[24]:http://openfermion.org -[25]:https://en.wikipedia.org/wiki/Fermion -[26]:https://en.wikipedia.org/wiki/Particle_physics -[27]:https://en.wikipedia.org/wiki/Fermi-Dirac_statistics -[28]:https://phys.org/news/2018-03-openfermion-tool-quantum-coding.html -[29]:https://en.wikipedia.org/wiki/Quantum_chemistry -[30]:https://en.wikipedia.org/wiki/Quantum_mechanics -[31]:https://ocw.mit.edu/courses/chemical-engineering/10-675j-computational-quantum-mechanics-of-molecular-and-extended-systems-fall-2004/lecture-notes/ -[32]:https://techcrunch.com/2018/03/05/googles-new-bristlecone-processor-brings-it-one-step-closer-to-quantum-supremacy/ -[33]:http://meetings.aps.org/Meeting/MAR18/Content/3475 -[34]:https://en.wikipedia.org/wiki/Superconducting_quantum_computing -[35]:https://en.wikipedia.org/wiki/Quantum_error_correction -[36]:https://en.wikipedia.org/wiki/Scalability -[37]:https://research.googleblog.com/2015/03/a-step-closer-to-quantum-computation.html -[38]:https://research.googleblog.com/2017/10/announcing-openfermion-open-source.html -[39]:https://research.googleblog.com/2016/06/quantum-annealing-with-digital-twist.html -[40]:https://arxiv.org/abs/1802.06002 -[41]:https://www.computerworld.com.au/article/644051/google-launches-quantum-framework-cirq-plans-bristlecone-cloud-move/ -[42]:https://en.wikipedia.org/wiki/Logic_gate diff --git a/sources/tech/20180828 Linux for Beginners- Moving Things Around.md b/sources/tech/20180828 Linux for Beginners- Moving Things Around.md deleted file mode 100644 index abefc7c6f5..0000000000 --- a/sources/tech/20180828 Linux for Beginners- Moving Things Around.md +++ /dev/null @@ -1,201 +0,0 @@ -Linux for Beginners: Moving Things Around -====== - - - -In previous installments of this series, [you learned about directories][1] and how [permissions to access directories work][2]. Most of what you learned in those articles can be applied to files, except how to make a file executable. - -So let's deal with that before moving on. - -### No _.exe_ Needed - -In other operating systems, the nature of a file is often determined by its extension. If a file has a _.jpg_ extension, the OS guesses it is an image; if it ends in _.wav_ , it is an audio file; and if it has an _.exe_ tacked onto the end of the file name, it is a program you can execute. - -This leads to serious problems, like trojans posing as documents. Fortunately, that is not how things work in Linux. Sure, you may see occasional executable file endings in _.sh_ that indicate they are runnable shell scripts, but this is mostly for the benefit of humans eyeballing files, the same way when you use `ls --color`, the names of executable files show up in bright green. - -The fact is most applications have no extension at all. What determines whether a file is really program is the _x_ (for _executable_ ) bit. You can make any file executable by running -``` -chmod a+x some_program - -``` - -regardless of its extension or lack thereof. The `x` in the command above sets the _x_ bit and the `a` says you are setting it for _all_ users. You could also set it only for the group of users that own the file (`g+x`), or for only one user, the owner (`u+x`). - -Although we will be covering creating and running scripts from the command line later in this series, know that you can run a program by writing the path to it and then tacking on the name of the program on the end: -``` -path/to/directory/some_program - -``` - -Or, if you are currently in the same directory, you can use: -``` -./some_program - -``` - -There are other ways of making your program available from anywhere in the directory tree (hint: look up the `$PATH` environment variable), but you will be reading about those when we talk about shell scripting. - -### Copying, Moving, Linking - -Obviously, there are more ways of modifying and handling files from the command line than just playing around with their permissions. Most applications will create a new file if you still try to open a file that doesn't exist. Both -``` -nano test.txt - -``` - -and -``` -vim test.txt - -``` - -([nano][3] and [vim][4] being to popular command line text editors) will create an empty _test.txt_ file for you to edit if _test.txt_ didn't exist beforehand. - -You can also create an empty file by _touching_ it: -``` -touch test.txt - -``` - -Will create a file, but not open it in any application. - -You can use `cp` to make a copy of a file in another location or under a new name: -``` -cp test.txt copy_of_test.txt - -``` - -You can also copy a whole bunch of files: -``` -cp *.png /home/images - -``` - -The instruction above copies all the PNG files in the current directory into an _images/_ directory hanging off of your home directory. The _images/_ directory has to exist before you try this, or `cp` will show an error. Also, be warned that, if you copy a file to a directory that contains another file with the same name, `cp` will silently overwrite the old file with the new one. - -You can use -``` -cp -i *.png /home/images - -``` - -If you want `cp` to warn you of any dangers (the `-i` options stands for _interactive_ ). - -You can also copy whole directories, but you need the `-r` option for that: -``` -cp -rv directory_a/ directory_b - -``` - -The `-r` option stands for _recursive_ , meaning that `cp` will drill down into _directory_a_ , copying over all the files and subdirectories contained within. I personally like to include the `-v` option, as it makes `cp` _verbose_ , meaning that it will show you what it is doing instead of just copying silently and then exiting. - -The `mv` command moves stuff. That is, it changes files from one location to another. In its simplest form, `mv` looks a lot like `cp`: -``` -mv test.txt new_test.txt - -``` - -The command above makes _new_test.txt_ appear and _test.txt_ disappear. -``` -mv *.png /home/images - -``` - -Moves all the PNG files in the current directory to a directory called _images/_ hanging of your home directory. Again you have to be careful you do not overwrite existing files by accident. Use -``` -mv -i *.png /home/images - -``` - -the same way you would with `cp` if you want to be on the safe side. - -Apart from moving versus copying, another difference between `mv` and `cp`is when you move a directory: -``` -mv directory_a/ directory_b - -``` - -No need for a recursive flag here. This is because what you are really doing is renaming the directory, the same way in the first example, you were renaming the file*. In fact, even when you "move" a file from one directory to another, as long as both directories are on the same storage device and partition, you are renaming the file. - -You can do an experiment to prove it. `time` is a tool that lets you measure how long a command takes to execute. Look for a hefty file, something that weighs several hundred MBs or even some GBs (say, something like a long video) and try copying it from one directory to another like this: -``` -$ time cp hefty_file.mkv another_directory/ -real 0m3,868s -user 0m0,016s -sys 0m0,887s - -``` - -In bold is what you have to type into the terminal and below what `time` outputs. The number to focus on is the one on the first line, _real_ time. It takes nearly 4 seconds to copy the 355 MBs of _hefty_file.mkv_ to _another_directory/_. - -Now let's try moving it: -``` -$ time mv hefty_file.mkv another_directory/ -real 0m0,004s -user 0m0,000s -sys 0m0,003s - -``` - -Moving is nearly instantaneous! This is counterintuitive, since it would seem that `mv` would have to copy the file and then delete the original. That is two things `mv` has to do versus `cp`'s one. But, somehow, `mv` is 1000 times faster. - -That is because the file system's structure, with all its tree of directories, only exists for the users convenience. At the beginning of each partition there is something called a _partition table_ that tells the operating system where to find each file on the actual physical disk. On the disk, data is not split up into directories or even files. [There are tracks, sectors and clusters instead][5]. When you "move" a file within the same partition, what the operating system does is just change the entry for that file in the partition table, but it still points to the same cluster of information on the disk. - -Yes! Moving is a lie! At least within the same partition that is. If you try and move a file to a different partition or a different device, `mv` is still fast, but is noticeably slower than moving stuff around within the same partition. That is because this time there is actually copying and erasing of data going on. - -### Renaming - -There are several distinct command line `rename` utilities around. None are fixtures like `cp` or `mv` and they can work in slightly different ways. What they all have in common is that they are used to change _parts_ of the names of files. - -In Debian and Ubuntu, the default `rename` utility uses [regular expressions][6] (patterns of strings of characters) to mass change files in a directory. The instruction: -``` -rename 's/\.JPEG$/.jpg/' * - -``` - -will change all the extensions of files with the extension _JPEG_ to _jpg_. The file _IMG001.JPEG_ becomes _IMG001.jpg_ , _my_pic.JPEG_ becomes _my_pic.jpg_ , and so on. - -Another version of `rename` available by default in Manjaro, a derivative of Arch, is much simpler, but arguably less powerful: -``` -rename .JPEG .jpg * - -``` - -This does the same renaming as you saw above. In this version, `.JPEG` is the string of characters you want to change, `.jpg` is what you want to change it to, and `*` represents all the files in the current directory. - -The bottom line is that you are better off using `mv` if all you want to do is rename one file or directory, and that's because `mv` is realiably the same in all distributions everywhere. - -### Learning more - -Check out the both `mv` and `cp`'s _man_ pages to learn more. Run -``` -man cp - -``` - -or -``` -man mv - -``` - -to read about all the options these commands come with and which make them more powerful and safer to use. - --------------------------------------------------------------------------------- - -via: https://www.linux.com/blog/2018/8/linux-beginners-moving-things-around - -作者：[Paul Brown][a] -选题：[lujun9972](https://github.com/lujun9972) -译者：[译者ID](https://github.com/译者ID) -校对：[校对者ID](https://github.com/校对者ID) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 - -[a]: https://www.linux.com/users/bro66 -[1]: https://www.linux.com/blog/learn/2018/5/manipulating-directories-linux -[2]: https://www.linux.com/blog/learn/intro-to-linux/2018/7/users-groups-and-other-linux-beasts-part-2 -[3]: https://www.nano-editor.org/ -[4]: https://www.vim.org/ -[5]: https://en.wikipedia.org/wiki/Disk_sector -[6]: https://en.wikipedia.org/wiki/Regular_expression diff --git a/sources/tech/20180829 4 open source monitoring tools.md b/sources/tech/20180829 4 open source monitoring tools.md index dbc59d8a29..a5b8bf6806 100644 --- a/sources/tech/20180829 4 open source monitoring tools.md +++ b/sources/tech/20180829 4 open source monitoring tools.md @@ -1,4 +1,3 @@ -translating by sd886393 4 open source monitoring tools ====== diff --git a/sources/tech/20180831 Get desktop notifications from Emacs shell commands .md b/sources/tech/20180831 Get desktop notifications from Emacs shell commands .md new file mode 100644 index 0000000000..7d04e6d0a7 --- /dev/null +++ b/sources/tech/20180831 Get desktop notifications from Emacs shell commands .md @@ -0,0 +1,65 @@ +[#]: collector: (lujun9972) +[#]: translator: (lujun9972) +[#]: reviewer: ( ) +[#]: publisher: ( ) +[#]: url: ( ) +[#]: subject: (Get desktop notifications from Emacs shell commands ·) +[#]: via: (https://blog.hoetzel.info/post/eshell-notifications/) +[#]: author: (Jürgen Hötzel https://blog.hoetzel.info) + +Get desktop notifications from Emacs shell commands · +====== +When interacting with the operating systems I always use [Eshell][1] because it integrates seamlessly with Emacs, supports (remote) [TRAMP][2] file names and also works nice on Windows. + +After starting shell commands (like long running build jobs) I often lose track the task when switching buffers. + +Thanks to Emacs [hooks][3] mechanism you can customize Emacs to call a elisp function when an external command finishes. + +I use [John Wiegleys][4] excellent [alert][5] package to send desktop notifications: + +``` +(require 'alert) + +(defun eshell-command-alert (process status) + "Send `alert' with severity based on STATUS when PROCESS finished." + (let* ((cmd (process-command process)) + (buffer (process-buffer process)) + (msg (format "%s: %s" (mapconcat 'identity cmd " ") status))) + (if (string-prefix-p "finished" status) + (alert msg :buffer buffer :severity 'normal) + (alert msg :buffer buffer :severity 'urgent)))) + +(add-hook 'eshell-kill-hook #'eshell-command-alert) +``` + +[alert][5] rules can be setup programmatically. In my case I only want to get notified if the corresponding buffer is not visible: + +``` +(alert-add-rule :status '(buried) ;only send alert when buffer not visible + :mode 'eshell-mode + :style 'notifications) +``` + +This even works on [TRAMP][2] buffers. Below is a screenshot showing a Gnome desktop notification of a failed `make` command. + +![../../img/eshell.png][6] + +-------------------------------------------------------------------------------- + +via: https://blog.hoetzel.info/post/eshell-notifications/ + +作者：[Jürgen Hötzel][a] +选题：[lujun9972][b] +译者：[lujun9972](https://github.com/lujun9972) +校对：[校对者ID](https://github.com/校对者ID) + +本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 + +[a]: https://blog.hoetzel.info +[b]: https://github.com/lujun9972 +[1]: https://www.gnu.org/software/emacs/manual/html_mono/eshell.html (Eshell) +[2]: https://www.gnu.org/software/tramp/ (TRAMP) +[3]: https://www.gnu.org/software/emacs/manual/html_node/emacs/Hooks.html (hooks) +[4]: https://github.com/jwiegley (John Wiegleys) +[5]: https://github.com/jwiegley/alert (alert) +[6]: https://blog.hoetzel.info/img/eshell.png (../../img/eshell.png) diff --git a/sources/tech/20180831 Publishing Markdown to HTML with MDwiki.md b/sources/tech/20180831 Publishing Markdown to HTML with MDwiki.md deleted file mode 100644 index c25239b7ba..0000000000 --- a/sources/tech/20180831 Publishing Markdown to HTML with MDwiki.md +++ /dev/null @@ -1,73 +0,0 @@ -Publishing Markdown to HTML with MDwiki -====== - - - -There are plenty of reasons to like Markdown, a simple language with an easy-to-learn syntax that can be used with any text editor. Using tools like [Pandoc][1], you can convert Markdown text to [a variety of popular formats][2], including HTML. You can also automate that conversion process in a web server. An HTML5 and JavaScript application called [MDwiki][3], created by Timo Dörr, can take a stack of Markdown files and turn them into a website when requested from a browser. The MDwiki site includes a how-to guide and other information to help you get started: - -![MDwiki site getting started][5] - -What an Mdwiki site looks like. - -Inside the web server, a basic MDwiki site looks like this: - -![MDwiki site inside web server][7] - -What the webserver folder for that site looks like. - -I renamed the MDwiki HTML file `START.HTML` for this project. There is also one Markdown file that deals with navigation and a JSON file to hold a few configuration settings. Everything else is site content. - -While the overall website design is pretty much fixed by MDwiki, the content, styling, and number of pages are not. You can view a selection of different sites generated by MDwiki at [the MDwiki site][8]. It is fair to say that MDwiki sites lack the visual appeal that a web designer could achieve—but they are functional, and users should balance their simple appearance against the speed and ease of creating and editing them. - -Markdown comes in various flavors that extend a stable core functionality for different specific purposes. MDwiki uses GitHub flavor [Markdown][9], which adds features such as formatted code blocks and syntax highlighting for popular programming languages, making it well-suited for producing program documentation and tutorials. - -MDwiki also supports what it calls "gimmicks," which add extra functionality such as embedding YouTube video content and displaying mathematical formulas. These are worth exploring if you need them for specific projects. I find MDwiki an ideal tool for creating technical documentation and educational resources. I have also discovered some tricks and hacks that might not be immediately apparent. - -MDwiki works with any modern web browser when deployed in a web server; however, you do not need a web server if you access MDwiki with Mozilla Firefox. Most MDwiki users will opt to deploy completed projects on a web server to avoid excluding potential users, but development and testing can be done with just a text editor and Firefox. Completed MDwiki projects that are loaded into a Moodle Virtual Learning Environment (VLE) can be read by any modern browser, which could be useful in educational contexts. (This is probably also true for other VLE software, but you should test that.) - -MDwiki's default color scheme is not ideal for all projects, but you can replace it with another theme downloaded from [Bootswatch.com][10]. To do this, simply open the MDwiki HTML file in an editor, take out the `extlib/css/bootstrap-3.0.0.min.css` code, and insert the downloaded Bootswatch theme. There is also an MDwiki gimmick that lets users choose a Bootswatch theme to replace the default after MDwiki loads in their browser. I often work with users who have visual impairments, and they tend to prefer high-contrast themes, with white text on a dark background. - -![MDwiki screen with Bootswatch Superhero theme][12] - -MDwiki screen using the Bootswatch Superhero theme - -MDwiki, Markdown files, and static images are fine for many purposes. However, you might sometimes want to include, say, a JavaScript slideshow or a feedback form. Markdown files can include HTML code, but mixing Markdown with HTML can get confusing. One solution is to create the feature you want in a separate HTML file and display it inside a Markdown file with an iframe tag. I took this idea from the [Twine Cookbook][13], a support site for the Twine interactive fiction engine. The Twine Cookbook doesn’t actually use MDwiki, but combining Markdown and iframe tags opens up a wide range of creative possibilities. - -Here is an example: - -This HTML will display an HTML page created by the Twine interactive fiction engine inside a Markdown file. -``` - -``` - -The result in an MDwiki-generated site looks like this: - - - -In short, MDwiki is an excellent small application that achieves its purpose extremely well. - --------------------------------------------------------------------------------- - -via: https://opensource.com/article/18/8/markdown-html-publishing - -作者：[Peter Cheer][a] -选题：[lujun9972](https://github.com/lujun9972) -译者：[译者ID](https://github.com/译者ID) -校对：[校对者ID](https://github.com/校对者ID) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 - -[a]: https://opensource.com/users/petercheer -[1]: https://pandoc.org/ -[2]: https://opensource.com/downloads/pandoc-cheat-sheet -[3]: http://dynalon.github.io/mdwiki/#!index.md -[4]: https://opensource.com/file/407306 -[5]: https://opensource.com/sites/default/files/uploads/1_-_mdwiki_screenshot.png (MDwiki site getting started) -[6]: https://opensource.com/file/407311 -[7]: https://opensource.com/sites/default/files/uploads/2_-_mdwiki_inside_web_server.png (MDwiki site inside web server) -[8]: http://dynalon.github.io/mdwiki/#!examples.md -[9]: https://guides.github.com/features/mastering-markdown/ -[10]: https://bootswatch.com/ -[11]: https://opensource.com/file/407316 -[12]: https://opensource.com/sites/default/files/uploads/3_-_mdwiki_bootswatch_superhero.png (MDwiki screen with Bootswatch Superhero theme) -[13]: https://github.com/iftechfoundation/twine-cookbook diff --git a/sources/tech/20180831 Test containers with Python and Conu.md b/sources/tech/20180831 Test containers with Python and Conu.md deleted file mode 100644 index 9911901d51..0000000000 --- a/sources/tech/20180831 Test containers with Python and Conu.md +++ /dev/null @@ -1,164 +0,0 @@ -translating by GraveAccent Test containers with Python and Conu -====== - - - -More and more developers are using containers to develop and deploy their applications. This means that easily testing containers is also becoming important. [Conu][1] (short for container utilities) is a Python library that makes it easy to write tests for your containers. This article shows you how to use it to test your containers. - -### Getting started - -First you need a container application to test. For that, the following commands create a new directory with a container Dockerfile, and a Flask application to be served by the container. -``` -$ mkdir container_test -$ cd container_test -$ touch Dockerfile -$ touch app.py - -``` - -Copy the following code inside the app.py file. This is the customary basic Flask application that returns the string “Hello Container World!” -``` -from flask import Flask -app = Flask(__name__) - -@app.route('/') -def hello_world(): - return 'Hello Container World!' - -if __name__ == '__main__': - app.run(debug=True,host='0.0.0.0') - -``` - -### Create and Build a Test Container - -To build the test container, add the following instructions to the Dockerfile. -``` -FROM registry.fedoraproject.org/fedora-minimal:latest -RUN microdnf -y install python3-flask && microdnf clean all -ADD ./app.py /srv -CMD ["python3", "/srv/app.py"] - -``` - -Then build the container using the Docker CLI tool. -``` -$ sudo dnf -y install docker -$ sudo systemctl start docker -$ sudo docker build . -t flaskapp_container - -``` - -Note : The first two commands are only needed if Docker is not installed on your system. - -After the build use the following command to run the container. -``` -$ sudo docker run -p 5000:5000 --rm flaskapp_container -* Running on http://0.0.0.0:5000/ (Press CTRL+C to quit) -* Restarting with stat -* Debugger is active! -* Debugger PIN: 473-505-51 - -``` - -Finally, use curl to check that the Flask application is correctly running inside the container: -``` -$ curl http://127.0.0.1:5000 -Hello Container World! - -``` - -With the flaskapp_container now running and ready for testing, you can stop it using **Ctrl+C**. - -### Create a test script - -Before you write the test script, you must install conu. Inside the previously created container_test directory run the following commands. -``` -$ python3 -m venv .venv -$ source .venv/bin/activate -(.venv)$ pip install --upgrade pip -(.venv)$ pip install conu - -$ touch test_container.py - -``` - -Then copy and save the following script in the test_container.py file. -``` -import conu - -PORT = 5000 - -with conu.DockerBackend() as backend: - image = backend.ImageClass("flaskapp_container") - options = ["-p", "5000:5000"] - container = image.run_via_binary(additional_opts=options) - - try: - # Check that the container is running and wait for the flask application to start. - assert container.is_running() - container.wait_for_port(PORT) - - # Run a GET request on / port 5000. - http_response = container.http_request(path="/", port=PORT) - - # Check the response status code is 200 - assert http_response.ok - - # Get the response content - response_content = http_response.content.decode("utf-8") - - # Check that the "Hello Container World!" string is served. - assert "Hello Container World!" in response_content - - # Get the logs from the container - logs = [line for line in container.logs()] - # Check the the Flask application saw the GET request. - assert b'"GET / HTTP/1.1" 200 -' in logs[-1] - - finally: - container.stop() - container.delete() - -``` - -#### Test Setup - -The script starts by setting conu to use Docker as a backend to run the container. Then it sets the container image to use the flaskapp_container you built in the first part of this tutorial. - -The next step is to configure the options needed to run the container. In this example, the Flask application serves the content on port 5000. Therefore you need to expose this port and map it to the same port on the host. - -Finally, the script starts the container, and it’s now ready to be tested. - -#### Testing methods - -Before testing a container, check that the container is running and ready. The example script is using container.is_running and container.wait_for_port. These methods ensure the container is running and the service is available on the expected port. - -The container.http_request is a wrapper around the [requests][2] library which makes it convenient to send HTTP requests during the tests. This method returns a [requests.Response][3]object, so it’s easy to access the content of the response for testing. - -Conu also gives access to the container logs. Once again, this can be useful during testing. In the example above, the container.logs method returns the container logs. You can use them to assert that a specific log was printed, or for example that no exceptions were raised during testing. - -Conu provides many other useful methods to interface with containers. A full list of the APIs is available in the [documentation][4]. You can also consult the examples available on [GitHub][5]. - -All the code and files needed to run this tutorial are available on [GitHub][6] as well. For readers who want to take this example further, you can look at using [pytest][7] to run the tests and build a container test suite. - - --------------------------------------------------------------------------------- - -via: https://fedoramagazine.org/test-containers-python-conu/ - -作者：[Clément Verna][a] -选题：[lujun9972](https://github.com/lujun9972) -译者：[译者ID](https://github.com/译者ID) -校对：[校对者ID](https://github.com/校对者ID) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 - -[a]: https://fedoramagazine.org/author/cverna/ -[1]: https://github.com/user-cont/conu -[2]: http://docs.python-requests.org/en/master/ -[3]: http://docs.python-requests.org/en/master/api/#requests.Response -[4]: https://conu.readthedocs.io/en/latest/index.html -[5]: https://github.com/user-cont/conu/tree/master/docs/source/examples -[6]: https://github.com/cverna/container_test_script -[7]: https://docs.pytest.org/en/latest/ diff --git a/sources/tech/20180907 6.828 lab tools guide.md b/sources/tech/20180907 6.828 lab tools guide.md deleted file mode 100644 index e9061a3097..0000000000 --- a/sources/tech/20180907 6.828 lab tools guide.md +++ /dev/null @@ -1,201 +0,0 @@ -6.828 lab tools guide -====== -### 6.828 lab tools guide - -Familiarity with your environment is crucial for productive development and debugging. This page gives a brief overview of the JOS environment and useful GDB and QEMU commands. Don't take our word for it, though. Read the GDB and QEMU manuals. These are powerful tools that are worth knowing how to use. - -#### Debugging tips - -##### Kernel - -GDB is your friend. Use the qemu-gdb target (or its `qemu-gdb-nox` variant) to make QEMU wait for GDB to attach. See the GDB reference below for some commands that are useful when debugging kernels. - -If you're getting unexpected interrupts, exceptions, or triple faults, you can ask QEMU to generate a detailed log of interrupts using the -d argument. - -To debug virtual memory issues, try the QEMU monitor commands info mem (for a high-level overview) or info pg (for lots of detail). Note that these commands only display the _current_ page table. - -(Lab 4+) To debug multiple CPUs, use GDB's thread-related commands like thread and info threads. - -##### User environments (lab 3+) - -GDB also lets you debug user environments, but there are a few things you need to watch out for, since GDB doesn't know that there's a distinction between multiple user environments, or between user and kernel. - -You can start JOS with a specific user environment using make run- _name_ (or you can edit `kern/init.c` directly). To make QEMU wait for GDB to attach, use the run- _name_ -gdb variant. - -You can symbolically debug user code, just like you can kernel code, but you have to tell GDB which symbol table to use with the symbol-file command, since it can only use one symbol table at a time. The provided `.gdbinit` loads the kernel symbol table, `obj/kern/kernel`. The symbol table for a user environment is in its ELF binary, so you can load it using symbol-file obj/user/ _name_. _Don't_ load symbols from any `.o` files, as those haven't been relocated by the linker (libraries are statically linked into JOS user binaries, so those symbols are already included in each user binary). Make sure you get the _right_ user binary; library functions will be linked at different EIPs in different binaries and GDB won't know any better! - -(Lab 4+) Since GDB is attached to the virtual machine as a whole, it sees clock interrupts as just another control transfer. This makes it basically impossible to step through user code because a clock interrupt is virtually guaranteed the moment you let the VM run again. The stepi command works because it suppresses interrupts, but it only steps one assembly instruction. Breakpoints generally work, but watch out because you can hit the same EIP in a different environment (indeed, a different binary altogether!). - -#### Reference - -##### JOS makefile - -The JOS GNUmakefile includes a number of phony targets for running JOS in various ways. All of these targets configure QEMU to listen for GDB connections (the `*-gdb` targets also wait for this connection). To start once QEMU is running, simply run gdb from your lab directory. We provide a `.gdbinit` file that automatically points GDB at QEMU, loads the kernel symbol file, and switches between 16-bit and 32-bit mode. Exiting GDB will shut down QEMU. - - * make qemu -Build everything and start QEMU with the VGA console in a new window and the serial console in your terminal. To exit, either close the VGA window or press `Ctrl-c` or `Ctrl-a x` in your terminal. - * make qemu-nox -Like `make qemu`, but run with only the serial console. To exit, press `Ctrl-a x`. This is particularly useful over SSH connections to Athena dialups because the VGA window consumes a lot of bandwidth. - * make qemu-gdb -Like `make qemu`, but rather than passively accepting GDB connections at any time, this pauses at the first machine instruction and waits for a GDB connection. - * make qemu-nox-gdb -A combination of the `qemu-nox` and `qemu-gdb` targets. - * make run- _name_ -(Lab 3+) Run user program _name_. For example, `make run-hello` runs `user/hello.c`. - * make run- _name_ -nox, run- _name_ -gdb, run- _name_ -gdb-nox, -(Lab 3+) Variants of `run-name` that correspond to the variants of the `qemu` target. - - - -The makefile also accepts a few useful variables: - - * make V=1 ... -Verbose mode. Print out every command being executed, including arguments. - * make V=1 grade -Stop after any failed grade test and leave the QEMU output in `jos.out` for inspection. - * make QEMUEXTRA=' _args_ ' ... -Specify additional arguments to pass to QEMU. - - - -##### JOS obj/ - -The JOS GNUmakefile includes a number of phony targets for running JOS in various ways. All of these targets configure QEMU to listen for GDB connections (thetargets also wait for this connection). To start once QEMU is running, simply runfrom your lab directory. We provide afile that automatically points GDB at QEMU, loads the kernel symbol file, and switches between 16-bit and 32-bit mode. Exiting GDB will shut down QEMU.The makefile also accepts a few useful variables: - -When building JOS, the makefile also produces some additional output files that may prove useful while debugging: - - * `obj/boot/boot.asm`, `obj/kern/kernel.asm`, `obj/user/hello.asm`, etc. -Assembly code listings for the bootloader, kernel, and user programs. - * `obj/kern/kernel.sym`, `obj/user/hello.sym`, etc. -Symbol tables for the kernel and user programs. - * `obj/boot/boot.out`, `obj/kern/kernel`, `obj/user/hello`, etc -Linked ELF images of the kernel and user programs. These contain symbol information that can be used by GDB. - - - -##### GDB - -See the [GDB manual][1] for a full guide to GDB commands. Here are some particularly useful commands for 6.828, some of which don't typically come up outside of OS development. - - * Ctrl-c -Halt the machine and break in to GDB at the current instruction. If QEMU has multiple virtual CPUs, this halts all of them. - * c (or continue) -Continue execution until the next breakpoint or `Ctrl-c`. - * si (or stepi) -Execute one machine instruction. - * b function or b file:line (or breakpoint) -Set a breakpoint at the given function or line. - * b * _addr_ (or breakpoint) -Set a breakpoint at the EIP _addr_. - * set print pretty -Enable pretty-printing of arrays and structs. - * info registers -Print the general purpose registers, `eip`, `eflags`, and the segment selectors. For a much more thorough dump of the machine register state, see QEMU's own `info registers` command. - * x/ _N_ x _addr_ -Display a hex dump of _N_ words starting at virtual address _addr_. If _N_ is omitted, it defaults to 1. _addr_ can be any expression. - * x/ _N_ i _addr_ -Display the _N_ assembly instructions starting at _addr_. Using `$eip` as _addr_ will display the instructions at the current instruction pointer. - * symbol-file _file_ -(Lab 3+) Switch to symbol file _file_. When GDB attaches to QEMU, it has no notion of the process boundaries within the virtual machine, so we have to tell it which symbols to use. By default, we configure GDB to use the kernel symbol file, `obj/kern/kernel`. If the machine is running user code, say `hello.c`, you can switch to the hello symbol file using `symbol-file obj/user/hello`. - - - -QEMU represents each virtual CPU as a thread in GDB, so you can use all of GDB's thread-related commands to view or manipulate QEMU's virtual CPUs. - - * thread _n_ -GDB focuses on one thread (i.e., CPU) at a time. This command switches that focus to thread _n_ , numbered from zero. - * info threads -List all threads (i.e., CPUs), including their state (active or halted) and what function they're in. - - - -##### QEMU - -QEMU includes a built-in monitor that can inspect and modify the machine state in useful ways. To enter the monitor, press Ctrl-a c in the terminal running QEMU. Press Ctrl-a c again to switch back to the serial console. - -For a complete reference to the monitor commands, see the [QEMU manual][2]. Here are some particularly useful commands: - - * xp/ _N_ x _paddr_ -Display a hex dump of _N_ words starting at _physical_ address _paddr_. If _N_ is omitted, it defaults to 1. This is the physical memory analogue of GDB's `x` command. - - * info registers -Display a full dump of the machine's internal register state. In particular, this includes the machine's _hidden_ segment state for the segment selectors and the local, global, and interrupt descriptor tables, plus the task register. This hidden state is the information the virtual CPU read from the GDT/LDT when the segment selector was loaded. Here's the CS when running in the JOS kernel in lab 1 and the meaning of each field: -``` - CS =0008 10000000 ffffffff 10cf9a00 DPL=0 CS32 [-R-] -``` - - * `CS =0008` -The visible part of the code selector. We're using segment 0x8. This also tells us we're referring to the global descriptor table (0x8 &4=0), and our CPL (current privilege level) is 0x8&3=0. - * `10000000` -The base of this segment. Linear address = logical address + 0x10000000. - * `ffffffff` -The limit of this segment. Linear addresses above 0xffffffff will result in segment violation exceptions. - * `10cf9a00` -The raw flags of this segment, which QEMU helpfully decodes for us in the next few fields. - * `DPL=0` -The privilege level of this segment. Only code running with privilege level 0 can load this segment. - * `CS32` -This is a 32-bit code segment. Other values include `DS` for data segments (not to be confused with the DS register), and `LDT` for local descriptor tables. - * `[-R-]` -This segment is read-only. - * info mem -(Lab 2+) Display mapped virtual memory and permissions. For example, -``` - ef7c0000-ef800000 00040000 urw - efbf8000-efc00000 00008000 -rw - -``` - -tells us that the 0x00040000 bytes of memory from 0xef7c0000 to 0xef800000 are mapped read/write and user-accessible, while the memory from 0xefbf8000 to 0xefc00000 is mapped read/write, but only kernel-accessible. - - * info pg -(Lab 2+) Display the current page table structure. The output is similar to `info mem`, but distinguishes page directory entries and page table entries and gives the permissions for each separately. Repeated PTE's and entire page tables are folded up into a single line. For example, -``` - VPN range Entry Flags Physical page - [00000-003ff] PDE[000] -------UWP - [00200-00233] PTE[200-233] -------U-P 00380 0037e 0037d 0037c 0037b 0037a .. - [00800-00bff] PDE[002] ----A--UWP - [00800-00801] PTE[000-001] ----A--U-P 0034b 00349 - [00802-00802] PTE[002] -------U-P 00348 - -``` - -This shows two page directory entries, spanning virtual addresses 0x00000000 to 0x003fffff and 0x00800000 to 0x00bfffff, respectively. Both PDE's are present, writable, and user and the second PDE is also accessed. The second of these page tables maps three pages, spanning virtual addresses 0x00800000 through 0x00802fff, of which the first two are present, user, and accessed and the third is only present and user. The first of these PTE's maps physical page 0x34b. - - - - -QEMU also takes some useful command line arguments, which can be passed into the JOS makefile using the - - * make QEMUEXTRA='-d int' ... -Log all interrupts, along with a full register dump, to `qemu.log`. You can ignore the first two log entries, "SMM: enter" and "SMM: after RMS", as these are generated before entering the boot loader. After this, log entries look like -``` - 4: v=30 e=0000 i=1 cpl=3 IP=001b:00800e2e pc=00800e2e SP=0023:eebfdf28 EAX=00000005 - EAX=00000005 EBX=00001002 ECX=00200000 EDX=00000000 - ESI=00000805 EDI=00200000 EBP=eebfdf60 ESP=eebfdf28 - ... - -``` - -The first line describes the interrupt. The `4:` is just a log record counter. `v` gives the vector number in hex. `e` gives the error code. `i=1` indicates that this was produced by an `int` instruction (versus a hardware interrupt). The rest of the line should be self-explanatory. See info registers for a description of the register dump that follows. - -Note: If you're running a pre-0.15 version of QEMU, the log will be written to `/tmp` instead of the current directory. - - - - --------------------------------------------------------------------------------- - -via: https://pdos.csail.mit.edu/6.828/2018/labguide.html - -作者：[csail.mit][a] -选题：[lujun9972][b] -译者：[译者ID](https://github.com/译者ID) -校对：[校对者ID](https://github.com/校对者ID) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 - -[a]: https://pdos.csail.mit.edu -[b]: https://github.com/lujun9972 -[1]: http://sourceware.org/gdb/current/onlinedocs/gdb/ -[2]: http://wiki.qemu.org/download/qemu-doc.html#pcsys_005fmonitor diff --git a/sources/tech/20180911 Know Your Storage- Block, File - Object.md b/sources/tech/20180911 Know Your Storage- Block, File - Object.md deleted file mode 100644 index 24f179d9d5..0000000000 --- a/sources/tech/20180911 Know Your Storage- Block, File - Object.md +++ /dev/null @@ -1,62 +0,0 @@ -Know Your Storage: Block, File & Object -====== - - - -Dealing with the tremendous amount of data generated today presents a big challenge for companies who create or consume such data. It’s a challenge for tech companies that are dealing with related storage issues. - -“Data is growing exponentially each year, and we find that the majority of data growth is due to increased consumption and industries adopting transformational projects to expand value. Certainly, the Internet of Things (IoT) has contributed greatly to data growth, but the key challenge for software-defined storage is how to address the use cases associated with data growth,” said Michael St. Jean, principal product marketing manager, Red Hat Storage. - -Every challenge is an opportunity. “The deluge of data being generated by old and new sources today is certainly presenting us with opportunities to meet our customers escalating needs in the areas of scale, performance, resiliency, and governance,” said Tad Brockway, General Manager for Azure Storage, Media and Edge. - -### Trinity of modern software-defined storage - -There are three different kinds of storage solutions -- block, file, and object -- each serving a different purpose while working with the others. - -Block storage is the oldest form of data storage, where data is stored in fixed-length blocks or chunks of data. Block storage is used in enterprise storage environments and usually is accessed using Fibre Channel or iSCSI interface. “Block storage requires an application to map where the data is stored on the storage device,” according to SUSE’s Larry Morris, Sr. Product Manager, Software Defined Storage. - -Block storage is virtualized in storage area network and software defined storage systems, which are abstracted logical devices that reside on a shared hardware infrastructure and are created and presented to the host operating system of a server, virtual server, or hypervisor via protocols like SCSI, SATA, SAS, FCP, FCoE, or iSCSI. - -“Block storage splits a single storage volume (like a virtual or cloud storage node, or a good old fashioned hard disk) into individual instances known as blocks,” said St. Jean. - -Each block exists independently and can be formatted with its own data transfer protocol and operating system — giving users complete configuration autonomy. Because block storage systems aren’t burdened with the same investigative file-finding duties as the file storage systems, block storage is a faster storage system. Pairing that speed with configuration flexibility makes block storage ideal for raw server storage or rich media databases. - -Block storage can be used to host operating systems, applications, databases, entire virtual machines and containers. Traditionally, block storage can only be accessed by individual machine, or machines in a cluster, to which it has been presented. - -### File-based storage - -File-based storage uses a filesystem to map where the data is stored on the storage device. It’s a dominant technology used on direct- and networked-attached storage system, and it takes care of two things: organizing data and representing it to users. “With file storage, data is arranged on the server side in the exact same format as the clients see it. This allows the user to request a file by some unique identifier — like a name, location, or URL — which is communicated to the storage system using specific data transfer protocols,” said St. Jean. - -The result is a type of hierarchical file structure that can be navigated from top to bottom. File storage is layered on top of block storage, allowing users to see and access data as files and folders, but restricting access to the blocks that stand up those files and folders. - -“File storage is typically represented by shared filesystems like NFS and CIFS/SMB that can be accessed by many servers over an IP network. Access can be controlled at a file, directory, and export level via user and group permissions. File storage can be used to store files needed by multiple users and machines, application binaries, databases, virtual machines, and can be used by containers,” explained Brockway. - -### Object storage - -Object storage is the newest form of data storage, and it provides a repository for unstructured data which separates the content from the indexing and allows the concatenation of multiple files into an object. An object is a piece of data paired with any associated metadata that provides context about the bytes contained within the object (things like how old or big the data is). Those two things together — the data and metadata — make an object. - -One advantage of object storage is the unique identifier associated with each piece of data. Accessing the data involves using the unique identifier and does not require the application or user to know where the data is actually stored. Object data is accessed through APIs. - -“The data stored in objects is uncompressed and unencrypted, and the objects themselves are arranged in object stores (a central repository filled with many other objects) or containers (a package that contains all of the files an application needs to run). Objects, object stores, and containers are very flat in nature — compared to the hierarchical structure of file storage systems — which allow them to be accessed very quickly at huge scale,” explained St. Jean. - -Object stores can scale to many petabytes to accommodate the largest datasets and are a great choice for images, audio, video, logs, backups, and data used by analytics services. - -### Conclusion - -Now you know about the various types of storage and how they are used. Stay tuned to learn more about software-defined storage as we examine the topic in the future. - -Join us at [Open Source Summit + Embedded Linux Conference Europe][1] in Edinburgh, UK on October 22-24, 2018, for 100+ sessions on Linux, Cloud, Containers, AI, Community, and more. - --------------------------------------------------------------------------------- - -via: https://www.linux.com/blog/2018/9/know-your-storage-block-file-object - -作者：[Swapnil Bhartiya][a] -选题：[lujun9972](https://github.com/lujun9972) -译者：[译者ID](https://github.com/译者ID) -校对：[校对者ID](https://github.com/校对者ID) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 - -[a]: https://www.linux.com/users/arnieswap -[1]: https://events.linuxfoundation.org/events/elc-openiot-europe-2018/ diff --git a/sources/tech/20180911 Tools Used in 6.828.md b/sources/tech/20180911 Tools Used in 6.828.md deleted file mode 100644 index c9afeae4ea..0000000000 --- a/sources/tech/20180911 Tools Used in 6.828.md +++ /dev/null @@ -1,247 +0,0 @@ -Tools Used in 6.828 -====== -### Tools Used in 6.828 - -You'll use two sets of tools in this class: an x86 emulator, QEMU, for running your kernel; and a compiler toolchain, including assembler, linker, C compiler, and debugger, for compiling and testing your kernel. This page has the information you'll need to download and install your own copies. This class assumes familiarity with Unix commands throughout. - -We highly recommend using a Debathena machine, such as athena.dialup.mit.edu, to work on the labs. If you use the MIT Athena machines that run Linux, then all the software tools you will need for this course are located in the 6.828 locker: just type 'add -f 6.828' to get access to them. - -If you don't have access to a Debathena machine, we recommend you use a virtual machine with Linux. If you really want to, you can build and install the tools on your own machine. We have instructions below for Linux and MacOS computers. - -It should be possible to get this development environment running under windows with the help of [Cygwin][1]. Install cygwin, and be sure to install the flex and bison packages (they are under the development header). - -For an overview of useful commands in the tools used in 6.828, see the [lab tools guide][2]. - -#### Compiler Toolchain - -A "compiler toolchain" is the set of programs, including a C compiler, assemblers, and linkers, that turn code into executable binaries. You'll need a compiler toolchain that generates code for 32-bit Intel architectures ("x86" architectures) in the ELF binary format. - -##### Test Your Compiler Toolchain - -Modern Linux and BSD UNIX distributions already provide a toolchain suitable for 6.828. To test your distribution, try the following commands: - -``` -% objdump -i - -``` - -The second line should say `elf32-i386`. - -``` -% gcc -m32 -print-libgcc-file-name - -``` - -The command should print something like `/usr/lib/gcc/i486-linux-gnu/version/libgcc.a` or `/usr/lib/gcc/x86_64-linux-gnu/version/32/libgcc.a` - -If both these commands succeed, you're all set, and don't need to compile your own toolchain. - -If the gcc command fails, you may need to install a development environment. On Ubuntu Linux, try this: - -``` -% sudo apt-get install -y build-essential gdb - -``` - -On 64-bit machines, you may need to install a 32-bit support library. The symptom is that linking fails with error messages like "`__udivdi3` not found" and "`__muldi3` not found". On Ubuntu Linux, try this to fix the problem: - -``` -% sudo apt-get install gcc-multilib - -``` - -##### Using a Virtual Machine - -Otherwise, the easiest way to get a compatible toolchain is to install a modern Linux distribution on your computer. With platform virtualization, Linux can cohabitate with your normal computing environment. Installing a Linux virtual machine is a two step process. First, you download the virtualization platform. - - * [**VirtualBox**][3] (free for Mac, Linux, Windows) — [Download page][3] - * [VMware Player][4] (free for Linux and Windows, registration required) - * [VMware Fusion][5] (Downloadable from IS&T for free). - - - -VirtualBox is a little slower and less flexible, but free! - -Once the virtualization platform is installed, download a boot disk image for the Linux distribution of your choice. - - * [Ubuntu Desktop][6] is what we use. - - - -This will download a file named something like `ubuntu-10.04.1-desktop-i386.iso`. Start up your virtualization platform and create a new (32-bit) virtual machine. Use the downloaded Ubuntu image as a boot disk; the procedure differs among VMs but is pretty simple. Type `objdump -i`, as above, to verify that your toolchain is now set up. You will do your work inside the VM. - -##### Building Your Own Compiler Toolchain - -This will take longer to set up, but give slightly better performance than a virtual machine, and lets you work in your own familiar environment (Unix/MacOS). Fast-forward to the end for MacOS instructions. - -###### Linux - -You can use your own tool chain by adding the following line to `conf/env.mk`: - -``` -GCCPREFIX= - -``` - -We assume that you are installing the toolchain into `/usr/local`. You will need a fair amount of disk space to compile the tools (around 1GiB). If you don't have that much space, delete each directory after its `make install` step. - -Download the following packages: - -+ ftp://ftp.gmplib.org/pub/gmp-5.0.2/gmp-5.0.2.tar.bz2 -+ https://www.mpfr.org/mpfr-3.1.2/mpfr-3.1.2.tar.bz2 -+ http://www.multiprecision.org/downloads/mpc-0.9.tar.gz -+ http://ftpmirror.gnu.org/binutils/binutils-2.21.1.tar.bz2 -+ http://ftpmirror.gnu.org/gcc/gcc-4.6.4/gcc-core-4.6.4.tar.bz2 -+ http://ftpmirror.gnu.org/gdb/gdb-7.3.1.tar.bz2 - -(You may also use newer versions of these packages.) Unpack and build the packages. The `green bold` text shows you how to install into `/usr/local`, which is what we recommend. To install into a different directory, $PFX, note the differences in lighter type ([hide][7]). If you have problems, see below. - -``` -export PATH=$PFX/bin:$PATH -export LD_LIBRARY_PATH=$PFX/lib:$LD_LIBRARY_PATH - -tar xjf gmp-5.0.2.tar.bz2 -cd gmp-5.0.2 -./configure --prefix=$PFX -make -make install # This step may require privilege (sudo make install) -cd .. - -tar xjf mpfr-3.1.2.tar.bz2 -cd mpfr-3.1.2 -./configure --prefix=$PFX --with-gmp=$PFX -make -make install # This step may require privilege (sudo make install) -cd .. - -tar xzf mpc-0.9.tar.gz -cd mpc-0.9 -./configure --prefix=$PFX --with-gmp=$PFX --with-mpfr=$PFX -make -make install # This step may require privilege (sudo make install) -cd .. - - -tar xjf binutils-2.21.1.tar.bz2 -cd binutils-2.21.1 -./configure --prefix=$PFX --target=i386-jos-elf --disable-werror -make -make install # This step may require privilege (sudo make install) -cd .. - -i386-jos-elf-objdump -i -# Should produce output like: -# BFD header file version (GNU Binutils) 2.21.1 -# elf32-i386 -# (header little endian, data little endian) -# i386... - - -tar xjf gcc-core-4.6.4.tar.bz2 -cd gcc-4.6.4 -mkdir build # GCC will not compile correctly unless you build in a separate directory -cd build -../configure --prefix=$PFX --with-gmp=$PFX --with-mpfr=$PFX --with-mpc=$PFX \ - --target=i386-jos-elf --disable-werror \ - --disable-libssp --disable-libmudflap --with-newlib \ - --without-headers --enable-languages=c MAKEINFO=missing -make all-gcc -make install-gcc # This step may require privilege (sudo make install-gcc) -make all-target-libgcc -make install-target-libgcc # This step may require privilege (sudo make install-target-libgcc) -cd ../.. - -i386-jos-elf-gcc -v -# Should produce output like: -# Using built-in specs. -# COLLECT_GCC=i386-jos-elf-gcc -# COLLECT_LTO_WRAPPER=/usr/local/libexec/gcc/i386-jos-elf/4.6.4/lto-wrapper -# Target: i386-jos-elf - - -tar xjf gdb-7.3.1.tar.bz2 -cd gdb-7.3.1 -./configure --prefix=$PFX --target=i386-jos-elf --program-prefix=i386-jos-elf- \ - --disable-werror -make all -make install # This step may require privilege (sudo make install) -cd .. - -``` - -###### Linux troubleshooting - - * Q. I can't run `make install` because I don't have root permission on this machine. -A. Our instructions assume you are installing into the `/usr/local` directory. However, this may not be allowed in your environment. If you can only install code into your home directory, that's OK. In the instructions above, replace `--prefix=/usr/local` with `--prefix=$HOME` (and [click here][7] to update the instructions further). You will also need to change your `PATH` and `LD_LIBRARY_PATH` environment variables, to inform your shell where to find the tools. For example: -``` - export PATH=$HOME/bin:$PATH - export LD_LIBRARY_PATH=$HOME/lib:$LD_LIBRARY_PATH -``` - -Enter these lines in your `~/.bashrc` file so you don't need to type them every time you log in. - - - - * Q. My build fails with an inscrutable message about "library not found". -A. You need to set your `LD_LIBRARY_PATH`. The environment variable must include the `PREFIX/lib` directory (for instance, `/usr/local/lib`). - - - -#### MacOS - -First begin by installing developer tools on Mac OSX: -`xcode-select --install` - -First begin by installing developer tools on Mac OSX: - -You can install the qemu dependencies from homebrew, however do not install qemu itself as you will need the 6.828 patched version. - -`brew install $(brew deps qemu)` - -The gettext utility does not add installed binaries to the path, so you will need to run - -`PATH=${PATH}:/usr/local/opt/gettext/bin make install` - -when installing qemu below. - -### QEMU Emulator - -[QEMU][8] is a modern and fast PC emulator. QEMU version 2.3.0 is set up on Athena for x86 machines in the 6.828 locker (`add -f 6.828`) - -Unfortunately, QEMU's debugging facilities, while powerful, are somewhat immature, so we highly recommend you use our patched version of QEMU instead of the stock version that may come with your distribution. The version installed on Athena is already patched. To build your own patched version of QEMU: - - 1. Clone the IAP 6.828 QEMU git repository `git clone https://github.com/mit-pdos/6.828-qemu.git qemu` - 2. On Linux, you may need to install several libraries. We have successfully built 6.828 QEMU on Debian/Ubuntu 16.04 after installing the following packages: libsdl1.2-dev, libtool-bin, libglib2.0-dev, libz-dev, and libpixman-1-dev. - 3. Configure the source code (optional arguments are shown in square brackets; replace PFX with a path of your choice) - 1. Linux: `./configure --disable-kvm --disable-werror [--prefix=PFX] [--target-list="i386-softmmu x86_64-softmmu"]` - 2. OS X: `./configure --disable-kvm --disable-werror --disable-sdl [--prefix=PFX] [--target-list="i386-softmmu x86_64-softmmu"]` The `prefix` argument specifies where to install QEMU; without it QEMU will install to `/usr/local` by default. The `target-list` argument simply slims down the architectures QEMU will build support for. - 4. Run `make && make install` - - - - --------------------------------------------------------------------------------- - -via: https://pdos.csail.mit.edu/6.828/2018/tools.html - -作者：[csail.mit][a] -选题：[lujun9972][b] -译者：[译者ID](https://github.com/译者ID) -校对：[校对者ID](https://github.com/校对者ID) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 - -[a]: https://pdos.csail.mit.edu -[b]: https://github.com/lujun9972 -[1]: http://www.cygwin.com -[2]: labguide.html -[3]: http://www.oracle.com/us/technologies/virtualization/oraclevm/ -[4]: http://www.vmware.com/products/player/ -[5]: http://www.vmware.com/products/fusion/ -[6]: http://www.ubuntu.com/download/desktop -[7]: -[8]: http://www.nongnu.org/qemu/ -[9]: mailto:6828-staff@lists.csail.mit.edu -[10]: https://i.creativecommons.org/l/by/3.0/us/88x31.png -[11]: https://creativecommons.org/licenses/by/3.0/us/ -[12]: https://pdos.csail.mit.edu/6.828/2018/index.html diff --git a/sources/tech/20180912 How to turn on an LED with Fedora IoT.md b/sources/tech/20180912 How to turn on an LED with Fedora IoT.md deleted file mode 100644 index 007cfc27ab..0000000000 --- a/sources/tech/20180912 How to turn on an LED with Fedora IoT.md +++ /dev/null @@ -1,201 +0,0 @@ -How to turn on an LED with Fedora IoT -====== - - - -Do you enjoy running Fedora, containers, and have a Raspberry Pi? What about using all three together to play with LEDs? This article introduces Fedora IoT and shows you how to install a preview image on a Raspberry Pi. You’ll also learn how to interact with GPIO in order to light up an LED. - -### What is Fedora IoT? - -Fedora IoT is one of the current Fedora Project objectives, with a plan to become a full Fedora Edition. The result will be a system that runs on ARM (aarch64 only at the moment) devices such as the Raspberry Pi, as well as on the x86_64 architecture. - -![][1] - -Fedora IoT is based on OSTree, like [Fedora Silverblue][2] and the former [Atomic Host][3]. - -### Download and install Fedora IoT - -The official Fedora IoT images are coming with the Fedora 29 release. However, in the meantime you can download a [Fedora 28-based image][4] for this experiment. - -You have two options to install the system: either flash the SD card using a dd command, or use a fedora-arm-installer tool. The Fedora Wiki offers more information about [setting up a physical device][5] for IoT. Also, remember that you might need to resize the third partition. - -Once you insert the SD card into the device, you’ll need to complete the installation by creating a user. This step requires either a serial connection, or a HDMI display with a keyboard to interact with the device. - -When the system is installed and ready, the next step is to configure a network connection. Log in to the system with the user you have just created choose one of the following options: - - * If you need to configure your network manually, run a command similar to the following. Remember to use the right addresses for your network: -``` - $ nmcli connection add con-name cable ipv4.addresses \ - 192.168.0.10/24 ipv4.gateway 192.168.0.1 \ - connection.autoconnect true ipv4.dns "8.8.8.8,1.1.1.1" \ - type ethernet ifname eth0 ipv4.method manual - -``` - - * If there’s a DHCP service on your network, run a command like this: - -``` - $ nmcli con add type ethernet con-name cable ifname eth0 -``` - - - - -### **The GPIO interface in Fedora** - -Many tutorials about GPIO on Linux focus on a legacy GPIO sysfis interface. This interface is deprecated, and the upstream Linux kernel community plan to remove it completely, due to security and other issues. - -The Fedora kernel is already compiled without this legacy interface, so there’s no /sys/class/gpio on the system. This tutorial uses a new character device /dev/gpiochipN provided by the upstream kernel. This is the current way of interacting with GPIO. - -To interact with this new device, you need to use a library and a set of command line interface tools. The common command line tools such as echo or cat won’t work with this device. - -You can install the CLI tools by installing the libgpiod-utils package. A corresponding Python library is provided by the python3-libgpiod package. - -### **Creating a container with Podman** - -[Podman][6] is a container runtime with a command line interface similar to Docker. The big advantage of Podman is it doesn’t run any daemon in the background. That’s especially useful for devices with limited resources. Podman also allows you to start containerized services with systemd unit files. Plus, it has many additional features. - -We’ll create a container in these two steps: - - 1. Create a layered image containing the required packages. - 2. Create a new container starting from our image. - - - -First, create a file Dockerfile with the content below. This tells podman to build an image based on the latest Fedora image available in the registry. Then it updates the system inside and installs some packages: - -``` -FROM fedora:latest -RUN dnf -y update -RUN dnf -y install libgpiod-utils python3-libgpiod - -``` - -You have created a build recipe of a container image based on the latest Fedora with updates, plus packages to interact with GPIO. - -Now, run the following command to build your base image: - -``` -$ sudo podman build --tag fedora:gpiobase -f ./Dockerfile - -``` - -You have just created your custom image with all the bits in place. You can play with this base container images as many times as you want without installing the packages every time you run it. - -### Working with Podman - -To verify the image is present, run the following command: - -``` -$ sudo podman images -REPOSITORY TAG IMAGE ID CREATED SIZE -localhost/fedora gpiobase 67a2b2b93b4b 10 minutes ago 488MB -docker.io/library/fedora latest c18042d7fac6 2 days ago 300MB - -``` - -Now, start the container and do some actual experiments. Containers are normally isolated and don’t have an access to the host system, including the GPIO interface. Therefore, you need to mount it inside while starting the container. To do this, use the –device option in the following command: - -``` -$ sudo podman run -it --name gpioexperiment --device=/dev/gpiochip0 localhost/fedora:gpiobase /bin/bash - -``` - -You are now inside the running container. Before you move on, here are some more container commands. For now, exit the container by typing exit or pressing **Ctrl+D**. - -To list the the existing containers, including those not currently running, such as the one you just created, run: - -``` -$ sudo podman container ls -a -CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES -64e661d5d4e8 localhost/fedora:gpiobase /bin/bash 37 seconds ago Exited (0) Less than a second ago gpioexperiment - -``` - -To create a new container, run this command: - -``` -$ sudo podman run -it --name newexperiment --device=/dev/gpiochip0 localhost/fedora:gpiobase /bin/bash - -``` - -Delete it with the following command: - -``` -$ sudo podman rm newexperiment - -``` - -### **Turn on an LED** - -Now you can use the container you already created. If you exited from the container, start it again with this command: - -``` -$ sudo podman start -ia gpioexperiment - -``` - -As already discussed, you can use the CLI tools provided by the libgpiod-utils package in Fedora. To list the available GPIO chips, run: - -``` -$ gpiodetect -gpiochip0 [pinctrl-bcm2835] (54 lines) - -``` - -To get the list of the lines exposed by a specific chip, run: - -``` -$ gpioinfo gpiochip0 - -``` - -Notice there’s no correlation between the number of physical pins and the number of lines printed by the previous command. What’s important is the BCM number, as shown on [pinout.xyz][7]. It is not advised to play with the lines that don’t have a corresponding BCM number. - -Now, connect an LED to the physical pin 40, that is BCM 21. Remember: the shorter leg of the LED (the negative leg, called the cathode) must be connected to a GND pin of the Raspberry Pi with a 330 ohm resistor, and the long leg (the anode) to the physical pin 40. - -To turn the LED on, run the following command. It will stay on until you press **Ctrl+C** : - -``` -$ gpioset --mode=wait gpiochip0 21=1 - -``` - -To light it up for a certain period of time, add the -b (run in the background) and -s NUM (how many seconds) parameters, as shown below. For example, to light the LED for 5 seconds, run: - -``` -$ gpioset -b -s 5 --mode=time gpiochip0 21=1 - -``` - -Another useful command is gpioget. It gets the status of a pin (high or low), and can be useful to detect buttons and switches. - -![Closeup of LED connection with GPIO][8] - -### **Conclusion** - -You can also play with LEDs using Python — [there are some examples here][9]. And you can also use the i2c devices inside the container as well. In addition, Podman is not strictly related to this Fedora edition. You can install it on any existing Fedora Edition, or try it on the two new OSTree-based systems in Fedora: [Fedora Silverblue][2] and [Fedora CoreOS][10]. - - --------------------------------------------------------------------------------- - -via: https://fedoramagazine.org/turnon-led-fedora-iot/ - -作者：[Alessio Ciregia][a] -选题：[lujun9972](https://github.com/lujun9972) -译者：[译者ID](https://github.com/译者ID) -校对：[校对者ID](https://github.com/校对者ID) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 - -[a]: http://alciregi.id.fedoraproject.org/ -[1]: https://fedoramagazine.org/wp-content/uploads/2018/08/oled-1024x768.png -[2]: https://teamsilverblue.org/ -[3]: https://www.projectatomic.io/ -[4]: https://kojipkgs.fedoraproject.org/compose/iot/latest-Fedora-IoT-28/compose/IoT/ -[5]: https://fedoraproject.org/wiki/InternetOfThings/GettingStarted#Setting_up_a_Physical_Device -[6]: https://github.com/containers/libpod -[7]: https://pinout.xyz/ -[8]: https://fedoramagazine.org/wp-content/uploads/2018/08/breadboard-1024x768.png -[9]: https://github.com/brgl/libgpiod/tree/master/bindings/python/examples -[10]: https://coreos.fedoraproject.org/ diff --git a/sources/tech/20180913 Lab 1- PC Bootstrap and GCC Calling Conventions.md b/sources/tech/20180913 Lab 1- PC Bootstrap and GCC Calling Conventions.md deleted file mode 100644 index 365b5eb5f8..0000000000 --- a/sources/tech/20180913 Lab 1- PC Bootstrap and GCC Calling Conventions.md +++ /dev/null @@ -1,616 +0,0 @@ -Lab 1: PC Bootstrap and GCC Calling Conventions -====== -### Lab 1: Booting a PC - -#### Introduction - -This lab is split into three parts. The first part concentrates on getting familiarized with x86 assembly language, the QEMU x86 emulator, and the PC's power-on bootstrap procedure. The second part examines the boot loader for our 6.828 kernel, which resides in the `boot` directory of the `lab` tree. Finally, the third part delves into the initial template for our 6.828 kernel itself, named JOS, which resides in the `kernel` directory. - -##### Software Setup - -The files you will need for this and subsequent lab assignments in this course are distributed using the [Git][1] version control system. To learn more about Git, take a look at the [Git user's manual][2], or, if you are already familiar with other version control systems, you may find this [CS-oriented overview of Git][3] useful. - -The URL for the course Git repository is +0 -K> - -``` - -Each line gives the file name and line within that file of the stack frame's `eip`, followed by the name of the function and the offset of the `eip` from the first instruction of the function (e.g., `monitor+106` means the return `eip` is 106 bytes past the beginning of `monitor`). - -Be sure to print the file and function names on a separate line, to avoid confusing the grading script. - -Tip: printf format strings provide an easy, albeit obscure, way to print non-null-terminated strings like those in STABS tables. `printf("%.*s", length, string)` prints at most `length` characters of `string`. Take a look at the printf man page to find out why this works. - -You may find that some functions are missing from the backtrace. For example, you will probably see a call to `monitor()` but not to `runcmd()`. This is because the compiler in-lines some function calls. Other optimizations may cause you to see unexpected line numbers. If you get rid of the `-O2` from `GNUMakefile`, the backtraces may make more sense (but your kernel will run more slowly). - -**This completes the lab.** In the `lab` directory, commit your changes with git commit and type make handin to submit your code. - --------------------------------------------------------------------------------- - -via: https://pdos.csail.mit.edu/6.828/2018/labs/lab1/ - -作者：[csail.mit][a] -选题：[lujun9972][b] -译者：[译者ID](https://github.com/译者ID) -校对：[校对者ID](https://github.com/校对者ID) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 - -[a]: -[b]: https://github.com/lujun9972 -[1]: http://www.git-scm.com/ -[2]: http://www.kernel.org/pub/software/scm/git/docs/user-manual.html -[3]: http://eagain.net/articles/git-for-computer-scientists/ -[4]: https://pdos.csail.mit.edu/6.828/2018/tools.html -[5]: https://6828.scripts.mit.edu/2018/handin.py/ -[6]: https://pdos.csail.mit.edu/6.828/2018/readings/pcasm-book.pdf -[7]: http://www.delorie.com/djgpp/doc/brennan/brennan_att_inline_djgpp.html -[8]: https://pdos.csail.mit.edu/6.828/2018/reference.html -[9]: https://pdos.csail.mit.edu/6.828/2018/readings/i386/toc.htm -[10]: http://www.intel.com/content/www/us/en/processors/architectures-software-developer-manuals.html -[11]: http://developer.amd.com/resources/developer-guides-manuals/ -[12]: http://www.qemu.org/ -[13]: http://www.gnu.org/software/gdb/ -[14]: http://web.archive.org/web/20040404164813/members.iweb.net.au/~pstorr/pcbook/book2/book2.htm -[15]: https://pdos.csail.mit.edu/6.828/2018/readings/boot-cdrom.pdf -[16]: https://pdos.csail.mit.edu/6.828/2018/labguide.html -[17]: http://www.amazon.com/C-Programming-Language-2nd/dp/0131103628/sr=8-1/qid=1157812738/ref=pd_bbs_1/104-1502762-1803102?ie=UTF8&s=books -[18]: http://library.mit.edu/F/AI9Y4SJ2L5ELEE2TAQUAAR44XV5RTTQHE47P9MKP5GQDLR9A8X-10422?func=item-global&doc_library=MIT01&doc_number=000355242&year=&volume=&sub_library= -[19]: https://pdos.csail.mit.edu/6.828/2018/labs/lab1/pointers.c -[20]: https://pdos.csail.mit.edu/6.828/2018/readings/pointers.pdf -[21]: https://pdos.csail.mit.edu/6.828/2018/readings/elf.pdf -[22]: http://en.wikipedia.org/wiki/Executable_and_Linkable_Format -[23]: https://sourceware.org/gdb/current/onlinedocs/gdb/Memory.html -[24]: http://web.cs.mun.ca/~michael/c/ascii-table.html -[25]: http://www.webopedia.com/TERM/b/big_endian.html -[26]: http://www.networksorcery.com/enp/ien/ien137.txt -[27]: http://rrbrandt.dee.ufcg.edu.br/en/docs/ansi/ diff --git a/sources/tech/20180914 Convert files at the command line with Pandoc.md b/sources/tech/20180914 Convert files at the command line with Pandoc.md deleted file mode 100644 index e2ae10bdfa..0000000000 --- a/sources/tech/20180914 Convert files at the command line with Pandoc.md +++ /dev/null @@ -1,396 +0,0 @@ -Translating by jlztan - -Convert files at the command line with Pandoc -====== - -This guide shows you how to use Pandoc to convert your documents into many different file formats - - - -Pandoc is a command-line tool for converting files from one markup language to another. Markup languages use tags to annotate sections of a document. Commonly used markup languages include Markdown, ReStructuredText, HTML, LaTex, ePub, and Microsoft Word DOCX. - -In plain English, [Pandoc][1] allows you to convert a bunch of files from one markup language into another one. Typical examples include converting a Markdown file into a presentation, LaTeX, PDF, or even ePub. - -This article will explain how to produce documentation in multiple formats from a single markup language (in this case Markdown) using Pandoc. It will guide you through Pandoc installation, show how to create several types of documents, and offer tips on how to write documentation that is easy to port to other formats. It will also explain the value of using meta-information files to create a separation between the content and the meta-information (e.g., author name, template used, bibliographic style, etc.) of your documentation. - -### Installation and requirements - -Pandoc is installed by default in most Linux distributions. This tutorial uses pandoc-2.2.3.2 and pandoc-citeproc-0.14.3. If you don't intend to generate PDFs, those two packages are enough. However, I recommend installing texlive as well, so you have the option to generate PDFs. - -To install these programs on Linux, type the following on the command line: - -``` -sudo apt-get install pandoc pandoc-citeproc texlive -``` - -You can find [installation instructions][2] for other platforms on Pandoc's website. - -I highly recommend installing [pandoc][3][-crossref][3], a "filter for numbering figures, equations, tables, and cross-references to them." The easiest option is to download a [prebuilt executable][4], but you can install it from Haskell's package manager, cabal, by typing: - -``` -cabal update -cabal install pandoc-crossref -``` - -Consult pandoc-crossref's GitHub repository if you need additional Haskell [installation information][5]. - -### Some examples - -I'll demonstrate how Pandoc works by explaining how to produce three types of documents: - - * A website from a LaTeX file containing math formulas - * A Reveal.js slideshow from a Markdown file - * A contract agreement document that mixes Markdown and LaTeX - - - -#### Create a website with math formulas - -One of the ways Pandoc excels is displaying math formulas in different output file formats. For instance, let's generate a website from a LaTeX document (named math.tex) containing some math symbols (written in LaTeX). - -The math.tex document looks like: - -``` -% Pandoc math demos - -$a^2 + b^2 = c^2$ - -$v(t) = v_0 + \frac{1}{2}at^2$ - -$\gamma = \frac{1}{\sqrt{1 - v^2/c^2}}$ - -$\exists x \forall y (Rxy \equiv Ryx)$ - -$p \wedge q \models p$ - -$\Box\diamond p\equiv\diamond p$ - -$\int_{0}^{1} x dx = \left[ \frac{1}{2}x^2 \right]_{0}^{1} = \frac{1}{2}$ - -$e^x = \sum_{n=0}^\infty \frac{x^n}{n!} = \lim_{n\rightarrow\infty} (1+x/n)^n$ -``` - -Convert the LaTeX document into a website named mathMathML.html by entering the following command: - -``` -pandoc math.tex -s --mathml -o mathMathML.html -``` - -The flag **-s** tells Pandoc to generate a standalone website (instead of a fragment, so it will include the head and body HTML tags), and the **–mathml** flag forces Pandoc to convert the math in LaTeX to MathML, which can be rendered by modern browsers. - - - -Take a look at the [website result][6] and the [code][7]; the code repository contains a Makefile to make things even simpler. - -#### Make a Reveal.js slideshow - -It's easy to generate simple presentations from a Markdown file using Pandoc. The slides contain top-level slides and nested slides underneath. The presentation can be controlled from the keyboard, and you can jump from one top-level slide to the next top-level slide or show the nested slides on a per-top-level basis. This structure is typical in HTML-based presentation frameworks. - -Let's create a slide document named SLIDES (see the [code repository][8]). First, add the slides' meta-information (e.g., title, author, and date) prepended by the **%** symbol: - -``` -% Case Study -% Kiko Fernandez Reyes -% Sept 27, 2017 -``` - -This meta-information also creates the first slide. To add more slides, declare top-level slides using Markdown heading H1 (line 5 in the example below, [heading 1 in Markdown][9] , designated by). - -For example, if we want to create a presentation with the title Case Study that starts with a top-level slide titled Wine Management System, write: - -``` -% Case Study -% Kiko Fernandez Reyes -% Sept 27, 2017 - -# Wine Management System -``` - -To put content (such as slides that explain a new management system and its implementation) inside this top-level section, use a Markdown header H2. Let's add two more slides (lines 7 and 14 below, [heading 2 in Markdown][9], designated by **##** ): - - * The first second-level slide has the title Idea and shows an image of the Swiss flag - * The second second-level slide has the title Implementation - - - -``` -% Case Study -% Kiko Fernandez Reyes -% Sept 27, 2017 - -# Wine Management System - -## 
Idea
-
-## Implementation
-```
-
-We now have a top-level slide ( **# Wine Management System** ) that contains two slides ( **## Idea** and **## Implementation** ).
-
-Let's put some content in these two slides using incremental bulleted lists by creating a Markdown list prepended by the symbol **>**. Continuing from above, add two items in the first slide (lines 9–10 below) and five items in the second slide (lines 16–20):
-
-```
-% Case Study
-% Kiko Fernandez Reyes
-% Sept 27, 2017
-
-# Wine Management System
-
-## Idea
-
->- Swiss love their **wine** and cheese
->- Create a *simple* wine tracker system
-
-
-
-## Implementation
-
->- Bottles have a RFID tag
->- RFID reader (emits and read signal)
->- **Raspberry Pi**
->- **Server (online shop)**
->- Mobile app
-```
-
-We added an image of the Matterhorn mountain. Your slides can be improved by using plain Markdown or adding plain HTML.
-
-To generate the slides, Pandoc needs to point to the Reveal.js library, so it must be in the same folder as the SLIDES file. The command to generate the slides is:
-
-```
-pandoc -t revealjs -s --self-contained SLIDES \
--V theme=white -V slideNumber=true -o index.html
-```
-
-
-
-The above Pandoc command uses the following flags:
-
- * **-t revealjs** specifies we are going to output a **revealjs** presentation
- * **-s** tells Pandoc to generate a standalone document
- * **\--self-contained** produces HTML with no external dependencies
- * **-V** sets the following variables:
-– **theme=white** sets the theme of the slideshow to **white**
-– **slideNumber=true** shows the slide number
- * **-o index.html** generates the slides in the file named **index.html**
-
-
-
-To make things simpler and avoid typing this long command, create the following Makefile:
-
-```
-all: generate
-
-generate:
- pandoc -t revealjs -s --self-contained SLIDES \
- -V theme=white -V slideNumber=true -o index.html
-
-clean: index.html
- rm index.html
-
-.PHONY: all clean generate
-```
-
-You can find all the code in [this repository][8].
-
-#### Make a multi-format contract
-
-Let's say you are preparing a document and (as things are nowadays) some people want it in Microsoft Word format, others use free software and would like an ODT, and others need a PDF. You do not have to use OpenOffice nor LibreOffice to generate the DOCX or PDF file. You can create your document in Markdown (with some bits of LaTeX if you need advanced formatting) and generate any of these file types.
-
-As before, begin by declaring the document's meta-information (title, author, and date):
-
-```
-% Contract Agreement for Software X
-% Kiko Fernandez-Reyes
-% August 28th, 2018
-```
-
-Then write the document in Markdown (and add LaTeX if you require advanced formatting). For example, create a table that needs fixed separation space (declared in LaTeX with **\hspace{3cm}** ) and a line where a client and a contractor should sign (declared in LaTeX with **\hrulefill** ). After that, add a table written in Markdown.
-
-Here's what the document will look like:
-
-
-
-The code to create this document is:
-
-```
-% Contract Agreement for Software X
-% Kiko Fernandez-Reyes
-% August 28th, 2018
-
-...
-
-### Work Order
-
-\begin{table}[h]
-\begin{tabular}{ccc}
-The Contractor & \hspace{3cm} & The Customer \\
-& & \\
-& & \\
-\hrulefill & \hspace{3cm} & \hrulefill \\
-%
-Name & \hspace{3cm} & Name \\
-& & \\
-& & \\
-\hrulefill & \hspace{3cm} & \hrulefill \\
-...
-\end{tabular}
-\end{table}
-
-\vspace{1cm}
-
-+--------------------------------------------|----------|-------------+
-| Type of Service | Cost | Total |
-+:===========================================+=========:+:===========:+
-| Game Engine | 70.0 | 70.0 |
-| | | |
-+--------------------------------------------|----------|-------------+
-| | | |
-+--------------------------------------------|----------|-------------+
-| Extra: Comply with defined API functions | 10.0 | 10.0 |
-| and expected returned format | | |
-+--------------------------------------------|----------|-------------+
-| | | |
-+--------------------------------------------|----------|-------------+
-| **Total Cost** | | **80.0** |
-+--------------------------------------------|----------|-------------+
-```
-
-To generate the three different output formats needed for this document, write a Makefile:
-
-```
-DOCS=contract-agreement.md
-
-all: $(DOCS)
- pandoc -s $(DOCS) -o $(DOCS:md=pdf)
- pandoc -s $(DOCS) -o $(DOCS:md=docx)
- pandoc -s $(DOCS) -o $(DOCS:md=odt)
-
-clean:
- rm *.pdf *.docx *.odt
-
-.PHONY: all clean
-```
-
-Lines 4–7 contain the commands to generate the different outputs.
-
-If you have several Markdown files and want to merge them into one document, issue a command with the files in the order you want them to appear. For example, when writing this article, I created three documents: an introduction document, three examples, and some advanced uses. The following tells Pandoc to merge these files together in the specified order and produce a PDF named document.pdf.
-
-```
-pandoc -s introduction.md examples.md advanced-uses.md -o document.pdf
-```
-
-### Templates and meta-information
-
-Writing a complex document is no easy task. You need to stick to a set of rules that are independent from your content, such as using a specific template, writing an abstract, embedding specific fonts, and maybe even declaring keywords. All of this has nothing to do with your content: simply put, it is meta-information.
-
-Pandoc uses templates to generate different output formats. There is a template for LaTeX, another for ePub, etc. These templates have unfulfilled variables that are set with the meta-information given to Pandoc. To find out what meta-information is available in a Pandoc template, type:
-
-```
-pandoc -D FORMAT
-```
-
-For example, the template for LaTeX would be:
-
-```
-pandoc -D latex
-```
-
-Which outputs something along these lines:
-
-```
-$if(title)$
-\title{$title$$if(thanks)$\thanks{$thanks$}$endif$}
-$endif$
-$if(subtitle)$
-\providecommand{\subtitle}[1]{}
-\subtitle{$subtitle$}
-$endif$
-$if(author)$
-\author{$for(author)$$author$$sep$ \and $endfor$}
-$endif$
-$if(institute)$
-\providecommand{\institute}[1]{}
-\institute{$for(institute)$$institute$$sep$ \and $endfor$}
-$endif$
-\date{$date$}
-$if(beamer)$
-$if(titlegraphic)$
-\titlegraphic{\includegraphics{$titlegraphic$}}
-$endif$
-$if(logo)$
-\logo{\includegraphics{$logo$}}
-$endif$
-$endif$
-
-\begin{document}
-```
-
-As you can see, there are **title** , **thanks** , **author** , **subtitle** , and **institute** template variables (and many others are available). These are easily set using YAML metablocks. In lines 1–5 of the example below, we declare a YAML metablock and set some of those variables (using the contract agreement example above):
-
-```
----
-title: Contract Agreement for Software X
-author: Kiko Fernandez-Reyes
-date: August 28th, 2018
----
-
-(continue writing document as in the previous example)
-```
-
-This works like a charm and is equivalent to the previous code:
-
-```
-% Contract Agreement for Software X
-% Kiko Fernandez-Reyes
-% August 28th, 2018
-```
-
-However, this ties the meta-information to the content; i.e., Pandoc will always use this information to output files in the new format. If you know you need to produce multiple file formats, you better be careful. For example, what if you need to produce the contract in ePub and in HTML, and the ePub and HTML need specific and different styling rules?
-
-Let's consider the cases:
-
- * If you simply try to embed the YAML variable **css: style-epub.css** , you would be excluding the one from the HTML version. This does not work.
- * Duplicating the document is obviously not a good solution either, as changes in one version would not be in sync with the other copy.
- * You can add variables to the Pandoc command line as follows:
-
-
-
-```
-pandoc -s -V css=style-epub.css document.md document.epub
-pandoc -s -V css=style-html.css document.md document.html
-```
-
-My opinion is that it is easy to overlook these variables from the command line, especially when you need to set tens of these (which can happen in complex documents). Now, if you put them all together under the same roof (a meta.yaml file), you only need to update or create a new meta-information file to produce the desired output. You would then write:
-
-```
-pandoc -s meta-pub.yaml document.md document.epub
-pandoc -s meta-html.yaml document.md document.html
-```
-
-This is a much cleaner version, and you can update all the meta-information from a single file without ever having to update the content of your document.
-
-### Wrapping up
-
-With these basic examples, I have shown how Pandoc can do a really good job at converting Markdown documents into other formats.
-
---------------------------------------------------------------------------------
-
-via: https://opensource.com/article/18/9/intro-pandoc
-
-作者：[Kiko Fernandez-Reyes][a]
-选题：[lujun9972](https://github.com/lujun9972)
-译者：[译者ID](https://github.com/译者ID)
-校对：[校对者ID](https://github.com/校对者ID)
-
-本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
-
-[a]: https://opensource.com/users/kikofernandez
-[1]: https://pandoc.org/
-[2]: http://pandoc.org/installing.html
-[3]: https://hackage.haskell.org/package/pandoc-crossref
-[4]: https://github.com/lierdakil/pandoc-crossref/releases/tag/v0.3.2.1
-[5]: https://github.com/lierdakil/pandoc-crossref#installation
-[6]: http://pandoc.org/demo/mathMathML.html
-[7]: https://github.com/kikofernandez/pandoc-examples/tree/master/math
-[8]: https://github.com/kikofernandez/pandoc-examples/tree/master/slides
-[9]: https://daringfireball.net/projects/markdown/syntax#header
diff --git a/sources/tech/20180919 Host your own cloud with Raspberry Pi NAS.md b/sources/tech/20180919 Host your own cloud with Raspberry Pi NAS.md
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+[#]: collector: (lujun9972)
+[#]: translator: ( )
+[#]: reviewer: ( )
+[#]: publisher: ( )
+[#]: url: ( )
+[#]: subject: (Host your own cloud with Raspberry Pi NAS)
+[#]: via: (https://opensource.com/article/18/9/host-cloud-nas-raspberry-pi?extIdCarryOver=true)
+[#]: author: (Manuel Dewald https://opensource.com/users/ntlx)
+
+Host your own cloud with Raspberry Pi NAS
+======
+
+Protect and secure your data with a self-hosted cloud powered by your Raspberry Pi.
+
+![Tree clouds][1]
+
+In the first two parts of this series, we discussed the [hardware and software fundamentals][2] for building network-attached storage (NAS) on a Raspberry Pi. We also put a proper [backup strategy][3] in place to secure the data on the NAS. In this third part, we will talk about a convenient way to store, access, and share your data with [Nextcloud][4].
+
+![Raspberry Pi NAS infrastructure with Nextcloud][6]
+
+### Prerequisites
+
+To use Nextcloud conveniently, you have to meet a few prerequisites. First, you should have a domain you can use for the Nextcloud instance. For the sake of simplicity in this how-to, we'll use **nextcloud.pi-nas.com**. This domain should be directed to your Raspberry Pi. If you want to run it on your home network, you probably need to set up dynamic DNS for this domain and enable port forwarding of ports 80 and 443 (if you go for an SSL setup, which is highly recommended; otherwise port 80 should be sufficient) from your router to the Raspberry Pi.
+
+You can automate dynamic DNS updates from the Raspberry Pi using [ddclient][7].
+
+### Install Nextcloud
+
+To run Nextcloud on your Raspberry Pi (using the setup described in the [first part][2] of this series), install the following packages as dependencies to Nextcloud using **apt**.
+
+```
+sudo apt install unzip wget php apache2 mysql-server php-zip php-mysql php-dom php-mbstring php-gd php-curl
+```
+
+The next step is to download Nextcloud. [Get the latest release's URL][8] and copy it to download via **wget** on the Raspberry Pi. In the first article in this series, we attached two disk drives to the Raspberry Pi, one for current data and one for backups. Install Nextcloud on the data drive to make sure data is backed up automatically every night.
+```
+sudo mkdir -p /nas/data/nextcloud
+sudo chown pi /nas/data/nextcloud
+cd /nas/data/
+wget '; +CREATE DATABASE nextcloud; +GRANT ALL ON nextcloud.* TO nextcloud; +``` + + +You can exit the SQL prompt by pressing **Ctrl+D** or entering **quit**. + +### Web server configuration + +Nextcloud can be configured to run using Nginx or other web servers, but for this how-to, I decided to go with the Apache web server on my Raspberry Pi NAS. (Feel free to try out another alternative and let me know if you think it performs better.) + +To set it up, configure a virtual host for the domain you created for your Nextcloud instance **nextcloud.pi-nas.com**. To create a virtual host, create the file **/etc/apache2/sites-available/001-nextcloud.conf** with content similar to the following. Make sure to adjust the ServerName to your domain and paths, if you didn't use the ones suggested earlier in this series. +``` + +ServerName nextcloud.pi-nas.com +ServerAdmin [admin@pi-nas.com][9] +DocumentRoot /var/www/nextcloud/ + + +``` + + +To enable this virtual host, run the following two commands. +``` +a2ensite 001-nextcloud +sudo systemctl reload apache2 +``` + + +With this configuration, you should now be able to reach the web server with your domain via the web browser. To secure your data, I recommend using HTTPS instead of HTTP to access Nextcloud. A very easy (and free) way is to obtain a [Let's Encrypt][10] certificate with [Certbot][11] and have a cron job automatically refresh it. That way you don't have to mess around with self-signed or expiring certificates. Follow Certbot's simple how-to [instructions to install it on your Raspberry Pi][12]. During Certbot configuration, you can even decide to automatically forward HTTP to HTTPS, so visitors to **+AllowOverride None + + If you like this book, please consider - spreading the word or - - buying me a coffee - -
- \``` -include-after: -- | - ```{=html} --- \``` ---- -``` - -Some variables to note: - - * The **header-includes** variable contains HTML that will be embedded inside the **< head>** tag. - * The line after calling a variable must be **\- |**. The next line must begin with triple backquotes that are aligned with the **|** or Pandoc will reject it. **{=html}** tells Pandoc that this is raw text and should not be processed as Markdown. (For this to work, you need to check that the **raw_attribute** extension in Pandoc is enabled. To check, type **pandoc --list-extensions | grep raw** and make sure the returned list contains an item named **+raw_html** ; the plus sign indicates it is enabled.) - * The variable **include-before** adds some HTML at the beginning of your website, and I ask readers to consider spreading the word or buying me a coffee. - * The **include-after** variable appends raw HTML at the end of the website and shows my book's license. - - - -These are only some of the fields available; take a look at the template variables in HTML (my article [introduction to Pandoc][1] covered this for LaTeX but the process is the same for HTML) to learn about others. - -#### Split the website into chapters - -The website can be generated as a whole, resulting in a long page with all the content, or split into chapters, which I think is easier to read. I'll explain how to divide the website into chapters so the reader doesn't get intimidated by a long website. - -To make the website easy to deploy on GitHub Pages, we need to create a root folder called docs (which is the root folder that GitHub Pages uses by default to render a website). Then we need to create folders for each chapter under docs, place the HTML chapters in their own folders, and the file content in a file named index.html. - -For example, the about.md file is converted to a file named index.html that is placed in a folder named about (about/index.html). This way, when users type **http://
-- --/about/**, the index.html file from the folder about will be displayed in their browser. - -The following Makefile does all of this: - -``` -# Your book files -DEPENDENCIES= toc preface about - -# Placement of your HTML files -DOCS=docs - -all: web - -web: setup $(DEPENDENCIES) - @cp $(DOCS)/toc/index.html $(DOCS) - - -# Creation and copy of stylesheet and images into -# the assets folder. This is important to deploy the -# website to Github Pages. -setup: - @mkdir -p $(DOCS) - @cp -r assets $(DOCS) - - -# Creation of folder and index.html file on a -# per-chapter basis - -$(DEPENDENCIES): - @mkdir -p $(DOCS)/$@ - @pandoc -s --toc web-metadata.yaml parts/$@.md \ - -c /assets/pandoc.css -o $(DOCS)/$@/index.html - -clean: - @rm -rf $(DOCS) - -.PHONY: all clean web setup -``` - -The option **-c /assets/pandoc.css** declares which CSS stylesheet to use; it will be fetched from **/assets/pandoc.css**. In other words, inside the **< head>** HTML tag, Pandoc adds the following line: - -``` - -``` - -To generate the website, type: - -``` -make -``` - -The root folder should contain now the following structure and files: - -``` -.---parts -| |--- toc.md -| |--- preface.md -| |--- about.md -| -|---docs - |--- assets/ - |--- index.html - |--- toc - | |--- index.html - | - |--- preface - | |--- index.html - | - |--- about - |--- index.html - -``` - -#### Deploy the website - -To deploy the website on GitHub, follow these steps: - - 1. Create a new repository - 2. Push your content to the repository - 3. Go to the GitHub Pages section in the repository's Settings and select the option for GitHub to use the content from the Master branch - - - -You can get more details on the [GitHub Pages][5] site. - -Check out [my book's website][6], generated using this process, to see the result. - -### Generating the ePub book - -#### Create the ePub meta-information file - -The ePub meta-information file, epub-meta.yaml, is similar to the HTML meta-information file. The main difference is that ePub offers other template variables, such as **publisher** and **cover-image**. Your ePub book's stylesheet will probably differ from your website's; mine uses one named epub.css. - -``` ---- -title: 'GRASP principles for the Object-oriented Mind' -publisher: 'Programming Language Fight Club' -author: Kiko Fernandez-Reyes -rights: 2017 Kiko Fernandez-Reyes, CC-BY-NC-SA 4.0 International -cover-image: assets/cover.png -stylesheet: assets/epub.css -... -``` - -Add the following content to the previous Makefile: - -``` -epub: - @pandoc -s --toc epub-meta.yaml \ - $(addprefix parts/, $(DEPENDENCIES:=.md)) -o $(DOCS)/assets/book.epub -``` - -The command for the ePub target takes all the dependencies from the HTML version (your chapter names), appends to them the Markdown extension, and prepends them with the path to the folder chapters' so Pandoc knows how to process them. For example, if **$(DEPENDENCIES)** was only **preface about** , then the Makefile would call: - -``` -@pandoc -s --toc epub-meta.yaml \ -parts/preface.md parts/about.md -o $(DOCS)/assets/book.epub -``` - -Pandoc would take these two chapters, combine them, generate an ePub, and place the book under the Assets folder. - -Here's an [example][7] of an ePub created using this process. - -### Summarizing the process - -The process to create a website and an ePub from a Markdown file isn't difficult, but there are a lot of details. The following outline may make it easier for you to follow. - - * HTML book: - * Write chapters in Markdown - * Add metadata - * Create a Makefile to glue pieces together - * Set up GitHub Pages - * Deploy - * ePub book: - * Reuse chapters from previous work - * Add new metadata file - * Create a Makefile to glue pieces together - * Set up GitHub Pages - * Deploy - - - --------------------------------------------------------------------------------- - -via: https://opensource.com/article/18/10/book-to-website-epub-using-pandoc - -作者：[Kiko Fernandez-Reyes][a] -选题：[lujun9972](https://github.com/lujun9972) -译者：[译者ID](https://github.com/译者ID) -校对：[校对者ID](https://github.com/校对者ID) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 - -[a]: https://opensource.com/users/kikofernandez -[1]: https://opensource.com/article/18/9/intro-pandoc -[2]: https://pandoc.org/ -[3]: https://www.programmingfightclub.com/ -[4]: https://github.com/kikofernandez/programmingfightclub -[5]: https://pages.github.com/ -[6]: https://www.programmingfightclub.com/grasp-principles/ -[7]: https://github.com/kikofernandez/programmingfightclub/raw/master/docs/web_assets/demo.epub diff --git a/sources/tech/20181002 Greg Kroah-Hartman Explains How the Kernel Community Is Securing Linux.md b/sources/tech/20181002 Greg Kroah-Hartman Explains How the Kernel Community Is Securing Linux.md deleted file mode 100644 index 31788a67b2..0000000000 --- a/sources/tech/20181002 Greg Kroah-Hartman Explains How the Kernel Community Is Securing Linux.md +++ /dev/null @@ -1,75 +0,0 @@ -qhwdw is translating - - -Greg Kroah-Hartman Explains How the Kernel Community Is Securing Linux -============================================================ - - - -Kernel maintainer Greg Kroah-Hartman talks about how the kernel community is hardening Linux against vulnerabilities.[Creative Commons Zero][2] - -As Linux adoption expands, it’s increasingly important for the kernel community to improve the security of the world’s most widely used technology. Security is vital not only for enterprise customers, it’s also important for consumers, as 80 percent of mobile devices are powered by Linux. In this article, Linux kernel maintainer Greg Kroah-Hartman provides a glimpse into how the kernel community deals with vulnerabilities. - -### There will be bugs - - - - -Greg Kroah-Hartman[The Linux Foundation][1] - -As Linus Torvalds once said, most security holes are bugs, and bugs are part of the software development process. As long as the software is being written, there will be bugs. - -“A bug is a bug. We don’t know if a bug is a security bug or not. There is a famous bug that I fixed and then three years later Red Hat realized it was a security hole,” said Kroah-Hartman. - -There is not much the kernel community can do to eliminate bugs, but it can do more testing to find them. The kernel community now has its own security team that’s made up of kernel developers who know the core of the kernel. - -“When we get a report, we involve the domain owner to fix the issue. In some cases it’s the same people, so we made them part of the security team to speed things up,” Kroah Hartman said. But he also stressed that all parts of the kernel have to be aware of these security issues because kernel is a trusted environment and they have to protect it. - -“Once we fix things, we can put them in our stack analysis rules so that they are never reintroduced,” he said. - -Besides fixing bugs, the community also continues to add hardening to the kernel. “We have realized that we need to have mitigations. We need hardening,” said Kroah-Hartman. - -Huge efforts have been made by Kees Cook and others to take the hardening features that have been traditionally outside of the kernel and merge or adapt them for the kernel. With every kernel released, Cook provides a summary of all the new hardening features. But hardening the kernel is not enough, vendors have to enable the new features and take advantage of them. That’s not happening. - -Kroah-Hartman [releases a stable kernel every week][5], and companies pick one to support for a longer period so that device manufacturers can take advantage of it. However, Kroah-Hartman has observed that, aside from the Google Pixel, most Android phones don’t include the additional hardening features, meaning all those phones are vulnerable. “People need to enable this stuff,” he said. - -“I went out and bought all the top of the line phones based on kernel 4.4 to see which one actually updated. I found only one company that updated their kernel,” he said. “I'm working through the whole supply chain trying to solve that problem because it's a tough problem. There are many different groups involved -- the SoC manufacturers, the carriers, and so on. The point is that they have to push the kernel that we create out to people.” - -The good news is that unlike with consumer electronics, the big vendors like Red Hat and SUSE keep the kernel updated even in the enterprise environment. Modern systems with containers, pods, and virtualization make this even easier. It’s effortless to update and reboot with no downtime. It is, in fact, easier to keep things secure than it used to be. - -### Meltdown and Spectre - -No security discussion is complete without the mention of Meltdown and Spectre. The kernel community is still working on fixes as new flaws are discovered. However, Intel has changed its approach in light of these events. - -“They are reworking on how they approach security bugs and how they work with the community because they know they did it wrong,” Kroah-Hartman said. “The kernel has fixes for almost all of the big Spectre issues, but there is going to be a long tail of minor things.” - -The good news is that these Intel vulnerabilities proved that things are getting better for the kernel community. “We are doing more testing. With the latest round of security patches, we worked on our own for four months before releasing them to the world because we were embargoed. But once they hit the real world, it made us realize how much we rely on the infrastructure we have built over the years to do this kind of testing, which ensures that we don’t have bugs before they hit other people,” he said. “So things are certainly getting better.” - -The increasing focus on security is also creating more job opportunities for talented people. Since security is an area that gets eyeballs, those who want to build a career in kernel space, security is a good place to get started with. - -“If there are people who want a job to do this type of work, we have plenty of companies who would love to hire them. I know some people who have started off fixing bugs and then got hired,” Kroah-Hartman said. - -You can hear more in the video below: - -[视频](https://youtu.be/jkGVabyMh1I) - - _Check out the schedule of talks for Open Source Summit Europe and sign up to receive updates:_ - --------------------------------------------------------------------------------- - -via: https://www.linux.com/blog/2018/10/greg-kroah-hartman-explains-how-kernel-community-securing-linux-0 - -作者：[SWAPNIL BHARTIYA][a] -选题：[oska874][b] -译者：[译者ID](https://github.com/译者ID) -校对：[校对者ID](https://github.com/校对者ID) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 - -[a]:https://www.linux.com/users/arnieswap -[b]:https://github.com/oska874 -[1]:https://www.linux.com/licenses/category/linux-foundation -[2]:https://www.linux.com/licenses/category/creative-commons-zero -[3]:https://www.linux.com/files/images/greg-k-hpng -[4]:https://www.linux.com/files/images/kernel-securityjpg-0 -[5]:https://www.kernel.org/category/releases.html diff --git a/sources/tech/20181003 Manage NTP with Chrony.md b/sources/tech/20181003 Manage NTP with Chrony.md new file mode 100644 index 0000000000..aaec88da26 --- /dev/null +++ b/sources/tech/20181003 Manage NTP with Chrony.md @@ -0,0 +1,291 @@ +[#]: collector: (lujun9972) +[#]: translator: ( ) +[#]: reviewer: ( ) +[#]: publisher: ( ) +[#]: url: ( ) +[#]: subject: (Manage NTP with Chrony) +[#]: via: (https://opensource.com/article/18/12/manage-ntp-chrony) +[#]: author: (David Both https://opensource.com/users/dboth) + +Manage NTP with Chrony +====== +Chronyd is a better choice for most networks than ntpd for keeping computers synchronized with the Network Time Protocol. + + +> "Does anybody really know what time it is? Does anybody really care?" +> – [Chicago][1], 1969 + +Perhaps that rock group didn't care what time it was, but our computers do need to know the exact time. Timekeeping is very important to computer networks. In banking, stock markets, and other financial businesses, transactions must be maintained in the proper order, and exact time sequences are critical for that. For sysadmins and DevOps professionals, it's easier to follow the trail of email through a series of servers or to determine the exact sequence of events using log files on geographically dispersed hosts when exact times are kept on the computers in question. + +I used to work at an organization that received over 20 million emails per day and had four servers just to accept and do a basic filter on the incoming flood of email. From there, emails were sent to one of four other servers to perform more complex anti-spam assessments, then they were delivered to one of several additional servers where the emails were placed in the correct inboxes. At each layer, the emails would be sent to one of the next-level servers, selected only by the randomness of round-robin DNS. Sometimes we had to trace a new message through the system until we could determine where it "got lost," according to the pointy-haired bosses. We had to do this with frightening regularity. + +Most of that email turned out to be spam. Some people actually complained that their [joke, cat pic, recipe, inspirational saying, or other-strange-email]-of-the-day was missing and asked us to find it. We did reject those opportunities. + +Our email and other transactional searches were aided by log entries with timestamps that—today—can resolve down to the nanosecond in even the slowest of modern Linux computers. In very high-volume transaction environments, even a few microseconds of difference in the system clocks can mean sorting thousands of transactions to find the correct one(s). + +### The NTP server hierarchy + +Computers worldwide use the [Network Time Protocol][2] (NTP) to synchronize their times with internet standard reference clocks via a hierarchy of NTP servers. The primary servers are at stratum 1, and they are connected directly to various national time services at stratum 0 via satellite, radio, or even modems over phone lines. The time service at stratum 0 may be an atomic clock, a radio receiver tuned to the signals broadcast by an atomic clock, or a GPS receiver using the highly accurate clock signals broadcast by GPS satellites. + +To prevent time requests from time servers lower in the hierarchy (i.e., with a higher stratum number) from overwhelming the primary reference servers, there are several thousand public NTP stratum 2 servers that are open and available for anyone to use. Many organizations with large numbers of hosts that need an NTP server will set up their own time servers so that only one local host accesses the stratum 2 time servers, then they configure the remaining network hosts to use the local time server which, in my case, is a stratum 3 server. + +### NTP choices + +The original NTP daemon, **ntpd** , has been joined by a newer one, **chronyd**. Both keep the local host's time synchronized with the time server. Both services are available, and I have seen nothing to indicate that this will change anytime soon. + +Chrony has features that make it the better choice for most environments for the following reasons: + + * Chrony can synchronize to the time server much faster than NTP. This is good for laptops or desktops that don't run constantly. + + * It can compensate for fluctuating clock frequencies, such as when a host hibernates or enters sleep mode, or when the clock speed varies due to frequency stepping that slows clock speeds when loads are low. + + * It handles intermittent network connections and bandwidth saturation. + + * It adjusts for network delays and latency. + + * After the initial time sync, Chrony never steps the clock. This ensures stable and consistent time intervals for system services and applications. + + * Chrony can work even without a network connection. In this case, the local host or server can be updated manually. + + + + +The NTP and Chrony RPM packages are available from standard Fedora repositories. You can install both and switch between them, but modern Fedora, CentOS, and RHEL releases have moved from NTP to Chrony as their default time-keeping implementation. I have found that Chrony works well, provides a better interface for the sysadmin, presents much more information, and increases control. + +Just to make it clear, NTP is a protocol that is implemented with either NTP or Chrony. If you'd like to know more, read this [comparison between NTP and Chrony][3] as implementations of the NTP protocol. + +This article explains how to configure Chrony clients and servers on a Fedora host, but the configuration for CentOS and RHEL current releases works the same. + +### Chrony structure + +The Chrony daemon, **chronyd** , runs in the background and monitors the time and status of the time server specified in the **chrony.conf** file. If the local time needs to be adjusted, **chronyd** does it smoothly without the programmatic trauma that would occur if the clock were instantly reset to a new time. + +Chrony's **chronyc** tool allows someone to monitor the current status of Chrony and make changes if necessary. The **chronyc** utility can be used as a command that accepts subcommands, or it can be used as an interactive text-mode program. This article will explain both uses. + +### Client configuration + +The NTP client configuration is simple and requires little or no intervention. The NTP server can be defined during the Linux installation or provided by the DHCP server at boot time. The default **/etc/chrony.conf** file (shown below in its entirety) requires no intervention to work properly as a client. For Fedora, Chrony uses the Fedora NTP pool, and CentOS and RHEL have their own NTP server pools. Like many Red Hat-based distributions, the configuration file is well commented. + +``` +# Use public servers from the pool.ntp.org project. +# Please consider joining the pool (http://www.pool.ntp.org/join.html). +pool 2.fedora.pool.ntp.org iburst + +# Record the rate at which the system clock gains/losses time. +driftfile /var/lib/chrony/drift + +# Allow the system clock to be stepped in the first three updates +# if its offset is larger than 1 second. +makestep 1.0 3 + +# Enable kernel synchronization of the real-time clock (RTC). + + +# Enable hardware timestamping on all interfaces that support it. +#hwtimestamp * + +# Increase the minimum number of selectable sources required to adjust +# the system clock. +#minsources 2 + +# Allow NTP client access from local network. +#allow 192.168.0.0/16 + +# Serve time even if not synchronized to a time source. +#local stratum 10 + +# Specify file containing keys for NTP authentication. +keyfile /etc/chrony.keys + +# Get TAI-UTC offset and leap seconds from the system tz database. +leapsectz right/UTC + +# Specify directory for log files. +logdir /var/log/chrony + +# Select which information is logged. +#log measurements statistics tracking +``` + +Let's look at the current status of NTP on a virtual machine I use for testing. The **chronyc** command, when used with the **tracking** subcommand, provides statistics that report how far off the local system is from the reference server. + +``` +[root@studentvm1 ~]# chronyc tracking +Reference ID : 23ABED4D (ec2-35-171-237-77.compute-1.amazonaws.com) +Stratum : 3 +Ref time (UTC) : Fri Nov 16 16:21:30 2018 +System time : 0.000645622 seconds slow of NTP time +Last offset : -0.000308577 seconds +RMS offset : 0.000786140 seconds +Frequency : 0.147 ppm slow +Residual freq : -0.073 ppm +Skew : 0.062 ppm +Root delay : 0.041452706 seconds +Root dispersion : 0.022665167 seconds +Update interval : 1044.2 seconds +Leap status : Normal +[root@studentvm1 ~]# +``` + +The Reference ID in the first line of the result is the server the host is synchronized to—in this case, a stratum 3 reference server that was last contacted by the host at 16:21:30 2018. The other lines are described in the [chronyc(1) man page][4]. + +The **sources** subcommand is also useful because it provides information about the time source configured in **chrony.conf**. + +``` +[root@studentvm1 ~]# chronyc sources +210 Number of sources = 5 +MS Name/IP address Stratum Poll Reach LastRx Last sample +=============================================================================== +^+ 192.168.0.51 3 6 377 0 -2613us[-2613us] +/- 63ms +^+ dev.smatwebdesign.com 3 10 377 28m -2961us[-3534us] +/- 113ms +^+ propjet.latt.net 2 10 377 465 -1097us[-1085us] +/- 77ms +^* ec2-35-171-237-77.comput> 2 10 377 83 +2388us[+2395us] +/- 95ms +^+ PBX.cytranet.net 3 10 377 507 -1602us[-1589us] +/- 96ms +[root@studentvm1 ~]# +``` + +The first source in the list is the time server I set up for my personal network. The others were provided by the pool. Even though my NTP server doesn't appear in the Chrony configuration file above, my DHCP server provides its IP address for the NTP server. The "S" column—Source State—indicates with an asterisk ( ***** ) the server our host is synced to. This is consistent with the data from the **tracking** subcommand. + +The **-v** option provides a nice description of the fields in this output. + +``` +[root@studentvm1 ~]# chronyc sources -v +210 Number of sources = 5 + + .-- Source mode '^' = server, '=' = peer, '#' = local clock. + / .- Source state '*' = current synced, '+' = combined , '-' = not combined, +| / '?' = unreachable, 'x' = time may be in error, '~' = time too variable. +|| .- xxxx [ yyyy ] +/- zzzz +|| Reachability register (octal) -. | xxxx = adjusted offset, +|| Log2(Polling interval) --. | | yyyy = measured offset, +|| \ | | zzzz = estimated error. +|| | | \ +MS Name/IP address Stratum Poll Reach LastRx Last sample +=============================================================================== +^+ 192.168.0.51 3 7 377 28 -2156us[-2156us] +/- 63ms +^+ triton.ellipse.net 2 10 377 24 +5716us[+5716us] +/- 62ms +^+ lithium.constant.com 2 10 377 351 -820us[ -820us] +/- 64ms +^* t2.time.bf1.yahoo.com 2 10 377 453 -992us[ -965us] +/- 46ms +^- ntp.idealab.com 2 10 377 799 +3653us[+3674us] +/- 87ms +[root@studentvm1 ~]# +``` + +If I wanted my server to be the preferred reference time source for this host, I would add the line below to the **/etc/chrony.conf** file. + +``` +server 192.168.0.51 iburst prefer +``` + +I usually place this line just above the first pool server statement near the top of the file. There is no special reason for this, except I like to keep the server statements together. It would work just as well at the bottom of the file, and I have done that on several hosts. This configuration file is not sequence-sensitive. + +The **prefer** option marks this as the preferred reference source. As such, this host will always be synchronized with this reference source (as long as it is available). We can also use the fully qualified hostname for a remote reference server or the hostname only (without the domain name) for a local reference time source as long as the search statement is set in the **/etc/resolv.conf** file. I prefer the IP address to ensure that the time source is accessible even if DNS is not working. In most environments, the server name is probably the better option, because NTP will continue to work even if the server's IP address changes. + +If you don't have a specific reference source you want to synchronize to, it is fine to use the defaults. + +### Configuring an NTP server with Chrony + +The nice thing about the Chrony configuration file is that this single file configures the host as both a client and a server. To add a server function to our host—it will always be a client, obtaining its time from a reference server—we just need to make a couple of changes to the Chrony configuration, then configure the host's firewall to accept NTP requests. + +Open the **/etc/ ** **chrony****.conf** file in your favorite text editor and uncomment the **local stratum 10** line. This enables the Chrony NTP server to continue to act as if it were connected to a remote reference server if the internet connection fails; this enables the host to continue to be an NTP server to other hosts on the local network. + +Let's restart **chronyd** and track how the service is working for a few minutes. Before we enable our host as an NTP server, we want to test a bit. + +``` +[root@studentvm1 ~]# systemctl restart chronyd ; watch chronyc tracking +``` + +The results should look like this. The **watch** command runs the **chronyc tracking** command every two seconds so we can watch changes occur over time. + +``` +Every 2.0s: chronyc tracking studentvm1: Fri Nov 16 20:59:31 2018 + +Reference ID : C0A80033 (192.168.0.51) +Stratum : 4 +Ref time (UTC) : Sat Nov 17 01:58:51 2018 +System time : 0.001598277 seconds fast of NTP time +Last offset : +0.001791533 seconds +RMS offset : 0.001791533 seconds +Frequency : 0.546 ppm slow +Residual freq : -0.175 ppm +Skew : 0.168 ppm +Root delay : 0.094823152 seconds +Root dispersion : 0.021242738 seconds +Update interval : 65.0 seconds +Leap status : Normal +``` + +Notice that my NTP server, the **studentvm1** host, synchronizes to the host at 192.168.0.51, which is my internal network NTP server, at stratum 4. Synchronizing directly to the Fedora pool machines would result in synchronization at stratum 3. Notice also that the amount of error decreases over time. Eventually, it should stabilize with a tiny variation around a fairly small range of error. The size of the error depends upon the stratum and other network factors. After a few minutes, use Ctrl+C to break out of the watch loop. + +To turn our host into an NTP server, we need to allow it to listen on the local network. Uncomment the following line to allow hosts on the local network to access our NTP server. + +``` +# Allow NTP client access from local network. +allow 192.168.0.0/16 +``` + +Note that the server can listen for requests on any local network it's attached to. The IP address in the "allow" line is just intended for illustrative purposes. Be sure to change the IP network and subnet mask in that line to match your local network's. + +Restart **chronyd**. + +``` +[root@studentvm1 ~]# systemctl restart chronyd +``` + +To allow other hosts on your network to access this server, configure the firewall to allow inbound UDP packets on port 123. Check your firewall's documentation to find out how to do that. + +### Testing + +Your host is now an NTP server. You can test it with another host or a VM that has access to the network on which the NTP server is listening. Configure the client to use the new NTP server as the preferred server in the **/etc/chrony.conf** file, then monitor that client using the **chronyc** tools we used above. + +### Chronyc as an interactive tool + +As I mentioned earlier, **chronyc** can be used as an interactive command tool. Simply run the command without a subcommand and you get a **chronyc** command prompt. + +``` +[root@studentvm1 ~]# chronyc +chrony version 3.4 +Copyright (C) 1997-2003, 2007, 2009-2018 Richard P. Curnow and others +chrony comes with ABSOLUTELY NO WARRANTY. This is free software, and +you are welcome to redistribute it under certain conditions. See the +GNU General Public License version 2 for details. + +chronyc> +``` + +You can enter just the subcommands at this prompt. Try using the **tracking** , **ntpdata** , and **sources** commands. The **chronyc** command line allows command recall and editing for **chronyc** subcommands. You can use the **help** subcommand to get a list of possible commands and their syntax. + +### Conclusion + +Chrony is a powerful tool for synchronizing the times of client hosts, whether they are all on the local network or scattered around the globe. It's easy to configure because, despite the large number of options available, only a few configurations are required for most circumstances. + +After my client computers have synchronized with the NTP server, I like to set the system hardware clock from the system (OS) time by using the following command: + +``` +/sbin/hwclock --systohc +``` + +This command can be added as a cron job or a script in **cron.daily** to keep the hardware clock synced with the system time. + +Chrony and NTP (the service) both use the same configuration, and the files' contents are interchangeable. The man pages for [chronyd][5], [chronyc][4], and [chrony.conf][6] contain an amazing amount of information that can help you get started or learn about esoteric configuration options. + +Do you run your own NTP server? Let us know in the comments and be sure to tell us which implementation you are using, NTP or Chrony. + +-------------------------------------------------------------------------------- + +via: https://opensource.com/article/18/12/manage-ntp-chrony + +作者：[David Both][a] +选题：[lujun9972][b] +译者：[译者ID](https://github.com/译者ID) +校对：[校对者ID](https://github.com/校对者ID) + +本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 + +[a]: https://opensource.com/users/dboth +[b]: https://github.com/lujun9972 +[1]: https://en.wikipedia.org/wiki/Does_Anybody_Really_Know_What_Time_It_Is%3F +[2]: https://en.wikipedia.org/wiki/Network_Time_Protocol +[3]: https://chrony.tuxfamily.org/comparison.html +[4]: https://linux.die.net/man/1/chronyc +[5]: https://linux.die.net/man/8/chronyd +[6]: https://linux.die.net/man/5/chrony.conf diff --git a/sources/tech/20181003 Oomox - Customize And Create Your Own GTK2, GTK3 Themes.md b/sources/tech/20181003 Oomox - Customize And Create Your Own GTK2, GTK3 Themes.md deleted file mode 100644 index e45d96470f..0000000000 --- a/sources/tech/20181003 Oomox - Customize And Create Your Own GTK2, GTK3 Themes.md +++ /dev/null @@ -1,128 +0,0 @@ -Oomox – Customize And Create Your Own GTK2, GTK3 Themes -====== - - - -Theming and Visual customization is one of the main advantages of Linux. Since all the code is open, you can change how your Linux system looks and behaves to a greater degree than you ever could with Windows/Mac OS. GTK theming is perhaps the most popular way in which people customize their Linux desktops. The GTK toolkit is used by a wide variety of desktop environments like Gnome, Cinnamon, Unity, XFCE, and budgie. This means that a single theme made for GTK can be applied to any of these Desktop Environments with little changes. - -There are a lot of very high quality popular GTK themes out there, such as **Arc** , **Numix** , and **Adapta**. But if you want to customize these themes and create your own visual design, you can use **Oomox**. - -The Oomox is a graphical app for customizing and creating your own GTK theme complete with your own color, icon and terminal style. It comes with several presets, which you can apply on a Numix, Arc, or Materia style theme to create your own GTK theme. - -### Installing Oomox - -On Arch Linux and its variants: - -Oomox is available on [**AUR**][1], so you can install it using any AUR helper programs like [**Yay**][2]. - -``` -$ yay -S oomox - -``` - -On Debian/Ubuntu/Linux Mint, download `oomox.deb`package from [**here**][3] and install it as shown below. As of writing this guide, the latest version was **oomox_1.7.0.5.deb**. - -``` -$ sudo dpkg -i oomox_1.7.0.5.deb -$ sudo apt install -f - -``` - -On Fedora, Oomox is available in third-party **COPR** repository. - -``` -$ sudo dnf copr enable tcg/themes -$ sudo dnf install oomox - -``` - -Oomox is also available as a [**Flatpak app**][4]. Make sure you have installed Flatpak as described in [**this guide**][5]. And then, install and run Oomox using the following commands: - -``` -$ flatpak install flathub com.github.themix_project.Oomox - -$ flatpak run com.github.themix_project.Oomox - -``` - -For other Linux distributions, go to the Oomox project page (Link is given at the end of this guide) on Github and compile and install it manually from source. - -### Customize And Create Your Own GTK2, GTK3 Themes - -**Theme Customization** - - - -You can change the colour of practically every UI element, like: - - 1. Headers - 2. Buttons - 3. Buttons inside Headers - 4. Menus - 5. Selected Text - - - -To the left, there are a number of presets, like the Cars theme, modern themes like Materia, and Numix, and retro themes. Then, at the top of the main window, there’s an option called **Theme Style** , that lets you set the overall visual style of the theme. You can choose from between Numix, Arc, and Materia. - -With certain styles like Numix, you can even change things like the Header Gradient, Outline Width and Panel Opacity. You can also add a Dark Mode for your theme that will be automatically created from the default theme. - - - -**Iconset Customization** - -You can customize the iconset that will be used for the theme icons. There are 2 options – Gnome Colors and Archdroid. You an change the base, and stroke colours of the iconset. - -**Terminal Customization** - -You can also customize the terminal colours. The app has several presets for this, but you can customize the exact colour code for each colour value like red, green,black, and so on. You can also auto swap the foreground and background colours. - -**Spotify Theme** - -A unique feature this app has is that you can theme the spotify app to your liking. You can change the foreground, background, and accent color of the spotify app to match the overall GTK theme. - -Then, just press the **Apply Spotify Theme** button, and you’ll get this window: - - - -Just hit apply, and you’re done. - -**Exporting your Theme** - -Once you’re done customizing the theme to your liking, you can rename it by clicking the rename button at the top left: - - - -And then, just hit **Export Theme** to export the theme to your system. - - - -You can also just export just the Iconset or the terminal theme. - -After this, you can open any Visual Customization app for your Desktop Environment, like Tweaks for Gnome based DEs, or the **XFCE Appearance Settings** , and select your exported GTK and Shell theme. - -### Verdict - -If you are a Linux theme junkie, and you know exactly how each button, how each header in your system should look like, Oomox is worth a look. For extreme customizers, it lets you change virtually everything about how your system looks. For people who just want to tweak an existing theme a little bit, it has many, many presets so you can get what you want without a lot of effort. - -Have you tried it? What are your thoughts on Oomox? Put them in the comments below! - - - --------------------------------------------------------------------------------- - -via: https://www.ostechnix.com/oomox-customize-and-create-your-own-gtk2-gtk3-themes/ - -作者：[EDITOR][a] -选题：[lujun9972](https://github.com/lujun9972) -译者：[译者ID](https://github.com/译者ID) -校对：[校对者ID](https://github.com/校对者ID) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 - -[a]: https://www.ostechnix.com/author/editor/ -[1]: https://aur.archlinux.org/packages/oomox/ -[2]: https://www.ostechnix.com/yay-found-yet-another-reliable-aur-helper/ -[3]: https://github.com/themix-project/oomox/releases -[4]: https://flathub.org/apps/details/com.github.themix_project.Oomox -[5]: https://www.ostechnix.com/flatpak-new-framework-desktop-applications-linux/ diff --git a/sources/tech/20181004 4 Must-Have Tools for Monitoring Linux.md b/sources/tech/20181004 4 Must-Have Tools for Monitoring Linux.md index 987809aa0d..beb3bab797 100644 --- a/sources/tech/20181004 4 Must-Have Tools for Monitoring Linux.md +++ b/sources/tech/20181004 4 Must-Have Tools for Monitoring Linux.md @@ -1,5 +1,3 @@ -### translating by way-ww - 4 Must-Have Tools for Monitoring Linux ====== diff --git a/sources/tech/20181004 Archiving web sites.md b/sources/tech/20181004 Archiving web sites.md deleted file mode 100644 index 558c057913..0000000000 --- a/sources/tech/20181004 Archiving web sites.md +++ /dev/null @@ -1,119 +0,0 @@ -Archiving web sites -====== - -I recently took a deep dive into web site archival for friends who were worried about losing control over the hosting of their work online in the face of poor system administration or hostile removal. This makes web site archival an essential instrument in the toolbox of any system administrator. As it turns out, some sites are much harder to archive than others. This article goes through the process of archiving traditional web sites and shows how it falls short when confronted with the latest fashions in the single-page applications that are bloating the modern web. - -### Converting simple sites - -The days of handcrafted HTML web sites are long gone. Now web sites are dynamic and built on the fly using the latest JavaScript, PHP, or Python framework. As a result, the sites are more fragile: a database crash, spurious upgrade, or unpatched vulnerability might lose data. In my previous life as web developer, I had to come to terms with the idea that customers expect web sites to basically work forever. This expectation matches poorly with "move fast and break things" attitude of web development. Working with the [Drupal][2] content-management system (CMS) was particularly challenging in that regard as major upgrades deliberately break compatibility with third-party modules, which implies a costly upgrade process that clients could seldom afford. The solution was to archive those sites: take a living, dynamic web site and turn it into plain HTML files that any web server can serve forever. This process is useful for your own dynamic sites but also for third-party sites that are outside of your control and you might want to safeguard. - -For simple or static sites, the venerable [Wget][3] program works well. The incantation to mirror a full web site, however, is byzantine: - -``` - $ nice wget --mirror --execute robots=off --no-verbose --convert-links \ - --backup-converted --page-requisites --adjust-extension \ - --base=./ --directory-prefix=./ --span-hosts \ - --domains=www.example.com,example.com http://www.example.com/ - -``` - -The above downloads the content of the web page, but also crawls everything within the specified domains. Before you run this against your favorite site, consider the impact such a crawl might have on the site. The above command line deliberately ignores [`robots.txt`][] rules, as is now [common practice for archivists][4], and hammer the website as fast as it can. Most crawlers have options to pause between hits and limit bandwidth usage to avoid overwhelming the target site. - -The above command will also fetch "page requisites" like style sheets (CSS), images, and scripts. The downloaded page contents are modified so that links point to the local copy as well. Any web server can host the resulting file set, which results in a static copy of the original web site. - -That is, when things go well. Anyone who has ever worked with a computer knows that things seldom go according to plan; all sorts of things can make the procedure derail in interesting ways. For example, it was trendy for a while to have calendar blocks in web sites. A CMS would generate those on the fly and make crawlers go into an infinite loop trying to retrieve all of the pages. Crafty archivers can resort to regular expressions (e.g. Wget has a `--reject-regex` option) to ignore problematic resources. Another option, if the administration interface for the web site is accessible, is to disable calendars, login forms, comment forms, and other dynamic areas. Once the site becomes static, those will stop working anyway, so it makes sense to remove such clutter from the original site as well. - -### JavaScript doom - -Unfortunately, some web sites are built with much more than pure HTML. In single-page sites, for example, the web browser builds the content itself by executing a small JavaScript program. A simple user agent like Wget will struggle to reconstruct a meaningful static copy of those sites as it does not support JavaScript at all. In theory, web sites should be using [progressive enhancement][5] to have content and functionality available without JavaScript but those directives are rarely followed, as anyone using plugins like [NoScript][6] or [uMatrix][7] will confirm. - -Traditional archival methods sometimes fail in the dumbest way. When trying to build an offsite backup of a local newspaper ([pamplemousse.ca][8]), I found that WordPress adds query strings (e.g. `?ver=1.12.4`) at the end of JavaScript includes. This confuses content-type detection in the web servers that serve the archive, which rely on the file extension to send the right `Content-Type` header. When such an archive is loaded in a web browser, it fails to load scripts, which breaks dynamic websites. - -As the web moves toward using the browser as a virtual machine to run arbitrary code, archival methods relying on pure HTML parsing need to adapt. The solution for such problems is to record (and replay) the HTTP headers delivered by the server during the crawl and indeed professional archivists use just such an approach. - -### Creating and displaying WARC files - -At the [Internet Archive][9], Brewster Kahle and Mike Burner designed the [ARC][10] (for "ARChive") file format in 1996 to provide a way to aggregate the millions of small files produced by their archival efforts. The format was eventually standardized as the WARC ("Web ARChive") [specification][11] that was released as an ISO standard in 2009 and revised in 2017. The standardization effort was led by the [International Internet Preservation Consortium][12] (IIPC), which is an "international organization of libraries and other organizations established to coordinate efforts to preserve internet content for the future", according to Wikipedia; it includes members such as the US Library of Congress and the Internet Archive. The latter uses the WARC format internally in its Java-based [Heritrix crawler][13]. - -A WARC file aggregates multiple resources like HTTP headers, file contents, and other metadata in a single compressed archive. Conveniently, Wget actually supports the file format with the `--warc` parameter. Unfortunately, web browsers cannot render WARC files directly, so a viewer or some conversion is necessary to access the archive. The simplest such viewer I have found is [pywb][14], a Python package that runs a simple webserver to offer a Wayback-Machine-like interface to browse the contents of WARC files. The following set of commands will render a WARC file on `http://localhost:8080/`: - -``` - $ pip install pywb - $ wb-manager init example - $ wb-manager add example crawl.warc.gz - $ wayback - -``` - -This tool was, incidentally, built by the folks behind the [Webrecorder][15] service, which can use a web browser to save dynamic page contents. - -Unfortunately, pywb has trouble loading WARC files generated by Wget because it [followed][16] an [inconsistency in the 1.0 specification][17], which was [fixed in the 1.1 specification][18]. Until Wget or pywb fix those problems, WARC files produced by Wget are not reliable enough for my uses, so I have looked at other alternatives. A crawler that got my attention is simply called [crawl][19]. Here is how it is invoked: - -``` - $ crawl https://example.com/ - -``` - -(It does say "very simple" in the README.) The program does support some command-line options, but most of its defaults are sane: it will fetch page requirements from other domains (unless the `-exclude-related` flag is used), but does not recurse out of the domain. By default, it fires up ten parallel connections to the remote site, a setting that can be changed with the `-c` flag. But, best of all, the resulting WARC files load perfectly in pywb. - -### Future work and alternatives - -There are plenty more [resources][20] for using WARC files. In particular, there's a Wget drop-in replacement called [Wpull][21] that is specifically designed for archiving web sites. It has experimental support for [PhantomJS][22] and [youtube-dl][23] integration that should allow downloading more complex JavaScript sites and streaming multimedia, respectively. The software is the basis for an elaborate archival tool called [ArchiveBot][24], which is used by the "loose collective of rogue archivists, programmers, writers and loudmouths" at [ArchiveTeam][25] in its struggle to "save the history before it's lost forever". It seems that PhantomJS integration does not work as well as the team wants, so ArchiveTeam also uses a rag-tag bunch of other tools to mirror more complex sites. For example, [snscrape][26] will crawl a social media profile to generate a list of pages to send into ArchiveBot. Another tool the team employs is [crocoite][27], which uses the Chrome browser in headless mode to archive JavaScript-heavy sites. - -This article would also not be complete without a nod to the [HTTrack][28] project, the "website copier". Working similarly to Wget, HTTrack creates local copies of remote web sites but unfortunately does not support WARC output. Its interactive aspects might be of more interest to novice users unfamiliar with the command line. - -In the same vein, during my research I found a full rewrite of Wget called [Wget2][29] that has support for multi-threaded operation, which might make it faster than its predecessor. It is [missing some features][30] from Wget, however, most notably reject patterns, WARC output, and FTP support but adds RSS, DNS caching, and improved TLS support. - -Finally, my personal dream for these kinds of tools would be to have them integrated with my existing bookmark system. I currently keep interesting links in [Wallabag][31], a self-hosted "read it later" service designed as a free-software alternative to [Pocket][32] (now owned by Mozilla). But Wallabag, by design, creates only a "readable" version of the article instead of a full copy. In some cases, the "readable version" is actually [unreadable][33] and Wallabag sometimes [fails to parse the article][34]. Instead, other tools like [bookmark-archiver][35] or [reminiscence][36] save a screenshot of the page along with full HTML but, unfortunately, no WARC file that would allow an even more faithful replay. - -The sad truth of my experiences with mirrors and archival is that data dies. Fortunately, amateur archivists have tools at their disposal to keep interesting content alive online. For those who do not want to go through that trouble, the Internet Archive seems to be here to stay and Archive Team is obviously [working on a backup of the Internet Archive itself][37]. - --------------------------------------------------------------------------------- - -via: https://anarc.at/blog/2018-10-04-archiving-web-sites/ - -作者：[Anarcat][a] -选题：[lujun9972](https://github.com/lujun9972) -译者：[译者ID](https://github.com/译者ID) -校对：[校对者ID](https://github.com/校对者ID) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 - -[a]: https://anarc.at -[1]: https://anarc.at/blog -[2]: https://drupal.org -[3]: https://www.gnu.org/software/wget/ -[4]: https://blog.archive.org/2017/04/17/robots-txt-meant-for-search-engines-dont-work-well-for-web-archives/ -[5]: https://en.wikipedia.org/wiki/Progressive_enhancement -[6]: https://noscript.net/ -[7]: https://github.com/gorhill/uMatrix -[8]: https://pamplemousse.ca/ -[9]: https://archive.org -[10]: http://www.archive.org/web/researcher/ArcFileFormat.php -[11]: https://iipc.github.io/warc-specifications/ -[12]: https://en.wikipedia.org/wiki/International_Internet_Preservation_Consortium -[13]: https://github.com/internetarchive/heritrix3/wiki -[14]: https://github.com/webrecorder/pywb -[15]: https://webrecorder.io/ -[16]: https://github.com/webrecorder/pywb/issues/294 -[17]: https://github.com/iipc/warc-specifications/issues/23 -[18]: https://github.com/iipc/warc-specifications/pull/24 -[19]: https://git.autistici.org/ale/crawl/ -[20]: https://archiveteam.org/index.php?title=The_WARC_Ecosystem -[21]: https://github.com/chfoo/wpull -[22]: http://phantomjs.org/ -[23]: http://rg3.github.io/youtube-dl/ -[24]: https://www.archiveteam.org/index.php?title=ArchiveBot -[25]: https://archiveteam.org/ -[26]: https://github.com/JustAnotherArchivist/snscrape -[27]: https://github.com/PromyLOPh/crocoite -[28]: http://www.httrack.com/ -[29]: https://gitlab.com/gnuwget/wget2 -[30]: https://gitlab.com/gnuwget/wget2/wikis/home -[31]: https://wallabag.org/ -[32]: https://getpocket.com/ -[33]: https://github.com/wallabag/wallabag/issues/2825 -[34]: https://github.com/wallabag/wallabag/issues/2914 -[35]: https://pirate.github.io/bookmark-archiver/ -[36]: https://github.com/kanishka-linux/reminiscence -[37]: http://iabak.archiveteam.org diff --git a/sources/tech/20181004 Functional programming in Python- Immutable data structures.md b/sources/tech/20181004 Functional programming in Python- Immutable data structures.md deleted file mode 100644 index b831ff726f..0000000000 --- a/sources/tech/20181004 Functional programming in Python- Immutable data structures.md +++ /dev/null @@ -1,190 +0,0 @@ -Functional programming in Python: Immutable data structures -====== -Immutability can help us better understand our code. Here's how to achieve it without sacrificing performance. - - - -In this two-part series, I will discuss how to import ideas from the functional programming methodology into Python in order to have the best of both worlds. - -This first post will explore how immutable data structures can help. The second part will explore higher-level functional programming concepts in Python using the **toolz** library. - -Why functional programming? Because mutation is hard to reason about. If you are already convinced that mutation is problematic, great. If you're not convinced, you will be by the end of this post. - -Let's begin by considering squares and rectangles. If we think in terms of interfaces, neglecting implementation details, are squares a subtype of rectangles? - -The definition of a subtype rests on the [Liskov substitution principle][1]. In order to be a subtype, it must be able to do everything the supertype does. - -How would we define an interface for a rectangle? - -``` -from zope.interface import Interface - -class IRectangle(Interface): - def get_length(self): - """Squares can do that""" - def get_width(self): - """Squares can do that""" - def set_dimensions(self, length, width): - """Uh oh""" -``` - -If this is the definition, then squares cannot be a subtype of rectangles; they cannot respond to a `set_dimensions` method if the length and width are different. - -A different approach is to choose to make rectangles immutable. - -``` -class IRectangle(Interface): - def get_length(self): - """Squares can do that""" - def get_width(self): - """Squares can do that""" - def with_dimensions(self, length, width): - """Returns a new rectangle""" -``` - -Now, a square can be a rectangle. It can return a new rectangle (which would not usually be a square) when `with_dimensions` is called, but it would not stop being a square. - -This might seem like an academic problem—until we consider that squares and rectangles are, in a sense, a container for their sides. After we understand this example, the more realistic case this comes into play with is more traditional containers. For example, consider random-access arrays. - -We have `ISquare` and `IRectangle`, and `ISquare` is a subtype of `IRectangle`. - -We want to put rectangles in a random-access array: - -``` -class IArrayOfRectangles(Interface): - def get_element(self, i): - """Returns Rectangle""" - def set_element(self, i, rectangle): - """'rectangle' can be any IRectangle""" -``` - -We want to put squares in a random-access array too: - -``` -class IArrayOfSquare(Interface): - def get_element(self, i): - """Returns Square""" - def set_element(self, i, square): - """'square' can be any ISquare""" -``` - -Even though `ISquare` is a subtype of `IRectangle`, no array can implement both `IArrayOfSquare` and `IArrayOfRectangle`. - -Why not? Assume `bucket` implements both. - -``` ->>> rectangle = make_rectangle(3, 4) ->>> bucket.set_element(0, rectangle) # This is allowed by IArrayOfRectangle ->>> thing = bucket.get_element(0) # That has to be a square by IArrayOfSquare ->>> assert thing.height == thing.width -Traceback (most recent call last): - File " ", line 1, in -AssertionError -``` - -Being unable to implement both means that neither is a subtype of the other, even though `ISquare` is a subtype of `IRectangle`. The problem is the `set_element` method: If we had a read-only array, `IArrayOfSquare` would be a subtype of `IArrayOfRectangle`. - -Mutability, in both the mutable `IRectangle` interface and the mutable `IArrayOf*` interfaces, has made thinking about types and subtypes much more difficult—and giving up on the ability to mutate meant that the intuitive relationships we expected to have between the types actually hold. - -Mutation can also have non-local effects. This happens when a shared object between two places is mutated by one. The classic example is one thread mutating a shared object with another thread, but even in a single-threaded program, sharing between places that are far apart is easy. Consider that in Python, most objects are reachable from many places: as a module global, or in a stack trace, or as a class attribute. - -If we cannot constrain the sharing, we might think about constraining the mutability. - -Here is an immutable rectangle, taking advantage of the [attrs][2] library: - -``` -@attr.s(frozen=True) -class Rectange(object): - length = attr.ib() - width = attr.ib() - @classmethod - def with_dimensions(cls, length, width): - return cls(length, width) -``` - -Here is a square: - -``` -@attr.s(frozen=True) -class Square(object): - side = attr.ib() - @classmethod - def with_dimensions(cls, length, width): - return Rectangle(length, width) -``` - -Using the `frozen` argument, we can easily have `attrs`-created classes be immutable. All the hard work of writing `__setitem__` correctly has been done by others and is completely invisible to us. - -It is still easy to modify objects; it's just nigh impossible to mutate them. - -``` -too_long = Rectangle(100, 4) -reasonable = attr.evolve(too_long, length=10) -``` - -The [Pyrsistent][3] package allows us to have immutable containers. - -``` -# Vector of integers -a = pyrsistent.v(1, 2, 3) -# Not a vector of integers -b = a.set(1, "hello") -``` - -While `b` is not a vector of integers, nothing will ever stop `a` from being one. - -What if `a` was a million elements long? Is `b` going to copy 999,999 of them? Pyrsistent comes with "big O" performance guarantees: All operations take `O(log n)` time. It also comes with an optional C extension to improve performance beyond the big O. - -For modifying nested objects, it comes with a concept of "transformers:" - -``` -blog = pyrsistent.m( - title="My blog", - links=pyrsistent.v("github", "twitter"), - posts=pyrsistent.v( - pyrsistent.m(title="no updates", - content="I'm busy"), - pyrsistent.m(title="still no updates", - content="still busy"))) -new_blog = blog.transform(["posts", 1, "content"], - "pretty busy") -``` - -`new_blog` will now be the immutable equivalent of - -``` -{'links': ['github', 'twitter'], - 'posts': [{'content': "I'm busy", - 'title': 'no updates'}, - {'content': 'pretty busy', - 'title': 'still no updates'}], - 'title': 'My blog'} -``` - -But `blog` is still the same. This means anyone who had a reference to the old object has not been affected: The transformation had only local effects. - -This is useful when sharing is rampant. For example, consider default arguments: - -``` -def silly_sum(a, b, extra=v(1, 2)): - extra = extra.extend([a, b]) - return sum(extra) -``` - -In this post, we have learned why immutability can be useful for thinking about our code, and how to achieve it without an extravagant performance price. Next time, we will learn how immutable objects allow us to use powerful programming constructs. - --------------------------------------------------------------------------------- - -via: https://opensource.com/article/18/10/functional-programming-python-immutable-data-structures - -作者：[Moshe Zadka][a] -选题：[lujun9972](https://github.com/lujun9972) -译者：[译者ID](https://github.com/译者ID) -校对：[校对者ID](https://github.com/校对者ID) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 - -[a]: https://opensource.com/users/moshez -[1]: https://en.wikipedia.org/wiki/Liskov_substitution_principle -[2]: https://www.attrs.org/en/stable/ -[3]: https://pyrsistent.readthedocs.io/en/latest/ diff --git a/sources/tech/20181005 Dbxfs - Mount Dropbox Folder Locally As Virtual File System In Linux.md b/sources/tech/20181005 Dbxfs - Mount Dropbox Folder Locally As Virtual File System In Linux.md deleted file mode 100644 index 691600a4cc..0000000000 --- a/sources/tech/20181005 Dbxfs - Mount Dropbox Folder Locally As Virtual File System In Linux.md +++ /dev/null @@ -1,133 +0,0 @@ -Dbxfs – Mount Dropbox Folder Locally As Virtual File System In Linux -====== - - - -A while ago, we summarized all the possible ways to **[mount Google drive locally][1]** as a virtual file system and access the files stored in the google drive from your Linux operating system. Today, we are going to learn to mount Dropbox folder in your local file system using **dbxfs** utility. The dbxfs is used to mount your Dropbox folder locally as a virtual filesystem in Unix-like operating systems. While it is easy to [**install Dropbox client**][2] in Linux, this approach slightly differs from the official method. It is a command line dropbox client and requires no disk space for access. The dbxfs application is free, open source and written for Python 3.5+. - -### Installing dbxfs - -The dbxfs officially supports Linux and Mac OS. However, it should work on any POSIX system that provides a **FUSE-compatible library** or has the ability to mount **SMB** shares. Since it is written for Python 3.5, it can installed using **pip3** package manager. Refer the following guide if you haven’t installed PIP yet. - -And, install FUSE library as well. - -On Debian-based systems, run the following command to install FUSE: - -``` -$ sudo apt install libfuse2 - -``` - -On Fedora: - -``` -$ sudo dnf install fuse - -``` - -Once you installed all required dependencies, run the following command to install dbxfs utility: - -``` -$ pip3 install dbxfs - -``` - -### Mount Dropbox folder locally - -Create a mount point to mount your dropbox folder in your local file system. - -``` -$ mkdir ~/mydropbox - -``` - -Then, mount the dropbox folder locally using dbxfs utility as shown below: - -``` -$ dbxfs ~/mydropbox - -``` - -You will be asked to generate an access token: - - - -To generate an access token, just navigate to the URL given in the above output from your web browser and click **Allow** to authenticate Dropbox access. You need to log in to your dropbox account to complete authorization process. - -A new authorization code will be generated in the next screen. Copy the code and head back to your Terminal and paste it into cli-dbxfs prompt to finish the process. - -You will be then asked to save the credentials for future access. Type **Y** or **N** whether you want to save or decline. And then, you need to enter a passphrase twice for the new access token. - -Finally, click **Y** to accept **“/home/username/mydropbox”** as the default mount point. If you want to set different path, type **N** and enter the location of your choice. - -[![Generate access token 2][3]][4] - -All done! From now on, you can see your Dropbox folder is locally mounted in your filesystem. - - - -### Change Access Token Storage Path - -By default, the dbxfs application will store your Dropbox access token in the system keyring or an encrypted file. However, you might want to store it in a **gpg** encrypted file or something else. If so, get an access token by creating a personal app on the [Dropbox developers app console][5]. - - - -Once the app is created, click **Generate** button in the next button. This access token can be used to access your Dropbox account via the API. Don’t share your access token with anyone. - - - -Once you created an access token, encrypt it using any encryption tools of your choice, such as [**Cryptomater**][6], [**Cryptkeeper**][7], [**CryptGo**][8], [**Cryptr**][9], [**Tomb**][10], [**Toplip**][11] and [**GnuPG**][12] etc., and store it in your preferred location. - -Next edit the dbxfs configuration file and add the following line in it: - -``` -"access_token_command": ["gpg", "--decrypt", "/path/to/access/token/file.gpg"] - -``` - -You can find the dbxfs configuration file by running the following command: - -``` -$ dbxfs --print-default-config-file - -``` - -For more details, refer dbxfs help section: - -``` -$ dbxfs -h - -``` - -As you can see, mounting Dropfox folder locally in your file system using Dbxfs utility is no big deal. As far tested, dbxfs just works fine as expected. Give it a try if you’re interested to see how it works and let us know about your experience in the comment section below. - -And, that’s all for now. Hope this was useful. More good stuff to come. Stay tuned! - -Cheers! - - - --------------------------------------------------------------------------------- - -via: https://www.ostechnix.com/dbxfs-mount-dropbox-folder-locally-as-virtual-file-system-in-linux/ - -作者：[SK][a] -选题：[lujun9972](https://github.com/lujun9972) -译者：[译者ID](https://github.com/译者ID) -校对：[校对者ID](https://github.com/校对者ID) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 - -[a]: https://www.ostechnix.com/author/sk/ -[1]: https://www.ostechnix.com/how-to-mount-google-drive-locally-as-virtual-file-system-in-linux/ -[2]: https://www.ostechnix.com/install-dropbox-in-ubuntu-18-04-lts-desktop/ -[3]: data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7 -[4]: http://www.ostechnix.com/wp-content/uploads/2018/10/Generate-access-token-2.png -[5]: https://dropbox.com/developers/apps -[6]: https://www.ostechnix.com/cryptomator-open-source-client-side-encryption-tool-cloud/ -[7]: https://www.ostechnix.com/how-to-encrypt-your-personal-foldersdirectories-in-linux-mint-ubuntu-distros/ -[8]: https://www.ostechnix.com/cryptogo-easy-way-encrypt-password-protect-files/ -[9]: https://www.ostechnix.com/cryptr-simple-cli-utility-encrypt-decrypt-files/ -[10]: https://www.ostechnix.com/tomb-file-encryption-tool-protect-secret-files-linux/ -[11]: https://www.ostechnix.com/toplip-strong-file-encryption-decryption-cli-utility/ -[12]: https://www.ostechnix.com/an-easy-way-to-encrypt-and-decrypt-files-from-commandline-in-linux/ diff --git a/sources/tech/20181005 Terminalizer - A Tool To Record Your Terminal And Generate Animated Gif Images.md b/sources/tech/20181005 Terminalizer - A Tool To Record Your Terminal And Generate Animated Gif Images.md deleted file mode 100644 index 7b77a9cf73..0000000000 --- a/sources/tech/20181005 Terminalizer - A Tool To Record Your Terminal And Generate Animated Gif Images.md +++ /dev/null @@ -1,173 +0,0 @@ -thecyanbird translating - -Terminalizer – A Tool To Record Your Terminal And Generate Animated Gif Images -====== -This is know topic for most of us and i don’t want to give you the detailed information about this flow. Also, we had written many article under this topics. - -Script command is the one of the standard command to record Linux terminal sessions. Today we are going to discuss about same kind of tool called Terminalizer. - -This tool will help us to record the users terminal activity, also will help us to identify other useful information from the output. - -### What Is Terminalizer - -Terminalizer allow users to record their terminal activity and allow them to generate animated gif images. It’s highly customizable CLI tool that user can share a link for an online player, web player for a recording file. - -**Suggested Read :** -**(#)** [Script – A Simple Command To Record Your Terminal Session Activity][1] -**(#)** [Automatically Record/Capture All Users Terminal Sessions Activity In Linux][2] -**(#)** [Teleconsole – A Tool To Share Your Terminal Session Instantly To Anyone In Seconds][3] -**(#)** [tmate – Instantly Share Your Terminal Session To Anyone In Seconds][4] -**(#)** [Peek – Create a Animated GIF Recorder in Linux][5] -**(#)** [Kgif – A Simple Shell Script to Create a Gif File from Active Window][6] -**(#)** [Gifine – Quickly Create An Animated GIF Video In Ubuntu/Debian][7] - -There is no distribution official package to install this utility and we can easily install it by using Node.js. - -### How To Install Noje.js in Linux - -Node.js can be installed in multiple ways. Here, we are going to teach you the standard method. - -For Ubuntu/LinuxMint use [APT-GET Command][8] or [APT Command][9] to install Node.js - -``` -$ curl -sL https://deb.nodesource.com/setup_8.x | sudo -E bash - -$ sudo apt-get install -y nodejs - -``` - -For Debian use [APT-GET Command][8] or [APT Command][9] to install Node.js - -``` -# curl -sL https://deb.nodesource.com/setup_8.x | bash - -# apt-get install -y nodejs - -``` - -For **`RHEL/CentOS`** , use [YUM Command][10] to install tmux. - -``` -$ sudo curl --silent --location https://rpm.nodesource.com/setup_8.x | sudo bash - -$ sudo yum install epel-release -$ sudo yum -y install nodejs - -``` - -For **`Fedora`** , use [DNF Command][11] to install tmux. - -``` -$ sudo dnf install nodejs - -``` - -For **`Arch Linux`** , use [Pacman Command][12] to install tmux. - -``` -$ sudo pacman -S nodejs npm - -``` - -For **`openSUSE`** , use [Zypper Command][13] to install tmux. - -``` -$ sudo zypper in nodejs6 - -``` - -### How to Install Terminalizer - -As you have already installed prerequisite package called Node.js, now it’s time to install Terminalizer on your system. Simple run the below npm command to install Terminalizer. - -``` -$ sudo npm install -g terminalizer - -``` - -### How to Use Terminalizer - -To record your session activity using Terminalizer, just run the following Terminalizer command. Once you started the recording then play around it and finally hit `CTRL+D` to exit and save the recording. - -``` -# terminalizer record 2g-session - -defaultConfigPath -The recording session is started -Press CTRL+D to exit and save the recording - -``` - -This will save your recording session as a YAML file, in this case my filename would be 2g-session-activity.yml. -![][15] - -Just type few commands to verify this and finally hit `CTRL+D` to exit the current capture. When you hit `CTRL+D` on the terminal and you will be getting the below output. - -``` -# logout -Successfully Recorded -The recording data is saved into the file: -/home/daygeek/2g-session.yml -You can edit the file and even change the configurations. - -``` - -![][16] - -### How to Play the Recorded File - -Use the below command format to paly your recorded YAML file. Make sure, you have to input your recorded file instead of us. - -``` -# terminalizer play 2g-session - -``` - -Render a recording file as an animated gif image. - -``` -# terminalizer render 2g-session - -``` - -`Note:` Below two commands are not implemented yet in the current version and will be available in the next version. - -If you would like to share your recording to others then upload a recording file and get a link for an online player and share it. - -``` -terminalizer share 2g-session - -``` - -Generate a web player for a recording file - -``` -# terminalizer generate 2g-session - -``` - --------------------------------------------------------------------------------- - -via: https://www.2daygeek.com/terminalizer-a-tool-to-record-your-terminal-and-generate-animated-gif-images/ - -作者：[Prakash Subramanian][a] -选题：[lujun9972](https://github.com/lujun9972) -译者：[译者ID](https://github.com/译者ID) -校对：[校对者ID](https://github.com/校对者ID) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 - -[a]: https://www.2daygeek.com/author/prakash/ -[1]: https://www.2daygeek.com/script-command-record-save-your-terminal-session-activity-linux/ -[2]: https://www.2daygeek.com/automatically-record-all-users-terminal-sessions-activity-linux-script-command/ -[3]: https://www.2daygeek.com/teleconsole-share-terminal-session-instantly-to-anyone-in-seconds/ -[4]: https://www.2daygeek.com/tmate-instantly-share-your-terminal-session-to-anyone-in-seconds/ -[5]: https://www.2daygeek.com/peek-create-animated-gif-screen-recorder-capture-arch-linux-mint-fedora-ubuntu/ -[6]: https://www.2daygeek.com/kgif-create-animated-gif-file-active-window-screen-recorder-capture-arch-linux-mint-fedora-ubuntu-debian-opensuse-centos/ -[7]: https://www.2daygeek.com/gifine-create-animated-gif-vedio-recorder-linux-mint-debian-ubuntu/ -[8]: https://www.2daygeek.com/apt-get-apt-cache-command-examples-manage-packages-debian-ubuntu-systems/ -[9]: https://www.2daygeek.com/apt-command-examples-manage-packages-debian-ubuntu-systems/ -[10]: https://www.2daygeek.com/yum-command-examples-manage-packages-rhel-centos-systems/ -[11]: https://www.2daygeek.com/dnf-command-examples-manage-packages-fedora-system/ -[12]: https://www.2daygeek.com/pacman-command-examples-manage-packages-arch-linux-system/ -[13]: https://www.2daygeek.com/zypper-command-examples-manage-packages-opensuse-system/ -[14]: data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7 -[15]: https://www.2daygeek.com/wp-content/uploads/2018/10/terminalizer-record-2g-session-1.gif -[16]: https://www.2daygeek.com/wp-content/uploads/2018/10/terminalizer-play-2g-session.gif diff --git a/sources/tech/20181006 LinuxBoot for Servers - Enter Open Source, Goodbye Proprietary UEFI.md b/sources/tech/20181006 LinuxBoot for Servers - Enter Open Source, Goodbye Proprietary UEFI.md deleted file mode 100644 index de0a4260db..0000000000 --- a/sources/tech/20181006 LinuxBoot for Servers - Enter Open Source, Goodbye Proprietary UEFI.md +++ /dev/null @@ -1,126 +0,0 @@ -qhwdw is translating - -LinuxBoot for Servers: Enter Open Source, Goodbye Proprietary UEFI -============================================================ - -[LinuxBoot][13] is an Open Source [alternative][14] to Proprietary [UEFI][15] firmware. It was released last year and is now being increasingly preferred by leading hardware manufacturers as default firmware. Last year, LinuxBoot was warmly [welcomed][16]into the Open Source family by The Linux Foundation. - -This project was an initiative by Ron Minnich, author of LinuxBIOS and lead of [coreboot][17] at Google, in January 2017. - -Google, Facebook, [Horizon Computing Solutions][18], and [Two Sigma][19] collaborated together to develop the [LinuxBoot project][20] (formerly called [NERF][21]) for server machines based on Linux. - -Its openness allows Server users to easily customize their own boot scripts, fix issues, build their own [runtimes][22] and [reflash their firmware][23] with their own keys. They do not need to wait for vendor updates. - -Following is a video of [Ubuntu Xenial][24] booting for the first time with NERF BIOS: - -[视频](https://youtu.be/HBkZAN3xkJg) - -Let’s talk about some other advantages by comparing it to UEFI in terms of Server hardware. - -### Advantages of LinuxBoot over UEFI - - - -Here are some of the major advantages of LinuxBoot over UEFI: - -### Significantly faster startup - -It can boot up Server boards in less than twenty seconds, versus multiple minutes on UEFI. - -### Significantly more flexible - -LinuxBoot can make use of any devices, filesystems and protocols that Linux supports. - -### Potentially more secure - -Linux device drivers and filesystems have significantly more scrutiny than through UEFI. - -We can argue that UEFI is partly open with [EDK II][25] and LinuxBoot is partly closed. But it has been [addressed][26] that even such EDK II code does not have the proper level of inspection and correctness as the [Linux Kernel][27] goes through, while there is a huge amount of other Closed Source components within UEFI development. - -On the other hand, LinuxBoot has a significantly smaller amount of binaries with only a few hundred KB, compared to the 32 MB of UEFI binaries. - -To be precise, LinuxBoot fits a whole lot better into the [Trusted Computing Base][28], unlike UEFI. - -[Suggested readBest Free and Open Source Alternatives to Adobe Products for Linux][29] - -LinuxBoot has a [kexec][30] based bootloader which does not support startup on Windows/non-Linux kernels, but that is insignificant since most clouds are Linux-based Servers. - -### LinuxBoot adoption - -In 2011, the [Open Compute Project][31] was started by [Facebook][32] who [open-sourced][33] designs of some of their Servers, built to make its data centers more efficient. LinuxBoot has been tested on a few Open Compute Hardware listed as under: - -* Winterfell - -* Leopard - -* Tioga Pass - -More [OCP][34] hardware are described [here][35] in brief. The OCP Foundation runs a dedicated project on firmware through [Open System Firmware][36]. - -Some other devices that support LinuxBoot are: - -* [QEMU][9] emulated [Q35][10] systems - -* [Intel S2600wf][11] - -* [Dell R630][12] - -Last month end, [Equus Compute Solutions][37] [announced][38] the release of its [WHITEBOX OPEN™][39] M2660 and M2760 Servers, as a part of their custom, cost-optimized Open-Hardware Servers and storage platforms. Both of them support LinuxBoot to customize the Server BIOS for flexibility, improved security, and create a blazingly fast booting experience. - -### What do you think of LinuxBoot? - -LinuxBoot is quite well documented [on GitHub][40]. Do you like the features that set it apart from UEFI? Would you prefer using LinuxBoot rather than UEFI for starting up Servers, owing to the former’s open-ended development and future? Let us know in the comments below. - --------------------------------------------------------------------------------- - -via: https://itsfoss.com/linuxboot-uefi/ - -作者：[ Avimanyu Bandyopadhyay][a] -选题：[oska874][b] -译者：[译者ID](https://github.com/译者ID) -校对：[校对者ID](https://github.com/校对者ID) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 - -[a]:https://itsfoss.com/author/avimanyu/ -[b]:https://github.com/oska874 -[1]:https://itsfoss.com/linuxboot-uefi/# -[2]:https://itsfoss.com/linuxboot-uefi/# -[3]:https://itsfoss.com/linuxboot-uefi/# -[4]:https://itsfoss.com/linuxboot-uefi/# -[5]:https://itsfoss.com/linuxboot-uefi/# -[6]:https://itsfoss.com/linuxboot-uefi/# -[7]:https://itsfoss.com/author/avimanyu/ -[8]:https://itsfoss.com/linuxboot-uefi/#comments -[9]:https://en.wikipedia.org/wiki/QEMU -[10]:https://wiki.qemu.org/Features/Q35 -[11]:https://trmm.net/S2600 -[12]:https://trmm.net/NERF#Installing_on_a_Dell_R630 -[13]:https://www.linuxboot.org/ -[14]:https://www.phoronix.com/scan.php?page=news_item&px=LinuxBoot-OSFC-2018-State -[15]:https://itsfoss.com/check-uefi-or-bios/ -[16]:https://www.linuxfoundation.org/blog/2018/01/system-startup-gets-a-boost-with-new-linuxboot-project/ -[17]:https://en.wikipedia.org/wiki/Coreboot -[18]:http://www.horizon-computing.com/ -[19]:https://www.twosigma.com/ -[20]:https://trmm.net/LinuxBoot_34c3 -[21]:https://trmm.net/NERF -[22]:https://trmm.net/LinuxBoot_34c3#Runtimes -[23]:http://www.tech-faq.com/flashing-firmware.html -[24]:https://itsfoss.com/features-ubuntu-1604/ -[25]:https://www.tianocore.org/ -[26]:https://media.ccc.de/v/34c3-9056-bringing_linux_back_to_server_boot_roms_with_nerf_and_heads -[27]:https://medium.com/@bhumikagoyal/linux-kernel-development-cycle-52b4c55be06e -[28]:https://en.wikipedia.org/wiki/Trusted_computing_base -[29]:https://itsfoss.com/adobe-alternatives-linux/ -[30]:https://en.wikipedia.org/wiki/Kexec -[31]:https://en.wikipedia.org/wiki/Open_Compute_Project -[32]:https://github.com/facebook -[33]:https://github.com/opencomputeproject -[34]:https://www.networkworld.com/article/3266293/lan-wan/what-is-the-open-compute-project.html -[35]:http://hyperscaleit.com/ocp-server-hardware/ -[36]:https://www.opencompute.org/projects/open-system-firmware -[37]:https://www.equuscs.com/ -[38]:http://www.dcvelocity.com/products/Software_-_Systems/20180924-equus-compute-solutions-introduces-whitebox-open-m2660-and-m2760-servers/ -[39]:https://www.equuscs.com/servers/whitebox-open/ -[40]:https://github.com/linuxboot/linuxboot diff --git a/sources/tech/20181008 Taking notes with Laverna, a web-based information organizer.md b/sources/tech/20181008 Taking notes with Laverna, a web-based information organizer.md index 71adf0112b..27616a9f6e 100644 --- a/sources/tech/20181008 Taking notes with Laverna, a web-based information organizer.md +++ b/sources/tech/20181008 Taking notes with Laverna, a web-based information organizer.md @@ -1,5 +1,3 @@ -translating by cyleft - Taking notes with Laverna, a web-based information organizer ====== diff --git a/sources/tech/20181011 Exploring the Linux kernel- The secrets of Kconfig-kbuild.md b/sources/tech/20181011 Exploring the Linux kernel- The secrets of Kconfig-kbuild.md index f2885b177c..2fd085eda0 100644 --- a/sources/tech/20181011 Exploring the Linux kernel- The secrets of Kconfig-kbuild.md +++ b/sources/tech/20181011 Exploring the Linux kernel- The secrets of Kconfig-kbuild.md @@ -1,4 +1,5 @@ -translating by leemeans +Translating by Jamskr + Exploring the Linux kernel: The secrets of Kconfig/kbuild ====== Dive into understanding how the Linux config/build system works. diff --git a/sources/tech/20181022 Improve login security with challenge-response authentication.md b/sources/tech/20181022 Improve login security with challenge-response authentication.md deleted file mode 100644 index 66ed2534b0..0000000000 --- a/sources/tech/20181022 Improve login security with challenge-response authentication.md +++ /dev/null @@ -1,183 +0,0 @@ -Improve login security with challenge-response authentication -====== - - - -### Introduction - -Today, Fedora offers multiple ways to improve the secure authentication of our user accounts. Of course it has the familiar user name and password to login. It also offers additional authentication options such as biometric, fingerprint, smart card, one-time password, and even challenge-response authentication. - -Each authentication method has clear pros and cons. That, in itself, could be a topic for a rather lengthy article. Fedora Magazine has covered a few of these options previously: - - -+ [Using the YubiKey4 with Fedora][1] -+ [Fedora 28: Better smart card support in OpenSSH][2] - - -One of the most secure methods in modern Fedora releases is offline hardware challenge-response. It’s also one of the easiest to deploy. Here’s how. - -### Challenge-response authentication - -Technically, when you provide a password, you’re responding to a user name challenge. The offline challenge response covered here requires your user name first. Next, Fedora challenges you to provide an encrypted physical hardware token. The token responds to the challenge with another encrypted key it stores via the Pluggable Authentication Modules (PAM) framework. Finally, Fedora prompts you for the password. This prevents someone from just using a found hardware token, or just using a user name and password without the correct encrypted key. - -This means that in addition to your user name and password, you must have previously registered one or more encrypted hardware tokens with the OS. And you have to provide that physical hardware token to be able to authenticate with your user name. - -Some challenge-response methods, like one time passwords (OTP), take an encrypted code key on the hardware token, and pass that key across the network to a remote authentication server. The server then tells Fedora’s PAM framework if it’s is a valid token for that user name. This is great if the authentication server(s) are on the local network. The downside is if the network connection is down or you’re working remote without a network connection, you can’t use this remote authentication method. You could be locked out of the system until you can connect through the network to the server. - -Sometimes a workplace requires use of Yubikey One Time Passwords (OTP) configuration. However, on home or personal systems you may prefer a local challenge-response configuration. Everything is local, and the method requires no remote network calls. The following process works on Fedora 27, 28, and 29. - -### Preparation - -#### Hardware token keys - -First you need a secure hardware token key. Specifically, this process requires a Yubikey 4, Yubikey NEO, or a recently released Yubikey 5 series device which also supports FIDO2. You should purchase two of them to provide a backup in case one becomes lost or damaged. You can use these keys on numerous workstations. The simpler FIDO or FIDO U2F only versions don’t work for this process, but are great for online services that use FIDO. - -#### Backup, backup, and backup - -Next, make a backup of all your important data. You may want to test the configuration in a Fedora 27/28/29 cloned VM to make sure you understand the process before setting up your personal workstation. - -#### Updating and installing - -Now make sure Fedora is up to date. Then install the required Fedora Yubikey packages via these dnf commands: - -``` -$ sudo dnf upgrade -$ sudo dnf install ykclient* ykpers* pam_yubico* -$ cd -``` - -If you’re in a VM environment, such as Virtual Box, make sure the Yubikey device is inserted in a USB port, and enable USB access to the Yubikey in the VM control. - -### Configuring Yubikey - -Verify that your user account has access to the USB Yubikey: - -``` -$ ykinfo -v -version: 3.5.0 -``` - -If the YubiKey is not detected, the following error message appears: - -``` -Yubikey core error: no yubikey present -``` - -Next, initialize each of your new Yubikeys with the following ykpersonalize command. This sets up the Yubikey configuration slot 2 with a Challenge Response using the HMAC-SHA1 algorithm, even with less than 64 characters. If you have already setup your Yubikeys for challenge-response, you don’t need to run ykpersonalize again. - -``` -ykpersonalize -2 -ochal-resp -ochal-hmac -ohmac-lt64 -oserial-api-visible -``` - -Some users leave the YubiKey in their workstation while using it, and even use challenge-response for virtual machines. However, for more security you may prefer to manually trigger the Yubikey to respond to challenge. - -To add that manual challenge button trigger, add the -ochal-btn-trig flag. This flag causes the Yubikey to flash the yubikey LED on a request. It waits for you to press the button on the hardware key area within 15 seconds to produce the response key. - -``` -$ ykpersonalize -2 -ochal-resp -ochal-hmac -ohmac-lt64 -ochal-btn-trig -oserial-api-visible -``` - -Do this for each of your new hardware keys, only once per key. Once you have programmed your keys, store the Yubikey configuration to ~/.yubico with the following command: - -``` -$ ykpamcfg -2 -v -debug: util.c:222 (check_firmware_version): YubiKey Firmware version: 4.3.4 - -Sending 63 bytes HMAC challenge to slot 2 -Sending 63 bytes HMAC challenge to slot 2 -Stored initial challenge and expected response in '/home/chuckfinley/.yubico/challenge-9992567'. -``` - -If you are setting up multiple keys for backup purposes, configure all the keys the same, and store each key’s challenge-response using the ykpamcfg utility. If you run the command ykpersonalize on an existing registered key, you must store the configuration again. - -### Configuring /etc/pam.d/sudo - -Now to verify this configuration worked, **in the same terminal window** you’ll setup sudo to require the use of the Yubikey challenge-response. Insert the following line into the /etc/pam.d/sudo file: - -``` -auth required pam_yubico.so mode=challenge-response -``` - -Insert the above auth line into the file above the auth include system-auth line. Then save the file and exit the editor. In a default Fedora 29 setup, /etc/pam.d/sudo should now look like this: - -``` -#%PAM-1.0 -auth required pam_yubico.so mode=challenge-response -auth include system-auth -account include system-auth -password include system-auth -session optional pam_keyinit.so revoke -session required pam_limits.so -session include system-auth -``` - -**Keep this original terminal window open** , and test by opening another new terminal window. In the new terminal window type: - -``` -$ sudo echo testing -``` - -You should notice the LED blinking on the key. Tap the Yubikey button and you should see a prompt for your sudo password. After you enter your password, you should see “testing” echoed in the terminal screen. - -Now test to ensure a correct failure. Start another terminal window and remove the Yubikey from the USB port. Verify that sudo no longer works without the Yubikey with this command: - -``` -$ sudo echo testing fail -``` - -You should immediately be prompted for the sudo password. Even if you enter the password, it should fail. - -### Configuring Gnome Desktop Manager - -Once your testing is complete, now you can add challenge-response support for the graphical login. Re-insert your Yubikey into the USB port. Next you’ll add the following line to the /etc/pam.d/gdm-password file: - -``` -auth required pam_yubico.so mode=challenge-response -``` - -Open a terminal window, and issue the following command. You can use another editor if desired: - -``` -$ sudo vi /etc/pam.d/gdm-password -``` - -You should see the yubikey LED blinking. Press the yubikey button, then enter the password at the prompt. - -Modify the /etc/pam.d/gdm-password file to add the new auth line above the existing line auth substack password-auth. The top of the file should now look like this: - -``` -auth [success=done ignore=ignore default=bad] pam_selinux_permit.so -auth required pam_yubico.so mode=challenge-response -auth substack password-auth -auth optional pam_gnome_keyring.so -auth include postlogin - -account required pam_nologin.so -``` - -Save the changes and exit the editor. If you use vi, the key sequence is to hit the **Esc** key, then type wq! at the prompt to save and exit. - -### Conclusion - -Now log out of GNOME. With the Yubikey inserted into the USB port, click on your user name in the graphical login. The Yubikey LED begins to flash. Touch the button, and you will be prompted for your password. - -If you lose the Yubikey, you can still use the secondary backup Yubikey in addition to your set password. You can also add additional Yubikey configurations to your user account. - -If someone gains access to your password, they still can’t login without your physical hardware Yubikey. Congratulations! You’ve now dramatically increased the security of your workstation login. - --------------------------------------------------------------------------------- - -via: https://fedoramagazine.org/login-challenge-response-authentication/ - -作者：[nabooengineer][a] -选题：[lujun9972][b] -译者：[译者ID](https://github.com/译者ID) -校对：[校对者ID](https://github.com/校对者ID) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 - -[a]: https://fedoramagazine.org/author/nabooengineer/ -[b]: https://github.com/lujun9972 -[1]: https://fedoramagazine.org/using-the-yubikey4-with-fedora/ -[2]: https://fedoramagazine.org/fedora-28-better-smart-card-support-openssh/ - diff --git a/sources/tech/20181025 How to write your favorite R functions in Python.md b/sources/tech/20181025 How to write your favorite R functions in Python.md deleted file mode 100644 index a06d3557b9..0000000000 --- a/sources/tech/20181025 How to write your favorite R functions in Python.md +++ /dev/null @@ -1,153 +0,0 @@ -How to write your favorite R functions in Python -====== -R or Python? This Python script mimics convenient R-style functions for doing statistics nice and easy. - - - -One of the great modern battles of data science and machine learning is "Python vs. R." There is no doubt that both have gained enormous ground in recent years to become top programming languages for data science, predictive analytics, and machine learning. In fact, according to a recent IEEE article, Python overtook C++ as the [top programming language][1] and R firmly secured its spot in the top 10. - -However, there are some fundamental differences between these two. [R was developed primarily][2] as a tool for statistical analysis and quick prototyping of a data analysis problem. Python, on the other hand, was developed as a general purpose, modern object-oriented language in the same vein as C++ or Java but with a simpler learning curve and more flexible demeanor. Consequently, R continues to be extremely popular among statisticians, quantitative biologists, physicists, and economists, whereas Python has slowly emerged as the top language for day-to-day scripting, automation, backend web development, analytics, and general machine learning frameworks and has an extensive support base and open source development community work. - -### Mimicking functional programming in a Python environment - -[R's nature as a functional programming language][3] provides users with an extremely simple and compact interface for quick calculations of probabilities and essential descriptive/inferential statistics for a data analysis problem. For example, wouldn't it be great to be able to solve the following problems with just a single, compact function call? - - * How to calculate the mean/median/mode of a data vector. - * How to calculate the cumulative probability of some event following a normal distribution. What if the distribution is Poisson? - * How to calculate the inter-quartile range of a series of data points. - * How to generate a few random numbers following a Student's t-distribution. - - - -The R programming environment can do all of these. - -On the other hand, Python's scripting ability allows analysts to use those statistics in a wide variety of analytics pipelines with limitless sophistication and creativity. - -To combine the advantages of both worlds, you just need a simple Python-based wrapper library that contains the most commonly used functions pertaining to probability distributions and descriptive statistics defined in R-style. This enables you to call those functions really fast without having to go to the proper Python statistical libraries and figure out the whole list of methods and arguments. - -### Python wrapper script for most convenient R-functions - -[I wrote a Python script][4] to define the most convenient and widely used R-functions in simple, statistical analysis—in Python. After importing this script, you will be able to use those R-functions naturally, just like in an R programming environment. - -The goal of this script is to provide simple Python subroutines mimicking R-style statistical functions for quickly calculating density/point estimates, cumulative distributions, and quantiles and generating random variates for important probability distributions. - -To maintain the spirit of R styling, the script uses no class hierarchy and only raw functions are defined in the file. Therefore, a user can import this one Python script and use all the functions whenever they're needed with a single name call. - -Note that I use the word mimic. Under no circumstance am I claiming to emulate R's true functional programming paradigm, which consists of a deep environmental setup and complex relationships between those environments and objects. This script allows me (and I hope countless other Python users) to quickly fire up a Python program or Jupyter notebook, import the script, and start doing simple descriptive statistics in no time. That's the goal, nothing more, nothing less. - -If you've coded in R (maybe in grad school) and are just starting to learn and use Python for data analysis, you will be happy to see and use some of the same well-known functions in your Jupyter notebook in a manner similar to how you use them in your R environment. - -Whatever your reason, using this script is fun. - -### Simple examples - -To start, just import the script and start working with lists of numbers as if they were data vectors in R. - -``` -from R_functions import * -lst=[20,12,16,32,27,65,44,45,22,18] - -``` - -Say you want to calculate the [Tuckey five-number][5] summary from a vector of data points. You just call one simple function, **fivenum** , and pass on the vector. It will return the five-number summary in a NumPy array. - -``` -lst=[20,12,16,32,27,65,44,45,22,18] -fivenum(lst) -> array([12. , 18.5, 24.5, 41. , 65. ]) -``` - -Maybe you want to know the answer to the following question: - -Suppose a machine outputs 10 finished goods per hour on average with a standard deviation of 2. The output pattern follows a near normal distribution. What is the probability that the machine will output at least 7 but no more than 12 units in the next hour? - -The answer is essentially this: - - - -You can obtain the answer with just one line of code using **pnorm** : - -``` -pnorm(12,10,2)-pnorm(7,10,2) -> 0.7745375447996848 -``` - -Or maybe you need to answer the following: - -Suppose you have a loaded coin with the probability of turning heads up 60% every time you toss it. You are playing a game of 10 tosses. How do you plot and map out the chances of all the possible number of wins (from 0 to 10) with this coin? - -You can obtain a nice bar chart with just a few lines of code using just one function, **dbinom** : - -``` -probs=[] -import matplotlib.pyplot as plt -for i in range(11): - probs.append(dbinom(i,10,0.6)) -plt.bar(range(11),height=probs) -plt.grid(True) -plt.show() -``` - - - -### Simple interface for probability calculations - -R offers an extremely simple and intuitive interface for quick calculations from essential probability distributions. The interface goes like this: - - * **d** {distribution} gives the density function value at a point **x** - * **p** {distribution} gives the cumulative value at a point **x** - * **q** {distribution} gives the quantile function value at a probability **p** - * **r** {distribution} generates one or multiple random variates - - - -In our implementation, we stick to this interface and its associated argument list so you can execute these functions exactly like you would in an R environment. - -### Currently implemented functions - -The following R-style functions are implemented in the script for fast calling. - - * Mean, median, variance, standard deviation - * Tuckey five-number summary, IQR - * Covariance of a matrix or between two vectors - * Density, cumulative probability, quantile function, and random variate generation for the following distributions: normal, uniform, binomial, Poisson, F, Student's t, Chi-square, beta, and gamma. - - - -### Work in progress - -Obviously, this is a work in progress, and I plan to add some other convenient R-functions to this script. For example, in R, a single line of command **lm** can get you an ordinary least-square fitted model to a numerical dataset with all the necessary inferential statistics (P-values, standard error, etc.). This is powerfully brief and compact! On the other hand, standard linear regression problems in Python are often tackled using [Scikit-learn][6], which needs a bit more scripting for this use, so I plan to incorporate this single function linear model fitting feature using Python's [statsmodels][7] backend. - -If you like and use this script in your work, please help others find it by starring or forking its [GitHub repository][8]. Also, you can check my other [GitHub repos][9] for fun code snippets in Python, R, or MATLAB and some machine learning resources. - -If you have any questions or ideas to share, please contact me at [tirthajyoti[AT]gmail.com][10]. If you are, like me, passionate about machine learning and data science, please [add me on LinkedIn][11] or [follow me on Twitter. ][12] - -Originally published on [Towards Data Science][13]. Reposted under [CC BY-SA 4.0][14]. - --------------------------------------------------------------------------------- - -via: https://opensource.com/article/18/10/write-favorite-r-functions-python - -作者：[Tirthajyoti Sarkar][a] -选题：[lujun9972][b] -译者：[译者ID](https://github.com/译者ID) -校对：[校对者ID](https://github.com/校对者ID) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 - -[a]: https://opensource.com/users/tirthajyoti -[b]: https://github.com/lujun9972 -[1]: https://spectrum.ieee.org/at-work/innovation/the-2018-top-programming-languages -[2]: https://www.coursera.org/lecture/r-programming/overview-and-history-of-r-pAbaE -[3]: http://adv-r.had.co.nz/Functional-programming.html -[4]: https://github.com/tirthajyoti/StatsUsingPython/blob/master/R_Functions.py -[5]: https://en.wikipedia.org/wiki/Five-number_summary -[6]: http://scikit-learn.org/stable/ -[7]: https://www.statsmodels.org/stable/index.html -[8]: https://github.com/tirthajyoti/StatsUsingPython -[9]: https://github.com/tirthajyoti?tab=repositories -[10]: mailto:tirthajyoti@gmail.com -[11]: https://www.linkedin.com/in/tirthajyoti-sarkar-2127aa7/ -[12]: https://twitter.com/tirthajyotiS -[13]: https://towardsdatascience.com/how-to-write-your-favorite-r-functions-in-python-11e1e9c29089 -[14]: https://creativecommons.org/licenses/by-sa/4.0/ diff --git a/sources/tech/20181025 Monitoring database health and behavior- Which metrics matter.md b/sources/tech/20181025 Monitoring database health and behavior- Which metrics matter.md deleted file mode 100644 index 520f08342b..0000000000 --- a/sources/tech/20181025 Monitoring database health and behavior- Which metrics matter.md +++ /dev/null @@ -1,82 +0,0 @@ -Monitoring database health and behavior: Which metrics matter? -====== -Monitoring your database can be overwhelming or seem not important. Here's how to do it right. - - -We don’t talk about our databases enough. In this age of instrumentation, we monitor our applications, our infrastructure, and even our users, but we sometimes forget that our database deserves monitoring, too. That’s largely because most databases do their job so well that we simply trust them to do it. Trust is great, but confirmation of our assumptions is even better. - - - -### Why monitor your databases? - -There are plenty of reasons to monitor your databases, most of which are the same reasons you'd monitor any other part of your systems: Knowing what’s going on in the various components of your applications makes you a better-informed developer who makes smarter decisions. - - - -More specifically, databases are great indicators of system health and behavior. Odd behavior in the database can point to problem areas in your applications. Alternately, when there’s odd behavior in your application, you can use database metrics to help expedite the debugging process. - -### The problem - -The slightest investigation reveals one problem with monitoring databases: Databases have a lot of metrics. "A lot" is an understatement—if you were Scrooge McDuck, you could swim through all of the metrics available. If this were Wrestlemania, the metrics would be folding chairs. Monitoring them all doesn’t seem practical, so how do you decide which metrics to monitor? - - - -### The solution - -The best way to start monitoring databases is to identify some foundational, database-agnostic metrics. These metrics create a great start to understanding the lives of your databases. - -### Throughput: How much is the database doing? - -The easiest way to start monitoring a database is to track the number of requests the database receives. We have high expectations for our databases; we expect them to store data reliably and handle all of the queries we throw at them, which could be one massive query a day or millions of queries from users all day long. Throughput can tell you which of those is true. - -You can also group requests by type (reads, writes, server-side, client-side, etc.) to begin analyzing the traffic. - -### Execution time: How long does it take the database to do its job? - -This metric seems obvious, but it often gets overlooked. You don’t just want to know how many requests the database received, but also how long the database spent on each request. It’s important to approach execution time with context, though: What's slow for a time-series database like InfluxDB isn’t the same as what's slow for a relational database like MySQL. Slow in InfluxDB might mean milliseconds, whereas MySQL’s default value for its `SLOW_QUERY` variable is ten seconds. - - - -Monitoring execution time is not the same thing as improving execution time, so beware of the temptation to spend time on optimizations if you have other problems in your app to fix. - -### Concurrency: How many jobs is the database doing at the same time? - -Once you know how many requests the database is handling and how long each one takes, you need to add a layer of complexity to start getting real value from these metrics. - -If the database receives ten requests and each one takes ten seconds to complete, is the database busy for 100 seconds, ten seconds—or somewhere in between? The number of concurrent tasks changes the way the database’s resources are used. When you consider things like the number of connections and threads, you’ll start to get a fuller picture of your database metrics. - -Concurrency can also affect latency, which includes not only the time it takes for the task to be completed (execution time) but also the time the task needs to wait before it’s handled. - -### Utilization: What percentage of the time was the database busy? - -Utilization is a culmination of throughput, execution time, and concurrency to determine how often the database was available—or alternatively, how often the database was too busy to respond to a request. - - - -This metric is particularly useful for determining the overall health and performance of your database. If it’s available to respond to requests only 80% of the time, you can reallocate resources, work on optimization, or otherwise make changes to get closer to high availability. - -### The good news - -It can seem overwhelming to monitor and analyze, especially because most of us aren’t database experts and we may not have time to devote to understanding these metrics. But the good news is that most of this work is already done for us. Many databases have an internal performance database (Postgres: pg_stats, CouchDB: Runtime_Statistics, InfluxDB: _internal, etc.), which is designed by database engineers to monitor the metrics that matter for that particular database. You can see things as broad as the number of slow queries or as detailed as the average microseconds each event in the database takes. - -### Conclusion - -Databases create enough metrics to keep us all busy for a long time, and while the internal performance databases are full of useful information, it’s not always clear which metrics you should care about. Start with throughput, execution time, concurrency, and utilization, which provide enough information for you to start understanding the patterns in your database. - - - -Are you monitoring your databases? Which metrics have you found to be useful? Tell me about it! - --------------------------------------------------------------------------------- - -via: https://opensource.com/article/18/10/database-metrics-matter - -作者：[Katy Farmer][a] -选题：[lujun9972][b] -译者：[译者ID](https://github.com/译者ID) -校对：[校对者ID](https://github.com/校对者ID) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 - -[a]: https://opensource.com/users/thekatertot -[b]: https://github.com/lujun9972 diff --git a/sources/tech/20181026 An Overview of Android Pie.md b/sources/tech/20181026 An Overview of Android Pie.md deleted file mode 100644 index 9fa365327f..0000000000 --- a/sources/tech/20181026 An Overview of Android Pie.md +++ /dev/null @@ -1,138 +0,0 @@ -An Overview of Android Pie -====== - - - -Let’s talk about Android for a moment. Yes, I know it’s only Linux by way of a modified kernel, but what isn’t these days? And seeing as how the developers of Android have released what many (including yours truly) believe to be the most significant evolution of the platform to date, there’s plenty to talk about. Of course, before we get into that, it does need to be mentioned (and most of you will already know this) that the whole of Android isn’t open source. Although much of it is, when you get into the bits that connect to Google services, things start to close up. One major service is the Google Play Store, a functionality that is very much proprietary. But this isn’t about how much of Android is open or closed, this is about Pie. -Delicious, nutritious … efficient and battery-saving Pie. - -I’ve been working with Android Pie on my Essential PH-1 daily driver (a phone that I really love, but understand how shaky the ground is under the company). After using Android Pie for a while now, I can safely say you want it. It’s that good. But what about the ninth release of Android makes it so special? Let’s dig in and find out. Our focus will be on the aspects that affect users, not developers, so I won’t dive deep into the underlying works. - -### Gesture-Based Navigation - -Much has been made about Android’s new gesture-based navigation—much of it not good. To be honest, this was a feature that aroused all of my curiosity. When it was first announced, no one really had much of an idea what it would be like. Would users be working with multi touch gestures to navigate around the Android interface? Or would this be something completely different. - - -![Android Pie][2] - -Figure 1: The Android Pie recent apps overview. - -[Used with permission][3] - -The reality is, gesture-based navigation is much more subtle and simple than what most assumed. And it all boils down to the Home button. With gesture-based navigation enabled, the Home button and the Recents button have been combined into a single feature. This means, in order to gain access to your recent apps, you can’t simply tap that square Recents button. Instead, the Recent apps overview (Figure 1) is opened with a short swipe up from the home button. - -Another change is how the App Drawer is accessed. In similar fashion to opening the Recents overview, the App Drawer is opened via a long swipe up from the Home button. - -As for the back button? It’s not been removed. Instead, what you’ll find is it appears (in the left side of the home screen dock) when an app calls for it. Sometimes that back button will appear, even if an app includes its own back button. - -Thing is, however, if you don’t like gesture-based navigation, you can disable it. To do so, follow these steps: - - 1. Open Settings - - 2. Scroll down and tap System > Gestures - - 3. Tap Swipe up on Home button - - 4. Tap the On/Off slider (Figure 2) until it’s in the Off position - - - - -### Battery Life - -AI has become a crucial factor in Android. In fact, it is AI that has helped to greatly improve battery life in Android. This new feature is called Adaptive Battery and works by prioritizing battery power for the apps and services you use most. By using AI, Android learns how you use your Apps and, after a short period, can then shut down unused apps, so they aren’t draining your battery while waiting in memory. - -The only caveat to Adaptive Battery is, should the AI pick up “bad habits” and your battery start to prematurely drain, the only way to reset the function is by way of a factory reset. Even with that small oversight, the improvement in battery life from Android Oreo to Pie is significant. - -### Changes to Split Screen - -Split Screen has been available to Android for some time. However, with Android Pie, how it’s used has slightly changed. This change only affects those who have gesture-based navigation enabled (otherwise, it remains the same). In order to work with Split Screen on Android 9.0, follow these steps: - -![Adding an app][5] - -Figure 3: Adding an app to split screen mode in Android Pie. - -[Used with permission][3] - - 1. Swipe upward from the Home button to open the Recent apps overview. - - 2. Locate the app you want to place in the top portion of the screen. - - 3. Long press the app’s circle icon (located at the top of the app card) to reveal a new popup menu (Figure 3) - - 4. Tap Split Screen and the app will open in the top half of the screen. - - 5. Locate the second app you want to open and, tap it to add it to the bottom half of the screen. - - - - -Using Split Screen and closing apps with the feature remains the same as it was. - -### - -![Actions][7] - -Figure 4: Android App Actions in action. - -[Used with permission][3] - -### App Actions - -This is another feature that was introduced some time ago, but was given some serious attention for the release of Android Pie. App Actions make it such that you can do certain things with an app, directly from the apps launcher. - -For instance, if you long-press the GMail launcher, you can select to reply to a recent email, or compose a new email. Back in Android Oreo, that feature came in the form of a popup list of actions. With Android Pie, the feature now better fits with the Material Design scheme of things (Figure 4). - -![Sound control][9] - -Figure 5: Sound control in Android Pie. - -[Used with permission][3] - -### Sound Controls - -Ah, the ever-changing world of sound controls on Android. Android Oreo had an outstanding method of controlling your sound, by way of minor tweaks to the Do Not Disturb feature. With Android Pie, that feature finds itself in a continued state of evolution. - -What Android Pie nailed is the quick access buttons to controlling sound on a device. Now, if you press either the volume up or down button, you’ll see a new popup menu that allows you to control if your device is silenced and/or vibrations are muted. By tapping the top icon in that popup menu (Figure 5), you can cycle through silence, mute, or full sound. - -### Screenshots - -Because I write about Android, I tend to take a lot of screenshots. With Android Pie came one of my favorite improvements: sharing screenshots. Instead of having to open Google Photos, locate the screenshot to be shared, open the image, and share the image, Pie gives you a pop-up menu (after you take a screenshot) that allows you to share, edit, or delete the image in question. - -![Sharing ][11] - -Figure 6: Sharing screenshots just got a whole lot easier. - -[Used with permission][3] - -If you want to share the screenshot, take it, wait for the menu to pop up, tap Share (Figure 6), and then share it from the standard Android sharing menu. - -### A More Satisfying Android Experience - -The ninth iteration of Android has brought about a far more satisfying user experience. What I’ve illustrated only scratches the surface of what Android Pie brings to the table. For more information, check out Google’s official [Android Pie website][12]. And if your device has yet to receive the upgrade, have a bit of patience. Pie is well worth the wait. - --------------------------------------------------------------------------------- - -via: https://www.linux.com/learn/2018/10/overview-android-pie - -作者：[Jack Wallen][a] -选题：[lujun9972][b] -译者：[译者ID](https://github.com/译者ID) -校对：[校对者ID](https://github.com/校对者ID) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 - -[a]: https://www.linux.com/users/jlwallen -[b]: https://github.com/lujun9972 -[1]: /files/images/pie1png -[2]: https://www.linux.com/sites/lcom/files/styles/floated_images/public/pie_1.png?itok=BsSe8kqS (Android Pie) -[3]: /licenses/category/used-permission -[4]: /files/images/pie3png -[5]: https://www.linux.com/sites/lcom/files/styles/floated_images/public/pie_3.png?itok=F-NB1dqI (Adding an app) -[6]: /files/images/pie4png -[7]: https://www.linux.com/sites/lcom/files/styles/floated_images/public/pie_4.png?itok=Ex-NzYSo (Actions) -[8]: /files/images/pie5png -[9]: https://www.linux.com/sites/lcom/files/styles/floated_images/public/pie_5.png?itok=NMW2vIlL (Sound control) -[10]: /files/images/pie6png -[11]: https://www.linux.com/sites/lcom/files/styles/floated_images/public/pie_6.png?itok=7Ik8_4jC (Sharing ) -[12]: https://www.android.com/versions/pie-9-0/ diff --git a/sources/tech/20181029 How I organize my knowledge as a Software Engineer.md b/sources/tech/20181029 How I organize my knowledge as a Software Engineer.md deleted file mode 100644 index c11e1c9c38..0000000000 --- a/sources/tech/20181029 How I organize my knowledge as a Software Engineer.md +++ /dev/null @@ -1,119 +0,0 @@ -@flowsnow is translating - - -How I organize my knowledge as a Software Engineer -============================================================ - - -Software Development and Technology in general are areas that evolve at a very fast pace and continuous learning is essential. -Some minutes navigating in the internet, in places like Twitter, Medium, RSS feeds, Hacker News and other specialized sites and communities, are enough to find lots of great pieces of information from articles, case studies, tutorials, code snippets, new applications and much more. - -Saving and organizing all that information can be a daunting task. In this post I will present some tools tools that I use to do it. - -One of the points I consider very important regarding knowledge management is to avoid lock-in in a particular platform. All the tools I use, allow to export your data in standard formats like Markdown and HTML. - -Note that, My workflow is not perfect and I am constantly searching for new tools and ways to optimize it. Also everyone is different, so what works for me might not working well for you. - -### Knowledge base with NotionHQ - -For me, the fundamental piece of Knowledge management is to have some kind of personal Knowledge base / wiki. A place where you can save links, bookmarks, notes etc in an organized manner. - -I use [NotionHQ][7] for that matter. I use it to keep notes on various topics, having lists of resources like great libraries or tutorials grouped by programming language, bookmarking interesting blog posts and tutorials, and much more, not only related to software development but also my personal life. - -What I really like about Notion, is how simple it is to create new content. You write it using Markdown and it is organized as tree. - -Here is my top level pages of my "Development" workspace: - - [][8] - -Notion has some nice other features like integrated spreadsheets / databases and Task boards. - -You will need to subscribe to paid Personal Plan, if you want to use Notion seriously as the free plan is somewhat limited. I think its worth the price. Notion allows to export your entire workspace to Markdown files. The export has some important problems, like loosing the page hierarchy, but hope Notion Team can improve that. - -As a free alternative I would probably use [VuePress][9] or [GitBook][10] to host my own. - -### Save interesting articles with Pocket - -[Pocket][11] is one of my favorite applications ever! With Pocket you can create a reading list of articles from the Internet. -Every time I see an article that looks interesting, I save it to Pocket using its Chrome Extension. Later on, I will read it and If I found it useful enough, I will use the "Archive" function of Pocket to permanently save that article and clean up my Pocket inbox. - -I try to keep the Reading list small enough and keep archiving information that I have dealt with. Pocket allows you to tag articles which will make it simpler to search articles for a particular topic later in time. - -You can also save a copy of the article in Pocket servers in case of the original site disappears, but you will need Pocket Premium for that. - -Pocket also have a "Discover" feature which suggests similar articles based on the articles you have saved. This is a great way to find new content to read. - -### Snippet Management with SnippetStore - -From GitHub, to Stack Overflow answers, to blog posts, its common to find some nice code snippets that you want to save for later. It could be some nice algorithm implementation, an useful script or an example of how to do X in Y language. - -I tried many apps from simple GitHub Gists to [Boostnote][12] until I discovered [SnippetStore][13]. - -SnippetStore is an open source snippet management app. What distinguish SnippetStore from others is its simplicity. You can organize snippets by Language or Tags and you can have multi file snippets. Its not perfect but it gets the job done. Boostnote, for example has more features, but I prefer the simpler way of organizing content of SnippetStore. - -For abbreviations and snippets that I use on a daily basis, I prefer to use my Editor / IDE snippets feature as it is more convenient to use. I use SnippetStore more like a reference of coding examples. - -[Cacher][14] is also an interesting alternative, since it has integrations with many editors, have a cli tool and uses GitHub Gists as backend, but 6$/month for its pro plan, its too much IMO. - -### Managing cheat sheets with DevHints - -[Devhints][15] is a collection of cheat sheets created by Rico Sta. Cruz. Its open source and powered by Jekyll, one of the most popular static site generator. - -The cheat sheets are written in Markdown with some extra formatting goodies like support for columns. - -I really like the looks of the interface and being Markdown makes in incredibly easy to add new content and keep it updated and in version control, unlike cheat sheets in PDF or Image format, that you can find on sites like [Cheatography][16]. - -As it is open source I have created my own fork, removed some cheat sheets that I dont need and add some more. - -I use cheat sheets as reference of how to use some library or programming language or to remember some commands. Its very handy to have a single page, with all the basic syntax of a specific programming language for example. - -I am still experimenting with this but its working great so far. - -### Diigo - -[Diigo][17] allows you to Annotate and Highlight parts of websites. I use it to annotate important information when studying new topics or to save particular paragraphs from articles, Stack Overflow answers or inspirational quotes from Twitter! ;) - -* * * - -And thats it. There might be some overlap in terms of functionality in some of the tools, but like I said in the beginning, this is an always evolving workflow, as I am always experimenting and searching for ways to improve and be more productive. - -What about you? How to you organize your Knowledge?. Please feel free to comment below. - -Thank you for reading. - ------------------------------------------------------------------------- - -作者简介： - -Bruno Paz -Web Engineer. Expert in #PHP and @Symfony Framework. Enthusiast about new technologies. Sports and @FCPorto fan! - --------------------------------------------------------------------------------- - -via: https://dev.to/brpaz/how-do-i-organize-my-knowledge-as-a-software-engineer-4387 - -作者：[ Bruno Paz][a] -译者：[译者ID](https://github.com/译者ID) -校对：[校对者ID](https://github.com/校对者ID) -选题：[oska874](https://github.com/oska874) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 - -[a]:http://brunopaz.net/ -[1]:https://dev.to/brpaz -[2]:http://twitter.com/brunopaz88 -[3]:http://github.com/brpaz -[4]:https://dev.to/t/knowledge -[5]:https://dev.to/t/learning -[6]:https://dev.to/t/development -[7]:https://www.notion.so/ -[8]:https://res.cloudinary.com/practicaldev/image/fetch/s--uMbaRUtu--/c_limit%2Cf_auto%2Cfl_progressive%2Cq_auto%2Cw_880/http://i.imgur.com/kRnuvMV.png -[9]:https://vuepress.vuejs.org/ -[10]:https://www.gitbook.com/?t=1 -[11]:https://getpocket.com/ -[12]:https://boostnote.io/ -[13]:https://github.com/ZeroX-DG/SnippetStore -[14]:https://www.cacher.io/ -[15]:https://devhints.io/ -[16]:https://cheatography.com/ -[17]:https://www.diigo.com/index diff --git a/sources/tech/20181102 How To Create A Bootable Linux USB Drive From Windows OS 7,8 and 10.md b/sources/tech/20181102 How To Create A Bootable Linux USB Drive From Windows OS 7,8 and 10.md deleted file mode 100644 index 2b4350316d..0000000000 --- a/sources/tech/20181102 How To Create A Bootable Linux USB Drive From Windows OS 7,8 and 10.md +++ /dev/null @@ -1,80 +0,0 @@ -translating---geekpi - -How To Create A Bootable Linux USB Drive From Windows OS 7,8 and 10? -====== -If you would like to learn about Linux, the first thing you have to do is install the Linux OS on your system. - -It can be achieved in two ways either go with virtualization applications like Virtualbox, VMWare, etc, or install Linux on your system. - -If you are preferring to move from windows OS to Linux OS or planning to install Linux operating system on your spare machine then you have to create a bootable USB stick for that. - -We had wrote many articles for creating [bootable USB drive on Linux][1] such as [BootISO][2], [Etcher][3] and [dd command][4] but we never get an opportunity to write an article about creating Linux bootable USB drive in windows. Somehow, we got a opportunity today to perform this task. - -In this article we are going to show you, how to create a bootable Ubuntu USB flash drive from windows 10. - -These step will work for other Linux as well but you have to choose the corresponding OS from the drop down instead of Ubuntu. - -### Step-1: Download Ubuntu ISO - -Visit [Ubuntu releases][5] page and download a latest version. I would like to advise you to download a latest LTS version and not for a normal release. - -Make sure you have downloaded the proper ISO by performing checksum using MD5 or SHA256. The output value should be matched with the Ubuntu releases page value. - -### Step-2: Download Universal USB Installer - -There are many applications are available for this but my preferred application is [Universal USB Installer][6] which is very simple to perform this task. Just visit Universal USB Installer page and download the app. - -### Step-3: How To Create a bootable Ubuntu ISO using Universal USB Installer - -There is no complication on this application to perform this. First connect your USB drive then hit the downloaded Universal USB Installer. Once it’s launched you can see the interface similar to us. -![][8] - - * **`Step-1:`** Select Ubuntu OS. - * **`Step-2:`** Navigate to Ubuntu ISO downloaded location. - * **`Step-3:`** By default it’s select a USB drive however verify this then check the option to format it. - - - -![][9] - -When you hit `Create` button, it will pop-up a window with warnings. No need to worry, just hit `Yes` to proceed further on this. -![][10] - -USB drive partition is in progress. -![][11] - -Wait for sometime to complete this. If you would like to move this process to background, yes, you can by hitting `Background` button. -![][12] - -Yes, it’s completed. -![][13] - -Now you are ready to perform [Ubuntu OS installation][14]. However, it’s offering a live mode also so, you can play around it if you want to try before performing the installation. - --------------------------------------------------------------------------------- - -via: https://www.2daygeek.com/create-a-bootable-live-usb-drive-from-windows-using-universal-usb-installer/ - -作者：[Prakash Subramanian][a] -选题：[lujun9972][b] -译者：[译者ID](https://github.com/译者ID) -校对：[校对者ID](https://github.com/校对者ID) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 - -[a]: https://www.2daygeek.com/author/prakash/ -[b]: https://github.com/lujun9972 -[1]: https://www.2daygeek.com/category/bootable-usb/ -[2]: https://www.2daygeek.com/bootiso-a-simple-bash-script-to-securely-create-a-bootable-usb-device-in-linux-from-iso-file/ -[3]: https://www.2daygeek.com/etcher-easy-way-to-create-a-bootable-usb-drive-sd-card-from-an-iso-image-on-linux/ -[4]: https://www.2daygeek.com/create-a-bootable-usb-drive-from-an-iso-image-using-dd-command-on-linux/ -[5]: http://releases.ubuntu.com/ -[6]: https://www.pendrivelinux.com/universal-usb-installer-easy-as-1-2-3/ -[7]: data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7 -[8]: https://www.2daygeek.com/wp-content/uploads/2018/11/create-a-live-linux-os-usb-from-windows-using-universal-usb-installer-1.png -[9]: https://www.2daygeek.com/wp-content/uploads/2018/11/create-a-live-linux-os-usb-from-windows-using-universal-usb-installer-2.png -[10]: https://www.2daygeek.com/wp-content/uploads/2018/11/create-a-live-linux-os-usb-from-windows-using-universal-usb-installer-3.png -[11]: https://www.2daygeek.com/wp-content/uploads/2018/11/create-a-live-linux-os-usb-from-windows-using-universal-usb-installer-4.png -[12]: https://www.2daygeek.com/wp-content/uploads/2018/11/create-a-live-linux-os-usb-from-windows-using-universal-usb-installer-5.png -[13]: https://www.2daygeek.com/wp-content/uploads/2018/11/create-a-live-linux-os-usb-from-windows-using-universal-usb-installer-6.png -[14]: https://www.2daygeek.com/how-to-install-ubuntu-16-04/ diff --git a/sources/tech/20181105 5 Minimal Web Browsers for Linux.md b/sources/tech/20181105 5 Minimal Web Browsers for Linux.md new file mode 100644 index 0000000000..1fbc18aeae --- /dev/null +++ b/sources/tech/20181105 5 Minimal Web Browsers for Linux.md @@ -0,0 +1,163 @@ +[#]: collector: (lujun9972) +[#]: translator: ( ) +[#]: reviewer: ( ) +[#]: publisher: ( ) +[#]: subject: (5 Minimal Web Browsers for Linux) +[#]: via: (https://www.linux.com/blog/intro-to-linux/2018/11/5-minimal-web-browsers-linux) +[#]: author: (Jack Wallen https://www.linux.com/users/jlwallen) +[#]: url: ( ) + +5 Minimal Web Browsers for Linux +====== + + +There are so many reasons to enjoy the Linux desktop. One reason I often state up front is the almost unlimited number of choices to be found at almost every conceivable level. From how you interact with the operating system (via a desktop interface), to how daemons run, to what tools you use, you have a multitude of options. + +The same thing goes for web browsers. You can use anything from open source favorites, such as [Firefox][1] and [Chromium][2], or closed sourced industry darlings like [Vivaldi][3] and [Chrome][4]. Those options are full-fledged browsers with every possible bell and whistle you’ll ever need. For some, these feature-rich browsers are perfect for everyday needs. + +There are those, however, who prefer using a web browser without all the frills. In fact, there are many reasons why you might prefer a minimal browser over a standard browser. For some, it’s about browser security, while others look at a web browser as a single-function tool (as opposed to a one-stop shop application). Still others might be running low-powered machines that cannot handle the requirements of, say, Firefox or Chrome. Regardless of the reason, Linux has you covered. + +Let’s take a look at five of the minimal browsers that can be installed on Linux. I’ll be demonstrating these browsers on the Elementary OS platform, but each of these browsers are available to nearly every distribution in the known Linuxverse. Let’s dive in. + +### GNOME Web + +GNOME Web (codename Epiphany, which means [“a usually sudden manifestation or perception of the essential nature or meaning of something”][5]) is the default web browser for Elementary OS, but it can be installed from the standard repositories. (Note, however, that the recommended installation of Epiphany is via Flatpak or Snap). If you choose to install via the standard package manager, issue a command such as sudo apt-get install epiphany-browser -y for successful installation. + +Epiphany uses the WebKit rendering engine, which is the same engine used in Apple’s Safari browser. Couple that rendering engine with the fact that Epiphany has very little in terms of bloat to get in the way, you will enjoy very fast page-rendering speeds. Epiphany development follows strict adherence to the following guidelines: + + * Simplicity - Feature bloat and user interface clutter are considered evil. + + * Standards compliance - No non-standard features will ever be introduced to the codebase. + + * Software freedom - Epiphany will always be released under a license that respects freedom. + + * Human interface - Epiphany follows the [GNOME Human Interface Guidelines][6]. + + * Minimal preferences - Preferences are only added when they make sense and after careful consideration. + + * Target audience - Non-technical users are the primary target audience (which helps to define the types of features that are included). + + + + +GNOME Web is as clean and simple a web browser as you’ll find (Figure 1). + +![GNOME Web][8] + +Figure 1: The GNOME Web browser displaying a minimal amount of preferences for the user. + +[Used with permission][9] + +The GNOME Web manifesto reads: + +A web browser is more than an application: it is a way of thinking, a way of seeing the world. Epiphany's principles are simplicity, standards compliance, and software freedom. + +### Netsurf + +The [Netsurf][10] minimal web browser opens almost faster than you can release the mouse button. Netsurf uses its own layout and rendering engine (designed completely from scratch), which is rather hit and miss in its rendering (Figure 2). + + + +Although you might find Netsurf to suffer from rendering issues on certain sites, understand the Hubbub HTML parser is following the work-in-progress HTML5 specification, so there will be issues popup now and then. To ease those rendering headaches, Netsurf does include HTTPS support, web page thumbnailing, URL completion, scale view, bookmarks, full-screen mode, keyboard shorts, and no particular GUI toolkit requirements. That last bit is important, especially when you switch from one desktop to another. + +For those curious as to the requirements for Netsurf, the browser can run on a machine as slow as a 30Mhz ARM 6 computer with 16MB of RAM. That’s impressive, by today’s standard. + +### QupZilla + +If you’re looking for a minimal browser that uses the Qt Framework and the QtWebKit rendering engine, [QupZilla][11] might be exactly what you’re looking for. QupZilla does include all the standard features and functions you’d expect from a web browser, such as bookmarks, history, sidebar, tabs, RSS feeds, ad blocking, flash blocking, and CA Certificates management. Even with those features, QupZilla still manages to remain a very fast lightweight web browser. Other features include: Fast startup, speed dial homepage, built-in screenshot tool, browser themes, and more. +One feature that should appeal to average users is that QupZilla has a more standard preferences tools than found in many lightweight browsers (Figure 3). So, if going too far outside the lines isn’t your style, but you still want something lighter weight, QupZilla is the browser for you. + +![QupZilla][13] + +Figure 3: The QupZilla preferences tool. + +[Used with permission][9] + +### Otter Browser + +Otter Browser is a free, open source attempt to recreate the closed-source offerings found in the Opera Browser. Otter Browser uses the WebKit rendering engine and has an interface that should be immediately familiar with any user. Although lightweight, Otter Browser does include full-blown features such as: + + * Passwords manager + + * Add-on manager + + * Content blocking + + * Spell checking + + * Customizable GUI + + * URL completion + + * Speed dial (Figure 4) + + * Bookmarks and various related features + + * Mouse gestures + + * User style sheets + + * Built-in Note tool + + +![Otter][15] + +Figure 4: The Otter Browser Speed Dial tab. + +[Used with permission][9] + +Otter Browser can be run on nearly any Linux distribution from an [AppImage][16], so there’s no installation required. Just download the AppImage file, give the file executable permissions (with the command chmod u+x otter-browser-*.AppImage), and then launch the app with the command ./otter-browser*.AppImage. + +Otter Browser does an outstanding job of rendering websites and could function as your go-to minimal browser with ease. + +### Lynx + +Let’s get really minimal. When I first started using Linux, back in ‘97, one of the web browsers I often turned to was a text-only take on the app called [Lynx][17]. It should come as no surprise that Lynx is still around and available for installation from the standard repositories. As you might expect, Lynx works from the terminal window and doesn’t display pretty pictures or render much in the way of advanced features (Figure 5). In fact, Lynx is as bare-bones a browser as you will find available. Because of how bare-bones this web browser is, it’s not recommended for everyone. But if you happen to have a gui-less web server and you have a need to be able to read the occasional website, Lynx can be a real lifesaver. + +![Lynx][19] + +Figure 5: The Lynx browser rendering the Linux.com page. + +[Used with permission][9] + +I have also found Lynx an invaluable tool when troubleshooting certain aspects of a website (or if some feature on a website is preventing me from viewing the content in a regular browser). Another good reason to use Lynx is when you only want to view the content (and not the extraneous elements). + +### Plenty More Where This Came From + +There are plenty more minimal browsers than this. But the list presented here should get you started down the path of minimalism. One (or more) of these browsers are sure to fill that need, whether you’re running it on a low-powered machine or not. + +Learn more about Linux through the free ["Introduction to Linux" ][20]course from The Linux Foundation and edX. + +-------------------------------------------------------------------------------- + +via: https://www.linux.com/blog/intro-to-linux/2018/11/5-minimal-web-browsers-linux + +作者：[Jack Wallen][a] +选题：[lujun9972][b] +译者：[译者ID](https://github.com/译者ID) +校对：[校对者ID](https://github.com/校对者ID) + +本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 + +[a]: https://www.linux.com/users/jlwallen +[b]: https://github.com/lujun9972 +[1]: https://www.mozilla.org/en-US/firefox/new/ +[2]: https://www.chromium.org/ +[3]: https://vivaldi.com/ +[4]: https://www.google.com/chrome/ +[5]: https://www.merriam-webster.com/dictionary/epiphany +[6]: https://developer.gnome.org/hig/stable/ +[7]: /files/images/minimalbrowsers1jpg +[8]: https://www.linux.com/sites/lcom/files/styles/rendered_file/public/minimalbrowsers_1.jpg?itok=Q7wZLF8B (GNOME Web) +[9]: /licenses/category/used-permission +[10]: https://www.netsurf-browser.org/ +[11]: https://qupzilla.com/ +[12]: /files/images/minimalbrowsers3jpg +[13]: https://www.linux.com/sites/lcom/files/styles/rendered_file/public/minimalbrowsers_3.jpg?itok=O8iMALWO (QupZilla) +[14]: /files/images/minimalbrowsers4jpg +[15]: https://www.linux.com/sites/lcom/files/styles/rendered_file/public/minimalbrowsers_4.jpg?itok=5bCa0z-e (Otter) +[16]: https://sourceforge.net/projects/otter-browser/files/ +[17]: https://lynx.browser.org/ +[18]: /files/images/minimalbrowsers5jpg +[19]: https://www.linux.com/sites/lcom/files/styles/rendered_file/public/minimalbrowsers_5.jpg?itok=p_Lmiuxh (Lynx) +[20]: https://training.linuxfoundation.org/linux-courses/system-administration-training/introduction-to-linux diff --git a/sources/tech/20181105 CPod- An Open Source, Cross-platform Podcast App.md b/sources/tech/20181105 CPod- An Open Source, Cross-platform Podcast App.md deleted file mode 100644 index 89a1f1f354..0000000000 --- a/sources/tech/20181105 CPod- An Open Source, Cross-platform Podcast App.md +++ /dev/null @@ -1,104 +0,0 @@ -CPod: An Open Source, Cross-platform Podcast App -====== -Podcasts are a great way to be entertained and informed. In fact, I listen to about ten different podcasts covering technology, mysteries, history, and comedy. Of course, [Linux podcasts][1] are also on this list. - -Today, we will take a look at a simple cross-platform application for handling your podcasts. - -![][2] -Recommended podcasts and podcast search - -### The Application - -[CPod][3] is the creation of [Zack Guard (z————-)][4]. **It is an[Election][5] app** , which gives it the ability to run on the largest operating systems (Linux, Windows, Mac OS). - -Trivia: CPod was originally named Cumulonimbus. - -The majority of the application is taken up by two large panels to display content and options. A small bar along the left side of the screen gives you access to the different parts of the application. The different sections of CPod include Home, Queue, Subscriptions, Explore and Settings. - -![cpod settings][6]Settings - -### Features of CPod - -Here is a list of features that CPod has to offer: - - * Simple, clean design - * Available on the top computer platforms - * Available as a Snap - * Search iTunes’ podcast directory - * Download and play episodes without downloading - * View podcast information and episode - * Search for an individual episode of a podcast - * Dark mode - * Change playback speed - * Keyboard shortcuts - * Sync your podcast subscriptions with gpodder.net - * Import and export subscriptions - * Sort subscriptions based on length, date, download status, and play progress - * Auto-fetch new episodes on application startup - * Multiple language support - - - -![search option in cpod application][7]Searching for ZFS episode - -### Experiencing CPod on Linux - -I ended up installing CPod on two systems: ArchLabs and Windows. There are two versions of CPod in the [Arch User Repository][8]. However, they are both out of date, one is version 1.14.0 and the other was 1.22.6. The most recent version of CPod is 1.27.0. Because of the version difference between ArchLabs and Windows, I had to different experiences. For this article, I will focus on 1.27.0, since that is the most current and has the most features. - -Right out of the gate, I was able to find most of my favorite podcasts. I was able to add the ones that were not on the iTunes’ list by pasting in the URL for the RSS feed. - -It was also very easy to find a particular episode of a podcast. for example, I was recently looking for an episode of [Late Night Linux][9] where they were talking about [ZFS][10]. I clicked on the podcast, typed “ZFS” in the search box and found it. - -I quickly discovered that the easiest way to play a bunch of podcast episodes was to add them to the queue. Once they are in the queue, you can either stream them or download them. You can also reorder them by dragging and dropping. As each episode played, it displayed a visualization of the sound wave, along with the episode summary. - -### Installating CPod - -On [GitHub][11], you can download an AppImage or Deb file for Linux, a .exe file for Windows or a .dmg file for Mac OS. - -You can also install CPod as a [Snap][12]. All you need to do is use the following command: - -``` -sudo snap install cpod -``` - -Like I said earlier, the [Arch User Repository][8] version of CPod is old. I already messaged one of the packagers. If you use Arch (or an Arch-based distro), I would recommend doing the same. - -![cpod for Linux pidcasts][13]Playing one of my favorite podcasts - -### Final Thoughts - -Overall, I liked CPod. It was nice looking and simple to use. In fact, I like the original name (Cumulonimbus) better, but it is a bit of a mouthful. - -I just had two problems with the application. First, I wish that the ratings were available for each podcast. Second, the menus that allow you to sort episodes based on length, date, download status, and play progress don’t work when the dork mode is turned on. - -Have you ever used CPod? If not, what is your favorite podcast app? What are some of your favorite podcasts? Let us know in the comments below. - -If you found this article interesting, please take a minute to share it on social media, Hacker News or [Red][14][d][14][it][14]. - --------------------------------------------------------------------------------- - -via: https://itsfoss.com/cpod-podcast-app/ - -作者：[John Paul][a] -选题：[lujun9972][b] -译者：[译者ID](https://github.com/译者ID) -校对：[校对者ID](https://github.com/校对者ID) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 - -[a]: https://itsfoss.com/author/john/ -[b]: https://github.com/lujun9972 -[1]: https://itsfoss.com/linux-podcasts/ -[2]: https://4bds6hergc-flywheel.netdna-ssl.com/wp-content/uploads/2018/10/cpod1.1.jpg -[3]: https://github.com/z-------------/CPod -[4]: https://github.com/z------------- -[5]: https://electronjs.org/ -[6]: https://4bds6hergc-flywheel.netdna-ssl.com/wp-content/uploads/2018/10/cpod2.1.png -[7]: https://4bds6hergc-flywheel.netdna-ssl.com/wp-content/uploads/2018/10/cpod4.1.jpg -[8]: https://aur.archlinux.org/packages/?O=0&K=cpod -[9]: https://latenightlinux.com/ -[10]: https://itsfoss.com/what-is-zfs/ -[11]: https://github.com/z-------------/CPod/releases -[12]: https://snapcraft.io/cumulonimbus -[13]: https://4bds6hergc-flywheel.netdna-ssl.com/wp-content/uploads/2018/10/cpod3.1.jpg -[14]: http://reddit.com/r/linuxusersgroup diff --git a/sources/tech/20181105 How to manage storage on Linux with LVM.md b/sources/tech/20181105 How to manage storage on Linux with LVM.md new file mode 100644 index 0000000000..9c0ee685d6 --- /dev/null +++ b/sources/tech/20181105 How to manage storage on Linux with LVM.md @@ -0,0 +1,238 @@ +[zianglei translating] +How to manage storage on Linux with LVM +====== +Create, expand, and encrypt storage pools as needed with the Linux LVM utilities. + + +Logical Volume Manager ([LVM][1]) is a software-based RAID-like system that lets you create "pools" of storage and add hard drive space to those pools as needed. There are lots of reasons to use it, especially in a data center or any place where storage requirements change over time. Many Linux distributions use it by default for desktop installations, though, because users find the flexibility convenient and there are some built-in encryption features that the LVM structure simplifies. + +However, if you aren't used to seeing an LVM volume when booting off of a Live CD for data rescue or migration purposes, LVM can be confusing because the **mount** command can't mount LVM volumes. For that, you need LVM tools installed. The chances are great that your distribution has LVM utils available—if they aren't already installed. + +This tutorial explains how to create and deal with LVM volumes. + +### Create an LVM pool + +This article assumes you have a working knowledge of how to interact with hard drives on Linux. If you need more information on the basics before continuing, read my [introduction to hard drives on Linux][2] + +Usually, you don't have to set up LVM at all. When you install Linux, it often defaults to creating a virtual "pool" of storage and adding your machine's hard drive(s) to that pool. However, manually creating an LVM storage pool is a great way to learn what happens behind the scenes. + +You can practice with two spare thumb drives of any size, or two hard drives, or a virtual machine with two imaginary drives defined. + +First, format the imaginary drive **/dev/sdx** so that you have a fresh drive ready to use for this demo. + +``` +# echo "warning, this ERASES everything on this drive." +warning, this ERASES everything on this drive. +# dd if=/dev/zero of=/dev/sdx count=8196 +# parted /dev/sdx print | grep Disk +Disk /dev/sdx: 100GB +# parted /dev/sdx mklabel gpt +# parted /dev/sdx mkpart primary 1s 100% +``` + +This LVM command creates a storage pool. A pool can consist of one or more drives, and right now it consists of one. This example storage pool is named **billiards** , but you can call it anything. + +``` +# vgcreate billiards /dev/sdx1 +``` + +Now you have a big, nebulous pool of storage space. Time to hand it out. To create two logical volumes (you can think of them as virtual drives), one called **vol0** and the other called **vol1** , enter the following: + +``` +# lvcreate billiards 49G --name vol0 +# lvcreate billiards 49G --name vol1 +``` + +Now you have two volumes carved out of one storage pool, but neither of them has a filesystem yet. To create a filesystem on each volume, you must bring the **billiards** volume group online. + +``` +# vgchange --activate y billiards +``` + +Now make the file systems. The **-L** option provides a label for the drive, which is displayed when the drive is mounted on your desktop. The path to the volume is a little different than the usual device paths you're used to because these are virtual devices in an LVM storage pool. + +``` +# mkfs.ext4 -L finance /dev/billiards/vol0 +# mkfs.ext4 -L production /dev/billiards/vol1 +``` + +You can mount these new volumes on your desktop or from a terminal. + +``` +# mkdir -p /mnt/vol0 /mnt/vol1 +# mount /dev/billiards/vol0 /mnt/vol0 +# mount /dev/billiards/vol1 /mnt/vol1 +``` + +### Add space to your pool + +So far, LVM has provided nothing more than partitioning a drive normally provides: two distinct sections of drive space on a single physical drive (in this example, 49GB and 49GB on a 100GB drive). Imagine now that the finance department needs more space. Traditionally, you'd have to restructure. Maybe you'd move the finance department data to a new, dedicated physical drive, or maybe you'd add a drive and then use an ugly symlink hack to provide users easy access to their additional storage space. With LVM, however, all you have to do is expand the storage pool. + +You can add space to your pool by formatting another drive and using it to create more additional space. + +First, create a partition on the new drive you're adding to the pool. + +``` +# part /dev/sdy mkpart primary 1s 100% +``` + +Then use the **vgextend** command to mark the new drive as part of the pool. + +``` +# vgextend billiards /dev/sdy1 +``` + +Finally, dedicate some portion of the newly available storage pool to the appropriate logical volume. + +``` +# lvextend -L +49G /dev/billiards/vol0 +``` + +Of course, the expansion doesn't have to be so linear. Imagine that the production department suddenly needs 100TB of additional space. With LVM, you can add as many physical drives as needed, adding each one and using **vgextend** to create a 100TB storage pool, then using **lvextend** to "stretch" the production department's storage space across 100TB of available space. + +### Use utils to understand your storage structure + +Once you start using LVM in earnest, the landscape of storage can get overwhelming. There are two commands to gather information about the structure of your storage infrastructure. + +First, there is **vgdisplay** , which displays information about your volume groups (you can think of these as LVM's big, high-level virtual drives). + +``` +# vgdisplay + --- Volume group --- + VG Name billiards + System ID + Format lvm2 + Metadata Areas 1 + Metadata Sequence No 4 + VG Access read/write + VG Status resizable + MAX LV 0 + Cur LV 3 + Open LV 3 + Max PV 0 + Cur PV 1 + Act PV 1 + VG Size <237.47 GiB + PE Size 4.00 MiB + Total PE 60792 + Alloc PE / Size 60792 / <237.47 GiB + Free PE / Size 0 / 0 + VG UUID j5RlhN-Co4Q-7d99-eM3K-G77R-eDJO-nMR9Yg +``` + +The second is **lvdisplay** , which displays information about your logical volumes (you can think of these as user-facing drives). + +``` +# lvdisplay + --- Logical volume --- + LV Path /dev/billiards/finance + LV Name finance + VG Name billiards + LV UUID qPgRhr-s0rS-YJHK-0Cl3-5MME-87OJ-vjjYRT + LV Write Access read/write + LV Creation host, time localhost, 2018-12-16 07:31:01 +1300 + LV Status available + # open 1 + LV Size 149.68 GiB + Current LE 46511 + Segments 1 + Allocation inherit + Read ahead sectors auto + - currently set to 256 + Block device 253:3 + +[...] +``` + +### Use LVM in a rescue environment + +The "problem" with LVM is that it wraps partitions in a way that is unfamiliar to many administrative users who are used to traditional drive partitioning. Under normal circumstances, LVM drives are activated and mounted fairly invisibly during the boot process or desktop LVM integration. It's not something you typically have to think about. It only becomes problematic when you find yourself in recovery mode after something goes wrong with your system. + +If you need to mount a volume that's "hidden" within the structure of LVM, you must make sure that the LVM toolchain is installed. If you have access to your **/usr/sbin** directory, you probably have access to all of your usual LVM commands. But if you've booted into a minimal shell or a rescue environment, you may not have those tools. A good rescue environment has LVM installed, so if you're in a minimal shell, find a rescue system that does. If you're using a rescue disc and it doesn't have LVM installed, either install it manually or find a rescue disc that already has it. + +For the sake of repetition and clarity, here's how to mount an LVM volume. + +``` +# vgchange --activate y +2 logical volume(s) in volume group "billiards" now active +# mkdir /mnt/finance +# mount /dev/billiards/finance /mnt/finance +``` + +### Integrate LVM with LUKS encryption + +Many Linux distributions use LVM by default when installing the operating system. This permits storage extension later, but it also integrates nicely with disk encryption provided by the Linux Unified Key Setup ([LUKS][3]) encryption toolchain. + +Encryption is pretty important, and there are two ways to encrypt things: you can encrypt on a per-file basis with a tool like GnuPG, or you can encrypt an entire partition. On Linux, encrypting a partition is easy with LUKS, which, being completely integrated into Linux by way of kernel modules, permits drives to be mounted for seamless reading and writing. + +Encrypting your entire main drive usually happens as an option during installation. You select to encrypt your entire drive or just your home partition when prompted, and from that point on you're using LUKS. It's mostly invisible to you, aside from a password prompt during boot. + +If your distribution doesn't offer this option during installation, or if you just want to encrypt a drive or partition manually, you can do that. + +You can follow this example by using a spare drive; I used a small 4GB thumb drive. + +First, plug the drive into your computer. Make sure it's safe to erase the drive and [use lsblk][2] to locate the drive on your system. + +If the drive isn't already partitioned, partition it now. If you don't know how to partition a drive, check out the link above for instructions. + +Now you can set up the encryption. First, format the partition with the **cryptsetup** command. + +``` +# cryptsetup luksFormat /dev/sdx1 +``` + +Note that you're encrypting the partition, not the physical drive itself. You'll see a warning that LUKS is going to erase your drive; you must accept it to continue. You'll be prompted to create a passphrase, so do that. Don't forget that passphrase. Without it, you will never be able to get into that drive again! + +You've encrypted the thumb drive's partition, but there's no filesystem on the drive yet. Of course, you can't write a filesystem to the drive while you're locked out of it, so open the drive with LUKS first. You can provide a human-friendly name for your drive; for this example, I used **mySafeDrive**. + +``` +# cryptsetup luksOpen /dev/sdx1 mySafeDrive +``` + +Enter your passphrase to open the drive. + +Look in **/dev/mapper** and you'll see that you've mounted the volume along with any other LVM volumes you might have, meaning you now have access to that drive. The custom name (e.g., mySafeDrive) is a symlink to an auto-generated designator in **/dev/mapper**. You can use either path when operating on this drive. + +``` +# ls -l /dev/mapper/mySafeDrive +lrwxrwxrwx. 1 root root 7 Oct 24 03:58 /dev/mapper/mySafeDrive -> ../dm-4 +``` + +Create your filesystem. + +``` +# mkfs.ext4 -o Linux -L mySafeExt4Drive /dev/mapper/mySafeDrive +``` + +Now do an **ls -lh** on **/dev/mapper** and you'll see that mySafeDrive is actually a symlink to some other dev; probably **/dev/dm0** or similar. That's the filesystem you can mount: + +``` +# mount /dev/mapper/mySafeExt4Drive /mnt/hd +``` + +Now the filesystem on the encrypted drive is mounted. You can read and write files as you'd expect with any drive. + +### Use encrypted drives with the desktop + +LUKS is built into the kernel, so your Linux system is fully aware of how to handle it. Detach the drive, plug it back in, and mount it from your desktop. In KDE's Dolphin file manager, you'll be prompted for a password before the drive is decrypted and mounted. + + + +Using LVM and LUKS is easy, and it provides flexibility for you as a user and an admin. Being tightly integrated into Linux itself, it's well-supported and a great way to add a layer of security to your data. Try it today! + +-------------------------------------------------------------------------------- + +via: https://opensource.com/article/18/11/manage-storage-lvm + +作者：[Seth Kenlon][a] +选题：[lujun9972][b] +译者：[译者ID](https://github.com/译者ID) +校对：[校对者ID](https://github.com/校对者ID) + +本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 + +[a]: https://opensource.com/users/seth +[b]: https://github.com/lujun9972 +[1]: https://en.wikipedia.org/wiki/Logical_Volume_Manager_(Linux) +[2]: https://opensource.com/article/18/10/partition-and-format-drive-linux +[3]: https://en.wikipedia.org/wiki/Linux_Unified_Key_Setup diff --git a/sources/tech/20181105 Revisiting the Unix philosophy in 2018.md b/sources/tech/20181105 Revisiting the Unix philosophy in 2018.md deleted file mode 100644 index 1088f0de5b..0000000000 --- a/sources/tech/20181105 Revisiting the Unix philosophy in 2018.md +++ /dev/null @@ -1,106 +0,0 @@ -Translating by Jamkr - -Revisiting the Unix philosophy in 2018 -====== -The old strategy of building small, focused applications is new again in the modern microservices environment. - - -In 1984, Rob Pike and Brian W. Kernighan published an article called "[Program Design in the Unix Environment][1]" in the AT&T Bell Laboratories Technical Journal, in which they argued the Unix philosophy, using the example of BSD's **cat -v** implementation. In a nutshell that philosophy is: Build small, focused programs—in whatever language—that do only one thing but do this thing well, communicate via **stdin** / **stdout** , and are connected through pipes. - -Sound familiar? - -Yeah, I thought so. That's pretty much the [definition of microservices][2] offered by James Lewis and Martin Fowler: - -> In short, the microservice architectural style is an approach to developing a single application as a suite of small services, each running in its own process and communicating with lightweight mechanisms, often an HTTP resource API. - -While one *nix program or one microservice may be very limited or not even very interesting on its own, it's the combination of such independently working units that reveals their true benefit and, therefore, their power. - -### *nix vs. microservices - -The following table compares programs (such as **cat** or **lsof** ) in a *nix environment against programs in a microservices environment. - -| | *nix | Microservices | -| ----------------------------------- | -------------------------- | ----------------------------------- | -| Unit of execution | program using stdin/stdout | service with HTTP or gRPC API | -| Data flow | Pipes | ? | -| Configuration & parameterization | Command-line arguments, | | -| environment variables, config files | JSON/YAML docs | | -| Discovery | Package manager, man, make | DNS, environment variables, OpenAPI | - -Let's explore each line in slightly greater detail. - -#### Unit of execution - -**stdin** and writes output to **stdout**. A microservices setup deals with a service that exposes one or more communication interfaces, such as HTTP or gRPC APIs. In both cases, you'll find stateless examples (essentially a purely functional behavior) and stateful examples, where, in addition to the input, some internal (persisted) state decides what happens. - -#### Data flow - -The unit of execution in *nix (such as Linux) is an executable file (binary or interpreted script) that, ideally, reads input fromand writes output to. A microservices setup deals with a service that exposes one or more communication interfaces, such as HTTP or gRPC APIs. In both cases, you'll find stateless examples (essentially a purely functional behavior) and stateful examples, where, in addition to the input, some internal (persisted) state decides what happens. - -Traditionally, *nix programs could communicate via pipes. In other words, thanks to [Doug McIlroy][3], you don't need to create temporary files to pass around and each can process virtually endless streams of data between processes. To my knowledge, there is nothing comparable to a pipe standardized in microservices, besides my little [Apache Kafka-based experiment from 2017][4]. - -#### Configuration and parameterization - -How do you configure a program or service—either on a permanent or a by-call basis? Well, with *nix programs you essentially have three options: command-line arguments, environment variables, or full-blown config files. In microservices, you typically deal with YAML (or even worse, JSON) documents, defining the layout and configuration of a single microservice as well as dependencies and communication, storage, and runtime settings. Examples include [Kubernetes resource definitions][5], [Nomad job specifications][6], or [Docker Compose][7] files. These may or may not be parameterized; that is, either you have some templating language, such as [Helm][8] in Kubernetes, or you find yourself doing an awful lot of **sed -i** commands. - -#### Discovery - -How do you know what programs or services are available and how they are supposed to be used? Well, in *nix, you typically have a package manager as well as good old man; between them, they should be able to answer all the questions you might have. In a microservices setup, there's a bit more automation in finding a service. In addition to bespoke approaches like [Airbnb's SmartStack][9] or [Netflix's Eureka][10], there usually are environment variable-based or DNS-based [approaches][11] that allow you to discover services dynamically. Equally important, [OpenAPI][12] provides a de-facto standard for HTTP API documentation and design, and [gRPC][13] does the same for more tightly coupled high-performance cases. Last but not least, take developer experience (DX) into account, starting with writing good [Makefiles][14] and ending with writing your docs with (or in?) [**style**][15]. - -### Pros and cons - -Both *nix and microservices offer a number of challenges and opportunities - -#### Composability - -It's hard to design something that has a clear, sharp focus and can also play well with others. It's even harder to get it right across different versions and to introduce respective error case handling capabilities. In microservices, this could mean retry logic and timeouts—maybe it's a better option to outsource these features into a service mesh? It's hard, but if you get it right, its reusability can be enormous. - -#### Observability - -In a monolith (in 2018) or a big program that tries to do it all (in 1984), it's rather straightforward to find the culprit when things go south. But, in a - -``` -yes | tr \\n x | head -c 450m | grep n -``` - -or a request path in a microservices setup that involves, say, 20 services, how do you even start to figure out which one is behaving badly? Luckily we have standards, notably [OpenCensus][16] and [OpenTracing][17]. Observability still might be the biggest single blocker if you are looking to move to microservices. - -#### Global state - -While it may not be such a big issue for *nix programs, in microservices, global state remains something of a discussion. Namely, how to make sure the local (persistent) state is managed effectively and how to make the global state consistent with as little effort as possible. - -### Wrapping up - -In the end, the question remains: Are you using the right tool for a given task? That is, in the same way a specialized *nix program implementing a range of functions might be the better choice for certain use cases or phases, it might be that a monolith [is the best option][18] for your organization or workload. Regardless, I hope this article helps you see the many, strong parallels between the Unix philosophy and microservices—maybe we can learn something from the former to benefit the latter. - --------------------------------------------------------------------------------- - -via: https://opensource.com/article/18/11/revisiting-unix-philosophy-2018 - -作者：[Michael Hausenblas][a] -选题：[lujun9972][b] -译者：[译者ID](https://github.com/译者ID) -校对：[校对者ID](https://github.com/校对者ID) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 - -[a]: https://opensource.com/users/mhausenblas -[b]: https://github.com/lujun9972 -[1]: http://harmful.cat-v.org/cat-v/ -[2]: https://martinfowler.com/articles/microservices.html -[3]: https://en.wikipedia.org/wiki/Douglas_McIlroy -[4]: https://speakerdeck.com/mhausenblas/distributed-named-pipes-and-other-inter-services-communication -[5]: http://kubernetesbyexample.com/ -[6]: https://www.nomadproject.io/docs/job-specification/index.html -[7]: https://docs.docker.com/compose/overview/ -[8]: https://helm.sh/ -[9]: https://github.com/airbnb/smartstack-cookbook -[10]: https://github.com/Netflix/eureka -[11]: https://kubernetes.io/docs/concepts/services-networking/service/#discovering-services -[12]: https://www.openapis.org/ -[13]: https://grpc.io/ -[14]: https://suva.sh/posts/well-documented-makefiles/ -[15]: https://www.linux.com/news/improve-your-writing-gnu-style-checkers -[16]: https://opencensus.io/ -[17]: https://opentracing.io/ -[18]: https://robertnorthard.com/devops-days-well-architected-monoliths-are-okay/ diff --git a/sources/tech/20181106 How To Check The List Of Packages Installed From Particular Repository.md b/sources/tech/20181106 How To Check The List Of Packages Installed From Particular Repository.md new file mode 100644 index 0000000000..81111b465c --- /dev/null +++ b/sources/tech/20181106 How To Check The List Of Packages Installed From Particular Repository.md @@ -0,0 +1,342 @@ +[#]: collector: (lujun9972) +[#]: translator: ( ) +[#]: reviewer: ( ) +[#]: publisher: ( ) +[#]: subject: (How To Check The List Of Packages Installed From Particular Repository?) +[#]: via: (https://www.2daygeek.com/how-to-check-the-list-of-packages-installed-from-particular-repository/) +[#]: author: (Prakash Subramanian https://www.2daygeek.com/author/prakash/) +[#]: url: ( ) + +How To Check The List Of Packages Installed From Particular Repository? +====== + +If you would like to check the list of package installed from particular repository then you are in the right place to get it done. + +Why we need this detail? It may helps you to isolate the installed packages list based on the repository. + +Like, it’s coming from distribution official repository or these are coming from PPA or these are coming from other resources, etc., + +You may want to know what are the packages came from third party repositories to keep eye on those to avoid any damages on your system. + +So many third party repositories and PPAs are available for Linux. These repositories are included set of packages which is not available in distribution repository due to some limitation. + +It helps administrator to easily install some of the important packages which is not available in the distribution official repository. Installing third party repository on production system is not advisable as this may not properly maintained by the repository maintainer due to many reasons. + +So, you have to decide whether you want to install or not. I can say, we can believe some of the third party repositories which is well maintained and suggested by Linux distributions like [EPEL repository][1], Copr (Cool Other Package Repo), etc,. + +If you would like to see the list of package was installed from the corresponding repo, use the following commands based on your distributions. + +[List of Major repositories][2] and it’s details are below. + + * **`CentOS:`** [EPEL][1], [ELRepo][3], etc is [CentOS Community Approved Repositories][4]. + * **`Fedora:`** [RPMfusion repo][5] is commonly used by most of the [Fedora][6] users. + * **`ArchLinux:`** ArchLinux community repository contains packages that have been adopted by Trusted Users from the Arch User Repository. + * **`openSUSE:`** [Packman repo][7] offers various additional packages for openSUSE, especially but not limited to multimedia related applications and libraries that are on the openSUSE Build Service application blacklist. It’s the largest external repository of openSUSE packages. + * **`Ubuntu:`** Personal Package Archives (PPAs) are a kind of repository. Developers create them in order to distribute their software. You can find this information on the PPA’s Launchpad page. Also, you can enable Cananical partners repositories. + + + +### What Is Repository? + +A software repository is a central place which stores the software packages for the particular application. + +All the Linux distributions are maintaining their own repositories and they allow users to retrieve and install packages on their machine. + +Each vendor offered a unique package management tool to manage their repositories such as search, install, update, upgrade, remove, etc. + +Most of the Linux distributions comes as freeware except RHEL and SUSE. To access their repositories you need to buy a subscriptions. + +### How To Check The List Of Packages Installed From Particular Repository on RHEL/CentOS Systems? + +This can be done in multiple ways. Here we will be giving you all the possible options and you can choose which one is best for you. + +### Method-1: Using Yum Command + +RHEL & CentOS systems are using RPM packages hence we can use the [Yum Package Manager][8] to get this information. + +YUM stands for Yellowdog Updater, Modified is an open-source command-line front-end package-management utility for RPM based systems such as Red Hat Enterprise Linux (RHEL) and CentOS. + +Yum is the primary tool for getting, installing, deleting, querying, and managing RPM packages from distribution repositories, as well as other third-party repositories. + +``` +[[email protected] ~]# yum list installed | grep @epel +apachetop.x86_64 0.15.6-1.el7 @epel +aria2.x86_64 1.18.10-2.el7.1 @epel +atop.x86_64 2.3.0-8.el7 @epel +axel.x86_64 2.4-9.el7 @epel +epel-release.noarch 7-11 @epel +lighttpd.x86_64 1.4.50-1.el7 @epel +``` + +Alternatively, you can use the yum command with other option to get the same details like above. + +``` +# yum repo-pkgs epel list installed +Loaded plugins: fastestmirror +Loading mirror speeds from cached hostfile + * epel: epel.mirror.constant.com +Installed Packages +apachetop.x86_64 0.15.6-1.el7 @epel +aria2.x86_64 1.18.10-2.el7.1 @epel +atop.x86_64 2.3.0-8.el7 @epel +axel.x86_64 2.4-9.el7 @epel +epel-release.noarch 7-11 @epel +lighttpd.x86_64 1.4.50-1.el7 @epel +``` + +### Method-2: Using Yumdb Command + +Yumdb info provides information similar to yum info but additionally it provides package checksum data, type, user info (who installed the package). Since yum 3.2.26 yum has started storing additional information outside of the rpmdatabase (where user indicates it was installed by the user, and dep means it was brought in as a dependency). + +``` +# yumdb search from_repo epel* |egrep -v '(from_repo|^$)' +Loaded plugins: fastestmirror +apachetop-0.15.6-1.el7.x86_64 +aria2-1.18.10-2.el7.1.x86_64 +atop-2.3.0-8.el7.x86_64 +axel-2.4-9.el7.x86_64 +epel-release-7-11.noarch +lighttpd-1.4.50-1.el7.x86_64 +``` + +### Method-3: Using Repoquery Command + +repoquery is a program for querying information from YUM repositories similarly to rpm queries. + +``` +# repoquery -a --installed --qf "%{ui_from_repo} %{name}" | grep '^@epel' +@epel apachetop +@epel aria2 +@epel atop +@epel axel +@epel epel-release +@epel lighttpd +``` + +### How To Check The List Of Packages Installed From Particular Repository on Fedora System? + +DNF stands for Dandified yum. We can tell DNF, the next generation of yum package manager (Fork of Yum) using hawkey/libsolv library for back-end. Aleš Kozumplík started working on DNF since Fedora 18 and its implemented/launched in Fedora 22 finally. + +[Dnf command][9] is used to install, update, search & remove packages on Fedora 22 and later system. It automatically resolve dependencies and make it smooth package installation without any trouble. + +``` +# dnf list installed | grep @updates +NetworkManager.x86_64 1:1.12.4-2.fc29 @updates +NetworkManager-adsl.x86_64 1:1.12.4-2.fc29 @updates +NetworkManager-bluetooth.x86_64 1:1.12.4-2.fc29 @updates +NetworkManager-libnm.x86_64 1:1.12.4-2.fc29 @updates +NetworkManager-libreswan.x86_64 1.2.10-1.fc29 @updates +NetworkManager-libreswan-gnome.x86_64 1.2.10-1.fc29 @updates +NetworkManager-openvpn.x86_64 1:1.8.8-1.fc29 @updates +NetworkManager-openvpn-gnome.x86_64 1:1.8.8-1.fc29 @updates +NetworkManager-ovs.x86_64 1:1.12.4-2.fc29 @updates +NetworkManager-ppp.x86_64 1:1.12.4-2.fc29 @updates +. +. +``` + +Alternatively, you can use the dnf command with other option to get the same details like above. + +``` +# dnf repo-pkgs updates list installed +Installed Packages +NetworkManager.x86_64 1:1.12.4-2.fc29 @updates +NetworkManager-adsl.x86_64 1:1.12.4-2.fc29 @updates +NetworkManager-bluetooth.x86_64 1:1.12.4-2.fc29 @updates +NetworkManager-libnm.x86_64 1:1.12.4-2.fc29 @updates +NetworkManager-libreswan.x86_64 1.2.10-1.fc29 @updates +NetworkManager-libreswan-gnome.x86_64 1.2.10-1.fc29 @updates +NetworkManager-openvpn.x86_64 1:1.8.8-1.fc29 @updates +NetworkManager-openvpn-gnome.x86_64 1:1.8.8-1.fc29 @updates +NetworkManager-ovs.x86_64 1:1.12.4-2.fc29 @updates +. +. +``` + +### How To Check The List Of Packages Installed From Particular Repository on openSUSE System? + +Zypper is a command line package manager which makes use of libzypp. [Zypper command][10] provides functions like repository access, dependency solving, package installation, etc. + +``` +zypper search -ir "Update Repository (Non-Oss)" +Loading repository data... +Reading installed packages... + +S | Name | Summary | Type +---+----------------------------+---------------------------------------------------+-------- +i | gstreamer-0_10-fluendo-mp3 | GStreamer plug-in from Fluendo for MP3 support | package +i+ | openSUSE-2016-615 | Test-update for openSUSE Leap 42.2 Non Free | patch +i+ | openSUSE-2017-724 | Security update for unrar | patch +i | unrar | A program to extract, test, and view RAR archives | package +``` + +Alternatively, we can use repo id instead of repo name. + +``` +zypper search -ir 2 +Loading repository data... +Reading installed packages... + +S | Name | Summary | Type +---+----------------------------+---------------------------------------------------+-------- +i | gstreamer-0_10-fluendo-mp3 | GStreamer plug-in from Fluendo for MP3 support | package +i+ | openSUSE-2016-615 | Test-update for openSUSE Leap 42.2 Non Free | patch +i+ | openSUSE-2017-724 | Security update for unrar | patch +i | unrar | A program to extract, test, and view RAR archives | package +``` + +### How To Check The List Of Packages Installed From Particular Repository on ArchLinux System? + +[Pacman command][11] stands for package manager utility. pacman is a simple command-line utility to install, build, remove and manage Arch Linux packages. Pacman uses libalpm (Arch Linux Package Management (ALPM) library) as a back-end to perform all the actions. + +``` +$ paclist community +acpi 1.7-2 +acpid 2.0.30-1 +adapta-maia-theme 3.94.0.149-1 +android-tools 9.0.0_r3-1 +blueman 2.0.6-1 +brotli 1.0.7-1 +. +. +ufw 0.35-5 +unace 2.5-10 +usb_modeswitch 2.5.2-1 +viewnior 1.7-1 +wallpapers-2018 1.0-1 +xcursor-breeze 5.11.5-1 +xcursor-simpleandsoft 0.2-8 +xcursor-vanilla-dmz-aa 0.4.5-1 +xfce4-whiskermenu-plugin-gtk3 2.3.0-1 +zeromq 4.2.5-1 +``` + +### How To Check The List Of Packages Installed From Particular Repository on Debian Based Systems? + +For Debian based systems, it can be done using grep command. + +If you want to know the list of installed repositories on your system, use the following command. + +``` +$ ls -lh /var/lib/apt/lists/ | uniq +total 370M +-rw-r--r-- 1 root root 10K Oct 26 10:53 archive.canonical.com_ubuntu_dists_bionic_InRelease +-rw-r--r-- 1 root root 6.4K Oct 26 10:53 archive.canonical.com_ubuntu_dists_bionic_partner_binary-amd64_Packages +-rw-r--r-- 1 root root 6.4K Oct 26 10:53 archive.canonical.com_ubuntu_dists_bionic_partner_binary-i386_Packages +-rw-r--r-- 1 root root 3.2K Jun 12 21:19 archive.canonical.com_ubuntu_dists_bionic_partner_i18n_Translation-en +drwxr-xr-x 2 _apt root 4.0K Jul 25 08:44 auxfiles +-rw-r--r-- 1 root root 3.7K Oct 16 15:13 download.virtualbox.org_virtualbox_debian_dists_bionic_contrib_binary-amd64_Packages +-rw-r--r-- 1 root root 7.2K Oct 16 15:13 download.virtualbox.org_virtualbox_debian_dists_bionic_contrib_Contents-amd64.lz4 +-rw-r--r-- 1 root root 4.4K Oct 16 15:13 download.virtualbox.org_virtualbox_debian_dists_bionic_InRelease +-rw-r--r-- 1 root root 34 Mar 19 2018 download.virtualbox.org_virtualbox_debian_dists_bionic_non-free_Contents-amd64.lz4 +-rw-r--r-- 1 root root 6.4K Sep 21 09:42 in.archive.ubuntu.com_ubuntu_dists_bionic-backports_Contents-amd64.lz4 +-rw-r--r-- 1 root root 6.4K Sep 21 09:42 in.archive.ubuntu.com_ubuntu_dists_bionic-backports_Contents-i386.lz4 +-rw-r--r-- 1 root root 73K Nov 6 11:16 in.archive.ubuntu.com_ubuntu_dists_bionic-backports_InRelease +. +. +-rw-r--r-- 1 root root 29 May 11 06:39 security.ubuntu.com_ubuntu_dists_bionic-security_main_dep11_icons-64x64.tar.gz +-rw-r--r-- 1 root root 747K Nov 5 23:57 security.ubuntu.com_ubuntu_dists_bionic-security_main_i18n_Translation-en +-rw-r--r-- 1 root root 2.8K Oct 9 22:37 security.ubuntu.com_ubuntu_dists_bionic-security_multiverse_binary-amd64_Packages +-rw-r--r-- 1 root root 3.7K Oct 9 22:37 security.ubuntu.com_ubuntu_dists_bionic-security_multiverse_binary-i386_Packages +-rw-r--r-- 1 root root 1.8K Jul 24 23:06 security.ubuntu.com_ubuntu_dists_bionic-security_multiverse_i18n_Translation-en +-rw-r--r-- 1 root root 519K Nov 5 20:12 security.ubuntu.com_ubuntu_dists_bionic-security_universe_binary-amd64_Packages +-rw-r--r-- 1 root root 517K Nov 5 20:12 security.ubuntu.com_ubuntu_dists_bionic-security_universe_binary-i386_Packages +-rw-r--r-- 1 root root 11K Nov 6 05:36 security.ubuntu.com_ubuntu_dists_bionic-security_universe_dep11_Components-amd64.yml.gz +-rw-r--r-- 1 root root 8.9K Nov 6 05:36 security.ubuntu.com_ubuntu_dists_bionic-security_universe_dep11_icons-48x48.tar.gz +-rw-r--r-- 1 root root 16K Nov 6 05:36 security.ubuntu.com_ubuntu_dists_bionic-security_universe_dep11_icons-64x64.tar.gz +-rw-r--r-- 1 root root 315K Nov 5 20:12 security.ubuntu.com_ubuntu_dists_bionic-security_universe_i18n_Translation-en +``` + +To get the list of installed packages from the `security.ubuntu.com` repository. + +``` +$ grep Package /var/lib/apt/lists/security.ubuntu.com_*_Packages | awk '{print $2;}' +amd64-microcode +apache2 +apache2-bin +apache2-data +apache2-dbg +apache2-dev +. +. +znc +znc-dev +znc-perl +znc-python +znc-tcl +zsh-static +zziplib-bin +``` + +The security repository containing multiple branches (main, multiverse and universe) and if you would like to list out the installed packages from the particular repository `universe` then use the following format. + +``` +$ grep Package /var/lib/apt/lists/security.ubuntu.com_ubuntu_dists_bionic-security_universe*_Packages | awk '{print $2;}' +ant +ant-doc +ant-optional +apache2-suexec-custom +apache2-suexec-pristine +apparmor-easyprof +apport-kde +apport-noui +apport-valgrind +apt-transport-https +. +. +xul-ext-gdata-provider +xul-ext-lightning +xvfb +znc +znc-dev +znc-perl +znc-python +znc-tcl +zsh-static +zziplib-bin +``` + +one more example for `ppa.launchpad.net` repository. + +``` +$ grep Package /var/lib/apt/lists/ppa.launchpad.net_*_Packages | awk '{print $2;}' +notepadqq +notepadqq-gtk +notepadqq-common +notepadqq +notepadqq-gtk +notepadqq-common +numix-gtk-theme +numix-icon-theme +numix-icon-theme-circle +numix-icon-theme-square +numix-gtk-theme +numix-icon-theme +numix-icon-theme-circle +numix-icon-theme-square +``` + +-------------------------------------------------------------------------------- + +via: https://www.2daygeek.com/how-to-check-the-list-of-packages-installed-from-particular-repository/ + +作者：[Prakash Subramanian][a] +选题：[lujun9972][b] +译者：[译者ID](https://github.com/译者ID) +校对：[校对者ID](https://github.com/校对者ID) + +本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 + +[a]: https://www.2daygeek.com/author/prakash/ +[b]: https://github.com/lujun9972 +[1]: https://www.2daygeek.com/install-enable-epel-repository-on-rhel-centos-scientific-linux-oracle-linux/ +[2]: https://www.2daygeek.com/category/repository/ +[3]: https://www.2daygeek.com/install-enable-elrepo-on-rhel-centos-scientific-linux/ +[4]: https://www.2daygeek.com/additional-yum-repositories-for-centos-rhel-fedora-systems/ +[5]: https://www.2daygeek.com/install-enable-rpm-fusion-repository-on-centos-fedora-rhel/ +[6]: https://fedoraproject.org/wiki/Third_party_repositories +[7]: https://www.2daygeek.com/install-enable-packman-repository-on-opensuse-leap/ +[8]: https://www.2daygeek.com/yum-command-examples-manage-packages-rhel-centos-systems/ +[9]: https://www.2daygeek.com/dnf-command-examples-manage-packages-fedora-system/ +[10]: https://www.2daygeek.com/zypper-command-examples-manage-packages-opensuse-system/ +[11]: https://www.2daygeek.com/pacman-command-examples-manage-packages-arch-linux-system/ diff --git a/sources/tech/20181109 Must-Have Tools for Writers on the Linux Platform.md b/sources/tech/20181109 Must-Have Tools for Writers on the Linux Platform.md new file mode 100644 index 0000000000..0ab375a008 --- /dev/null +++ b/sources/tech/20181109 Must-Have Tools for Writers on the Linux Platform.md @@ -0,0 +1,118 @@ +Must-Have Tools for Writers on the Linux Platform +====== + + +I’ve been a writer for more than 20 years. I’ve written thousands of articles and how-tos on various technical topics and have penned more than 40 works of fiction. So, the written word is not only important to me, it’s familiar to the point of being second nature. And through those two decades (and counting) I’ve done nearly all my work on the Linux platform. I must confess, during those early years it wasn’t always easy. Formats didn’t always mesh with what an editor required and, in some cases, the open source platform simply didn’t have the necessary tools required to get the job done. + +That was then, this is now. + +A perfect storm of Linux evolution and web-based tools have made it such that any writer can get the job done (and done well) on Linux. But what tools will you need? You might be surprised to find out that, in some instances, the job cannot be efficiently done with 100% open source tools. Even with that caveat, the job can be done. Let’s take a look at the tools I’ve been using as both a tech writer and author of fiction. I’m going to outline this by way of my writing process for both nonfiction and fiction (as the process is different and requires specific tools). + +A word of warning to seriously hard-core Linux users. A long time ago, I gave up on using tools like LaTeX and DocBook for my writing. Why? Because, for me, the focus must be on the content, not the process. When you’re facing deadlines, efficiency must take precedent. + +### Nonfiction + +We’ll start with nonfiction, as that process is the simpler of the two. For writing technical how-tos, I collaborate with different editors and, in some cases, have to copy/paste content into a CMS. But like with my fiction, the process always starts with Google Drive. This is the point at which many open source purists will check out. Fear not, you can always opt to either keep all of your files locally, or use a more open-friendly cloud service (such as [Zoho][1] or [nextCloud][2]). + +Why start on the cloud? Over the years, I’ve found I need to be able to access that content from anywhere at any time. The simplest solution was to migrate the cloud. I’ve also become paranoid about losing work. To that end, I make use of a tool like [Insync][3] to keep my Google Drive in sync with my desktop. With that desktop sync in place, I know there’s always a backup of my work, in case something should go awry with Google Drive. + +For those clients with whom I must enter content into a Content Management System (CMS), the process ends there. I can copy/paste directly from a Google Doc into the CMS and be done with it. Of course, with technical content, there are always screenshots involved. For that, I use [Gimp][4], which makes taking screenshots simple: + +![screenshot with Gimp][6] + +Figure 1: Taking a screenshot with Gimp. + +[Used with permission][7] + + 1. Open Gimp. + + 2. Click File > Create > Screenshot. + + 3. Select from a single window, the entire screen, or a region to grab (Figure 1). + + 4. Click Snap. + + + + +The majority of my clients tend to prefer I work with Google Docs, because I can share folders so that they have reliable access to the content. There are a few clients I have that do not work with Google Docs, and so I must download the files into a format that can be used. What I do for this is download in .odt format, open the document in [LibreOffice][8] (Figure 2), format as needed, save in a format required by the client, and send the document on. + +![Google Doc][10] + +Figure 2: My Google Doc download opened in LibreOffice. + +[Used with permission][7] + +And that, is the end of the line for nonfiction. + +### Fiction + +This is where it gets a bit more complicated. The beginning steps are the same, as I always write every first draft of a novel in Google Docs. Once that is complete, I then download the file to my Linux desktop, open the file in LibreOffice, format as necessary, and then save as a file type supported by my editor (unfortunately, that means .docx). + +The next step in the process gets a bit dicey. My editor prefers to use comments over track changes (as it makes it easier for both of us to read the document as we make changes). Because of this, a 60k word doc can include hundreds upon hundreds of comments, which slows LibreOffice to a useless crawl. Once upon a time, you could up the memory used for documents, but as of LibreOffice 6, that is no longer possible. This means any larger, novel-length, document with numerous comments will become unusable. Because of that, I’ve had to take drastic measures and use [WPS Office][11] (Figure 3). Although this isn’t an open source solution, WPS Office does a fine job with numerous comments in a document, so there’s no need to deal with the frustration that is LibreOffice (when working with these large files with hundreds of comments). + +![comments][13] + +Figure 3: WPS handles numerous comments with ease. + +[Used with permission][7] + +Once my editor and I finish up the edits for the book (and all comments have been removed), I can then open the file in LibreOffice for final formatting. When the formatting is complete, I save the file in .html format and then open the file in [Calibre][14] for exporting the file to .mobi and .epub formats. + +Calibre is a must-have for anyone looking to publish on Amazon, Barnes & Noble, Smashwords, or other platforms. One thing Calibre does better than other, similar, solutions is enable you to directly edit the .epub files (Figure 4). For the likes of Smashword, this is an absolute necessity (as the export process will add elements not accepted on the Smashwords conversion tool). + +![Calibre][16] + +Figure 4: Editing an epub file directly in Calibre. + +[Creative Commons Zero][17] + +After the writing process is over (or sometimes while waiting for an editor to complete a pass), I’ll start working on the cover for the book. That task is handled completely in Gimp (Figure 5). + +![Using Gimp][19] + +Figure 5: Creating the cover of POTUS in Gimp. + +[Used with permission][7] + +And that finishes up the process of creating a work of fiction on the Linux platform. Because of the length of the documents, and how some editors work, it can get a bit more complicated than the process of creating nonfiction, but it’s far from challenging. In fact, creating fiction on Linux is just as simple (and more reliable) than other platforms. + +### HTH + +I hope this helps aspiring writers to have the confidence to write on the Linux platform. There are plenty of other tools available to use, but the ones I have listed here have served me quite well over the years. And although I do make use of a couple of proprietary tools, as long as they keep working well on Linux, I’m okay with that. + +Learn more about Linux in the[ Introduction to Open Source Development, Git, and Linux (LFD201) ][20]training course from The Linux Foundation, and sign up now to start your open source journey. + +-------------------------------------------------------------------------------- + +via: https://www.linux.com/learn/2018/11/must-have-tools-writers-linux-platform + +作者：[Jack Wallen][a] +选题：[lujun9972][b] +译者：[译者ID](https://github.com/译者ID) +校对：[校对者ID](https://github.com/校对者ID) + +本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 + +[a]: https://www.linux.com/users/jlwallen +[b]: https://github.com/lujun9972 +[1]: https://www.zoho.com/ +[2]: https://nextcloud.com/ +[3]: https://www.insynchq.com +[4]: https://www.gimp.org/ +[5]: /files/images/writingtools1jpg +[6]: https://www.linux.com/sites/lcom/files/styles/floated_images/public/writingtools_1.jpg?itok=Uko7DZ8U (screenshot with Gimp) +[7]: /licenses/category/used-permission +[8]: https://www.libreoffice.org/ +[9]: /files/images/writingtools2jpg +[10]: https://www.linux.com/sites/lcom/files/styles/rendered_file/public/writingtools_2.jpg?itok=vDgxd8hu (Google Doc) +[11]: https://www.wps.com/en-US/ +[12]: /files/images/writingtools3jpg +[13]: https://www.linux.com/sites/lcom/files/styles/rendered_file/public/writingtools_3.jpg?itok=AYrsfz01 (comments) +[14]: https://calibre-ebook.com/ +[15]: /files/images/writingtools4jpg +[16]: https://www.linux.com/sites/lcom/files/styles/rendered_file/public/writingtools_4.jpg?itok=wFMEsL7b (Calibre) +[17]: /licenses/category/creative-commons-zero +[18]: /files/images/writingtools5jpg +[19]: https://www.linux.com/sites/lcom/files/styles/rendered_file/public/writingtools_5.jpg?itok=e7SZCgip (Using Gimp) +[20]: https://training.linuxfoundation.org/training/introduction-to-open-source-development-git-and-linux/?utm_source=linux.com&utm_medium=article&utm_campaign=lfd201 diff --git a/sources/tech/20181112 Behind the scenes with Linux containers.md b/sources/tech/20181112 Behind the scenes with Linux containers.md new file mode 100644 index 0000000000..0f813ac517 --- /dev/null +++ b/sources/tech/20181112 Behind the scenes with Linux containers.md @@ -0,0 +1,205 @@ +Behind the scenes with Linux containers +====== +Become a better container troubleshooter by using LXC to understand how they work. + + +Can you have Linux containers without [Docker][1]? Without [OpenShift][2]? Without [Kubernetes][3]? + +Yes, you can. Years before Docker made containers a household term (if you live in a data center, that is), the [LXC][4] project developed the concept of running a kind of virtual operating system, sharing the same kernel, but contained within defined groups of processes. + +Docker built on LXC, and today there are plenty of platforms that leverage the work of LXC both directly and indirectly. Most of these platforms make creating and maintaining containers sublimely simple, and for large deployments, it makes sense to use such specialized services. However, not everyone's managing a large deployment or has access to big services to learn about containerization. The good news is that you can create, use, and learn containers with nothing more than a PC running Linux and this article. This article will help you understand containers by looking at LXC, how it works, why it works, and how to troubleshoot when something goes wrong. + +### Sidestepping the simplicity + +If you're looking for a quick-start guide to LXC, refer to the excellent [Linux Containers][5] website. + +### Installing LXC + +If it's not already installed, you can install [LXC][6] with your package manager. + +On Fedora or similar, enter: + +``` +$ sudo dnf install lxc lxc-templates lxc-doc +``` + +On Debian, Ubuntu, and similar, enter: + +``` +$ sudo apt install lxc +``` + +### Creating a network bridge + +Most containers assume a network will be available, and most container tools expect the user to be able to create virtual network devices. The most basic unit required for containers is the network bridge, which is more or less the software equivalent of a network switch. A network switch is a little like a smart Y-adapter used to split a headphone jack so two people can hear the same thing with separate headsets, except instead of an audio signal, a network switch bridges network data. + +You can create your own software network bridge so your host computer and your container OS can both send and receive different network data over a single network device (either your Ethernet port or your wireless card). This is an important concept that often gets lost once you graduate from manually generating containers, because no matter the size of your deployment, it's highly unlikely you have a dedicated physical network card for each container you run. It's vital to understand that containers talk to virtual network devices, so you know where to start troubleshooting if a container loses its network connection. + +To create a network bridge on your machine, you must have the appropriate permissions. For this article, use the **sudo** command to operate with root privileges. (However, LXC docs provide a configuration to grant users permission to do this without using **sudo**.) + +``` +$ sudo ip link add br0 type bridge +``` + +Verify that the imaginary network interface has been created: + +``` +$ sudo ip addr show br0 +7: br0: . +Failed to install release agent, ignoring: No such file or directory +[ OK ] Reached target Swap. +[ OK ] Listening on Journal Socket (/dev/log). +[ OK ] Started Dispatch Password Requests to Console Directory Watch. +[ OK ] Reached target Encrypted Volumes. +[ OK ] Created slice System Slice. + Mounting POSIX Message Queue File System... +[ OK ] Listening on Journal Socket. + Starting Set the console keyboard layout... + Starting Restore / save the current clock... + Starting Journal Service... + Starting Remount Root and Kernel File Systems... +[ OK ] Mounted POSIX Message Queue File System. +[ OK ] Started Journal Service. +[ OK ] Started Remount Root and Kernel File Systems. + Starting Flush Journal to Persistent Storage... +[ OK ] Started Restore / save the current clock. +[ OK ] Started Flush Journal to Persistent Storage. +[ OK ] Started Set the console keyboard layout. +[ OK ] Reached target Local File Systems (Pre). +[ OK ] Reached target Local File Systems. + Starting Create Volatile Files and Directories... +[ OK ] Started Create Volatile Files and Directories. +[ OK ] Reached target System Time Synchronized. + Starting Update UTMP about System Boot/Shutdown... +[ OK ] Started Update UTMP about System Boot/Shutdown. +[ OK ] Reached target System Initialization. +[ OK ] Started Rescue Shell. +[ OK ] Reached target Rescue Mode. + Starting Update UTMP about System Runlevel Changes... +[ OK ] Started Update UTMP about System Runlevel Changes. +You are in rescue mode. After logging in, type "journalctl -xb" to view +system logs, "systemctl reboot" to reboot, "systemctl default" or ^D to +boot into default mode. +Give root password for maintenance +(or press Control-D to continue): +``` + +In this output, you can see **systemd** launching as the init process in the container and detecting that it is being run inside a container so it can adjust its behavior appropriately. Various unit files are started to bring the container to a usable state, then the target system's root password is requested. You can enter the root password here if you want a shell prompt with root permissions, or you can press **Ctrl+D** to allow the startup process to continue, which will display a normal console login prompt. + +When you have completed the necessary changes to the target system, press **Ctrl+]** three times in rapid succession; this will terminate the container and return you to your original shell. From there, you can clean up by unmounting the target system's filesystem and removing the temporary directory: + +``` +$ umount /tmp/target-rescue +$ rmdir /tmp/target-rescue +``` + +That's it! You can now remove the target system's storage device(s) and return them to the target system. + +The idea to use **systemd-nspawn** this way, especially the **\--boot parameter** , came from [a question][3] posted on StackExchange. Thanks to Shibumi and kirbyfan64sos for providing useful answers to this question! + +-------------------------------------------------------------------------------- + +via: https://opensource.com/article/18/11/systemd-nspawn-system-recovery + +作者：[Kevin P.Fleming][a] +选题：[lujun9972][b] +译者：[译者ID](https://github.com/译者ID) +校对：[校对者ID](https://github.com/校对者ID) + +本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 + +[a]: https://opensource.com/users/kpfleming +[b]: https://github.com/lujun9972 +[1]: https://www.freedesktop.org/wiki/Software/systemd/ +[2]: https://www.freedesktop.org/software/systemd/man/systemd-nspawn.html +[3]: https://unix.stackexchange.com/questions/457819/running-systemd-utilities-like-systemctl-under-an-nspawn diff --git a/sources/tech/20181115 11 Things To Do After Installing elementary OS 5 Juno.md b/sources/tech/20181115 11 Things To Do After Installing elementary OS 5 Juno.md new file mode 100644 index 0000000000..5e23c6e5c4 --- /dev/null +++ b/sources/tech/20181115 11 Things To Do After Installing elementary OS 5 Juno.md @@ -0,0 +1,260 @@ +11 Things To Do After Installing elementary OS 5 Juno +====== +I’ve been using [elementary OS 5 Juno][1] for over a month and it has been an amazing experience. It is easily the [best Mac OS inspired Linux distribution][2] and one of the [best Linux distribution for beginners][3]. + +However, you will need to take care of a couple of things after installing it. +In this article, we will discuss the most important things that you need to do after installing [elementary OS][4] 5 Juno. + +### Things to do after installing elementary OS 5 Juno + +![Things to do after installing elementary OS Juno][5] + +Things I mentioned in this list are from my personal experience and preference. Of course, you are not restricted to these few things. You can explore and tweak the system as much as you like. However, if you follow (some of) these recommendations, things might be smoother for you. + +#### 1.Run a System Update + +![terminal showing system updates in elementary os 5 Juno][6] + +Even when you download the latest version of a distribution – it is always recommended to check for the latest System updates. You might have a quick fix for an annoying bug, or, maybe there’s an important security patch that you shouldn’t ignore. So, no matter what – you should always ensure that you have everything up-to-date. + +To do that, you need to type in the following command in the terminal: + +``` +sudo apt-get update +``` + +#### 2\. Set Window Hotcorner + +![][7] + +You wouldn’t notice the minimize button for a window. So, how do you do it? + +Well, you can just bring up the dock and click the app icon again to minimize it or press **Windows key + H** as a shortcut to minimize the active window. + +But, I’ll recommend something way more easy and intuitive. Maybe you already knew it, but for the users who were unaware of the “ **hotcorners** ” feature, here’s what it does: + +Whenever you hover the cursor to any of the 4 corners of the window, you can set a preset action to happen when you do that. For example, when you move your cursor to the **left corner** of the screen you get the **multi-tasking view** to switch between apps – which acts like a “gesture“. + +In order to utilize the functionality, you can follow the steps below: + + 1. Head to the System Settings. + 2. Click on the “ **Desktop** ” option (as shown in the image above). + 3. Next, select the “ **Hot Corner** ” section (as shown in the image below). + 4. Depending on what corner you prefer, choose an appropriate action (refer to the image below – that’s what I personally prefer as my settings) + + + +#### 3\. Install Multimedia codecs + +I’ve tried playing MP3/MP4 files – it just works fine. However, there are a lot of file formats when it comes to multimedia. + +So, just to be able to play almost every format of multimedia, you should install the codecs. Here’s what you need to enter in the terminal: + +To get certain proprietary codecs: + +``` +sudo apt install ubuntu-restricted-extras +``` + +To specifically install [Libav][8]: + +``` +sudo apt install libavcodec-extra +``` + +To install a codec in order to facilitate playing video DVDs: + +``` +sudo apt install libdvd-pkg +``` + +#### 4\. Install GDebi + +You don’t get to install .deb files by just double-clicking it on elementary OS 5 Juno. It just does not let you do that. + +So, you need an additional tool to help you install .deb files. + +We’ll recommend you to use **GDebi**. I prefer it because it lets you know about the dependencies even before trying to install it – that way – you can be sure about what you need in order to correctly install an application. + +Simply install GDebi and open any .deb files by performing a right-click on them **open in GDebi Package Installer.** + +To install it, type in the following command: + +``` +sudo apt install gdebi +``` + +#### 5\. Add a PPA for your Favorite App + +Yes, elementary OS 5 Juno now supports PPA (unlike its previous version). So, you no longer need to enable the support for PPAs explicitly. + +Just grab a PPA and add it via terminal to install something you like. + +#### 6\. Install Essential Applications + +If you’re a Linux power user, you already know what you want and where to get it, but if you’re new to this Linux distro and looking out for some applications to have installed, I have a few recommendations: + +**Steam app** : If you’re a gamer, this is a must-have app. You just need to type in a single command to install it: + +``` +sudo apt install steam +``` + +**GIMP** : It is the best photoshop alternative across every platform. Get it installed for every type of image manipulation: + +``` +sudo apt install gimp +``` + +**Wine** : If you want to install an application that only runs on Windows, you can try using Wine to run such Windows apps here on Linux. To install, follow the command: + +``` +sudo apt install wine-stable +``` + +**qBittorrent** : If you prefer downloading Torrent files, you should have this installed as your Torrent client. To install it, enter the following command: + +``` +sudo apt install qbittorrent +``` + +**Flameshot** : You can obviously utilize the default screenshot tool to take screenshots. But, if you want to instantly share your screenshots and the ability to annotate – install flameshot. Here’s how you can do that: + +``` +sudo apt install flameshot +``` + +**Chrome/Firefox: **The default browser isn’t much useful. So, you should install Chrome/Firefox – as per your choice. + +To install chrome, enter the command: + +``` +sudo apt install chromium-browser +``` + +To install Firefox, enter: + +``` +sudo apt install firefox +``` + +These are some of the most common applications you should definitely have installed. For the rest, you should browse through the App Center or the Flathub to install your favorite applications. + +#### 7\. Install Flatpak (Optional) + +It’s just my personal recommendation – I find flatpak to be the preferred way to install apps on any Linux distro I use. + +You can try it and learn more about it at its [official website][9]. + +To install flatpak, type in: + +``` +sudo apt install flatpak +``` + +After you are done installing flatpak, you can directly head to [Flathub][10] to install some of your favorite apps and you will also find the command/instruction to install it via the terminal. + +In case you do not want to launch the browser, you can search for your app by typing in (example – finding Discord and installing it): + +``` +flatpak search discord flathub +``` + +After gettting the application ID, you can proceed installing it by typing in: + +``` +flatpak install flathub com.discordapp.Discord +``` + +#### 8\. Enable the Night Light + +![Night Light in elementary OS Juno][11] + +You might have installed Redshift as per our recommendation for [elemantary OS 0.4 Loki][12] to filter the blue light to avoid straining our eyes- but you do not need any 3rd party tool anymore. + +It comes baked in as the “ **Night Light** ” feature. + +You just head to System Settings and click on “ **Displays** ” (as shown in the image above). + +Select the **Night Light** section and activate it with your preferred settings. + +#### 9\. Install NVIDIA driver metapackage (for NVIDIA GPUs) + +![Nvidia drivers in elementary OS juno][13] + +The NVIDIA driver metapackage should be listed right at the App Center – so you can easily the NVIDIA driver. + +However, it’s not the latest driver version – I have version **390.77** installed and it’s performing just fine. + +If you want the latest version for Linux, you should check out NVIDIA’s [official download page][14]. + +Also, if you’re curious about the version installed, just type in the following command: + +``` +nvidia-smi +``` + +#### 10\. Install TLP for Advanced Power Management + +We’ve said it before. And, we’ll still recommend it. + +If you want to manage your background tasks/activity and prevent overheating of your system – you should install TLP. + +It does not offer a GUI, but you don’t have to bother. You just install it and let it manage whatever it takes to prevent overheating. + +It’s very helpful for laptop users. + +To install, type in: + +``` +supo apt install tlp tlp-rdw +``` + +#### 11\. Perform visual customizations + +![][15] + +If you need to change the look of your Linux distro, you can install GNOME tweaks tool to get the options. In order to install the tweak tool, type in: + +``` +sudo apt install gnome-tweaks +``` + +Once you install it, head to the application launcher and search for “Tweaks”, you’ll find something like this: + +Here, you can select the icon, theme, wallpaper, and you’ll also be able to tweak a couple more options that’s not limited to the visual elements. + +### Wrapping Up + +It’s the least you should do after installing elementary OS 5 Juno. However, considering that elementary OS 5 Juno comes with numerous new features – you can explore a lot more new things as well. + +Let us know what you did first after installing elementary OS 5 Juno and how’s your experience with it so far? + +-------------------------------------------------------------------------------- + +via: https://itsfoss.com/things-to-do-after-installing-elementary-os-5-juno/ + +作者：[Ankush Das][a] +选题：[lujun9972][b] +译者：[译者ID](https://github.com/译者ID) +校对：[校对者ID](https://github.com/校对者ID) + +本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 + +[a]: https://itsfoss.com/author/ankush/ +[b]: https://github.com/lujun9972 +[1]: https://itsfoss.com/elementary-os-juno-features/ +[2]: https://itsfoss.com/macos-like-linux-distros/ +[3]: https://itsfoss.com/best-linux-beginners/ +[4]: https://elementary.io/ +[5]: https://i2.wp.com/itsfoss.com/wp-content/uploads/2018/11/things-to-do-after-installing-elementary-os-juno.jpeg?ssl=1 +[6]: https://i1.wp.com/itsfoss.com/wp-content/uploads/2018/11/elementary-os-system-update.jpg?ssl=1 +[7]: https://i1.wp.com/itsfoss.com/wp-content/uploads/2018/11/elementary-os-hotcorners.jpg?ssl=1 +[8]: https://libav.org/ +[9]: https://flatpak.org/ +[10]: https://flathub.org/home +[11]: https://i0.wp.com/itsfoss.com/wp-content/uploads/2018/11/elementary-os-night-light.jpg?ssl=1 +[12]: https://itsfoss.com/things-to-do-after-installing-elementary-os-loki/ +[13]: https://i2.wp.com/itsfoss.com/wp-content/uploads/2018/11/elementary-os-nvidia-metapackage.jpg?ssl=1 +[14]: https://www.nvidia.com/Download/index.aspx +[15]: https://i0.wp.com/itsfoss.com/wp-content/uploads/2018/11/elementary-os-gnome-tweaks.jpg?ssl=1 diff --git a/sources/tech/20181122 Getting started with Jenkins X.md b/sources/tech/20181122 Getting started with Jenkins X.md new file mode 100644 index 0000000000..1c2aab6903 --- /dev/null +++ b/sources/tech/20181122 Getting started with Jenkins X.md @@ -0,0 +1,148 @@ +[#]: collector: (lujun9972) +[#]: translator: ( ) +[#]: reviewer: ( ) +[#]: publisher: ( ) +[#]: subject: (Getting started with Jenkins X) +[#]: via: (https://opensource.com/article/18/11/getting-started-jenkins-x) +[#]: author: (Dave Johnson https://opensource.com/users/snoopdave) +[#]: url: ( ) + +Getting started with Jenkins X +====== +Jenkins X provides continuous integration, automated testing, and continuous delivery to Kubernetes. + + +[Jenkins X][1] is an open source system that offers software developers continuous integration, automated testing, and continuous delivery, known as CI/CD, in Kubernetes. Jenkins X-managed projects get a complete CI/CD process with a Jenkins pipeline that builds and packages project code for deployment to Kubernetes and access to pipelines for promoting projects to staging and production environments. + +Developers are already benefiting from running "classic" open source Jenkins and CloudBees Jenkins on Kubernetes, thanks in part to the Jenkins Kubernetes plugin, which allows you to dynamically spin-up Kubernetes pods to run Jenkins build agents. Jenkins X adds what's missing from Jenkins: comprehensive support for continuous delivery and managing the promotion of projects to preview, staging, and production environments running in Kubernetes. + +This article is a high-level explanation of how Jenkins X works; it assumes you have some knowledge of Kubernetes and classic Jenkins. + +### What you get with Jenkins X + +If you're running on one of the major cloud providers (Amazon Elastic Container Service for Kubernetes, Google Kubernetes Engine, or Microsoft Azure Kubernetes Service), installing and deploying Jenkins X is easy. Download the Jenkins X command-line interface and run the **jx create cluster** command. You'll be prompted for the necessary information and, if you take the defaults, Jenkins X will create a starter-size Kubernetes cluster and install Jenkins X. + +When you deploy Jenkins X, a number of services are put in motion to watch your Git repositories and respond by building, testing, and promoting your applications to staging, production, and other environments you define. Jenkins X also deploys a set of supporting services, including [Jenkins][2], [Docker Registry][3], [Chart Museum][4], and [Monocular][5] to manage [Helm][6] charts, and [Nexus][7], which serves as a Maven and npm repository. + +The Jenkins X deployment also creates two Git repositories, one for your staging environment and one for production. These are in addition to the Git repositories you use to manage your project source code. Jenkins X uses these repositories to manage what is deployed to each environment, and promotions are done via Git pull requests (PRs)—this approach is known as [GitOps][8]. Each repository contains a Helm chart that specifies the applications to be deployed to the corresponding environment. Each repository also has a Jenkins pipeline to handle promotions. + +### Creating a new project with Jenkins X + +To create a new project with Jenkins X, use the **jx create quickstart** command. If you don't specify any options, jx will prompt you to select a project name and a platform—which can be just about anything. SpringBoot, Go, Python, Node, ASP.NET, Rust, Angular, and React are all supported, and the list keeps growing. Once you have chosen your project name and platform, Jenkins X will: + + * Create a new project that includes a "hello-world"-style web project + * Add the appropriate type of makefile or build script for the chosen platform + * Add a Jenkinsfile to manage promotions to staging and production environments + * Add a Dockerfile and Helm charts, created via [Draft][9] + * Add a [Skaffold][10] configuration for deploying the application to Kubernetes + * Create a Git repository and push the new project code there + + + +Next, a webhook from Git will notify Jenkins X that a project changed, and it will run your project's Jenkins pipeline to build and push your Docker image and Helm charts. + +Finally, the pipeline will submit a PR to the staging environment's Git repository with the changes needed to promote the application. + +Once the PR is merged, the staging pipeline will run to apply those changes and do the promotion. A couple of minutes after creating your project, you'll have end-to-end CI/CD, and your project will be running in staging and available for use. + +![Developer commits changes, project deployed to staging][12] + +Developer commits changes, project deployed to the staging environment. + +The figure above illustrates the repositories, registries, and pipelines and how they interact in a Jenkins X promotion to staging. Here are the steps: + + 1. The developer commits and pushes the change to the project's Git repository + 2. Jenkins X is notified and runs the project's Jenkins pipeline in a Docker image that includes the project's language and supporting frameworks + 3. The project pipeline builds, tests, and pushes the project's Helm chart to Chart Museum and its Docker image to the registry + 4. The project pipeline creates a PR with changes needed to add the project to the staging environment + 5. Jenkins X automatically merges the PR to Master + 6. Jenkins X is notified and runs the staging pipeline + 7. The staging pipeline runs Helm, which deploys the environment, pulling Helm charts from Chart Museum and Docker images from the Docker registry. Kubernetes creates the project's resources, typically a pod, service, and ingress. + + + +### Importing your existing projects into Jenkins X + +**jx import** , Jenkins X adds the things needed for your project to be deployed to Kubernetes and participate in CI/CD. It will add a Jenkins pipeline, Helm charts, and a Skaffold configuration for deploying the application to Kubernetes. Jenkins X will create a Git repository and push the changes there. Next, a webhook from Git will notify Jenkins X that a project changed, and promotion to staging will happen as described above for new projects. + +### Promoting your project to production + +When you import a project via, Jenkins X adds the things needed for your project to be deployed to Kubernetes and participate in CI/CD. It will add a Jenkins pipeline, Helm charts, and a Skaffold configuration for deploying the application to Kubernetes. Jenkins X will create a Git repository and push the changes there. Next, a webhook from Git will notify Jenkins X that a project changed, and promotion to staging will happen as described above for new projects. + +To promote a version of your project to the production environment, use the **jx promote** command. This command will prepare a Git PR that contains the Helm chart changes needed to deploy into the production environment and submit this request to the production environment's Git repository. Once the request is manually approved, Jenkins X will run the production pipeline to deploy your project via Helm. + +![Promoting project to production][14] + +Developer promotes the project to production. + +This figure illustrates the repositories, registries, and pipelines and how they interact in a Jenkins X promotion to production. Here are the steps: + + 1. The developer runs the **jx promote** command to promote a project to production + 2. Jenkins X creates a PR with changes needed to add the project to the production environment + 3. The developer manually approves the PR, and it is merged to Master + 4. Jenkins X is notified and runs the production pipeline + 5. The production pipeline runs Helm, which deploys the environment, pulling Helm charts from Chart Museum and Docker images from the Docker registry. Kubernetes creates the project's resources, typically a pod, service, and ingress. + + + +### Other features of Jenkins X + +Other interesting and appealing features of Jenkins X include: + +#### Preview environments + +When you create a PR to add a new feature to your project, you can ask Jenkins X to create a preview environment so you can make your new feature available for preview and testing before the PR is merged. + +#### Extensions + +It is possible to create extensions to Jenkins X. An extension is code that runs at specific times in the CI/CD process. An extension can provide code that runs when the extension is installed, uninstalled, as well as before and after each pipeline. + +#### Serverless Jenkins + +Instead of running the Jenkins web application, which continually consumes CPU and memory resources, you can run Jenkins only when you need it. During the past year, the Jenkins community created a version of Jenkins that can run classic Jenkins pipelines via the command line with the configuration defined by code instead of HTML forms. + +This capability is now available in Jenkins X. When you create a Jenkins X cluster, you can choose to use Serverless Jenkins. If you do, Jenkins X will deploy [Prow][15] to handle webhooks from GitHub and [Knative][16] to run Jenkins pipelines. + +### Jenkins X limitations + +Jenkins X also has some limitations that should be considered: + + * **Jenkins X is currently limited to projects that use Git:** Jenkins X is opinionated about CI/CD and assumes everybody wants to run and deploy software to Kubernetes and everybody is happy to use Git for source code and defining environments. Also, the Serverless Jenkins feature currently works only with GitHub. + * **Jenkins X is limited to Kubernetes:** It is true that Jenkins X can run automated builds, testing, and continuous integration for any type of software, but the continuous delivery part targets a Kubernetes namespace managed by Jenkins X. + * **Jenkins X requires cluster-admin level Kubernetes access:** Jenkins X needs cluster-admin access so it can define and manage a Kubernetes custom resource definition. Hopefully, this is a temporary limitation, because it could be a show-stopper for some. + + + +### Conclusions + +Jenkins X looks to be a good way to implement CI/CD for Kubernetes, and I'm looking forward to putting it to the test in production. Using Jenkins X is also a good way to learn about some useful open source tools for deploying to Kubernetes, including Helm, Draft, Skaffold, Prow, and more. These are things you might want to use even if you decide Jenkins X is not for you. If you're deploying to Kubernetes, take Jenkins X for a spin. + +-------------------------------------------------------------------------------- + +via: https://opensource.com/article/18/11/getting-started-jenkins-x + +作者：[Dave Johnson][a] +选题：[lujun9972][b] +译者：[译者ID](https://github.com/译者ID) +校对：[校对者ID](https://github.com/校对者ID) + +本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 + +[a]: https://opensource.com/users/snoopdave +[b]: https://github.com/lujun9972 +[1]: https://jenkins-x.io/ +[2]: https://jenkins.io/ +[3]: https://docs.docker.com/registry/ +[4]: https://github.com/helm/chartmuseum +[5]: https://github.com/helm/monocular +[6]: https://helm.sh +[7]: https://www.sonatype.com/nexus-repository-oss +[8]: https://www.weave.works/blog/gitops-operations-by-pull-request +[9]: https://draft.sh/ +[10]: https://github.com/GoogleContainerTools/skaffold +[11]: /file/414941 +[12]: https://opensource.com/sites/default/files/uploads/jenkinsx_fig1.png (Developer commits changes, project deployed to staging) +[13]: /file/414946 +[14]: https://opensource.com/sites/default/files/uploads/jenkinsx_fig2.png (Promoting project to production) +[15]: https://github.com/kubernetes/test-infra/tree/master/prow +[16]: https://cloud.google.com/knative/ diff --git a/sources/tech/20181127 Bio-Linux- A stable, portable scientific research Linux distribution.md b/sources/tech/20181127 Bio-Linux- A stable, portable scientific research Linux distribution.md new file mode 100644 index 0000000000..a38acec9da --- /dev/null +++ b/sources/tech/20181127 Bio-Linux- A stable, portable scientific research Linux distribution.md @@ -0,0 +1,79 @@ +[#]: collector: (lujun9972) +[#]: translator: ( ) +[#]: reviewer: ( ) +[#]: publisher: ( ) +[#]: subject: (Bio-Linux: A stable, portable scientific research Linux distribution) +[#]: via: (https://opensource.com/article/18/11/bio-linux) +[#]: author: (Matt Calverley https://opensource.com/users/mattcalverley) +[#]: url: ( ) + +Bio-Linux: A stable, portable scientific research Linux distribution +====== +Linux distro's integrated software approach offers powerful bioinformatic data analysis with a familiar look and feel. + + +Bio-Linux was introduced and detailed in a [Nature Biotechnology paper in July 2006][1]. The distribution was a group effort by the Natural Environment Research Council in the UK. As the creators and authors point out, the analysis demands of high-throughput “-omic” (genomic, proteomic, metabolomic) science has necessitated the development of integrated computing solutions to analyze the resultant mountains of experimental data. + +From this need, Bio-Linux was born. The distribution, [according to its creators][2], serves as a “free bioinformatics workstation platform that can be installed on anything from a laptop to a large server.” The current distro version, Bio-Linux 8, is built on an Ubuntu 14.04 LTS base. Thus, the general look and feel of Bio-Linux is similar to that of Ubuntu. + +In my own work as a research immunologist, I can attest to both the need for and success of the integrated software approach in Bio-Linux's design and development. Bio-Linux functions as a true turnkey solution to data pipeline requirements of modern science. As the website mentions, Bio-Linux includes [more than 250 pre-installed software packages][3], many of which are specific to the requirements of bioinformatic data analysis. + +The power of this approach becomes immediately evident when you try to duplicate the software installation process under another operating system. Integrating all software components and installing all required dependencies is immensely time-consuming, and in some instances is not even possible outside of the Linux operating system. The Bio-Linux distro provides a portable, stable, integrated environment with pre-installed software sufficient to begin a vast array of bioinformatic analysis tasks. + +By now you’re probably saying, “I’m sold—how do I get this amazing distro?” + +I’m glad you asked. I'll start by saying that there is excellent documentation on the Bio-Linux website. This [documentation][4] covers both installation instructions and a very thorough overview of using the distro. + +The distro can be installed and run locally, run off a CD/DVD or USB, installed on a server, or run out of a virtual machine environment. To begin the installation process for local installation, [download the disk image or ISO][5] for the Bio-Linux distro. The disk image is a 3.3GB file, and depending on your internet download speed, this may be a good time to get a cup of coffee or take a nice nap. + +Once the ISO has been downloaded, the Bio-Linux developers recommend using [UNetBootin][6], a freely available cross-platform software package used to make bootable USBs. There is a link provided for UNetBootin on the Bio-Linux website. I can attest to the effectiveness of UNetBootin in both Mac and Linux operating systems. + +On Unix family operating systems (Mac OS and Linux), it is also possible to make a bootable USB from the command line using the `dd `command: + +``` +sudo umount “USB location” + +sudo dd bs=4M if=”ISO location” of =”USB location” conv=fdatasync +``` +Regardless of the method you use, this might be another good time for a coffee break. + +At this point in my installation, UNetBootin appeared to freeze at the `squashfs` file transfer during bootable USB creation. However, a quick check of the Ubuntu disks application confirmed that the file was still being written to the USB. In other words, be patient—it takes quite some time to make the bootable USB. + +Once you’ve had your coffee and you have a finished USB in hand, you are ready to use Bio-Linux. As the Bio-Linux website points out, if you are trying to use a bootable USB with a Mac computer (particularly newer hardware versions), you may not be able to boot from the USB. There are workarounds, but they involve configuring the system for dual boot. Likewise, on Windows-based machines, it may be necessary to make changes to the boot order and possibly the secure boot settings for the machine from within BIOS. + +From this point, how you use the distro is up to you. You can run the distro from the USB to test it. You can install the distro to your computer. You can even follow the instructions on the Bio-Linux website to make a VM instance of the distro or run it on a server. Regardless of how you use it, you have a high-powered bioinformatic data analysis workstation at your disposal. + +Maybe you have a professional need for such a workstation, but even if you never use Bio-Linux as a professional researcher, it could provide a great resource for biology teaching professionals at all levels to introduce students to modern bioinformatics principles. For the price of a laptop and a USB, every school can have an in silico teaching resource to complement classroom lessons in the “-omics” age. Your only limitations are your creativity and the performance of your hardware. + +### More on Linux + +As an open source operating system with strong community support, the Linux kernel shares many of the strengths common to other successful open source software endeavors. Linux tends to be both stable and amenable to customization. It is also fairly hardware-agnostic, capable of running alongside other operating systems on a wide array of hardware configurations. In fact, installing Linux is a common method of regaining usability from dated hardware that is incapable of running other modern operating systems. Linux is also highly portable and can be run from any bootable external storage device, such as a USB drive, without the need to permanently install the operating system. + +It is this combination of stability, customizability, and portability that initially drew me to Linux. Each Linux operating system variant is referred to as a distribution (or distro), and it seems as though there is a Linux distribution for every imaginable computing scenario or desire. The options can actually be rather intimidating, and I suspect they may often discourage people from trying Linux. + +“How many different distributions can there possibly be?” you might wonder. If you have a few minutes, or even a few hours, have a look at [DistroWatch.com][7]. As its name implies, this site is devoted to the cataloging of all things Linux distribution-related. For visual learners, there is an amazing [Linux family tree][8] that really puts it into perspective. + +While [entire books][9] are devoted to the topic of Linux distributions, the differences often depend on what software is included in the base installation, how the software is managed, and graphical differences affecting the “look and feel” of the distribution. Certainly, there are also subtleties of hardware compatibility, speed, and stability. + +-------------------------------------------------------------------------------- + +via: https://opensource.com/article/18/11/bio-linux + +作者：[Matt Calverley][a] +选题：[lujun9972][b] +译者：[译者ID](https://github.com/译者ID) +校对：[校对者ID](https://github.com/校对者ID) + +本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 + +[a]: https://opensource.com/users/mattcalverley +[b]: https://github.com/lujun9972 +[1]: https://www.nature.com/articles/nbt0706-801 +[2]: http://environmentalomics.org/bio-linux/ +[3]: http://environmentalomics.org/bio-linux-software-list/ +[4]: http://nebc.nerc.ac.uk/downloads/courses/Bio-Linux/bl8_latest.pdf +[5]: http://environmentalomics.org/bio-linux-download/ +[6]: https://unetbootin.github.io/ +[7]: https://distrowatch.com/ +[8]: https://distrowatch.com/images/other/distro-family-tree.png +[9]: https://www.amazon.com/Introducing-Linux-Distros-Dieguez-Castro/dp/1484213939 diff --git a/sources/tech/20181128 Building custom documentation workflows with Sphinx.md b/sources/tech/20181128 Building custom documentation workflows with Sphinx.md new file mode 100644 index 0000000000..7d9137fa40 --- /dev/null +++ b/sources/tech/20181128 Building custom documentation workflows with Sphinx.md @@ -0,0 +1,126 @@ +[#]: collector: (lujun9972) +[#]: translator: ( ) +[#]: reviewer: ( ) +[#]: publisher: ( ) +[#]: subject: (Building custom documentation workflows with Sphinx) +[#]: via: (https://opensource.com/article/18/11/building-custom-workflows-sphinx) +[#]: author: ([Mark Meyer](https://opensource.com/users/ofosos)) +[#]: url: ( ) + +Building custom documentation workflows with Sphinx +====== +Create documentation the way that works best for you. + + +[Sphinx][1] is a popular application for creating documentation, similar to JavaDoc or Jekyll. However, Sphinx's reStructured Text input allows for a higher degree of customization than those other tools. + +This tutorial will explain how to customize Sphinx to suit your workflow. You can follow along using sample code on [GitHub][2]. + +### Some definitions + +Sphinx goes far beyond just enabling you to style text with predefined tags. It allows you to shape and automate your documentation by defining new roles and directives. A role is a single word element that usually is rendered inline in your documentation, while a directive can contain more complex content. These can be contained in a domain. + +A Sphinx domain is a collection of directives and roles as well as a few other things, such as an index definition. Your next Sphinx domain could be a specific programming language (Sphinx was developed to create Python's documentation). Or you might have a command line tool that implements the same command pattern (e.g., **tool \--args**) over and over. You can document it with a custom domain, adding directives and indexes along the way. + +Here's an example from our **recipe** domain: + +``` +The recipe contains `tomato` and `cilantro`. + +.. rcp:recipe:: TomatoSoup + :contains: tomato cilantro salt pepper + + This recipe is a tasty tomato soup, combine all ingredients + and cook. +``` + +Now that we've defined the recipe **TomatoSoup** , we can reference it anywhere in our documentation using the custom role **refef**. For example: + +``` +You can use the :rcp:reref:`TomatoSoup` recipe to feed your family. +``` + +This enables our recipes to show up in two indices: the first lists all recipes, and the second lists all recipes by ingredient. + +### What's in a domain? + +A Sphinx domain is a specialized container that ties together roles, directives, and indices, among other things. The domain has a name ( **rcp** ) to address its components in the documentation source. It announces its existence to Sphinx in the **setup()** method of the package. From there, Sphinx can find roles and directives, since these are part of the domain. + +This domain also serves as the central catalog of objects in this sample. Using initial data, it defines two variables, **objects** and **obj2ingredient**. These contain a list of all objects defined (all recipes) and a hash that maps a canonical ingredient name to the list of objects. + +``` +initial_data = { + 'objects': [], # object list + 'obj2ingredient': {}, # ingredient -> [objects] +} +``` + +The way we name objects is common across our extension. For each object created, the canonical name is **rcp. . **, where **< typename>** is the Python type of the object, and **< objectname>** is the name the documentation writer gives the object. This enables the extension to use different object types that share the same name. + +Having a canonical name and central place for our objects is a huge advantage. Both our indices and our cross-referencing code use this feature. + +### Custom roles and directives + +In our example, **.. rcp:recipe::** indicates a custom directive. You might think it's overly specific to create custom syntax for these items, but it illustrates the degree of customization you can get in Sphinx. This provides rich markup that structures documents and leads to better docs. Specialization allows us to extract information from our docs. + +Our definition for this directive will provide minimal formatting, but it will be functional. + +``` +class RecipeNode(ObjectDescription): + """A custom node that describes a recipe.""" + + required_arguments = 1 + + option_spec = { + 'contains': rst.directives.unchanged_required + } +``` + +For this directive, **required_arguments** tells Sphinx to expect one parameter, the recipe name. **option_spec** lists the optional arguments, including their names. Finally, **has_content** specifies that there will be more reStructured Text as a child to this node. + +We also implement multiple methods: + + * **handle_signature()** implements parsing the signature of the directive and passes on the object's name and type to its superclass + * **add_taget_and_index()** adds a target (to link to) and an entry to the index for this node + + + +### Creating indices + +Both **IngredientIndex** and **RecipeIndex** are derived from Sphinx's **Index** class. They implement custom logic to generate a tuple of values that define the index. Note that **RecipeIndex** is a degenerate index that has only one entry. Extending it to cover more object types—and moving from a **RecipeDomain** to a **CookbookDomain** —is not yet part of the code. + +Both indices use the method **generate()** to do their work. This method combines the information from our domain, sorts it, and returns it in a list structure that will be accepted by Sphinx. See the [Sphinx Domain API][3] page for more information. + +The first time you visit the Domain API page, you may be a little overwhelmed by the structure. But our ingredient index is just a list of tuples, like **('tomato', 'TomatoSoup', 'test', 'rec-TomatoSoup',...)**. + +### Referencing recipes + +Adding cross-references is not difficult (but it's also not a given). Add an **XRefRole** to the domain and implement the method **resolve_xref()**. Having a custom role to reference a type allows us to unambiguously reference any object, even if two objects have the same name. If you look at the parameters of **resolve_xref()** in **Domain** , you'll see **typ** and **target**. These define the cross-reference type and its target name. We'll use **target** to resolve our destination from our domain's **objects** because we currently have only one type of node. + +We can add the cross-reference role to **RecipeDomain** in the following way: + +``` +roles = { + 'reref': XRefRole() +} +``` + +There's nothing for us to implement. Defining a working **resolve_xref()** and attaching an **XRefRole** to the domain is all you need to do. + + +-------------------------------------------------------------------------------- + +via: https://opensource.com/article/18/11/building-custom-workflows-sphinx + +作者：[Mark Meyer][a] +选题：[lujun9972][b] +译者：[译者ID](https://github.com/译者ID) +校对：[校对者ID](https://github.com/校对者ID) + +本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 + +[a]: https://opensource.com/users/ofosos +[b]: https://github.com/lujun9972 +[1]: http://www.sphinx-doc.org/en/master/ +[2]: https://github.com/ofosos/sphinxrecipes +[3]: https://www.sphinx-doc.org/en/master/extdev/domainapi.html#sphinx.domains.Index.generate diff --git a/sources/tech/20181128 How to test your network with PerfSONAR.md b/sources/tech/20181128 How to test your network with PerfSONAR.md new file mode 100644 index 0000000000..9e9e66ef62 --- /dev/null +++ b/sources/tech/20181128 How to test your network with PerfSONAR.md @@ -0,0 +1,148 @@ +[#]: collector: (lujun9972) +[#]: translator: ( ) +[#]: reviewer: ( ) +[#]: publisher: ( ) +[#]: subject: (How to test your network with PerfSONAR) +[#]: via: (https://opensource.com/article/18/11/how-test-your-network-perfsonar) +[#]: author: (Jessica Repka https://opensource.com/users/jrepka) +[#]: url: ( ) + +How to test your network with PerfSONAR +====== +Set up a single-node configuration to measure your network performance. + + +[PerfSONAR][1] is a network measurement toolkit collection for testing and sharing data on end-to-end network perfomance. + +The overall benefit of using network measurement tools like PerfSONAR is they can find issues before they become a large elephant in the room that nobody wants to talk about. Specifically, with the right answers from the right tools, patching can become more stringent, network traffic can be shaped to speed connections across the board, and the network infrastructure design can be improved. + +PerfSONAR is licensed under the open source Apache 2.0 license, which makes it more affordable than most tools that do this type of analysis, a key advantage given constrained network infrastructure budgets. + +### PerfSONAR versions + +Several versions of PerfSONAR are available: + + * **Perfsonar-tools:** The command line client version meant for on-demand testing. + * **Perfsonar-testpoint:** Adds automated testing and central management testing to PerfSONAR-tools. It has an archiving feature, but the archive must be set to an external node. + * **Perfsonar-core:** Includes everything in the testpoint software, but with local rather than external archiving. + * **Perfsonar-toolkit:** The core software; it includes a web UI with systemwide security settings. + * **Perfsonar-centralmanagement:** A completely separate version of PerfSONAR that uses mass grids of nodes to display results. It also has a feature to push out task templates to every node that is sending measurements back to the central host. + + + +This tutorial will use **PerfSonar-toolkit** ; the tools used in this software include [iPerf, iPerf3][2], and [OWAMP][3]. + +### Requirements + + * **Recommended operating system:** CentOS/RHEL7 + * **ISO:** [Downloading][4] the full installation ISO is the fastest way to get the software up and running. While there is a [Debian version][5], it is much harder and more complicated to use. + * **Minimum hardware requirements:** 2 cores and 4GB RAM + * **Recommended hardware:** 200GB HDD, 4 cores, 6GB of RAM + + + +### Installing and configuring PerfSONAR + +The installation is a quick CentOS install where you pick your timezone and configuration for the hard drive and user. I suggest using hard drive autoconfiguration, as you only need to choose "Install Toolkit" and follow the prompts from there. + +Select your language. + +Select a destination. + +After base installation, you see the Linux login screen. + +After you log in, you are prompted to create a user ID and password to log into PerfSONAR's web frontend—make sure to remember your login information. + +You're also asked to disable SSH access for root and create a new user for sudo; just follow the steps to create the new user. + +You can use a provisioning service to automatically provide an IP address and hostname. Otherwise, you will have to set the hostname (optional) and configure the IP address. + +### Log into the web frontend + +Once the base configuration is complete, you can log into the web frontend via ** Scribus Online Manual + ++
+ + + ++ +
+
+
++``` + +For more options and usage details, refer the help secion: + +``` +$ hyperfine --help +``` + +And, that’s all for now. If you ever be in a situation where you need to benchmark similar and alternative programs, these tools might help to compare how they performs and share the details with your peers and colleagues. + +More good stuffs to come. Stay tuned! + +Cheers! + + + +-------------------------------------------------------------------------------- + +via: https://www.ostechnix.com/how-to-benchmark-linux-commands-and-programs-from-commandline/ + +作者：[SK][a] +选题：[lujun9972][b] +译者：[译者ID](https://github.com/译者ID) +校对：[校对者ID](https://github.com/校对者ID) + +本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 + +[a]: https://www.ostechnix.com/author/sk/ +[b]: https://github.com/lujun9972 +[1]: https://www.ostechnix.com/some-alternatives-to-top-command-line-utility-you-might-want-to-know/ +[2]: https://aur.archlinux.org/packages/hyperfine +[3]: https://www.ostechnix.com/yay-found-yet-another-reliable-aur-helper/ +[4]: https://github.com/sharkdp/hyperfine/releases diff --git a/sources/tech/20181213 Podman and user namespaces- A marriage made in heaven.md b/sources/tech/20181213 Podman and user namespaces- A marriage made in heaven.md new file mode 100644 index 0000000000..adc14c6111 --- /dev/null +++ b/sources/tech/20181213 Podman and user namespaces- A marriage made in heaven.md @@ -0,0 +1,145 @@ +[#]: collector: (lujun9972) +[#]: translator: ( ) +[#]: reviewer: ( ) +[#]: publisher: ( ) +[#]: url: ( ) +[#]: subject: (Podman and user namespaces: A marriage made in heaven) +[#]: via: (https://opensource.com/article/18/12/podman-and-user-namespaces) +[#]: author: (Daniel J Walsh https://opensource.com/users/rhatdan) + +Podman and user namespaces: A marriage made in heaven +====== +Learn how to use Podman to run containers in separate user namespaces. + + +[Podman][1], part of the [libpod][2] library, enables users to manage pods, containers, and container images. In my last article, I wrote about [Podman as a more secure way to run containers][3]. Here, I'll explain how to use Podman to run containers in separate user namespaces. + +I have always thought of [user namespace][4], primarily developed by Red Hat's Eric Biederman, as a great feature for separating containers. User namespace allows you to specify a user identifier (UID) and group identifier (GID) mapping to run your containers. This means you can run as UID 0 inside the container and UID 100000 outside the container. If your container processes escape the container, the kernel will treat them as UID 100000. Not only that, but any file object owned by a UID that isn't mapped into the user namespace will be treated as owned by "nobody" (65534, kernel.overflowuid), and the container process will not be allowed access unless the object is accessible by "other" (world readable/writable). + +If you have a file owned by "real" root with permissions [660][5], and the container processes in the user namespace attempt to read it, they will be prevented from accessing it and will see the file as owned by nobody. + +### An example + +Here's how that might work. First, I create a file in my system owned by root. + +``` +$ sudo bash -c "echo Test > /tmp/test" +$ sudo chmod 600 /tmp/test +$ sudo ls -l /tmp/test +-rw-------. 1 root root 5 Dec 17 16:40 /tmp/test +``` + +Next, I volume-mount the file into a container running with a user namespace map 0:100000:5000. + +``` +$ sudo podman run -ti -v /tmp/test:/tmp/test:Z --uidmap 0:100000:5000 fedora sh +# id +uid=0(root) gid=0(root) groups=0(root) +# ls -l /tmp/test +-rw-rw----. 1 nobody nobody 8 Nov 30 12:40 /tmp/test +# cat /tmp/test +cat: /tmp/test: Permission denied +``` + +The **\--uidmap** setting above tells Podman to map a range of 5000 UIDs inside the container, starting with UID 100000 outside the container (so the range is 100000-104999) to a range starting at UID 0 inside the container (so the range is 0-4999). Inside the container, if my process is running as UID 1, it is 100001 on the host + +Since the real UID=0 is not mapped into the container, any file owned by root will be treated as owned by nobody. Even if the process inside the container has **CAP_DAC_OVERRIDE** , it can't override this protection. **DAC_OVERRIDE** enables root processes to read/write any file on the system, even if the process was not owned by root or world readable or writable. + +User namespace capabilities are not the same as capabilities on the host. They are namespaced capabilities. This means my container root has capabilities only within the container—really only across the range of UIDs that were mapped into the user namespace. If a container process escaped the container, it wouldn't have any capabilities over UIDs not mapped into the user namespace, including UID=0. Even if the processes could somehow enter another container, they would not have those capabilities if the container uses a different range of UIDs. + +Note that SELinux and other technologies also limit what would happen if a container process broke out of the container. + +### Using `podman top` to show user namespaces + +We have added features to **podman top** to allow you to examine the usernames of processes running inside a container and identify their real UIDs on the host. + +Let's start by running a sleep container using our UID mapping. + +``` +$ sudo podman run --uidmap 0:100000:5000 -d fedora sleep 1000 +``` + +Now run **podman top** : + +``` +$ sudo podman top --latest user huser +USER HUSER +root 100000 + +$ ps -ef | grep sleep +100000 21821 21809 0 08:04 ? 00:00:00 /usr/bin/coreutils --coreutils-prog-shebang=sleep /usr/bin/sleep 1000 +``` + +Notice **podman top** reports that the user process is running as root inside the container but as UID 100000 on the host (HUSER). Also the **ps** command confirms that the sleep process is running as UID 100000. + +Now let's run a second container, but this time we will choose a separate UID map starting at 200000. + +``` +$ sudo podman run --uidmap 0:200000:5000 -d fedora sleep 1000 +$ sudo podman top --latest user huser +USER HUSER +root 200000 + +$ ps -ef | grep sleep +100000 21821 21809 0 08:04 ? 00:00:00 /usr/bin/coreutils --coreutils-prog-shebang=sleep /usr/bin/sleep 1000 +200000 23644 23632 1 08:08 ? 00:00:00 /usr/bin/coreutils --coreutils-prog-shebang=sleep /usr/bin/sleep 1000 +``` + +Notice that **podman top** reports the second container is running as root inside the container but as UID=200000 on the host. + +Also look at the **ps** command—it shows both sleep processes running: one as 100000 and the other as 200000. + +This means running the containers inside separate user namespaces gives you traditional UID separation between processes, which has been the standard security tool of Linux/Unix from the beginning. + +### Problems with user namespaces + +For several years, I've advocated user namespace as the security tool everyone wants but hardly anyone has used. The reason is there hasn't been any filesystem support or a shifting file system. + +In containers, you want to share the **base** image between lots of containers. The examples above use the Fedora base image in each example. Most of the files in the Fedora image are owned by real UID=0. If I run a container on this image with the user namespace 0:100000:5000, by default it sees all of these files as owned by nobody, so we need to shift all of these UIDs to match the user namespace. For years, I've wanted a mount option to tell the kernel to remap these file UIDs to match the user namespace. Upstream kernel storage developers continue to investigate and make progress on this feature, but it is a difficult problem. + + +Podman can use different user namespaces on the same image because of automatic [chowning][6] built into [containers/storage][7] by a team led by Nalin Dahyabhai. Podman uses containers/storage, and the first time Podman uses a container image in a new user namespace, container/storage "chowns" (i.e., changes ownership for) all files in the image to the UIDs mapped in the user namespace and creates a new image. Think of this as the **fedora:0:100000:5000** image. + +When Podman runs another container on the image with the same UID mappings, it uses the "pre-chowned" image. When I run the second container on 0:200000:5000, containers/storage creates a second image, let's call it **fedora:0:200000:5000**. + +Note if you are doing a **podman build** or **podman commit** and push the newly created image to a container registry, Podman will use container/storage to reverse the shift and push the image with all files chowned back to real UID=0. + +This can cause a real slowdown in creating containers in new UID mappings since the **chown** can be slow depending on the number of files in the image. Also, on a normal [OverlayFS][8], every file in the image gets copied up. The normal Fedora image can take up to 30 seconds to finish the chown and start the container. + +Luckily, the Red Hat kernel storage team, primarily Vivek Goyal and Miklos Szeredi, added a new feature to OverlayFS in kernel 4.19. The feature is called **metadata only copy-up**. If you mount an overlay filesystem with **metacopy=on** as a mount option, it will not copy up the contents of the lower layers when you change file attributes; the kernel creates new inodes that include the attributes with references pointing at the lower-level data. It will still copy up the contents if the content changes. This functionality is available in the Red Hat Enterprise Linux 8 Beta, if you want to try it out. + +This means container chowning can happen in a couple of seconds, and you won't double the storage space for each container. + +This makes running containers with tools like Podman in separate user namespaces viable, greatly increasing the security of the system. + +### Going forward + +I want to add a new flag, like **\--userns=auto** , to Podman that will tell it to automatically pick a unique user namespace for each container you run. This is similar to the way SELinux works with separate multi-category security (MCS) labels. If you set the environment variable **PODMAN_USERNS=auto** , you won't even need to set the flag. + +Podman is finally allowing users to run containers in separate user namespaces. Tools like [Buildah][9] and [CRI-O][10] will also be able to take advantage of user namespaces. For CRI-O, however, Kubernetes needs to understand which user namespace will run the container engine, and the upstream is working on that. + +In my next article, I will explain how to run Podman as non-root in a user namespace. + +-------------------------------------------------------------------------------- + +via: https://opensource.com/article/18/12/podman-and-user-namespaces + +作者：[Daniel J Walsh][a] +选题：[lujun9972][b] +译者：[译者ID](https://github.com/译者ID) +校对：[校对者ID](https://github.com/校对者ID) + +本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 + +[a]: https://opensource.com/users/rhatdan +[b]: https://github.com/lujun9972 +[1]: https://podman.io/ +[2]: https://github.com/containers/libpod +[3]: https://opensource.com/article/18/10/podman-more-secure-way-run-containers +[4]: http://man7.org/linux/man-pages/man7/user_namespaces.7.html +[5]: https://chmodcommand.com/chmod-660/ +[6]: https://en.wikipedia.org/wiki/Chown +[7]: https://github.com/containers/storage +[8]: https://en.wikipedia.org/wiki/OverlayFS +[9]: https://buildah.io/ +[10]: http://cri-o.io/ diff --git a/sources/tech/20181214 Tips for using Flood Element for performance testing.md b/sources/tech/20181214 Tips for using Flood Element for performance testing.md new file mode 100644 index 0000000000..90994b0724 --- /dev/null +++ b/sources/tech/20181214 Tips for using Flood Element for performance testing.md @@ -0,0 +1,180 @@ +[#]: collector: (lujun9972) +[#]: translator: ( ) +[#]: reviewer: ( ) +[#]: publisher: ( ) +[#]: url: ( ) +[#]: subject: (Tips for using Flood Element for performance testing) +[#]: via: (https://opensource.com/article/18/12/tips-flood-element-testing) +[#]: author: (Nicole van der Hoeven https://opensource.com/users/nicolevanderhoeven) + +Tips for using Flood Element for performance testing +====== +Get started with this powerful, intuitive load testing tool. + + +In case you missed it, there’s a new performance test tool on the block: [Flood Element][1]. It’s a scalable, browser-based tool that allows you to write scripts in JavaScript that interact with web pages like a real user would. + +Browser Level Users is a [newer approach to load testing][2] that overcomes many of the common challenges we hear about traditional methods of testing. It offers: + + * Scripting that is akin to common functional tools like Selenium and easier to learn + * More realistic results that are based on true browser performance rather than API response + * The ability to test against all components of your web app, including things like JavaScript that are rendered via the browser + + + +Given the above benefits, it’s a no-brainer to check out Flood Element for your web load testing, especially if you have struggled with existing tools like JMeter or HP LoadRunner. + +Pairing Element with [Flood][3] turns it into a pretty powerful load test tool. We have a [great guide here][4] that you can follow if you’d like to get started. I’ve been using and testing Element for several months now, and I’d like to share some tips I’ve learned along the way. + +### Initializing your script + +You can always start from scratch, but the quickest way to get started is to type `element init myfirstelementtest` from your terminal, filling in your preferred project name. + +You’ll then be asked to type the title of your test as well as the URL you’d like to script against. After a minute, you’ll see that a new directory has been created: + + + +Element will automatically create a file called **test.ts**. This file contains the skeleton of a script, along with some sample code to help you find a button and then click on it. But before you open it, let’s move on to… + +### Choosing the right text editor + +Scripting in Element is already pretty simple, but two things that help are syntax highlighting and code completion. Syntax highlighting will greatly improve the experience of learning a new test tool like Element, and code completion will make your scripting lightning-fast as you become more experienced. My text editor of choice is [Visual Studio Code][5], which has both of those features. It’s slick and clean, and it does the job. + +Syntax highlighting is when the text editor intelligently changes the font color of your code according to its role in the programming language you’re using. Here’s a screenshot of the **test.ts** file we generated earlier in VS Code to show you what I mean: + + + +This makes it easier to make sense of the code at a glance: Comments are in green, values and labels are in orange, etc. + +Code completion is when you start to type something, and VS Code helpfully opens a context menu with suggestions for methods you can use. + +![][6] + +I love this because it means I don’t need to remember the exact name of the method. It also suggests names of variables you’ve already defined and highlights code that doesn’t make sense. This will help to make your tests more maintainable and readable for others, which is a great benefit as you look to scale your testing out in the future. + + + +### Taking screenshots + +One of the most powerful features of Element is its ability to take screenshots. I find it immensely useful when debugging because sometimes it’s just easier to see what’s going on visually. With protocol-based tools, debugging can be a much more involved and technical process. + +There are two ways to take screenshots in Element: + + 1. Add a setting to automatically take a screenshot when an error is encountered. You can do this by setting `screenshotOnFailure` to "true" in `TestSettings`: + + + +``` +export const settings: TestSettings = { + device: Device.iPadLandscape, + userAgent: 'flood-chrome-test', + clearCache: true, + disableCache: true, + screenshotOnFailure: true, +} +``` + + 2. Explicitly take a screenshot at a particular point in the script. You can do this by adding + + + +``` +await browser.takeScreenshot() +``` + +to your code. + +### Viewing screenshots + +Once you’ve taken screenshots within your tests, you will probably want to view them and know that they will be stored for future safekeeping. Whether you are running your test locally on have uploaded it to Flood to run with increased concurrency, Flood Element has you covered. + +**Locally run tests** + +Screenshots will be saved as .jpg files in a timestamped folder corresponding to your run. It should look something like this: **…myfirstelementtest/tmp/element-results/test/2018-11-20T135700.595Z/flood/screenshots/**. The screenshots will be uniquely named so that new screenshots, even for the same step, don’t overwrite older ones. + +However, I rarely need to look up the screenshots in that folder because I prefer to see them in iTerm2 for MacOS. iTerm is an alternative to the terminal that works particularly well with Element. When you take a screenshot, iTerm actually shows it in-line: + + + +**Tests run in Flood** + +Running an Element script on Flood is ideal when you need larger concurrency. Rather than accessing your screenshot locally, Flood will centralize the images into your account, so the images remain even after the cloud load injectors are destroyed. You can get to the screenshot files by downloading Archived Results: + + + +You can also click on a step on the dashboard to see a filmstrip of your test: + + + +### Using logs + +You may need to check out the logs for more technical debugging, especially when the screenshots don’t tell the whole story. Again, whether you are running your test locally or have uploaded it to Flood to run with increased concurrency, Flood Element has you covered. + +**Locally run tests** + +You can print to the console by typing, for example: `console.log('orderValues = ’ + orderValues)` + +This will print the value of the variable `orderValues` at that point in the script. You would see this in your terminal if you’re running Element locally. + +**Tests run in Flood** + +If you’re running the script on Flood, you can either download the log (in the same Archived Results zipped file mentioned earlier) or click on the Logs tab: + + + +### Fun with flags + +Element comes with a few flags that give you more control over how the script is run locally. Here are a few of my favorites: + +**Headless flag** + +When in doubt, run Element in non-headless mode to see the script actually opening the web app on Chrome and interacting with the page. This is only possible locally, but there’s nothing like actually seeing for yourself what’s happening in real time instead of relying on screenshots and logs after the fact. To enable this mode, add the flag when running your test: + +``` +element run myfirstelementtest.ts --no-headless +``` + +**Watch flag** + +Element will automatically close the browser window when it encounters an error or finishes the iteration. Adding `--watch` will leave the browser window open and then monitor the script. As soon as the script is saved, it will automatically run it in the same window from the beginning. Simply add this flag like the above example: + +``` +--watch +``` + +**Dev tools flag** + +This opens a browser instance and runs the script with the Chrome Dev Tools open, allowing you to find locators for the next action you want to script. Simply add this flag as in the first example: + +``` +--dev-tools +``` + +For more flags, use `element run --help`. + +### Try Element + +You’ve just gotten a crash course on Flood Element and are ready to get started. [Download Element][1] to start writing functional test scripts and reusing them as load test scripts on Flood. If you don’t have a Flood account, you can easily sign up for a free trial [on the Flood website][7]. + +We’re proud to contribute to the open source community and can’t wait to have you try this new addition to the Flood line. + +-------------------------------------------------------------------------------- + +via: https://opensource.com/article/18/12/tips-flood-element-testing + +作者：[Nicole van der Hoeven][a] +选题：[lujun9972][b] +译者：[译者ID](https://github.com/译者ID) +校对：[校对者ID](https://github.com/校对者ID) + +本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 + +[a]: https://opensource.com/users/nicolevanderhoeven +[b]: https://github.com/lujun9972 +[1]: https://element.flood.io/ +[2]: https://flood.io/blog/why-you-should-load-test-with-browsers/ +[3]: https://flood.io/ +[4]: https://help.flood.io/getting-started-with-load-testing/step-by-step-guide-flood-element +[5]: https://code.visualstudio.com/ +[6]: https://flood.io/wp-content/uploads/2018/11/vscode-codecompletion2.gif +[7]: https://flood.io/load-performance-testing-tool/free-load-testing-trial/ diff --git a/sources/tech/20181217 6 tips and tricks for using KeePassX to secure your passwords.md b/sources/tech/20181217 6 tips and tricks for using KeePassX to secure your passwords.md new file mode 100644 index 0000000000..ad688a7820 --- /dev/null +++ b/sources/tech/20181217 6 tips and tricks for using KeePassX to secure your passwords.md @@ -0,0 +1,78 @@ +[#]: collector: (lujun9972) +[#]: translator: ( ) +[#]: reviewer: ( ) +[#]: publisher: ( ) +[#]: url: ( ) +[#]: subject: (6 tips and tricks for using KeePassX to secure your passwords) +[#]: via: (https://opensource.com/article/18/12/keepassx-security-best-practices) +[#]: author: (Michael McCune https://opensource.com/users/elmiko) + +6 tips and tricks for using KeePassX to secure your passwords +====== +Get more out of your password manager by following these best practices. + + +Our increasingly interconnected digital world makes security an essential and common discussion topic. We hear about [data breaches][1] with alarming regularity and are often on our own to make informed decisions about how to use technology securely. Although security is a deep and nuanced topic, there are some easy daily habits you can keep to reduce your attack surface. + +Securing passwords and account information is something that affects anyone today. Technologies like [OAuth][2] help make our lives simpler by reducing the number of accounts we need to create, but we are still left with a staggering number of places where we need new, unique information to keep our records secure. An easy way to deal with the increased mental load of organizing all this sensitive information is to use a password manager like [KeePassX][3]. + +In this article, I will explain the importance of keeping your password information secure and offer suggestions for getting the most out of KeePassX. For an introduction to KeePassX and its features, I highly recommend Ricardo Frydman's article "[Managing passwords in Linux with KeePassX][4]." + +### Why are unique passwords important? + +Using a different password for each account is the first step in ensuring that your accounts are not vulnerable to shared information leaks. Generating new credentials for every account is time-consuming, and it is extremely common for people to fall into the trap of using the same password on several accounts. The main problem with reusing passwords is that you increase the number of accounts an attacker could access if one of them experiences a credential breach. + +It may seem like a burden to create new credentials for each account, but the few minutes you spend creating and recording this information will pay for itself many times over in the event of a data breach. This is where password management tools like KeePassX are invaluable for providing convenience and reliability in securing your logins. + +### 3 tips for getting the most out of KeePassX + +I have been using KeePassX to manage my password information for many years, and it has become a primary resource in my digital toolbox. Overall, it's fairly simple to use, but there are a few best practices I've learned that I think are worth highlighting. + + 1. Add the direct login URL for each account entry. KeePassX has a very convenient shortcut to open the URL listed with an entry. (It's Control+Shift+U on Linux.) When creating a new account entry for a website, I spend some time to locate the site's direct login URL. Although most websites have a login widget in their navigation toolbars, they also usually have direct pages for login forms. By putting this URL into the URL field on the account entry setup form, I can use the shortcut to directly open the login page in my browser. + + + + 2. Use the Notes field to record extra security information. In addition to passwords, most websites will ask several questions to create additional authentication factors for an account. I use the Notes sections in my account entries to record these additional factors. + + + + 3. Turn on automatic database locking. In the **Application Settings** under the **Tools** menu, there is an option to lock the database after a period of inactivity. Enabling this option is a good common-sense measure, similar to enabling a password-protected screen lock, that will help ensure your password database is not left open and unprotected if someone else gains access to your computer. + + + +### Food for thought + +Protecting your accounts with better password practices and daily habits is just the beginning. Once you start using a password manager, you need to consider issues like protecting the password database file and ensuring you don't forget or lose the master credentials. + +The cloud-native world of disconnected devices and edge computing makes having a central password store essential. The practices and methodologies you adopt will help minimize your risk while you explore and work in the digital world. + + 1. Be aware of retention policies when storing your database in the cloud. KeePassX's database has an open format used by several tools on multiple platforms. Sooner or later, you will want to transfer your database to another device. As you do this, consider the medium you will use to transfer the file. The best option is to use some sort of direct transfer between devices, but this is not always convenient. Always think about where the database file might be stored as it winds its way through the information superhighway; an email may get cached on a server, an object store may move old files to a trash folder. Learn about these interactions for the platforms you are using before deciding where and how you will share your database file. + + 2. Consider the source of truth for your database while you're making edits. After you share your database file between devices, you might need to create accounts for new services or change information for existing services while using a device. To ensure your information is always correct across all your devices, you need to make sure any edits you make on one device end up in all copies of the database file. There is no easy solution to this problem, but you might think about making all edits from a single device or storing the master copy in a location where all your devices can make edits. + + 3. Do you really need to know your passwords? This is more of a philosophical question that touches on the nature of memorable passwords, convenience, and secrecy. I hardly look at passwords as I create them for new accounts; in most cases, I don't even click the "Show Password" checkbox. There is an idea that you can be more secure by not knowing your passwords, as it would be impossible to compel you to provide them. This may seem like a worrisome idea at first, but consider that you can recover or reset passwords for most accounts through alternate verification methods. When you consider that you might want to change your passwords on a semi-regular basis, it almost makes more sense to treat them as ephemeral information that can be regenerated or replaced. + + + + +Here are a few more ideas to consider as you develop your best practices. + +I hope these tips and tricks have helped expand your knowledge of password management and KeePassX. You can find tools that support the KeePass database format on nearly every platform. If you are not currently using a password manager or have never tried KeePassX, I highly recommend doing so now! + +-------------------------------------------------------------------------------- + +via: https://opensource.com/article/18/12/keepassx-security-best-practices + +作者：[Michael McCune][a] +选题：[lujun9972][b] +译者：[译者ID](https://github.com/译者ID) +校对：[校对者ID](https://github.com/校对者ID) + +本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 + +[a]: https://opensource.com/users/elmiko +[b]: https://github.com/lujun9972 +[1]: https://vigilante.pw/ +[2]: https://en.wikipedia.org/wiki/OAuth +[3]: https://www.keepassx.org/ +[4]: https://opensource.com/business/16/5/keepassx diff --git a/sources/tech/20181218 Insync- The Hassleless Way of Using Google Drive on Linux.md b/sources/tech/20181218 Insync- The Hassleless Way of Using Google Drive on Linux.md new file mode 100644 index 0000000000..c10e7ae4ed --- /dev/null +++ b/sources/tech/20181218 Insync- The Hassleless Way of Using Google Drive on Linux.md @@ -0,0 +1,137 @@ +[#]: collector: (lujun9972) +[#]: translator: ( ) +[#]: reviewer: ( ) +[#]: publisher: ( ) +[#]: url: ( ) +[#]: subject: (Insync: The Hassleless Way of Using Google Drive on Linux) +[#]: via: (https://itsfoss.com/insync-linux-review/) +[#]: author: (Abhishek Prakash https://itsfoss.com/author/abhishek/) + +Insync: The Hassleless Way of Using Google Drive on Linux +====== + +Using Google Drive on Linux is a pain and you probably already know that. There is no official desktop client of Google Drive for Linux. It’s been [more than six years since Google promised Google Drive on Linux][1] but it doesn’t seem to be happening. + +In the absence of the official Google Drive client on Linux, you have no option other than trying the alternatives. I have already discussed a number of [tools that allow you to use Google Drive on Linux][2]. One of those to[ols is][3] Insync, and in my opinion, this is your best bet for a native Google Drive experience on desktop Linux. + +Note that Insync is not an open source software. Heck, it is not even free to use. + +But it has so many features that it becomes an essential tool for those Linux users who rely heavily on Google Drive. + +I briefly discussed Insync in the old article about [Google Drive and Linux][2]. In this article, I’ll discuss Insync features in detail. + +### Insync brings native Google Drive experience to Linux desktop + +![Use insync to access Google Drive in Linux][4] + +The core competency of Insync is syncing your Google Drive, but the app is much more than that. It has features to help you maximize and control your productivity, your Google Drive and your files such as: + + * Cross-platform access (supports Linux, Windows and macOS) + * Easy multiple Google Drive accounts access + * Choose your syncing location. Sync files to your hard drive, external drives and NAS! + * Support for features like file matching, symlink and ignore list + + + +Let me show you some of the main features in action: + +#### Cross-platform in true sense + +Insync claims to run the same app across all operating systems i.e., Linux, Windows, and macOS. That means that you can access the same UI across different OSes, making it easy for you to manage your files across multiple machines. + +![The UI of Insync and the default location of the Insync folder.][5]The UI of Insync and the default location of the Insync folder. + +#### Multiple Google account management + +Insync interface allows you to manage multiple Google Drive accounts seamlessly. You can easily switch between several accounts just by clicking your Google account. + +![Switching between multiple Google accounts in Insync][6]Switching between multiple Google accounts + +#### Custom sync folders + +Customize the way you sync your files and folders. You can easily set your syncing destination anywhere on your machine including external drive and network drives. + +![Customize sync location in Insync][7]Customize sync location + +The selective syncing mode also allows you to easily select a number of files and folders you’d want to sync (or unsync) in your local machine. This includes selectively syncing files within folders. + +![Selective synchronization in Insync][8]Selective synchronization + +It has features like file matching and ‘ignore list’ to help you filter files you don’t want to sync or files that you already have on your machine. + +![File matching feature in Insync][9]Avoids duplication of files + +The ‘ignore list’ allows you to set rules to exclude certain type of files from synchronization. + +![Selective syncing based on rules in Insync][10]Selective syncing based on rules + +If you prefer to work out of the desktop, you have an “Add to Insync” feature that will allow you to add any local file to your Drive. + +![Sync files right from your desktop][11]Sync files right from your desktop + +Insync also supports symlinks for those with workflows that use symbolic links. To learn more about Insync and symlinks, you can refer to [this article.][12] + +#### Exclusive features for Linux + +Insync supports the most commonly used 64-bit Linux distributions like **Ubuntu, Debian and Fedora**. You can check out the full list of distribution support [here][13]. + +Insync also has [headless][14] support for those looking to sync through the command line interface. This is perfect if you use a distro that is not fully supported by the GUI app or if you are working with servers or if you simply prefer the CLI. + +![Insync CLI][15]Command Line Interface + +You can learn more about installing and running Insync headless [here][16]. + +### Insync pricing and special discount + +Insync is a premium tool and it comes with a [price tag][17]. You have 2 licenses to choose from: + + * **Prime** is priced at $29.99 per Google account. You’ll get access to: cross-platform syncing, multiple accounts access and **support**. + * **Teams** is priced at $49.99 per Google account. You’ll be able to access all the Prime features + Team Drives syncing + + + +It’s a one-time fee which means once you buy it, you don’t have to pay it again. In a world where everything is paid monthly, it’s refreshing to pay for software that is still one-time! + +Each Google account has a 15-day free trial that will allow you to test the full suite of features, including [Team Drives][18] syncing. + +If you think it’s a bit expensive for your budget, I have good news for you. As an It’s FOSS reader, you get Insync at 25% discount. + +Just use the code ITSFOSS25 at checkout time and you will get 25% immediate discount on any license. Isn’t it cool? + +If you are not certain yet, you can try Insync free for 15 days. And if you think it’s worth the money, purchase the license with **ITSFOSS25** coupon code. + +You can download Insync from their website. + +I have used Insync from the time when it was available for free and I have always liked it. They have added more features over the time and improved its UI and performance. Overall, it’s a nice-to-have application if you use Google Drive a lot and do not mind paying for the efforts of the developers. + +-------------------------------------------------------------------------------- + +via: https://itsfoss.com/insync-linux-review/ + +作者：[Abhishek Prakash][a] +选题：[lujun9972][b] +译者：[译者ID](https://github.com/译者ID) +校对：[校对者ID](https://github.com/校对者ID) + +本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 + +[a]: https://itsfoss.com/author/abhishek/ +[b]: https://github.com/lujun9972 +[1]: https://abevoelker.github.io/how-long-since-google-said-a-google-drive-linux-client-is-coming/ +[2]: https://itsfoss.com/use-google-drive-linux/ +[3]: https://www.insynchq.com +[4]: https://i0.wp.com/itsfoss.com/wp-content/uploads/2018/12/google-drive-linux-insync.jpeg?resize=800%2C450&ssl=1 +[5]: https://i2.wp.com/itsfoss.com/wp-content/uploads/2018/11/insync_interface.jpeg?fit=800%2C501&ssl=1 +[6]: https://i0.wp.com/itsfoss.com/wp-content/uploads/2018/11/insync_multiple_google_account.jpeg?ssl=1 +[7]: https://i0.wp.com/itsfoss.com/wp-content/uploads/2018/11/insync_folder_settings.png?ssl=1 +[8]: https://i0.wp.com/itsfoss.com/wp-content/uploads/2018/11/insync_selective_sync.png?ssl=1 +[9]: https://i0.wp.com/itsfoss.com/wp-content/uploads/2018/11/insync_file_matching.jpeg?ssl=1 +[10]: https://i0.wp.com/itsfoss.com/wp-content/uploads/2018/11/insync_ignore_list_1.png?ssl=1 +[11]: https://i2.wp.com/itsfoss.com/wp-content/uploads/2018/11/add-to-insync-shortcut.jpeg?ssl=1 +[12]: https://help.insynchq.com/key-features-and-syncing-explained/syncing-superpowers/using-symlinks-on-google-drive-with-insync +[13]: https://www.insynchq.com/downloads +[14]: https://en.wikipedia.org/wiki/Headless_software +[15]: https://i1.wp.com/itsfoss.com/wp-content/uploads/2018/11/insync_cli.jpeg?fit=800%2C478&ssl=1 +[16]: https://help.insynchq.com/installation-on-windows-linux-and-macos/advanced/linux-controlling-insync-via-command-line-cli +[17]: https://www.insynchq.com/pricing +[18]: https://gsuite.google.com/learning-center/products/drive/get-started-team-drive/#!/ diff --git a/sources/tech/20181220 Getting started with Prometheus.md b/sources/tech/20181220 Getting started with Prometheus.md new file mode 100644 index 0000000000..79704addb7 --- /dev/null +++ b/sources/tech/20181220 Getting started with Prometheus.md @@ -0,0 +1,166 @@ +[#]: collector: (lujun9972) +[#]: translator: ( ) +[#]: reviewer: ( ) +[#]: publisher: ( ) +[#]: url: ( ) +[#]: subject: (Getting started with Prometheus) +[#]: via: (https://opensource.com/article/18/12/introduction-prometheus) +[#]: author: (Michael Zamot https://opensource.com/users/mzamot) + +Getting started with Prometheus +====== +Learn to install and write queries for the Prometheus monitoring and alerting system. + + +[Prometheus][1] is an open source monitoring and alerting system that directly scrapes metrics from agents running on the target hosts and stores the collected samples centrally on its server. Metrics can also be pushed using plugins like **collectd_exporter** —although this is not Promethius' default behavior, it may be useful in some environments where hosts are behind a firewall or prohibited from opening ports by security policy. + +Prometheus, a project of the [Cloud Native Computing Foundation][2], scales up using a federation model, which enables one Prometheus server to scrape another Prometheus server. This allows creation of a hierarchical topology, where a central system or higher-level Prometheus server can scrape aggregated data already collected from subordinate instances. + +Besides the Prometheus server, its most common components are its [Alertmanager][3] and its exporters. + +Alerting rules can be created within Prometheus and configured to send custom alerts to Alertmanager. Alertmanager then processes and handles these alerts, including sending notifications through different mechanisms like email or third-party services like [PagerDuty][4]. + +Prometheus' exporters can be libraries, processes, devices, or anything else that exposes the metrics that will be scraped by Prometheus. The metrics are available at the endpoint **/metrics** , which allows Prometheus to scrape them directly without needing an agent. The tutorial in this article uses **node_exporter** to expose the target hosts' hardware and operating system metrics. Exporters' outputs are plaintext and highly readable, which is one of Prometheus' strengths. + +In addition, you can configure [Grafana][5] to use Prometheus as a backend to provide data visualization and dashboarding functions. + +### Making sense of Prometheus' configuration file + +The number of seconds between when **/metrics** is scraped controls the granularity of the time-series database. This is defined in the configuration file as the **scrape_interval** parameter, which by default is set to 60 seconds. + +Targets are set for each scrape job in the **scrape_configs** section. Each job has its own name and a set of labels that can help filter, categorize, and make it easier to identify the target. One job can have many targets. + +### Installing Prometheus + +In this tutorial, for simplicity, we will install a Prometheus server and **node_exporter** with docker. Docker should already be installed and configured properly on your system. For a more in-depth, automated method, I recommend Steve Ovens' article [How to use Ansible to set up system monitoring with Prometheus][6]. + +Before starting, create the Prometheus configuration file **prometheus.yml** in your work directory as follows: + +``` +global: + scrape_interval: 15s + evaluation_interval: 15s + +scrape_configs: + - job_name: 'prometheus' + + static_configs: + - targets: ['localhost:9090'] + + - job_name: 'webservers' + + static_configs: + - targets: [' :9100'] +``` + +Start Prometheus with Docker by running the following command: + +``` +$ sudo docker run -d -p 9090:9090 -v +/path/to/prometheus.yml:/etc/prometheus/prometheus.yml +prom/prometheus +``` + +By default, the Prometheus server will use port 9090. If this port is already in use, you can change it by adding the parameter **\--web.listen-address=" : "** at the end of the previous command. + +In the machine you want to monitor, download and run the **node_exporter** container by using the following command: + +``` +$ sudo docker run -d -v "/proc:/host/proc" -v "/sys:/host/sys" -v +"/:/rootfs" --net="host" prom/node-exporter --path.procfs +/host/proc --path.sysfs /host/sys --collector.filesystem.ignored- +mount-points "^/(sys|proc|dev|host|etc)($|/)" +``` + +For the purposes of this learning exercise, you can install **node_exporter** and Prometheus on the same machine. Please note that it's not wise to run **node_exporter** under Docker in production—this is for testing purposes only. + +To verify that **node_exporter** is running, open your browser and navigate to **http:// :9100/metrics**. All the metrics collected will be displayed; these are the same metrics Prometheus will scrape. + + + +To verify the Prometheus server installation, open your browser and navigate to + 3361 0.00s 0.01s 0K 0K NE 0 0 E - 0% + 3363 0.01s 0.00s 0K 0K NE 0 0 E - 0% +31357 0.00s 0.00s 0K 0K -- - 1 S 1 0% bash + 3364 0.00s 0.00s 8032K 756K N- - 1 S 1 0% sleep + 2931 0.00s 0.00s 0K 0K -- - 1 I 1 0% kworker/u8:2-e + 3356 0.00s 0.00s 0K 0K -E 0 0 E - 0% + 3360 0.00s 0.00s 0K 0K NE 0 0 E - 0% + 3362 0.00s 0.00s 0K 0K NE 0 0 E - 0% +``` + +If you want to look at _just_ the disk stats, you can easily manage that with a command like this: + +``` +$ atop | grep DSK +$ atop | grep DSK +DSK | sda | busy 0% | read 122901 | write 3318e3 | avio 0.67 ms | +DSK | sdb | busy 0% | read 1168 | write 103 | avio 0.73 ms | +DSK | sda | busy 2% | read 0 | write 92 | avio 2.39 ms | +DSK | sda | busy 2% | read 0 | write 94 | avio 2.47 ms | +DSK | sda | busy 2% | read 0 | write 99 | avio 2.26 ms | +DSK | sda | busy 2% | read 0 | write 94 | avio 2.43 ms | +DSK | sda | busy 2% | read 0 | write 94 | avio 2.43 ms | +DSK | sda | busy 2% | read 0 | write 92 | avio 2.43 ms | +^C +``` + +### Being in the know with disk I/O + +Linux provides enough commands to give you good insights into how hard your disks are working and help you focus on potential problems or slowdowns. Hopefully, one of these commands will tell you just what you need to know when it's time to question disk performance. Occasional use of these commands will help ensure that especially busy or slow disks will be obvious when you need to check them. + +Join the Network World communities on [Facebook][2] and [LinkedIn][3] to comment on topics that are top of mind. + +-------------------------------------------------------------------------------- + +via: https://www.networkworld.com/article/3330497/linux/linux-commands-for-measuring-disk-activity.html + +作者：[Sandra Henry-Stocker][a] +选题：[lujun9972][b] +译者：[译者ID](https://github.com/译者ID) +校对：[校对者ID](https://github.com/校对者ID) + +本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 + +[a]: https://www.networkworld.com/author/Sandra-Henry_Stocker/ +[b]: https://github.com/lujun9972 +[1]: https://www.networkworld.com/article/3291616/linux/examining-linux-system-performance-with-dstat.html +[2]: https://www.facebook.com/NetworkWorld/ +[3]: https://www.linkedin.com/company/network-world diff --git a/sources/tech/20181231 Easily Upload Text Snippets To Pastebin-like Services From Commandline.md b/sources/tech/20181231 Easily Upload Text Snippets To Pastebin-like Services From Commandline.md new file mode 100644 index 0000000000..58b072f2fc --- /dev/null +++ b/sources/tech/20181231 Easily Upload Text Snippets To Pastebin-like Services From Commandline.md @@ -0,0 +1,259 @@ +[#]: collector: (lujun9972) +[#]: translator: ( ) +[#]: reviewer: ( ) +[#]: publisher: ( ) +[#]: url: ( ) +[#]: subject: (Easily Upload Text Snippets To Pastebin-like Services From Commandline) +[#]: via: (https://www.ostechnix.com/how-to-easily-upload-text-snippets-to-pastebin-like-services-from-commandline/) +[#]: author: (SK https://www.ostechnix.com/author/sk/) + +Easily Upload Text Snippets To Pastebin-like Services From Commandline +====== + + + +Whenever there is need to share the code snippets online, the first one probably comes to our mind is Pastebin.com, the online text sharing site launched by **Paul Dixon** in 2002. Now, there are several alternative text sharing services available to upload and share text snippets, error logs, config files, a command’s output or any sort of text files. If you happen to share your code often using various Pastebin-like services, I do have a good news for you. Say hello to **Wgetpaste** , a command line BASH utility to easily upload text snippets to pastebin-like services. Using Wgetpaste script, anyone can quickly share text snippets to their friends, colleagues, or whoever wants to see/use/review the code from command line in Unix-like systems. + +### Installing Wgetpaste + +Wgetpaste is available in Arch Linux [Community] repository. To install it on Arch Linux and its variants like Antergos and Manjaro Linux, just run the following command: + +``` +$ sudo pacman -S wgetpaste +``` + +For other distributions, grab the source code from [**Wgetpaste website**][1] and install it manually as described below. + +First download the latest Wgetpaste tar file: + +``` +$ wget http://wgetpaste.zlin.dk/wgetpaste-2.28.tar.bz2 +``` + +Extract it: + +``` +$ tar -xvjf wgetpaste-2.28.tar.bz2 +``` + +It will extract the contents of the tar file in a folder named “wgetpaste-2.28”. + +Go to that directory: + +``` +$ cd wgetpaste-2.28/ +``` + +Copy the wgetpaste binary to your $PATH, for example **/usr/local/bin/**. + +``` +$ sudo cp wgetpaste /usr/local/bin/ +``` + +Finally, make it executable using command: + +``` +$ sudo chmod +x /usr/local/bin/wgetpaste +``` + +### Upload Text Snippets To Pastebin-like Services + +Uploading text snippets using Wgetpaste is trivial. Let me show you a few examples. + +**1\. Upload text files** + +To upload any text file using Wgetpaste, just run: + +``` +$ wgetpaste mytext.txt +``` + +This command will upload the contents of mytext.txt file. + +Sample output: + +``` +Your paste can be seen here: https://paste.pound-python.org/show/eO0aQjTgExP0wT5uWyX7/ +``` + + + +You can share the pastebin URL via any medium like mail, message, whatsapp or IRC etc. Whoever has this URL can visit it and view the contents of the text file in a web browser of their choice. + +Here is the contents of mytext.txt file in web browser: + + + +You can also use **‘tee’** command to display what is being pasted, instead of uploading them blindly. + +To do so, use **-t** option like below. + +``` +$ wgetpaste -t mytext.txt +``` + +![][3] + +**2. Upload text snippets to different services +** + +By default, Wgetpaste will upload the text snippets to **poundpython** ( +``` + +For example, if you want to use [Lodash][8] in your project, you can add it using Yarn like this: + +``` +yarn add lodash +yarn add v1.12.3 +info No lockfile found. +[1/4] Resolving packages… +[2/4] Fetching packages… +[3/4] Linking dependencies… +[4/4] Building fresh packages… +success Saved lockfile. +success Saved 1 new dependency. +info Direct dependencies +└─ [email protected] +info All dependencies +└─ [email protected] +Done in 2.67s. +``` + +And you can see that this dependency has been added automatically in the package.json file: + +``` +{ + "name": "test_yarn_proect", + "version": "0.1", + "description": "Test Yarn", + "main": "index.js", + "author": "abhishek", + "license": "MIT", + "dependencies": { + "lodash": "^4.17.11" + } +} +``` + +By default, Yarn will add the latest version of a package in the dependency. If you want to use a specific version, you may specify it while adding. + +As always, you can also update the package.json file manually. + +#### Upgrading dependencies with Yarn + +You can upgrade a particular dependency to its latest version with the following command: + +``` +yarn upgrade +``` + +It will see if the package in question has a newer version and will update it accordingly. + +You can also change the version of an already added dependency in the following manner: + +You can also upgrade all the dependencies of your project to their latest version with one single command: + +``` +yarn upgrade +``` + +It will check the versions of all the dependencies and will update them if there are any newer versions. + +#### Removing dependencies with Yarn + +You can remove a package from the dependencies of your project in this way: + +``` +yarn remove +``` + +#### Install all project dependencies + +If you made any changes to the project.json file, you should run either + +``` +yarn +``` + +or + +``` +yarn install +``` + +to install all the dependencies at once. + +### How to remove Yarn from Ubuntu or Debian + +I’ll complete this tutorial by mentioning the steps to remove Yarn from your system if you used the above steps to install it. If you ever realized that you don’t need Yarn anymore, you will be able to remove it. + +Use the following command to remove Yarn and its dependencies. + +``` +sudo apt purge yarn +``` + +You should also remove the Yarn repository from the repository list: + +``` +sudo rm /etc/apt/sources.list.d/yarn.list +``` + +The optional next step is to remove the GPG key you had added to the trusted keys. But for that, you need to know the key. You can get that using the apt-key command: + +Warning: apt-key output should not be parsed (stdout is not a terminal) pub rsa4096 2016-10-05 [SC] 72EC F46A 56B4 AD39 C907 BBB7 1646 B01B 86E5 0310 uid [ unknown] Yarn Packaging + +Warning: apt-key output should not be parsed (stdout is not a terminal) pub rsa4096 2016-10-05 [SC] 72EC F46A 56B4 AD39 C907 BBB7 1646 B01B 86E5 0310 uid [ unknown] Yarn Packaging yarn@dan.cx sub rsa4096 2016-10-05 [E] sub rsa4096 2019-01-02 [S] [expires: 2020-02-02] + +The key here is the last 8 characters of the GPG key’s fingerprint in the line starting with pub. + +So, in my case, the key is 86E50310 and I’ll remove it using this command: + +``` +sudo apt-key del 86E50310 +``` + +You’ll see an OK in the output and the GPG key of Yarn package will be removed from the list of GPG keys your system trusts. + +I hope this tutorial helped you to install Yarn on Ubuntu, Debian, Linux Mint, elementary OS etc. I provided some basic Yarn commands to get you started along with complete steps to remove Yarn from your system. + +I hope you liked this tutorial and if you have any questions or suggestions, please feel free to leave a comment below. + + +-------------------------------------------------------------------------------- + +via: https://itsfoss.com/install-yarn-ubuntu + +作者：[Abhishek Prakash][a] +选题：[lujun9972][b] +译者：[译者ID](https://github.com/译者ID) +校对：[校对者ID](https://github.com/校对者ID) + +本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 + +[a]: https://itsfoss.com/author/abhishek/ +[b]: https://github.com/lujun9972 +[1]: https://yarnpkg.com/lang/en/ +[2]: https://code.fb.com/ +[3]: https://www.npmjs.com/ +[4]: https://itsfoss.com/checksum-tools-guide-linux/ +[5]: https://itsfoss.com/install-nodejs-ubuntu/ +[6]: https://i2.wp.com/itsfoss.com/wp-content/uploads/2019/01/yarn-js-ubuntu-debian.jpeg?resize=800%2C450&ssl=1 +[7]: https://itsfoss.com/update-ubuntu/ +[8]: https://lodash.com/ diff --git a/sources/tech/20190104 Search, Study And Practice Linux Commands On The Fly.md b/sources/tech/20190104 Search, Study And Practice Linux Commands On The Fly.md new file mode 100644 index 0000000000..fa92d3450a --- /dev/null +++ b/sources/tech/20190104 Search, Study And Practice Linux Commands On The Fly.md @@ -0,0 +1,223 @@ +[#]: collector: (lujun9972) +[#]: translator: ( ) +[#]: reviewer: ( ) +[#]: publisher: ( ) +[#]: url: ( ) +[#]: subject: (Search, Study And Practice Linux Commands On The Fly!) +[#]: via: (https://www.ostechnix.com/search-study-and-practice-linux-commands-on-the-fly/) +[#]: author: (SK https://www.ostechnix.com/author/sk/) + +Search, Study And Practice Linux Commands On The Fly! +====== + + + +The title may look like sketchy and click bait. Allow me to explain what I am about to explain in this tutorial. Let us say you want to download an archive file, extract it and move the file from one location to another from command line. As per the above scenario, we may need at least three Linux commands, one for downloading the file, one for extracting the downloaded file and one for moving the file. If you’re intermediate or advanced Linux user, you could do this easily with an one-liner command or a script in few seconds/minutes. But, if you are a noob who don’t know much about Linux commands, you might need little help. + +Of course, a quick google search may yield many results. Or, you could use [**man pages**][1]. But some man pages are really long, comprehensive and lack in useful example. You might need to scroll down for quite a long time when you’re looking for a particular information on the specific flags/options. Thankfully, there are some [**good alternatives to man pages**][2], which are focused on mostly practical commands. One such good alternative is **TLDR pages**. Using TLDR pages, we can quickly and easily learn a Linux command with practical examples. To access the TLDR pages, we require a TLDR client. There are many clients available. Today, we are going to learn about one such client named **“Tldr++”**. + +Tldr++ is a fast and interactive tldr client written with **Go** programming language. Unlike the other Tldr clients, it is fully interactive. That means, you can pick a command, read all examples , and immediately run any command without having to retype or copy/paste each command in the Terminal. Still don’t get it? No problem. Read on to learn and practice Linux commands on the fly. + +### Install Tldr++ + +Installing Tldr++ is very simple. Download tldr++ latest version from the [**releases page**][3]. Extract it and move the tldr++ binary to your $PATH. + +``` +$ wget https://github.com/isacikgoz/tldr/releases/download/v0.5.0/tldr_0.5.0_linux_amd64.tar.gz + +$ tar xzf tldr_0.5.0_linux_amd64.tar.gz + +$ sudo mv tldr /usr/local/bin + +$ sudo chmod +x /usr/local/bin/tldr +``` + +Now, run ‘tldr’ binary to populate the tldr pages in your local system. + +``` +$ tldr +``` + +Sample output: + +``` +Enumerating objects: 6, done. +Counting objects: 100% (6/6), done. +Compressing objects: 100% (6/6), done. +Total 18157 (delta 0), reused 3 (delta 0), pack-reused 18151 +Successfully cloned into: /home/sk/.local/share/tldr +``` + + + +Tldr++ is available in AUR. If you’re on Arch Linux, you can install it using any AUR helper, for example [**YaY**][4]. Make sure you have removed any existing tldr client from your system and run the following command to install tldr++. + +``` +$ yay -S tldr++ +``` + +Alternatively, you can build from source as described below. Since Tldr++ is written using Go language, make sure you have installed it on your Linux box. If it isn’t installed yet, refer the following guide. + ++ [How To Install Go Language In Linux](https://www.ostechnix.com/install-go-language-linux/) + +After installing Go, run the following command to install Tldr++. + +``` +$ go get -u github.com/isacikgoz/tldr +``` + +This command will download the contents of tldr repository in a folder named **‘go’** in the current working directory. + +Now run the ‘tldr’ binary to populate all tldr pages in your local system using command: + +``` +$ go/bin/tldr +``` + +Sample output: + +![][6] + +Finally, copy the tldr binary to your PATH. + +``` +$ sudo mv tldr /usr/local/bin +``` + +It is time to see some examples. + +### Tldr++ Usage + +Type ‘tldr’ command without any options to display all command examples in alphabetical order. + +![][7] + +Use the **UP/DOWN arrows** to navigate through the commands, type any letters to search or type a command name to view the examples of that respective command. Press **?** for more and **Ctrl+c** to return/exit. + +To display the example commands of a specific command, for example **apt** , simply do: + +``` +$ tldr apt +``` + +![][8] + +Choose any example command from the list and hit ENTER. You will see a *** symbol** before the selected command. For example, I choose the first command i.e ‘sudo apt update’. Now, it will ask you whether to continue or not. If the command is correct, just type ‘y’ to continue and type your sudo password to run the selected command. + +![][9] + +See? You don’t need to copy/paste or type the actual command in the Terminal. Just choose it from the list and run on the fly! + +There are hundreds of Linux command examples are available in Tldr pages. You can choose one or two commands per day and learn them thoroughly. And keep this practice everyday to learn as much as you can. + +### Learn And Practice Linux Commands On The Fly Using Tldr++ + +Now think of the scenario that I mentioned in the first paragraph. You want to download a file, extract it and move it to different location and make it executable. Let us see how to do it interactively using Tldr++ client. + +**Step 1 – Download a file from Internet** + +To download a file from command line, we mostly use **‘curl’** or **‘wget’** commands. Let me use ‘wget’ to download the file. To open tldr page of wget command, just run: + +``` +$ tldr wget +``` + +Here is the examples of wget command. + + + +You can use **UP/DOWN** arrows to go through the list of commands. Once you choose the command of your choice, press ENTER. Here I chose the first command. + +Now, enter the path of the file to download. + + + +You will then be asked to confirm if it is the correct command or not. If the command is correct, simply type ‘yes’ or ‘y’ to start downloading the file. + +![][10] + +We have downloaded the file. Let us go ahead and extract this file. + +**Step 2 – Extract downloaded archive** + +We downloaded the **tar.gz** file. So I am going to open the ‘tar’ tldr page. + +``` +$ tldr tar +``` + +You will see the list of example commands. Go through the examples and find which command is suitable to extract tar.gz(gzipped archive) file and hit ENTER key. In our case, it is the third command. + +![][11] + +Now, you will be prompted to enter the path of the tar.gz file. Just type the path and hit ENTER key. Tldr++ supports smart file suggestions. That means it will suggest the file name automatically as you type. Just press TAB key for auto-completion. + +![][12] + +If you downloaded the file to some other location, just type the full path, for example **/home/sk/Downloads/tldr_0.5.0_linux_amd64.tar.gz.** + +Once you enter the path of the file to extract, press ENTER and then, type ‘y’ to confirm. + +![][13] + +**Step 3 – Move file from one location to another** + +We extracted the archive. Now we need to move the file to another location. To move the files from one location to another, we use ‘mv’ command. So, let me open the tldr page for mv command. + +``` +$ tldr mv +``` + +Choose the correct command to move the files from one location to another. In our case, the first command will work, so let me choose it. + +![][14] + +Type the path of the file that you want to move and enter the destination path and hit ENTER key. + +![][15] + +**Note:** Type **y!** or **yes!** to run command with **sudo** privileges. + +As you see in the above screenshot, I moved the file named **‘tldr’** to **‘/usr/local/bin/’** location. + +For more details, refer the project’s GitHub page given at the end. + + +### Conclusion + +Don’t get me wrong. **Man pages are great!** There is no doubt about it. But, as I already said, many man pages are comprehensive and doesn’t have useful examples. There is no way I could memorize all lengthy commands with tricky flags. Some times I spent much time on man pages and remained clueless. The Tldr pages helped me to find what I need within few minutes. Also, we use some commands once in a while and then we forget them completely. Tldr pages on the other hand actually helps when it comes to using commands we rarely use. Tldr++ client makes this task much easier with smart user interaction. Give it a go and let us know what you think about this tool in the comment section below. + +And, that’s all. More good stuffs to come. Stay tuned! + +Good luck! + + + +-------------------------------------------------------------------------------- + +via: https://www.ostechnix.com/search-study-and-practice-linux-commands-on-the-fly/ + +作者：[SK][a] +选题：[lujun9972][b] +译者：[译者ID](https://github.com/译者ID) +校对：[校对者ID](https://github.com/校对者ID) + +本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 + +[a]: https://www.ostechnix.com/author/sk/ +[b]: https://github.com/lujun9972 +[1]: https://www.ostechnix.com/learn-use-man-pages-efficiently/ +[2]: https://www.ostechnix.com/3-good-alternatives-man-pages-every-linux-user-know/ +[3]: https://github.com/isacikgoz/tldr/releases +[4]: https://www.ostechnix.com/yay-found-yet-another-reliable-aur-helper/ +[5]: data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7 +[6]: http://www.ostechnix.com/wp-content/uploads/2019/01/tldr-1.png +[7]: http://www.ostechnix.com/wp-content/uploads/2019/01/tldr-11.png +[8]: http://www.ostechnix.com/wp-content/uploads/2019/01/tldr-12.png +[9]: http://www.ostechnix.com/wp-content/uploads/2019/01/tldr-13.png +[10]: http://www.ostechnix.com/wp-content/uploads/2019/01/tldr-4.png +[11]: http://www.ostechnix.com/wp-content/uploads/2019/01/tldr-6.png +[12]: http://www.ostechnix.com/wp-content/uploads/2019/01/tldr-7.png +[13]: http://www.ostechnix.com/wp-content/uploads/2019/01/tldr-8.png +[14]: http://www.ostechnix.com/wp-content/uploads/2019/01/tldr-9.png +[15]: http://www.ostechnix.com/wp-content/uploads/2019/01/tldr-10.png diff --git a/sources/tech/20190104 Three Ways To Reset And Change Forgotten Root Password on RHEL 7-CentOS 7 Systems.md b/sources/tech/20190104 Three Ways To Reset And Change Forgotten Root Password on RHEL 7-CentOS 7 Systems.md new file mode 100644 index 0000000000..6619cfe65a --- /dev/null +++ b/sources/tech/20190104 Three Ways To Reset And Change Forgotten Root Password on RHEL 7-CentOS 7 Systems.md @@ -0,0 +1,254 @@ +[#]: collector: (lujun9972) +[#]: translator: ( ) +[#]: reviewer: ( ) +[#]: publisher: ( ) +[#]: url: ( ) +[#]: subject: (Three Ways To Reset And Change Forgotten Root Password on RHEL 7/CentOS 7 Systems) +[#]: via: (https://www.2daygeek.com/linux-reset-change-forgotten-root-password-in-rhel-7-centos-7/) +[#]: author: (Prakash Subramanian https://www.2daygeek.com/author/prakash/) + +Three Ways To Reset And Change Forgotten Root Password on RHEL 7/CentOS 7 Systems +====== + +If you are forget to remember your root password for RHEL 7 and CentOS 7 systems and want to reset the forgotten root password? + +If so, don’t worry we are here to help you out on this. + +Navigate to the following link if you want to **[reset forgotten root password on RHEL 6/CentOS 6][1]**. + +This is generally happens when you use different password in vast environment or if you are not maintaining the proper inventory. + +Whatever it is. No issues, we will help you through this article. + +It can be done in many ways but we are going to show you the best three methods which we tried many times for our clients. + +In Linux servers there are three different users are available. These are, Normal User, System User and Super User. + +As everyone knows the Root user is known as super user in Linux and Administrator is in Windows. + +We can’t perform any major activity without root password so, make sure you should have the right root password when you perform any major tasks. + +If you don’t know or don’t have it, try to reset using one of the below method. + + * Reset Forgotten Root Password By Booting into Single User Mode using `rd.break` + * Reset Forgotten Root Password By Booting into Single User Mode using `init=/bin/bash` + * Reset Forgotten Root Password By Booting into Rescue Mode + + + +### Method-1: Reset Forgotten Root Password By Booting into Single User Mode + +Just follow the below procedure to reset the forgotten root password in RHEL 7/CentOS 7 systems. + +To do so, reboot your system and follow the instructions carefully. + +**`Step-1:`** Reboot your system and interrupt at the boot menu by hitting **`e`** key to modify the kernel arguments. +![][3] + +**`Step-2:`** In the GRUB options, find `linux16` word and add the `rd.break` word in the end of the file then press `Ctrl+x` or `F10` to boot into single user mode. +![][4] + +**`Step-3:`** At this point of time, your root filesystem will be mounted in Read only (RO) mode to /sysroot. Run the below command to confirm this. + +``` +# mount | grep root +``` + +![][5] + +**`Step-4:`** Based on the above output, i can say that i’m in single user mode and my root file system is mounted in read only mode. + +It won’t allow you to make any changes on your system until you mount the root filesystem with Read and write (RW) mode to /sysroot. To do so, use the following command. + +``` +# mount -o remount,rw /sysroot +``` + +![][6] + +**`Step-5:`** Currently your file systems are mounted as a temporary partition. Now, your command prompt shows **switch_root:/#**. + +Run the following command to get into a chroot jail so that /sysroot is used as the root of the file system. + +``` +# chroot /sysroot +``` + +![][7] + +**`Step-6:`** Now you can able to reset the root password with help of `passwd` command. + +``` +# echo "CentOS7$#123" | passwd --stdin root +``` + +![][8] + +**`Step-7:`** By default CentOS 7/RHEL 7 use SELinux in enforcing mode, so create a following hidden file which will automatically perform a relabel of all files on next boot. + +It allow us to fix the context of the **/etc/shadow** file. + +``` +# touch /.autorelabel +``` + +![][9] + +**`Step-8:`** Issue `exit` twice to exit from the chroot jail environment and reboot the system. +![][10] + +**`Step-9:`** Now you can login to your system with your new password. +![][11] + +### Method-2: Reset Forgotten Root Password By Booting into Single User Mode + +Alternatively we can use the below procedure to reset the forgotten root password in RHEL 7/CentOS 7 systems. + +**`Step-1:`** Reboot your system and interrupt at the boot menu by hitting **`e`** key to modify the kernel arguments. +![][3] + +**`Step-2:`** In the GRUB options, find `rhgb quiet` word and replace with the `init=/bin/bash` or `init=/bin/sh` word then press `Ctrl+x` or `F10` to boot into single user mode. + +Screenshot for **`init=/bin/bash`**. +![][12] + +Screenshot for **`init=/bin/sh`**. +![][13] + +**`Step-3:`** At this point of time, your root system will be mounted in Read only mode to /. Run the below command to confirm this. + +``` +# mount | grep root +``` + +![][14] + +**`Step-4:`** Based on the above ouput, i can say that i’m in single user mode and my root file system is mounted in read only (RO) mode. + +It won’t allow you to make any changes on your system until you mount the root file system with Read and write (RW) mode. To do so, use the following command. + +``` +# mount -o remount,rw / +``` + +![][15] + +**`Step-5:`** Now you can able to reset the root password with help of `passwd` command. + +``` +# echo "RHEL7$#123" | passwd --stdin root +``` + +![][16] + +**`Step-6:`** By default CentOS 7/RHEL 7 use SELinux in enforcing mode, so create a following hidden file which will automatically perform a relabel of all files on next boot. + +It allow us to fix the context of the **/etc/shadow** file. + +``` +# touch /.autorelabel +``` + +![][17] + +**`Step-7:`** Finally `Reboot` the system. + +``` +# exec /sbin/init 6 +``` + +![][18] + +**`Step-9:`** Now you can login to your system with your new password. +![][11] + +### Method-3: Reset Forgotten Root Password By Booting into Rescue Mode + +Alternatively, we can reset the forgotten Root password for RHEL 7 and CentOS 7 systems using Rescue mode. + +**`Step-1:`** Insert the bootable media through USB or DVD drive which is compatible for you and reboot your system. It will take to you to the below screen. + +Hit `Troubleshooting` to launch the `Rescue` mode. +![][19] + +**`Step-2:`** Choose `Rescue a CentOS system` and hit `Enter` button. +![][20] + +**`Step-3:`** Here choose `1` and the rescue environment will now attempt to find your Linux installation and mount it under the directory `/mnt/sysimage`. +![][21] + +**`Step-4:`** Simple hit `Enter` to get a shell. +![][22] + +**`Step-5:`** Run the following command to get into a chroot jail so that /mnt/sysimage is used as the root of the file system. + +``` +# chroot /mnt/sysimage +``` + +![][23] + +**`Step-6:`** Now you can able to reset the root password with help of **passwd** command. + +``` +# echo "RHEL7$#123" | passwd --stdin root +``` + +![][24] + +**`Step-7:`** By default CentOS 7/RHEL 7 use SELinux in enforcing mode, so create a following hidden file which will automatically perform a relabel of all files on next boot. +It allow us to fix the context of the /etc/shadow file. + +``` +# touch /.autorelabel +``` + +![][25] + +**`Step-8:`** Remove the bootable media then initiate the reboot. + +**`Step-9:`** Issue `exit` twice to exit from the chroot jail environment and reboot the system. +![][26] + +**`Step-10:`** Now you can login to your system with your new password. +![][11] + +-------------------------------------------------------------------------------- + +via: https://www.2daygeek.com/linux-reset-change-forgotten-root-password-in-rhel-7-centos-7/ + +作者：[Prakash Subramanian][a] +选题：[lujun9972][b] +译者：[译者ID](https://github.com/译者ID) +校对：[校对者ID](https://github.com/校对者ID) + +本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 + +[a]: https://www.2daygeek.com/author/prakash/ +[b]: https://github.com/lujun9972 +[1]: https://www.2daygeek.com/linux-reset-change-forgotten-root-password-in-rhel-6-centos-6/ +[2]: data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7 +[3]: https://www.2daygeek.com/wp-content/uploads/2018/12/reset-forgotten-root-password-on-rhel-7-centos-7-2.png +[4]: https://www.2daygeek.com/wp-content/uploads/2018/12/reset-forgotten-root-password-on-rhel-7-centos-7-3.png +[5]: https://www.2daygeek.com/wp-content/uploads/2018/12/reset-forgotten-root-password-on-rhel-7-centos-7-5.png +[6]: https://www.2daygeek.com/wp-content/uploads/2018/12/reset-forgotten-root-password-on-rhel-7-centos-7-6.png +[7]: https://www.2daygeek.com/wp-content/uploads/2018/12/reset-forgotten-root-password-on-rhel-7-centos-7-8.png +[8]: https://www.2daygeek.com/wp-content/uploads/2018/12/reset-forgotten-root-password-on-rhel-7-centos-7-10.png +[9]: https://www.2daygeek.com/wp-content/uploads/2018/12/reset-forgotten-root-password-on-rhel-7-centos-7-10a.png +[10]: https://www.2daygeek.com/wp-content/uploads/2018/12/reset-forgotten-root-password-on-rhel-7-centos-7-11.png +[11]: https://www.2daygeek.com/wp-content/uploads/2018/12/reset-forgotten-root-password-on-rhel-7-centos-7-12.png +[12]: https://www.2daygeek.com/wp-content/uploads/2018/12/method-reset-forgotten-root-password-on-rhel-7-centos-7-1.png +[13]: https://www.2daygeek.com/wp-content/uploads/2018/12/method-reset-forgotten-root-password-on-rhel-7-centos-7-1a.png +[14]: https://www.2daygeek.com/wp-content/uploads/2018/12/method-reset-forgotten-root-password-on-rhel-7-centos-7-3.png +[15]: https://www.2daygeek.com/wp-content/uploads/2018/12/method-reset-forgotten-root-password-on-rhel-7-centos-7-4.png +[16]: https://www.2daygeek.com/wp-content/uploads/2018/12/method-reset-forgotten-root-password-on-rhel-7-centos-7-5.png +[17]: https://www.2daygeek.com/wp-content/uploads/2018/12/method-reset-forgotten-root-password-on-rhel-7-centos-7-6.png +[18]: https://www.2daygeek.com/wp-content/uploads/2018/12/method-reset-forgotten-root-password-on-rhel-7-centos-7-7.png +[19]: https://www.2daygeek.com/wp-content/uploads/2018/12/rescue-reset-forgotten-root-password-on-rhel-7-centos-7-1.png +[20]: https://www.2daygeek.com/wp-content/uploads/2018/12/rescue-reset-forgotten-root-password-on-rhel-7-centos-7-2.png +[21]: https://www.2daygeek.com/wp-content/uploads/2018/12/rescue-reset-forgotten-root-password-on-rhel-7-centos-7-3.png +[22]: https://www.2daygeek.com/wp-content/uploads/2018/12/rescue-reset-forgotten-root-password-on-rhel-7-centos-7-4.png +[23]: https://www.2daygeek.com/wp-content/uploads/2018/12/rescue-reset-forgotten-root-password-on-rhel-7-centos-7-5.png +[24]: https://www.2daygeek.com/wp-content/uploads/2018/12/rescue-reset-forgotten-root-password-on-rhel-7-centos-7-6.png +[25]: https://www.2daygeek.com/wp-content/uploads/2018/12/rescue-reset-forgotten-root-password-on-rhel-7-centos-7-7.png +[26]: https://www.2daygeek.com/wp-content/uploads/2018/12/rescue-reset-forgotten-root-password-on-rhel-7-centos-7-8.png diff --git a/sources/tech/20190105 Setting up an email server, part 1- The Forwarder.md b/sources/tech/20190105 Setting up an email server, part 1- The Forwarder.md new file mode 100644 index 0000000000..c6c520e339 --- /dev/null +++ b/sources/tech/20190105 Setting up an email server, part 1- The Forwarder.md @@ -0,0 +1,224 @@ +[#]: collector: (lujun9972) +[#]: translator: ( ) +[#]: reviewer: ( ) +[#]: publisher: ( ) +[#]: url: ( ) +[#]: subject: (Setting up an email server, part 1: The Forwarder) +[#]: via: (https://blog.jak-linux.org/2019/01/05/setting-up-an-email-server-part1/) +[#]: author: (Julian Andres Klode https://blog.jak-linux.org/) + +Setting up an email server, part 1: The Forwarder +====== + +This week, I’ve been working on rolling out mail services on my server. I started working on a mail server setup at the end of November, while the server was not yet in use, but only for about two days, and then let it rest. + +As my old shared hosting account expired on January 1, I had to move mail forwarding duties over to the new server. Yes forwarding - I do plan to move hosting the actual email too, but at the moment it’s “just” forwarding to gmail. + +### The Software + +As you might know from the web server story, my server runs on Ubuntu 18.04. I set up a mail server on this system using + + * [Postfix][1] for SMTP duties (warning, they oddly do not have an https page) + * [rspamd][2] for spam filtering, and signing DKIM / ARC + * [bind9][3] for DNS resolving + * [postsrsd][4] for SRS + + + +You might wonder why bind9 is in there. It turns out that DNS blacklists used by spam filters block the caching DNS servers you usually use, so you have to use your own recursive DNS server. Ubuntu offers you the choice between bind9 and dnsmasq in main, and it seems like bind9 is more appropriate here than dnsmasq. + +### Setting up postfix + +Most of the postfix configuration is fairly standard. So, let’s skip TLS configuration and outbound SMTP setups (this is email, and while they support TLS, it’s all optional, so let’s not bother that much here). + +The most important part is restrictions in `main.cf`. + +First of all, relay restrictions prevent us from relaying emails to weird domains: + +``` +# Relay Restrictions +smtpd_relay_restrictions = reject_non_fqdn_recipient reject_unknown_recipient_domain permit_mynetworks permit_sasl_authenticated defer_unauth_destination +``` + +We also only accept mails from hosts that know their own full qualified name: + +``` +# Helo restrictions (hosts not having a proper fqdn) +smtpd_helo_required = yes +smtpd_helo_restrictions = permit_mynetworks reject_invalid_helo_hostname reject_non_fqdn_helo_hostname reject_unknown_helo_hostname +``` + +We also don’t like clients (other servers) that send data too early, or have an unknown hostname: + +``` +smtpd_data_restrictions = reject_unauth_pipelining +smtpd_client_restrictions = permit_mynetworks reject_unknown_client_hostname +``` + +I also set up a custom apparmor profile that’s pretty lose, I plan to migrate to the one in the apparmor git eventually but it needs more testing and some cleanup. + +### Sender rewriting scheme + +For SRS using postsrsd, we define the `SRS_DOMAIN` in `/etc/default/postsrsd` and then configure postfix to talk to it: + +``` +# Handle SRS for forwarding +recipient_canonical_maps = tcp:localhost:10002 +recipient_canonical_classes= envelope_recipient,header_recipient + +sender_canonical_maps = tcp:localhost:10001 +sender_canonical_classes = envelope_sender +``` + +This has a minor issue that it also rewrites the `Return-Path` when it delivers emails locally, but as I am only forwarding, I’m worrying about that later. + +### rspamd basics + +rspamd is a great spam filtering system. It uses a small core written in C and a bunch of Lua plugins, such as: + + * IP score, which keeps track of how good a specific server was in the past + * Replies, which can check whether an email is a reply to another one + * DNS blacklisting + * DKIM and ARC validation and signing + * DMARC validation + * SPF validation + + + +It also has a nice web UI: + +![rspamd web ui status][5] + +rspamd web ui status + +![rspamd web ui investigating a spam message][6] + +rspamd web ui investigating a spam message + +Setting up rspamd is quite easy. You basically just drop a bunch of configuration overrides into `/etc/rspamd/local.d` and you’re done. Heck, it mostly works out of the box. There’s a fancy `rspamadm configwizard` too. + +What you do want for rspamd is a redis server. redis is needed in [many places][7], such as rate limiting, greylisting, dmarc, reply tracking, ip scoring, neural networks. + +I made a few changes to the defaults: + + * I enabled subject rewriting instead of adding headers, so spam mail subjects get `[SPAM]` prepended, in `local.d/actions.conf`: + +``` + reject = 15; +rewrite_subject = 6; +add_header = 6; +greylist = 4; +subject = "[SPAM] %s"; +``` + + * I set `autolearn = true;` in `local.d/classifier-bayes.conf` to make it learn that an email that has a score of at least 15 (those that are rejected) is spam, and emails with negative scores are ham. + + * I set `extended_spam_headers = true;` in `local.d/milter_headers.conf` to get a report from rspamd in the header seeing the score and how the score came to be. + + + + +### ARC setup + +[ARC][8] is the ‘Authenticated Received Chain’ and is currently a DMARC working group work item. It allows forwarders / mailing lists to authenticate their forwarding of the emails and the checks they have performed. + +rspamd is capable of validating and signing emails with ARC, but I’m not sure how much influence ARC has on gmail at the moment, for example. + +There are three parts to setting up ARC: + + 1. Generate a DKIM key pair (use `rspamadm dkim_keygen`) + 2. Setup rspamd to sign incoming emails using the private key + 3. Add a DKIM `TXT` record for the public key. `rspamadm` helpfully tells you how it looks like. + + + +For step two, what we need to do is configure `local.d/arc.conf`. You can basically use the example configuration from the [rspamd page][9], the key point for signing incoming email is to specifiy `sign_incoming = true;` and `use_domain_sign_inbound = "recipient";` (FWIW, none of these options are documented, they are fairly new, and nobody updated the documentation for them). + +My configuration looks like this at the moment: + +``` +# If false, messages with empty envelope from are not signed +allow_envfrom_empty = true; +# If true, envelope/header domain mismatch is ignored +allow_hdrfrom_mismatch = true; +# If true, multiple from headers are allowed (but only first is used) +allow_hdrfrom_multiple = false; +# If true, username does not need to contain matching domain +allow_username_mismatch = false; +# If false, messages from authenticated users are not selected for signing +auth_only = true; +# Default path to key, can include '$domain' and '$selector' variables +path = "${DBDIR}/arc/$domain.$selector.key"; +# Default selector to use +selector = "arc"; +# If false, messages from local networks are not selected for signing +sign_local = true; +# +sign_inbound = true; +# Symbol to add when message is signed +symbol_signed = "ARC_SIGNED"; +# Whether to fallback to global config +try_fallback = true; +# Domain to use for ARC signing: can be "header" or "envelope" +use_domain = "header"; +use_domain_sign_inbound = "recipient"; +# Whether to normalise domains to eSLD +use_esld = true; +# Whether to get keys from Redis +use_redis = false; +# Hash for ARC keys in Redis +key_prefix = "ARC_KEYS"; +``` + +This would also sign any outgoing email, but I’m not sure that’s necessary - my understanding is that we only care about ARC when forwarding/receiving incoming emails, not when sending them (at least that’s what gmail does). + +### Other Issues + +There are few other things to keep in mind when running your own mail server. I probably don’t know them all yet, but here we go: + + * You must have a fully qualified hostname resolving to a public IP address + + * Your public IP address must resolve back to the fully qualified host name + + * Again, you should run a recursive DNS resolver so your DNS blacklists work (thanks waldi for pointing that out) + + * Setup an SPF record. Mine looks like this: + +`jak-linux.org. 3600 IN TXT "v=spf1 +mx ~all"` + +this states that all my mail servers may send email, but others probably should not (a softfail). Not having an SPF record can punish you; for example, rspamd gives missing SPF and DKIM a score of 1. + + * All of that software is sandboxed using AppArmor. Makes you question its security a bit less! + + + + +### Source code, outlook + +As always, you can find the Ansible roles on [GitHub][10]. Feel free to point out bugs! 😉 + +In the next installment of this series, we will be looking at setting up Dovecot, and configuring DKIM. We probably also want to figure out how to run notmuch on the server, keep messages in matching maildirs, and have my laptop synchronize the maildir and notmuch state with the server. Ugh, sounds like a lot of work. + +-------------------------------------------------------------------------------- + +via: https://blog.jak-linux.org/2019/01/05/setting-up-an-email-server-part1/ + +作者：[Julian Andres Klode][a] +选题：[lujun9972][b] +译者：[译者ID](https://github.com/译者ID) +校对：[校对者ID](https://github.com/校对者ID) + +本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 + +[a]: https://blog.jak-linux.org/ +[b]: https://github.com/lujun9972 +[1]: http://www.postfix.org/ +[2]: https://rspamd.com/ +[3]: https://www.isc.org/downloads/bind/ +[4]: https://github.com/roehling/postsrsd +[5]: https://blog.jak-linux.org/2019/01/05/setting-up-an-email-server-part1/rspamd-status.png +[6]: https://blog.jak-linux.org/2019/01/05/setting-up-an-email-server-part1/rspamd-spam.png +[7]: https://rspamd.com/doc/configuration/redis.html +[8]: http://arc-spec.org/ +[9]: https://rspamd.com/doc/modules/arc.html +[10]: https://github.com/julian-klode/ansible.jak-linux.org diff --git a/sources/tech/20190107 Aliases- To Protect and Serve.md b/sources/tech/20190107 Aliases- To Protect and Serve.md new file mode 100644 index 0000000000..783c59dc41 --- /dev/null +++ b/sources/tech/20190107 Aliases- To Protect and Serve.md @@ -0,0 +1,176 @@ +[#]: collector: (lujun9972) +[#]: translator: ( ) +[#]: reviewer: ( ) +[#]: publisher: ( ) +[#]: url: ( ) +[#]: subject: (Aliases: To Protect and Serve) +[#]: via: (https://www.linux.com/blog/learn/2019/1/aliases-protect-and-serve) +[#]: author: (Paul Brown https://www.linux.com/users/bro66) + +Aliases: To Protect and Serve +====== + + + +Happy 2019! Here in the new year, we’re continuing our series on aliases. By now, you’ve probably read our [first article on aliases][1], and it should be quite clear how they are the easiest way to save yourself a lot of trouble. You already saw, for example, that they helped with muscle-memory, but let's see several other cases in which aliases come in handy. + +### Aliases as Shortcuts + +One of the most beautiful things about Linux's shells is how you can use zillions of options and chain commands together to carry out really sophisticated operations in one fell swoop. All right, maybe beauty is in the eye of the beholder, but let's agree that this feature published practical. + +The downside is that you often come up with recipes that are often hard to remember or cumbersome to type. Say space on your hard disk is at a premium and you want to do some New Year's cleaning. Your first step may be to look for stuff to get rid off in you home directory. One criteria you could apply is to look for stuff you don't use anymore. `ls` can help with that: + +``` +ls -lct +``` + +The instruction above shows the details of each file and directory (`-l`) and also shows when each item was last accessed (`-c`). It then orders the list from most recently accessed to least recently accessed (`-t`). + +Is this hard to remember? You probably don’t use the `-c` and `-t` options every day, so perhaps. In any case, defining an alias like + +``` +alias lt='ls -lct' +``` + +will make it easier. + +Then again, you may want to have the list show the oldest files first: + +``` +alias lo='lt -F | tac' +``` + +![aliases][3] + +Figure 1: The lt and lo aliases in action. + +[Used with permission][4] + +There are a few interesting things going here. First, we are using an alias (`lt`) to create another alias -- which is perfectly okay. Second, we are passing a new parameter to `lt` (which, in turn gets passed to `ls` through the definition of the `lt` alias). + +The `-F` option appends special symbols to the names of items to better differentiate regular files (that get no symbol) from executable files (that get an `*`), files from directories (end in `/`), and all of the above from links, symbolic and otherwise (that end in an `@` symbol). The `-F` option is throwback to the days when terminals where monochrome and there was no other way to easily see the difference between items. You use it here because, when you pipe the output from `lt` through to `tac` you lose the colors from `ls`. + +The third thing to pay attention to is the use of piping. Piping happens when you pass the output from an instruction to another instruction. The second instruction can then use that output as its own input. In many shells (including Bash), you pipe something using the pipe symbol (`|`). + +In this case, you are piping the output from `lt -F` into `tac`. `tac`'s name is a bit of a joke. You may have heard of `cat`, the instruction that was nominally created to con _cat_ enate files together, but that in practice is used to print out the contents of a file to the terminal. `tac` does the same, but prints out the contents it receives in reverse order. Get it? `cat` and `tac`. Developers, you so funny! + +The thing is both `cat` and `tac` can also print out stuff piped over from another instruction, in this case, a list of files ordered chronologically. + +So... after that digression, what comes out of the other end is the list of files and directories of the current directory in inverse order of freshness. + +The final thing you have to bear in mind is that, while `lt` will work the current directory and any other directory... + +``` +# This will work: +lt +# And so will this: +lt /some/other/directory +``` + +... `lo` will only work with the current directory: + +``` +# This will work: +lo +# But this won't: +lo /some/other/directory +``` + +This is because Bash expands aliases into their components. When you type this: + +``` +lt /some/other/directory +``` + +Bash REALLY runs this: + +``` +ls -lct /some/other/directory +``` + +which is a valid Bash command. + +However, if you type this: + +``` +lo /some/other/directory +``` + +Bash tries to run this: + +``` +ls -lct -F | tac /some/other/directory +``` + +which is not a valid instruction, because `tac` mainly because _/some/other/directory_ is a directory, and `cat` and `tac` don't do directories. + +### More Alias Shortcuts + + * `alias lll='ls -R'` prints out the contents of a directory and then drills down and prints out the contents of its subdirectories and the subdirectories of the subdirectories, and so on and so forth. It is a way of seeing everything you have under a directory. + + * `mkdir='mkdir -pv'` let's you make directories within directories all in one go. With the base form of `mkdir`, to make a new directory containing a subdirectory you have to do this: + +``` + mkdir newdir +mkdir newdir/subdir +``` + +Or this: + +``` +mkdir -p newdir/subdir +``` + +while with the alias you would only have to do this: + +``` +mkdir newdir/subdir +``` + +Your new `mkdir` will also tell you what it is doing while is creating new directories. + + + + +### Aliases as Safeguards + +The other thing aliases are good for is as safeguards against erasing or overwriting your files accidentally. At this stage you have probably heard the legendary story about the new Linux user who ran: + +``` +rm -rf / +``` + +as root, and nuked the whole system. Then there's the user who decided that: + +``` +rm -rf /some/directory/ * +``` + +was a good idea and erased the complete contents of their home directory. Notice how easy it is to overlook that space separating the directory path and the `*`. + +Both things can be avoided with the `alias rm='rm -i'` alias. The `-i` option makes `rm` ask the user whether that is what they really want to do and gives you a second chance before wreaking havoc in your file system. + +The same goes for `cp`, which can overwrite a file without telling you anything. Create an alias like `alias cp='cp -i'` and stay safe! + +### Next Time + +We are moving more and more into scripting territory. Next time, we'll take the next logical step and see how combining instructions on the command line gives you really interesting and sophisticated solutions to everyday admin problems. + + +-------------------------------------------------------------------------------- + +via: https://www.linux.com/blog/learn/2019/1/aliases-protect-and-serve + +作者：[Paul Brown][a] +选题：[lujun9972][b] +译者：[译者ID](https://github.com/译者ID) +校对：[校对者ID](https://github.com/校对者ID) + +本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 + +[a]: https://www.linux.com/users/bro66 +[b]: https://github.com/lujun9972 +[1]: https://www.linux.com/blog/learn/2019/1/aliases-protect-and-serve +[2]: https://www.linux.com/files/images/fig01png-0 +[3]: https://www.linux.com/sites/lcom/files/styles/rendered_file/public/fig01_0.png?itok=crqTm_va (aliases) +[4]: https://www.linux.com/licenses/category/used-permission diff --git a/sources/tech/20190107 Different Ways To Update Linux Kernel For Ubuntu.md b/sources/tech/20190107 Different Ways To Update Linux Kernel For Ubuntu.md new file mode 100644 index 0000000000..32a6a7dd3e --- /dev/null +++ b/sources/tech/20190107 Different Ways To Update Linux Kernel For Ubuntu.md @@ -0,0 +1,232 @@ +[#]: collector: (lujun9972) +[#]: translator: ( ) +[#]: reviewer: ( ) +[#]: publisher: ( ) +[#]: url: ( ) +[#]: subject: (Different Ways To Update Linux Kernel For Ubuntu) +[#]: via: (https://www.ostechnix.com/different-ways-to-update-linux-kernel-for-ubuntu/) +[#]: author: (SK https://www.ostechnix.com/author/sk/) + +Different Ways To Update Linux Kernel For Ubuntu +====== + + + +In this guide, we have given 7 different ways to update Linux kernel for Ubuntu. Among the 7 methods, five methods requires system reboot to apply the new Kernel and two methods don’t. Before updating Linux Kernel, it is **highly recommended to backup your important data!** All methods mentioned here are tested on Ubuntu OS only. We are not sure if they will work on other Ubuntu flavors (Eg. Xubuntu) and Ubuntu derivatives (Eg. Linux Mint). + +### Part A – Kernel Updates with reboot + +The following methods requires you to reboot your system to apply the new Linux Kernel. All of the following methods are recommended for personal or testing systems. Again, please backup your important data, configuration files and any other important stuff from your Ubuntu system. + +#### Method 1 – Update the Linux Kernel with dpkg (The manual way) + +This method helps you to manually download and install the latest available Linux kernel from **[kernel.ubuntu.com][1]** website. If you want to install most recent version (either stable or release candidate), this method will help. Download the Linux kernel version from the above link. As of writing this guide, the latest available version was **5.0-rc1** and latest stable version was **v4.20**. + +![][3] + +Click on the Linux Kernel version link of your choice and find the section for your architecture (‘Build for XXX’). In that section, download the two files with these patterns (where X.Y.Z is the highest version): + + 1. linux-image-*X.Y.Z*-generic-*.deb + 2. linux-modules-X.Y.Z*-generic-*.deb + + + +In a terminal, change directory to where the files are and run this command to manually install the kernel: + +``` +$ sudo dpkg --install *.deb +``` + +Reboot to use the new kernel: + +``` +$ sudo reboot +``` + +Check the kernel is as expected: + +``` +$ uname -r +``` + +For step by step instructions, please check the section titled under “Install Linux Kernel 4.15 LTS On DEB based systems” in the following guide. + ++ [Install Linux Kernel 4.15 In RPM And DEB Based Systems](https://www.ostechnix.com/install-linux-kernel-4-15-rpm-deb-based-systems/) + +The above guide is specifically written for 4.15 version. However, all the steps are same for installing latest versions too. + +**Pros:** No internet needed (You can download the Linux Kernel from any system). + +**Cons:** Manual update. Reboot necessary. + +#### Method 2 – Update the Linux Kernel with apt-get (The recommended method) + +This is the recommended way to install latest Linux kernel on Ubuntu-like systems. Unlike the previous method, this method will download and install latest Kernel version from Ubuntu official repositories instead of **kernel.ubuntu.com** website.. + +To update the whole system including the Kernel, just do: + +``` +$ sudo apt-get update + +$ sudo apt-get upgrade +``` + +If you want to update the Kernel only, run: + +``` +$ sudo apt-get upgrade linux-image-generic +``` + +**Pros:** Simple. Recommended method. + +**Cons:** Internet necessary. Reboot necessary. + +Updating Kernel from official repositories will mostly work out of the box without any problems. If it is the production system, this is the recommended way to update the Kernel. + +Method 1 and 2 requires user intervention to update Linux Kernels. The following methods (3, 4 & 5) are mostly automated. + +#### Method 3 – Update the Linux Kernel with Ukuu + +**Ukuu** is a Gtk GUI and command line tool that downloads the latest main line Linux kernel from **kernel.ubuntu.com** , and install it automatically in your Ubuntu desktop and server editions. Ukku is not only simplifies the process of manually downloading and installing new Kernels, but also helps you to safely remove the old and unnecessary Kernels. For more details, refer the following guide. + ++ [Ukuu – An Easy Way To Install And Upgrade Linux Kernel In Ubuntu-based Systems](https://www.ostechnix.com/ukuu-an-easy-way-to-install-and-upgrade-linux-kernel-in-ubuntu-based-systems/) + +**Pros:** Easy to install and use. Automatically installs main line Kernel. + +**Cons:** Internet necessary. Reboot necessary. + +#### Method 4 – Update the Linux Kernel with UKTools + +Just like Ukuu, the **UKTools** also fetches the latest stable Kernel from from **kernel.ubuntu.com** site and installs it automatically on Ubuntu and its derivatives like Linux Mint. More details about UKTools can be found in the link given below. + ++ [UKTools – Upgrade Latest Linux Kernel In Ubuntu And Derivatives](https://www.ostechnix.com/uktools-upgrade-latest-linux-kernel-in-ubuntu-and-derivatives/) + +**Pros:** Simple. Automated. + +**Cons:** Internet necessary. Reboot necessary. + +#### Method 5 – Update the Linux Kernel with Linux Kernel Utilities + +**Linux Kernel Utilities** is yet another program that makes the process of updating Linux kernel easy in Ubuntu-like systems. It is actually a set of BASH shell scripts used to compile and/or update latest Linux kernels for Debian and derivatives. It consists of three utilities, one for manually compiling and installing Kernel from source from [**http://www.kernel.org**][4] website, another for downloading and installing pre-compiled Kernels from from ** /.kodi/userdata/advancedsettings.xml**. This file can contain a lot of very advanced, tweakable settings. My devices have these settings: + +``` + + +``` + +The **< cache>** section—which sets how much of a file Kodi will buffer over the network— is optional in this scenario. See the [Kodi wiki][9] for a full breakdown of this file and its options. + +Once the configuration is complete, it's a good idea to close and reopen Kodi to make sure the settings are applied. + +The final step is configuring all the Kodi clients to use the same network share for all their content. Only one client needs to scrap/refresh the metadata if everything is created successfully. When data is collected, you should see that Kodi creates a new database on your SQL server: + +``` +[kodi@kodi-mysql ~]$ mysql -u root -p +Enter password: +Welcome to the MariaDB monitor. Commands end with ; or \g. +Your MariaDB connection id is 180 +Server version: 10.1.37-MariaDB MariaDB Server + +Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others. + +Type 'help;' or '\h' for help. Type '\c' to clear the current input statement. + +MariaDB [(none)]> show databases; ++--------------------+ +| Database | ++--------------------+ +| MyVideos107 | +| information_schema | +| mysql | +| performance_schema | ++--------------------+ +4 rows in set (0.00 sec) +``` + +### Wrapping up + +This article walked through how to get up and running with the basic functionality of Kodi. You should be able to add content and pull down metadata to make browsing your media more convenient. + +You also know how to search for, install, and potentially configure add-ons for additional features. Be extra careful when downloading add-ons, as they are provided by the community at large and not the core developers. It's best to use add-ons only from organizations or companies you trust. + +And you know a bit about sharing metadata across multiple devices. You've been introduced to **advancedsettings.xml** ; hopefully it has piqued your interest. Kodi has a lot of dials and knobs to turn, and you can squeeze a lot of performance and functionality out of the platform with enough experimentation. + +Are you interested in doing more tweaking? What are some of your favorite add-ons or settings? Do you want to know how to change the user interface? What are some of your favorite skins? Let me know in the comments! + +-------------------------------------------------------------------------------- + +via: https://opensource.com/article/19/1/manage-your-media-kodi + +作者：[Steve Ovens][a] +选题：[lujun9972][b] +译者：[译者ID](https://github.com/译者ID) +校对：[校对者ID](https://github.com/校对者ID) + +本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 + +[a]: https://opensource.com/users/stratusss +[b]: https://github.com/lujun9972 +[1]: https://en.wikipedia.org/wiki/ISO_image +[2]: https://kodi.tv/ +[3]: https://kodi.wiki/view/HOW-TO:Install_Kodi_for_Linux#Fedora +[4]: https://en.wikipedia.org/wiki/Server_Message_Block +[5]: https://en.wikipedia.org/wiki/Zero-configuration_networking +[6]: https://www.plex.tv +[7]: https://www.samba.org/ +[8]: https://wiki.archlinux.org/index.php/MySQL +[9]: https://kodi.wiki/view/Advancedsettings.xml diff --git a/sources/tech/20190107 Testing isn-t everything.md b/sources/tech/20190107 Testing isn-t everything.md new file mode 100644 index 0000000000..b2a2daaaac --- /dev/null +++ b/sources/tech/20190107 Testing isn-t everything.md @@ -0,0 +1,135 @@ +[#]: collector: (lujun9972) +[#]: translator: ( ) +[#]: reviewer: ( ) +[#]: publisher: ( ) +[#]: url: ( ) +[#]: subject: (Testing isn't everything) +[#]: via: (https://arp242.net/weblog/testing.html) +[#]: author: (Martin Tournoij https://arp242.net/) + +Testing isn't everything +====== + +This is adopted from a discussion about [Want to write good unit tests in go? Don’t panic… or should you?][1] While this mainly talks about Go a lot of the points also apply to other languages. + +Some of the most difficult code I’ve worked with is code that is “easily testable”. Code that abstracts everything to the point where you have no idea what’s going on, just so that it can add a “unit test” to what would otherwise be a very straightforward function. DHH called this [Test-induced design damage][2]. + +Testing is just one tool to make sure that your program works, out of several. Another very important tool is writing code in such a way that it is easy to understand and reason about (“simplicity”). + +Books that advocate extensive testing – such as Robert C. Martin’s Clean Code – were written, in part, as a response to ever more complex programs, where you read 1,000 lines of code but still had no idea what’s going on. I recently had to port a simple Java “emoji replacer” (😂 ➙ 😂) to Go. To ensure compatibility I looked up the implementation. It was a whole bunch of classes, factories, and whatnot which all just resulted in calling a regexp on a string. 🤷 + +In dynamic languages like Ruby and Python tests are important for a different reason, as something like this will “work” just fine: + +``` +if condition: + print('w00t') +else: + nonexistent_function() +``` + +Except of course if that `else` branch is entered. It’s easy to typo stuff, or mix stuff up. + +In Go, both of these problems are less of a concern. It has a good static type system, and the focus is on simple straightforward code that is easy to comprehend. Even for a number of dynamic languages there are optional typing systems (function annotations in Python, TypeScript for JavaScript). + +Sometimes you can do a straightforward implementation that doesn’t sacrifice anything for testability; great! But sometimes you have to strike a balance. For some code, not adding a unit test is fine. + +Intensive focus on “unit tests” can be incredibly damaging to a code base. Some codebases have a gazillion unit tests, which makes any change excessively time-consuming as you’re fixing up a whole bunch of tests for even trivial changes. Often times a lot of these tests are just duplicates; adding tests to every layer of a simple CRUD HTTP endpoint is a common example. In many apps it’s fine to just rely on a single integration test. + +Stuff like SQL mocks is another great example. It makes code more complex, harder to change, all so we can say we added a “unit test” to `select * from foo where x=?`. The worst part is, it doesn’t even test anything other than verifying you didn’t typo an SQL query. As soon as the test starts doing anything useful, such as verifying that it actually returns the correct rows from the database, the Unit Test purists will start complaining that it’s not a True Unit Test™ and that You’re Doing It Wrong™. +For most queries, the integration tests and/or manual tests are fine, and extensive SQL mocks are entirely superfluous at best, and harmful at worst. + +There are exceptions, of course; if you’ve got a lot of `if cond { q += "more sql" }` then adding SQL mocks to verify the correctness of that logic might be a good idea. Even in those cases a “non-unit unit test” (e.g. one that just accesses the database) is still a viable option. Integration tests are also still an option. A lot of applications don’t have those kind of complex queries anyway. + +One important reason for the focus on unit tests is to ensure test code runs fast. This was a response to massive test harnesses that take a day to run. This, again, is not really a problem in Go. All integration tests I’ve written run in a reasonable amount of time (several seconds at most, usually faster). The test cache introduced in Go 1.10 makes it even less of a concern. + +Last year a coworker refactored our ETag-based caching library. The old code was very straightforward and easy to understand, and while I’m not claiming it was guaranteed bug-free, it did work very well for a long time. + +It should have been written with some tests in place, but it wasn’t (I didn’t write the original version). Note that the code was not completely untested, as we did have integration tests. + +The refactored version is much more complex. Aside from the two weeks lost on refactoring a working piece of code to … another working piece of code (topic for another post), I’m not so convinced it’s actually that much better. I consider myself a reasonably accomplished and experienced programmer, with a reasonable knowledge and experience in Go. I think that in general, based on feedback from peers and performance reviews, I am at least a programmer of “average” skill level, if not more. + +If an average programmer has trouble comprehending what is in essence a handful of simple functions because there are so many layers of abstractions, then something has gone wrong. The refactor traded one tool to verify correctness (simplicity) with another (testing). Simplicity is hardly a guarantee to ensure correctness, but neither are unit tests. Ideally, we should do both. + +Postscript: the refactor introduced a bug and removed a feature that was useful, but is now harder to add, not in the least because the code is much more complex. + +All units working correctly gives exactly zero guarantees that the program is working correctly. A lot of logic errors won’t be caught because the logic consists of several units working together. So you need integration tests, and if the integration tests duplicate half of your unit tests, then why bother with those unit tests? + +Test Driven Development (TDD) is also just one tool. It works well for some problems; not so much for others. In particular, I think that “forced to write code in tiny units” can be terribly harmful in some cases. Some code is just a serial script which says “do this, and then that, and then this”. Splitting that up in a whole bunch of “tiny units” can greatly reduce how easy the code is to understand, and thus harder to verify that it is correct. + +I’ve had to fix some Ruby code where everything was in tiny units – there is a strong culture of TDD in the Ruby community – and even though the units were easy to understand I found it incredibly hard to understand the application logic. If everything is split in “tiny units” then understanding how everything fits together to create an actual program that does something useful will be much harder. + +You see the same friction in the old microkernel vs. monolithic kernel debate, or the more recent microservices vs. monolithic app one. In principle splitting everything up in small parts sounds like a great idea, but in practice it turns out that making all the small parts work together is a very hard problem. A hybrid approach seems to work best for kernels and app design, balancing the advantages and downsides of both approaches. I think the same applies to code. + +To be clear, I am not against unit tests or TDD and claiming we should all gung-go cowboy code our way through life 🤠. I write unit tests and practice TDD, when it makes sense. My point is that unit tests and TDD are not the solution to every single last problem and should applied indiscriminately. This is why I use words such as “some” and “often” so frequently. + +This brings me to the topic of testing frameworks. I have never understood what problem libraries such as [goblin][3] are solving. How is this: + +``` +Expect(err).To(nil) +Expect(out).To(test.wantOut) +``` + +An improvement over this? + +``` +if err != nil { + t.Fatal(err) +} + +if out != tt.want { + t.Errorf("out: %q\nwant: %q", out, tt.want) +} +``` + +What’s wrong with `if` and `==`? Why do we need to abstract it? Note that with table-driven tests you’re only typing these checks once, so you’re saving just a few lines here. + +[Ginkgo][4] is even worse. It turns a very simple, straightforward, and understandable piece of code and doesn’t just abstract `if`, it also chops up the execution in several different functions (`BeforeEach()` and `DescribeTable()`). + +This is known as Behaviour-driven development (BDD). I am not entirely sure what to think of BDD. I am skeptical, but I’ve never properly used it in a large project so I’m hesitant to just dismiss it. Note that I said “properly”: most projects don’t really use BDD, they just use a library with a BDD syntax and shoehorn their testing code in to that. That’s ad-hoc BDD, or faux-BDD. + +Whatever merits BDD may have, they are not present simply because your testing code vaguely resembles BDD-style syntax. This on its own demonstrates that BDD is perhaps not a great idea for many projects. + +I think there are real problems with these BDD(-ish) test tools, as they obfuscate what you’re actually doing. No matter what, testing remains a matter of getting the output of a function and checking if that matches what you expected. No testing methodology is going to change that fundamental. The more layers you add on top of that, the harder it will be to debug. + +When determining if something is “easy” then my prime concern is not how easy something is to write, but how easy something is to debug when things fail. I will gladly spend a bit more effort writing things if that makes things a lot easier to debug. + +All code – including testing code – can fail in confusing, surprising, and unexpected ways (a “bug”), and then you’re expected to debug that code. The more complex the code, the harder it is to debug. + +You should expect all code – including testing code – to go through several debugging cycles. Note that with debugging cycle I don’t mean “there is a bug in the code you need to fix”, but rather “I need to look at this code to fix the bug”. + +In general, I already find testing code harder to debug than regular code, as the “code surface” tends to be larger. You have the testing code and the actual implementation code to think of. That’s a lot more than just thinking of the implementation code. + +Adding these abstractions means you will now also have to think about that, too! This might be okay if the abstractions would reduce the scope of what you have to think about, which is a common reason to add abstractions in regular code, but it doesn’t. It just adds more things to think about. + +So these are exactly the wrong kind of abstractions: they wrap and obfuscate, rather than separate concerns and reduce the scope. + +If you’re interested in soliciting contributions from other people in open source projects then making your tests understandable is a very important concern (it’s also important in business context, but a bit less so, as you’ve got actual time to train people). + +Seeing PRs with “here’s the code, it works, but I couldn’t figure out the tests, plz halp!” is not uncommon; and I’m fairly sure that at least a few people never even bothered to submit PRs just because they got stuck on the tests. I know I have. + +There is one open source project that I contributed to, and would like to contribute more to, but don’t because it’s just too hard to write and run tests. Every change is “write working code in 15 minutes, spend 45 minutes dealing with tests”. It’s … no fun at all. + +Writing good software is hard. I’ve got some ideas on how to do it, but don’t have a comprehensive view. I’m not sure if anyone really does. I do know that “always add unit tests” and “always practice TDD” isn’t the answer, in spite of them being useful concepts. To give an analogy: most people would agree that a free market is a good idea, but at the same time even most libertarians would agree it’s not the complete solution to every single problem (well, [some do][5], but those ideas are … rather misguided). + +You can mail me at [martin@arp242.net][6] or [create a GitHub issue][7] for feedback, questions, etc. + +-------------------------------------------------------------------------------- + +via: https://arp242.net/weblog/testing.html + +作者：[Martin Tournoij][a] +选题：[lujun9972][b] +译者：[译者ID](https://github.com/译者ID) +校对：[校对者ID](https://github.com/校对者ID) + +本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 + +[a]: https://arp242.net/ +[b]: https://github.com/lujun9972 +[1]: https://medium.com/@jens.neuse/want-to-write-good-unit-tests-in-go-dont-panic-or-should-you-ba3eb5bf4f51 +[2]: http://david.heinemeierhansson.com/2014/test-induced-design-damage.html +[3]: https://github.com/franela/goblin +[4]: https://github.com/onsi/ginkgo +[5]: https://en.wikipedia.org/wiki/Murray_Rothbard#Children's_rights_and_parental_obligations +[6]: mailto:martin@arp242.net +[7]: https://github.com/Carpetsmoker/arp242.net/issues/new diff --git a/sources/tech/20190108 Create your own video streaming server with Linux.md b/sources/tech/20190108 Create your own video streaming server with Linux.md new file mode 100644 index 0000000000..24dd44524d --- /dev/null +++ b/sources/tech/20190108 Create your own video streaming server with Linux.md @@ -0,0 +1,301 @@ +[#]: collector: (lujun9972) +[#]: translator: ( ) +[#]: reviewer: ( ) +[#]: publisher: ( ) +[#]: url: ( ) +[#]: subject: (Create your own video streaming server with Linux) +[#]: via: (https://opensource.com/article/19/1/basic-live-video-streaming-server) +[#]: author: (Aaron J.Prisk https://opensource.com/users/ricepriskytreat) + +Create your own video streaming server with Linux +====== +Set up a basic live streaming server on a Linux or BSD operating system. + + +Live video streaming is incredibly popular—and it's still growing. Platforms like Amazon's Twitch and Google's YouTube boast millions of users that stream and consume countless hours of live and recorded media. These services are often free to use but require you to have an account and generally hold your content behind advertisements. Some people don't need their videos to be available to the masses or just want more control over their content. Thankfully, with the power of open source software, anyone can set up a live streaming server. + +### Getting started + +In this tutorial, I'll explain how to set up a basic live streaming server with a Linux or BSD operating system. + +This leads to the inevitable question of system requirements. These can vary, as there are a lot of variables involved with live streaming, such as: + + * **Stream quality:** Do you want to stream in high definition or will standard definition fit your needs? + * **Viewership:** How many viewers are you expecting for your videos? + * **Storage:** Do you plan on keeping saved copies of your video stream? + * **Access:** Will your stream be private or open to the world? + + + +There are no set rules when it comes to system requirements, so I recommend you experiment and find what works best for your needs. I installed my server on a virtual machine with 4GB RAM, a 20GB hard drive, and a single Intel i7 processor core. + +This project uses the Real-Time Messaging Protocol (RTMP) to handle audio and video streaming. There are other protocols available, but I chose RTMP because it has broad support. As open standards like WebRTC become more compatible, I would recommend that route. + +It's also very important to know that "live" doesn't always mean instant. A video stream must be encoded, transferred, buffered, and displayed, which often adds delays. The delay can be shortened or lengthened depending on the type of stream you're creating and its attributes. + +### Setting up a Linux server + +You can use many different distributions of Linux, but I prefer Ubuntu, so I downloaded the [Ubuntu Server][1] edition for my operating system. If you prefer your server to have a graphical user interface (GUI), feel free to use [Ubuntu Desktop][2] or one of its many flavors. Then, I fired up the Ubuntu installer on my computer or virtual machine and chose the settings that best matched my environment. Below are the steps I took. + +Note: Because this is a server, you'll probably want to set some static network settings. + + + +After the installer finishes and your system reboots, you'll be greeted with a lovely new Ubuntu system. As with any newly installed operating system, install any updates that are available: + +``` +sudo apt update +sudo apt upgrade +``` + +This streaming server will use the very powerful and versatile Nginx web server, so you'll need to install it: + +``` +sudo apt install nginx +``` + +Then you'll need to get the RTMP module so Nginx can handle your media stream: + +``` +sudo add-apt-repository universe +sudo apt install libnginx-mod-rtmp +``` + +Adjust your web server's configuration so it can accept and deliver your media stream. + +``` +sudo nano /etc/nginx/nginx.conf +``` + +Scroll to the bottom of the configuration file and add the following code: + +``` +rtmp { + server { + listen 1935; + chunk_size 4096; + + application live { + live on; + record off; + } + } +} +``` + + + +Save the config. Because I'm a heretic, I use [Nano][3] for editing configuration files. In Nano, you can save your config by pressing **Ctrl+X** , **Y** , and then **Enter.** + +This is a very minimal config that will create a working streaming server. You'll add to this config later, but this is a great starting point. + +However, before you can begin your first stream, you'll need to restart Nginx with its new configuration: + +``` +sudo systemctl restart nginx +``` + +### Setting up a BSD server + +If you're of the "beastie" persuasion, getting a streaming server up and running is also devilishly easy. + +Head on over to the [FreeBSD][4] website and download the latest release. Fire up the FreeBSD installer on your computer or virtual machine and go through the initial steps and choose settings that best match your environment. Since this is a server, you'll likely want to set some static network settings. + +After the installer finishes and your system reboots, you should have a shiny new FreeBSD system. Like any other freshly installed system, you'll likely want to get everything updated (from this step forward, make sure you're logged in as root): + +``` +pkg update +pkg upgrade +``` + +I install [Nano][3] for editing configuration files: + +``` +pkg install nano +``` + +This streaming server will use the very powerful and versatile Nginx web server. You can build Nginx using the excellent ports system that FreeBSD boasts. + +First, update your ports tree: + +``` +portsnap fetch +portsnap extract +``` + +Browse to the Nginx ports directory: + +``` +cd /usr/ports/www/nginx +``` + +And begin building Nginx by running: + +``` +make install +``` + +You'll see a screen asking what modules to include in your Nginx build. For this project, you'll need to add the RTMP module. Scroll down until the RTMP module is selected and press **Space**. Then Press **Enter** to proceed with the rest of the build and installation. + +Once Nginx has finished installing, it's time to configure it for streaming purposes. + +First, add an entry into **/etc/rc.conf** to ensure the Nginx server starts when your system boots: + +``` +nano /etc/rc.conf +``` + +Add this text to the file: + +``` +nginx_enable="YES" +``` + + + +Next, create a webroot directory from where Nginx will serve its content. I call mine **stream** : + +``` +cd /usr/local/www/ +mkdir stream +chmod -R 755 stream/ +``` + +Now that you have created your stream directory, configure Nginx by editing its configuration file: + +``` +nano /usr/local/etc/nginx/nginx.conf +``` + +Load your streaming modules at the top of the file: + +``` +load_module /usr/local/libexec/nginx/ngx_stream_module.so; +load_module /usr/local/libexec/nginx/ngx_rtmp_module.so; +``` + + + +Under the **Server** section, change the webroot location to match the one you created earlier: + +``` +Location / { +root /usr/local/www/stream +} +``` + + + +And finally, add your RTMP settings so Nginx will know how to handle your media streams: + +``` +rtmp { + server { + listen 1935; + chunk_size 4096; + + application live { + live on; + record off; + } + } +} +``` + +Save the config. In Nano, you can do this by pressing **Ctrl+X** , **Y** , and then **Enter.** + +As you can see, this is a very minimal config that will create a working streaming server. Later, you'll add to this config, but this will provide you with a great starting point. + +However, before you can begin your first stream, you'll need to restart Nginx with its new config: + +``` +service nginx restart +``` + +### Set up your streaming software + +#### Broadcasting with OBS + +Now that your server is ready to accept your video streams, it's time to set up your streaming software. This tutorial uses the powerful and open source Open Broadcast Studio (OBS). + +Head over to the [OBS website][5] and find the build for your operating system and install it. Once OBS launches, you should see a first-time-run wizard that will help you configure OBS with the settings that best fit your hardware. + + + +OBS isn't capturing anything because you haven't supplied it with a source. For this tutorial, you'll just capture your desktop for the stream. Simply click the **+** button under **Source** , choose **Screen Capture** , and select which desktop you want to capture. + +Click OK, and you should see OBS mirroring your desktop. + +Now it's time to send your newly configured video stream to your server. In OBS, click **File** > **Settings**. Click on the **Stream** section, and set **Stream Type** to **Custom Streaming Server**. + +In the URL box, enter the prefix **rtmp://** followed the IP address of your streaming server followed by **/live**. For example, **rtmp://IP-ADDRESS/live**. + +Next, you'll probably want to enter a Stream key—a special identifier required to view your stream. Enter whatever key you want (and can remember) in the **Stream key** box. + + + +Click **Apply** and then **OK**. + +Now that OBS is configured to send your stream to your server, you can start your first stream. Click **Start Streaming**. + +If everything worked, you should see the button change to **Stop Streaming** and some bandwidth metrics will appear at the bottom of OBS. + + + +If you receive an error, double-check Stream Settings in OBS for misspellings. If everything looks good, there could be another issue preventing it from working. + +### Viewing your stream + +A live video isn't much good if no one is watching it, so be your first viewer! + +There are a multitude of open source media players that support RTMP, but the most well-known is probably [VLC media player][6]. + +After you install and launch VLC, open your stream by clicking on **Media** > **Open Network Stream**. Enter the path to your stream, adding the Stream Key you set up in OBS, then click **Play**. For example, **rtmp://IP-ADDRESS/live/SECRET-KEY**. + +You should now be viewing your very own live video stream! + + + +### Where to go next? + +This is a very simple setup that will get you off the ground. Here are two other features you likely will want to use. + + * **Limit access:** The next step you might want to take is to limit access to your server, as the default setup allows anyone to stream to and from the server. There are a variety of ways to set this up, such as an operating system firewall, [.htaccess file][7], or even using the [built-in access controls in the STMP module][8]. + + * **Record streams:** This simple Nginx configuration will only stream and won't save your videos, but this is easy to add. In the Nginx config, under the RTMP section, set up the recording options and the location where you want to save your videos. Make sure the path you set exists and Nginx is able to write to it. + + + + +``` +application live { + live on; + record all; + record_path /var/www/html/recordings; + record_unique on; +} +``` + +The world of live streaming is constantly evolving, and if you're interested in more advanced uses, there are lots of other great resources you can find floating around the internet. Good luck and happy streaming! + +-------------------------------------------------------------------------------- + +via: https://opensource.com/article/19/1/basic-live-video-streaming-server + +作者：[Aaron J.Prisk][a] +选题：[lujun9972][b] +译者：[译者ID](https://github.com/译者ID) +校对：[校对者ID](https://github.com/校对者ID) + +本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 + +[a]: https://opensource.com/users/ricepriskytreat +[b]: https://github.com/lujun9972 +[1]: https://www.ubuntu.com/download/server +[2]: https://www.ubuntu.com/download/desktop +[3]: https://www.nano-editor.org/ +[4]: https://www.freebsd.org/ +[5]: https://obsproject.com/ +[6]: https://www.videolan.org/vlc/index.html +[7]: https://httpd.apache.org/docs/current/howto/htaccess.html +[8]: https://github.com/arut/nginx-rtmp-module/wiki/Directives#access diff --git a/sources/tech/20190109 Automating deployment strategies with Ansible.md b/sources/tech/20190109 Automating deployment strategies with Ansible.md new file mode 100644 index 0000000000..175244e760 --- /dev/null +++ b/sources/tech/20190109 Automating deployment strategies with Ansible.md @@ -0,0 +1,152 @@ +[#]: collector: (lujun9972) +[#]: translator: ( ) +[#]: reviewer: ( ) +[#]: publisher: ( ) +[#]: url: ( ) +[#]: subject: (Automating deployment strategies with Ansible) +[#]: via: (https://opensource.com/article/19/1/automating-deployment-strategies-ansible) +[#]: author: (Jario da Silva Junior https://opensource.com/users/jairojunior) + +Automating deployment strategies with Ansible +====== +Use automation to eliminate time sinkholes due to repetitive tasks and unplanned work. + + +When you examine your technology stack from the bottom layer to the top—hardware, operating system (OS), middleware, and application—with their respective configurations, it's clear that changes are far more frequent as you go up in the stack. Your hardware will hardly change, your OS has a long lifecycle, and your middleware will keep up with the application's needs, but even if your release cycle is long (weeks or months), your applications will be the most volatile. + + + +In [The Practice of System and Network Administration][1], the authors categorize the biggest "time sinkholes" in IT as manual/non-standard provisioning of OSes and application deployments. These time sinkholes will consume you with repetitive tasks or unplanned work. + +How so? Let's say you provision a new server without Network Time Protocol (NTP) properly configured, and a small percentage of your requests—in a cluster of dozens of servers—start to behave strangely because an application uses some sort of scheduler that relies on correct time. When you look at it like this, it is an easy problem to fix, but how long it would it take your team figure it out? Incidents or unplanned work consume a lot of your time and, even worse, your greatest talents. Should you really be wasting time investigating production systems like this? Wouldn't it be better to set this server aside and automatically provision a new one from scratch? + +What about manual deployment? Imagine 20 binaries deployed across a farm or nodes with their respective configuration files? How error-prone is this? Inevitably, it will eventually end up in unplanned work. + +The [State of DevOps Report 2018][2] introduces the stages of DevOps adoption, and it's no surprise that Stage 0 includes deployment automation and reuse of deployment patterns, while Stage 1 and 2 focus on standardization of your infrastructure stack to reduce inconsistencies across your environment. + +Note that, more than once, I have seen an ops team using this "standardization" as an excuse to limit a development team's ability to deliver, forcing them to use a hammer on something that is definitely not a nail. Don't do it; the price is extremely high. + +The lesson to be learned here is that lack of automation not only increases your lead time but also the rate of problems in your process and the amount of unplanned work you face. If you've read [The Phoenix Project][3], you know this is the root of all evil in any value stream, and if you don't get rid of it, it will eventually kill your business. + +When trying to fill the biggest time sinkholes, why not start with automating operating system installation? We could, but the results would take longer to appear since new virtual machines are not created as frequently as applications are deployed. In other words, this may not free up the time we need to power our initiative, so it could die prematurely. + +Still not convinced? Smaller and more frequent releases are also extremely positive from the development side. Let's explain a little further… + +### Deploy ≠ Release + +The first thing to understand is that, although they're used interchangeably, deployment and release do **NOT** mean the same thing. Release refers to providing the user a new version, while deployment is the technical process of deploying the new version. Let's focus on the technical process of deployment. + +### Tasks, groups, and Ansible + +We need to understand the deployment process from the beginning to the end, including everything in the middle—the tasks, which servers are involved in the process, and which steps are executed—to avoid falling into the pitfalls described by Mattias Geniar in [Automating the unknown][4]. + +#### Tasks + +The steps commonly executed in a regular deployment process include: + + * Deploy application(s)/database(s) or database(s) change(s) + * Stop/start services and monitoring + * Add/remove the server from our load balancers + * Verify application state—is it ready to serve requests? + * Manual approval—is it necessary? + + + +For some people, automating the deployment process but leaving a manual approval step is like riding a bike with training wheels. As someone once told me: "It's better to ride with training wheels than not ride at all." + +What if a tool doesn't include an API or a command-line interface (CLI) to enable task automation? Well, maybe it's time to think about changing tools. There are many open source application servers, databases, monitoring systems, and load balancers that are easily automated—thanks in large part to the [Unix way][5]. When adopting a new technology, eliminate options that are not automated and use your creativity to support your legacy technologies. For example, I've seen people versioning network appliance configuration files and updating them using FTP. + +And guess what? It's a wonderful time to adopt open source tools. The recent [Accelerate: State of DevOps][6] report found that open source technologies are in predominant use in high-performance organizations. The logic is pretty simple: open source projects function in a "Darwinist" model, where those that do not adapt and evolve will die for lack of a user base or contributions. Feedback is paramount to software evolution. + +#### Groups + +To identify groups of servers to target for automation, think about the most tasks you want to automate, such as those that: + + * Deploy application(s)/database(s) or database change(s) + * Stop/start services and monitoring + * Add/remove server(s) from load balancer(s) + * Verify application state—is it ready to serve requests? + + + +#### The playbook + +A high-level deployment process could be: + + 1. Stop monitoring (to avoid false-positives) + 2. Remove server from the load balancer (to prevent the user from receiving an error code) + 3. Stop the service (to enable a graceful shutdown) + 4. Deploy the new version of the application + 5. Wait for the application to be ready to receive new requests + 6. Execute steps 3, 2, and 1. + 7. Do the same for the next N servers. + + + +Having documentation of your process is nice, but having an executable documenting your deployment is better! Here's what steps 1–5 would look like in Ansible for a fully open source stack: + +``` +- name: Disable alerts + nagios: + action: disable_alerts + host: "{{ inventory_hostname }}" + services: webserver + delegate_to: "{{ item }}" + loop: "{{ groups.monitoring }}" + +- name: Disable servers in the LB + haproxy: + host: "{{ inventory_hostname }}" + state: disabled + backend: app + delegate_to: "{{ item }}" + loop: " {{ groups.lbserver }}" + +- name: Stop the service + service: name=httpd state=stopped + +- name: Deploy a new version + unarchive: src=app.tar.gz dest=/var/www/app + +- name: Verify application state + uri: + url: "http://{{ inventory_hostname }}/app/healthz" + status_code: 200 + retries: 5 +``` + +### Why Ansible? + +There are other alternatives for application deployment, but the things that make Ansible an excellent choice include: + + * Multi-tier orchestration (i.e., **delegate_to** ) allowing you to orderly target different groups of servers: monitoring, load balancer, application server, database, etc. + * Rolling upgrade (i.e., serial) to control how changes are made (e.g., 1 by 1, N by N, X% at a time, etc.) + * Error control, **max_fail_percentage** and **any_errors_fatal** , is my process all-in or will it tolerate fails? + * A vast library of modules for: + * Monitoring (e.g., Nagios, Zabbix, etc.) + * Load balancers (e.g., HAProxy, F5, Netscaler, Cisco, etc.) + * Services (e.g., service, command, file) + * Deployment (e.g., copy, unarchive) + * Programmatic verifications (e.g., command, Uniform Resource Identifier) + + + +-------------------------------------------------------------------------------- + +via: https://opensource.com/article/19/1/automating-deployment-strategies-ansible + +作者：[Jario da Silva Junior][a] +选题：[lujun9972][b] +译者：[译者ID](https://github.com/译者ID) +校对：[校对者ID](https://github.com/校对者ID) + +本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 + +[a]: https://opensource.com/users/jairojunior +[b]: https://github.com/lujun9972 +[1]: https://www.amazon.com/Practice-System-Network-Administration-Enterprise/dp/0321919165/ref=dp_ob_title_bk +[2]: https://puppet.com/resources/whitepaper/state-of-devops-report +[3]: https://www.amazon.com/Phoenix-Project-DevOps-Helping-Business/dp/0988262592 +[4]: https://ma.ttias.be/automating-unknown/ +[5]: https://en.wikipedia.org/wiki/Unix_philosophy +[6]: https://cloudplatformonline.com/2018-state-of-devops.html diff --git a/sources/tech/20190109 GoAccess - A Real-Time Web Server Log Analyzer And Interactive Viewer.md b/sources/tech/20190109 GoAccess - A Real-Time Web Server Log Analyzer And Interactive Viewer.md new file mode 100644 index 0000000000..3bad5ba969 --- /dev/null +++ b/sources/tech/20190109 GoAccess - A Real-Time Web Server Log Analyzer And Interactive Viewer.md @@ -0,0 +1,187 @@ +[#]: collector: (lujun9972) +[#]: translator: ( ) +[#]: reviewer: ( ) +[#]: publisher: ( ) +[#]: url: ( ) +[#]: subject: (GoAccess – A Real-Time Web Server Log Analyzer And Interactive Viewer) +[#]: via: (https://www.2daygeek.com/goaccess-a-real-time-web-server-log-analyzer-and-interactive-viewer/) +[#]: author: (Vinoth Kumar https://www.2daygeek.com/author/vinoth/) + +GoAccess – A Real-Time Web Server Log Analyzer And Interactive Viewer +====== + +Analyzing a log file is a big headache for Linux administrators as it’s capturing a lot of things. + +Most of the newbies and L1 administrators doesn’t know how to analyze this. + +If you have good knowledge to analyze a logs then you will be a legend for NIX system. + +There are many tools available in Linux to analyze the logs easily. + +GoAccess is one of the tool which allow users to analyze web server logs easily. + +We will be going to discuss in details about GoAccess tool in this article. + +### What is GoAccess? + +GoAccess is a real-time web log analyzer and interactive viewer that runs in a terminal in *nix systems or through your browser. + +GoAccess has minimal requirements, it’s written in C and requires only ncurses. + +It will support Apache, Nginx and Lighttpd logs. It provides fast and valuable HTTP statistics for system administrators that require a visual server report on the fly. + +GoAccess parses the specified web log file and outputs the data to the X terminal and browser. + +GoAccess was designed to be a fast, terminal-based log analyzer. Its core idea is to quickly analyze and view web server statistics in real time without needing to use your browser. + +Terminal output is the default output, it has the capability to generate a complete, self-contained, real-time HTML report, as well as a JSON, and CSV report. + +GoAccess allows any custom log format and the following (Combined Log Format (XLF/ELF) Apache | Nginx & Common Log Format (CLF) Apache) predefined log format options are included, but not limited to. + +### GoAccess Features + + * **`Completely Real Time:`** All the metrics are updated every 200 ms on the terminal and every second on the HTML output. + * **`Track Application Response Time:`** Track the time taken to serve the request. Extremely useful if you want to track pages that are slowing down your site. + * **`Visitors:`** Determine the amount of hits, visitors, bandwidth, and metrics for slowest running requests by the hour, or date. + * **`Metrics per Virtual Host:`** Have multiple Virtual Hosts (Server Blocks)? It features a panel that displays which virtual host is consuming most of the web server resources. + + + +### How to Install GoAccess? + +I would advise users to install GoAccess from distribution official repository with help of Package Manager. It is available in most of the distributions official repository. + +As we know, we will be getting bit outdated package for standard release distribution and rolling release distributions always include latest package. + +If you are running the OS with standard release distributions, i would suggest you to check the alternative options such as PPA or Official GoAccess maintainer repository, etc, to get a latest package. + +For **`Debian/Ubuntu`** systems, use **[APT-GET Command][1]** or **[APT Command][2]** to install GoAccess on your systems. + +``` +# apt install goaccess +``` + +To get a latest GoAccess package, use the below GoAccess official repository. + +``` +$ echo "deb https://deb.goaccess.io/ $(lsb_release -cs) main" | sudo tee -a /etc/apt/sources.list.d/goaccess.list +$ wget -O - https://deb.goaccess.io/gnugpg.key | sudo apt-key add - +$ sudo apt-get update +$ sudo apt-get install goaccess +``` + +For **`RHEL/CentOS`** systems, use **[YUM Package Manager][3]** to install GoAccess on your systems. + +``` +# yum install goaccess +``` + +For **`Fedora`** system, use **[DNF Package Manager][4]** to install GoAccess on your system. + +``` +# dnf install goaccess +``` + +For **`ArchLinux/Manjaro`** based systems, use **[Pacman Package Manager][5]** to install GoAccess on your systems. + +``` +# pacman -S goaccess +``` + +For **`openSUSE Leap`** system, use **[Zypper Package Manager][6]** to install GoAccess on your system. + +``` +# zypper install goaccess + +# zypper ar -f obs://server:http + +# zypper ref && zypper in goaccess +``` + +### How to Use GoAccess? + +After successful installation of GoAccess. Just enter the goaccess command and followed by the web server log location to view it. + +``` +# goaccess [options] /path/to/Web Server/access.log + +# goaccess /var/log/apache/2daygeek_access.log +``` + +When you execute the above command, it will ask you to select the **Log Format Configuration**. +![][8] + +I had tested this with Apache access log. The Apache log is splitted in fifteen section. The details are below. The main section shows the summary about the fifteen section. + +The below screenshots included four sessions such as Unique Visitors, Requested files, Static Requests, Not found URLs. +![][9] + +The below screenshots included four sessions such as Visitor Hostnames and IPs, Operating Systems, Browsers, Time Distribution. +![][10] + +The below screenshots included four sessions such as Referrers URLs, Referring Sites, Google’s search engine results, HTTP status codes. +![][11] + +If you would like to generate a html report, use the following format. + +Initially i got an error when i was trying to generate the html report. + +``` +# goaccess 2daygeek_access.log -a > report.html + +GoAccess - version 1.3 - Nov 23 2018 11:28:19 +Config file: No config file used + +Fatal error has occurred +Error occurred at: src/parser.c - parse_log - 2764 +No time format was found on your conf file.Parsing... [0] [0/s] +``` + +It says “No time format was found on your conf file”. To overcome this issue, add the “COMBINED” log format option on it. + +``` +# goaccess -f 2daygeek_access.log --log-format=COMBINED -o 2daygeek.html +Parsing...[0,165] [50,165/s] +``` + +![][12] + +GoAccess allows you to access and analyze the real-time log filtering and parsing. + +``` +# tail -f /var/log/apache/2daygeek_access.log | goaccess - +``` + +For more details navigate to man or help page. + +``` +# man goaccess +or +# goaccess --help +``` + +-------------------------------------------------------------------------------- + +via: https://www.2daygeek.com/goaccess-a-real-time-web-server-log-analyzer-and-interactive-viewer/ + +作者：[Vinoth Kumar][a] +选题：[lujun9972][b] +译者：[译者ID](https://github.com/译者ID) +校对：[校对者ID](https://github.com/校对者ID) + +本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 + +[a]: https://www.2daygeek.com/author/vinoth/ +[b]: https://github.com/lujun9972 +[1]: https://www.2daygeek.com/apt-get-apt-cache-command-examples-manage-packages-debian-ubuntu-systems/ +[2]: https://www.2daygeek.com/apt-command-examples-manage-packages-debian-ubuntu-systems/ +[3]: https://www.2daygeek.com/yum-command-examples-manage-packages-rhel-centos-systems/ +[4]: https://www.2daygeek.com/dnf-command-examples-manage-packages-fedora-system/ +[5]: https://www.2daygeek.com/pacman-command-examples-manage-packages-arch-linux-system/ +[6]: https://www.2daygeek.com/zypper-command-examples-manage-packages-opensuse-system/ +[7]: data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7 +[8]: https://www.2daygeek.com/wp-content/uploads/2019/01/goaccess-a-real-time-web-server-log-analyzer-and-interactive-viewer-1.png +[9]: https://www.2daygeek.com/wp-content/uploads/2019/01/goaccess-a-real-time-web-server-log-analyzer-and-interactive-viewer-2.png +[10]: https://www.2daygeek.com/wp-content/uploads/2019/01/goaccess-a-real-time-web-server-log-analyzer-and-interactive-viewer-3.png +[11]: https://www.2daygeek.com/wp-content/uploads/2019/01/goaccess-a-real-time-web-server-log-analyzer-and-interactive-viewer-4.png +[12]: https://www.2daygeek.com/wp-content/uploads/2019/01/goaccess-a-real-time-web-server-log-analyzer-and-interactive-viewer-5.png diff --git a/sources/tech/20190111 Build a retro gaming console with RetroPie.md b/sources/tech/20190111 Build a retro gaming console with RetroPie.md new file mode 100644 index 0000000000..eedac575c9 --- /dev/null +++ b/sources/tech/20190111 Build a retro gaming console with RetroPie.md @@ -0,0 +1,82 @@ +[#]: collector: (lujun9972) +[#]: translator: ( ) +[#]: reviewer: ( ) +[#]: publisher: ( ) +[#]: url: ( ) +[#]: subject: (Build a retro gaming console with RetroPie) +[#]: via: (https://opensource.com/article/19/1/retropie) +[#]: author: (Jay LaCroix https://opensource.com/users/jlacroix) + +Build a retro gaming console with RetroPie +====== +Play your favorite classic Nintendo, Sega, and Sony console games on Linux. + + +The most common question I get on [my YouTube channel][1] and in person is what my favorite Linux distribution is. If I limit the answer to what I run on my desktops and laptops, my answer will typically be some form of an Ubuntu-based Linux distro. My honest answer to this question may surprise many. My favorite Linux distribution is actually [RetroPie][2]. + +As passionate as I am about Linux and open source software, I'm equally passionate about classic gaming, specifically video games produced in the '90s and earlier. I spend most of my surplus income on older games, and I now have a collection of close to a thousand games for over 20 gaming consoles. In my spare time, I raid flea markets, yard sales, estate sales, and eBay buying games for various consoles, including almost every iteration made by Nintendo, Sega, and Sony. There's something about classic games that I adore, a charm that seems lost in games released nowadays. + +Unfortunately, collecting retro games has its fair share of challenges. Cartridges with memory for save files will lose their charge over time, requiring the battery to be replaced. While it's not hard to replace save batteries (if you know how), it's still time-consuming. Games on CD-ROMs are subject to disc rot, which means that even if you take good care of them, they'll still lose data over time and become unplayable. Also, sometimes it's difficult to find replacement parts for some consoles. This wouldn't be so much of an issue if the majority of classic games were available digitally, but the vast majority are never re-released on a digital platform. + +### Gaming on RetroPie + +RetroPie is a great project and an asset to retro gaming enthusiasts like me. RetroPie is a Raspbian-based distribution designed for use on the Raspberry Pi (though it is possible to get it working on other platforms, such as a PC). RetroPie boots into a graphical interface that is completely controllable via a gamepad or joystick and allows you to easily manage digital copies (ROMs) of your favorite games. You can scrape information from the internet to organize your collection better and manage lists of favorite games, and the entire interface is very user-friendly and efficient. From the interface, you can launch directly into a game, then exit the game by pressing a combination of buttons on your gamepad. You rarely need a keyboard, unless you have to enter your WiFi password or manually edit configuration files. + +I use RetroPie to host a digital copy of every physical game I own in my collection. When I purchase a game from a local store or eBay, I also download the ROM. As a collector, this is very convenient. If I don't have a particular physical console within arms reach, I can boot up RetroPie and enjoy a game quickly without having to connect cables or clean cartridge contacts. There's still something to be said about playing a game on the original hardware, but if I'm pressed for time, RetroPie is very convenient. I also don't have to worry about dead save batteries, dirty cartridge contacts, disc rot, or any of the other issues collectors like me have to regularly deal with. I simply play the game. + +Also, RetroPie allows me to be very clever and utilize my technical know-how to achieve additional functionality that's not normally available. For example, I have three RetroPies set up, each of them synchronizing their files between each other by leveraging [Syncthing][3], a popular open source file synchronization tool. The synchronization happens automatically, and it means I can start a game on one television and continue in the same place on another unit since the save files are included in the synchronization. To take it a step further, I also back up my save and configuration files to [Backblaze B2][4], so I'm protected if an SD card becomes defective. + +### Setting up RetroPie + +Setting up RetroPie is very easy, and if you've ever set up a Raspberry Pi Linux distribution before (such as Raspbian) the process is essentially the same—you simply download the IMG file and flash it to your SD card by utilizing another tool, such as [Etcher][5], and insert it into your RetroPie. Then plug in an AC adapter and gamepad and hook it up to your television via HDMI. Optionally, you can buy a case to protect your RetroPie from outside elements and add visual appeal. Here is a listing of things you'll need to get started: + + * Raspberry Pi board (Model 3B+ or higher recommended) + * SD card (16GB or larger recommended) + * A USB gamepad + * UL-listed micro USB power adapter, at least 2.5 amp + + + +If you choose to add the optional Raspberry Pi case, I recommend the Super NES and Super Famicom themed cases from [RetroFlag][6]. Not only do these cases look cool, but they also have fully functioning power and reset buttons. This means you can configure the reset and power buttons to directly trigger the operating system's halt process, rather than abruptly terminating power. This definitely makes for a more professional experience, but it does require the installation of a special script. The instructions are on [RetroFlag's GitHub page][7]. Be wary: there are many cases available on Amazon and eBay of varying quality. Some of them are cheap knock-offs of RetroFlag cases, and others are just a lower quality overall. In fact, even cases by RetroFlag vary in quality—I had some power-distribution issues with the NES-themed case that made for an unstable experience. If in doubt, I've found that RetroFlag's Super NES and Super Famicom themed cases work very well. + +### Adding games + +When you boot RetroPie for the first time, it will resize the filesystem to ensure you have full access to the available space on your SD card and allow you to set up your gamepad. I can't give you links for game ROMs, so I'll leave that part up to you to figure out. When you've found them, simply add them to the RetroPie SD card in the designated folder, which would be located under **/home/pi/RetroPie/roms/+ +mysql +mysql-arch.example.com +3306 +kodi +kodi ++ +true +true ++ + +1 +322122547 +20 +**. You can use your favorite tool for transferring the ROMs to the Pi, such as [SCP][8] in a terminal, [WinSCP][9], [Samba][10], etc. Once you've added the games, you can rescan them by pressing start and choosing the option to restart EmulationStation. When it restarts, it should automatically add menu entries for the ROMs you've added. That's basically all there is to it. + +(The rescan updates EmulationStation’s game inventory. If you don’t do that, it won’t list any newly added games you copy over.) + +Regarding the games' performance, your mileage will vary depending on which consoles you're emulating. For example, I've noticed that Sega Dreamcast games barely run at all, and most Nintendo 64 games will run sluggishly with a bad framerate. Many PlayStation Portable (PSP) games also perform inconsistently. However, all of the 8-bit and 16-bit consoles emulate seemingly perfectly—I haven't run into a single 8-bit or 16-bit game that doesn't run well. Surprisingly, games designed for the original PlayStation run great for me, which is a great feat considering the lower-performance potential of the Raspberry Pi. + +Overall, RetroPie's performance is great, but the Raspberry Pi is not as powerful as a gaming PC, so adjust your expectations accordingly. + +### Conclusion + +RetroPie is a fantastic open source project dedicated to preserving classic games and an asset to game collectors everywhere. Having a digital copy of my physical game collection is extremely convenient. If I were to tell my childhood self that one day I could have an entire game collection on one device, I probably wouldn't believe it. But RetroPie has become a staple in my household and provides hours of fun and enjoyment. + +If you want to see the parts I mentioned as well as a quick installation overview, I have [a video][11] on [my YouTube channel][12] that goes over the process and shows off some gameplay at the end. + +-------------------------------------------------------------------------------- + +via: https://opensource.com/article/19/1/retropie + +作者：[Jay LaCroix][a] +选题：[lujun9972][b] +译者：[译者ID](https://github.com/译者ID) +校对：[校对者ID](https://github.com/校对者ID) + +本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 + +[a]: https://opensource.com/users/jlacroix +[b]: https://github.com/lujun9972 +[1]: https://www.youtube.com/channel/UCxQKHvKbmSzGMvUrVtJYnUA +[2]: https://retropie.org.uk/ +[3]: https://syncthing.net/ +[4]: https://www.backblaze.com/b2/cloud-storage.html +[5]: https://www.balena.io/etcher/ +[6]: https://www.amazon.com/shop/learnlinux.tv?listId=1N9V89LEH5S8K +[7]: https://github.com/RetroFlag/retroflag-picase +[8]: https://en.wikipedia.org/wiki/Secure_copy +[9]: https://winscp.net/eng/index.php +[10]: https://www.samba.org/ +[11]: https://www.youtube.com/watch?v=D8V-KaQzsWM +[12]: http://www.youtube.com/c/LearnLinuxtv diff --git a/sources/tech/20190111 Top 5 Linux Distributions for Productivity.md b/sources/tech/20190111 Top 5 Linux Distributions for Productivity.md new file mode 100644 index 0000000000..fbd8b9d120 --- /dev/null +++ b/sources/tech/20190111 Top 5 Linux Distributions for Productivity.md @@ -0,0 +1,170 @@ +[#]: collector: (lujun9972) +[#]: translator: ( ) +[#]: reviewer: ( ) +[#]: publisher: ( ) +[#]: url: ( ) +[#]: subject: (Top 5 Linux Distributions for Productivity) +[#]: via: (https://www.linux.com/blog/learn/2019/1/top-5-linux-distributions-productivity) +[#]: author: (Jack Wallen https://www.linux.com/users/jlwallen) + +Top 5 Linux Distributions for Productivity +====== + + + +I have to confess, this particular topic is a tough one to address. Why? First off, Linux is a productive operating system by design. Thanks to an incredibly reliable and stable platform, getting work done is easy. Second, to gauge effectiveness, you have to consider what type of work you need a productivity boost for. General office work? Development? School? Data mining? Human resources? You see how this question can get somewhat complicated. + +That doesn’t mean, however, that some distributions aren’t able to do a better job of configuring and presenting that underlying operating system into an efficient platform for getting work done. Quite the contrary. Some distributions do a much better job of “getting out of the way,” so you don’t find yourself in a work-related hole, having to dig yourself out and catch up before the end of day. These distributions help strip away the complexity that can be found in Linux, thereby making your workflow painless. + +Let’s take a look at the distros I consider to be your best bet for productivity. To help make sense of this, I’ve divided them into categories of productivity. That task itself was challenging, because everyone’s productivity varies. For the purposes of this list, however, I’ll look at: + + * General Productivity: For those who just need to work efficiently on multiple tasks. + + * Graphic Design: For those that work with the creation and manipulation of graphic images. + + * Development: For those who use their Linux desktops for programming. + + * Administration: For those who need a distribution to facilitate their system administration tasks. + + * Education: For those who need a desktop distribution to make them more productive in an educational environment. + + + + +Yes, there are more categories to be had, many of which can get very niche-y, but these five should fill most of your needs. + +### General Productivity + +For general productivity, you won’t get much more efficient than [Ubuntu][1]. The primary reason for choosing Ubuntu for this category is the seamless integration of apps, services, and desktop. You might be wondering why I didn’t choose Linux Mint for this category? Because Ubuntu now defaults to the GNOME desktop, it gains the added advantage of GNOME Extensions (Figure 1). + +![GNOME Clipboard][3] + +Figure 1: The GNOME Clipboard Indicator extension in action. + +[Used with permission][4] + +These extensions go a very long way to aid in boosting productivity (so Ubuntu gets the nod over Mint). But Ubuntu didn’t just accept a vanilla GNOME desktop. Instead, they tweaked it to make it slightly more efficient and user-friendly, out of the box. And because Ubuntu contains just the right mixture of default, out-of-the-box, apps (that just work), it makes for a nearly perfect platform for productivity. + +Whether you need to write a paper, work on a spreadsheet, code a new app, work on your company website, create marketing images, administer a server or network, or manage human resources from within your company HR tool, Ubuntu has you covered. The Ubuntu desktop distribution also doesn’t require the user to jump through many hoops to get things working … it simply works (and quite well). Finally, thanks to it’s Debian base, Ubuntu makes installing third-party apps incredibly easy. + +Although Ubuntu tends to be the go-to for nearly every list of “top distributions for X,” it’s very hard to argue against this particular distribution topping the list of general productivity distributions. + +### Graphic Design + +If you’re looking to up your graphic design productivity, you can’t go wrong with [Fedora Design Suite][5]. This Fedora respin was created by the team responsible for all Fedora-related art work. Although the default selection of apps isn’t a massive collection of tools, those it does include are geared specifically for the creation and manipulation of images. + +With apps like GIMP, Inkscape, Darktable, Krita, Entangle, Blender, Pitivi, Scribus, and more (Figure 2), you’ll find everything you need to get your image editing jobs done and done well. But Fedora Design Suite doesn’t end there. This desktop platform also includes a bevy of tutorials that cover countless subjects for many of the installed applications. For anyone trying to be as productive as possible, this is some seriously handy information to have at the ready. I will say, however, the tutorial entry in the GNOME Favorites is nothing more than a link to [this page][6]. + +![Fedora Design Suite Favorites][8] + +Figure 2: The Fedora Design Suite Favorites menu includes plenty of tools for getting your graphic design on. + +[Used with permission][4] + +Those that work with a digital camera will certainly appreciate the inclusion of the Entangle app, which allows you to control your DSLR from the desktop. + +### Development + +Nearly all Linux distributions are great platforms for programmers. However, one particular distributions stands out, above the rest, as one of the most productive tools you’ll find for the task. That OS comes from [System76][9] and it’s called [Pop!_OS][10]. Pop!_OS is tailored specifically for creators, but not of the artistic type. Instead, Pop!_OS is geared toward creators who specialize in developing, programming, and making. If you need an environment that is not only perfected suited for your development work, but includes a desktop that’s sure to get out of your way, you won’t find a better option than Pop!_OS (Figure 3). + +What might surprise you (given how “young” this operating system is), is that Pop!_OS is also one of the single most stable GNOME-based platforms you’ll ever use. This means Pop!_OS isn’t just for creators and makers, but anyone looking for a solid operating system. One thing that many users will greatly appreciate with Pop!_OS, is that you can download an ISO specifically for your video hardware. If you have Intel hardware, [download][10] the version for Intel/AMD. If your graphics card is NVIDIA, download that specific release. Either way, you are sure go get a solid platform for which to create your masterpiece. + +![Pop!_OS][12] + +Figure 3: The Pop!_OS take on GNOME Overview. + +[Used with permission][4] + +Interestingly enough, with Pop!_OS, you won’t find much in the way of pre-installed development tools. You won’t find an included IDE, or many other dev tools. You can, however, find all the development tools you need in the Pop Shop. + +### Administration + +If you’re looking to find one of the most productive distributions for admin tasks, look no further than [Debian][13]. Why? Because Debian is not only incredibly reliable, it’s one of those distributions that gets out of your way better than most others. Debian is the perfect combination of ease of use and unlimited possibility. On top of which, because this is the distribution for which so many others are based, you can bet if there’s an admin tool you need for a task, it’s available for Debian. Of course, we’re talking about general admin tasks, which means most of the time you’ll be using a terminal window to SSH into your servers (Figure 4) or a browser to work with web-based GUI tools on your network. Why bother making use of a desktop that’s going to add layers of complexity (such as SELinux in Fedora, or YaST in openSUSE)? Instead, chose simplicity. + +![Debian][15] + +Figure 4: SSH’ing into a remote server on Debian. + +[Used with permission][4] + +And because you can select which desktop you want (from GNOME, Xfce, KDE, Cinnamon, MATE, LXDE), you can be sure to have the interface that best matches your work habits. + +### Education + +If you are a teacher or student, or otherwise involved in education, you need the right tools to be productive. Once upon a time, there existed the likes of Edubuntu. That distribution never failed to be listed in the top of education-related lists. However, that distro hasn’t been updated since it was based on Ubuntu 14.04. Fortunately, there’s a new education-based distribution ready to take that title, based on openSUSE. This spin is called [openSUSE:Education-Li-f-e][16] (Linux For Education - Figure 5), and is based on openSUSE Leap 42.1 (so it is slightly out of date). + +openSUSE:Education-Li-f-e includes tools like: + + * Brain Workshop - A dual n-back brain exercise + + * GCompris - An educational software suite for young children + + * gElemental - A periodic table viewer + + * iGNUit - A general purpose flash card program + + * Little Wizard - Development environment for children based on Pascal + + * Stellarium - An astronomical sky simulator + + * TuxMath - An math tutor game + + * TuxPaint - A drawing program for young children + + * TuxType - An educational typing tutor for children + + * wxMaxima - A cross platform GUI for the computer algebra system + + * Inkscape - Vector graphics program + + * GIMP - Graphic image manipulation program + + * Pencil - GUI prototyping tool + + * Hugin - Panorama photo stitching and HDR merging program + + +![Education][18] + +Figure 5: The openSUSE:Education-Li-f-e distro has plenty of tools to help you be productive in or for school. + +[Used with permission][4] + +Also included with openSUSE:Education-Li-f-e is the [KIWI-LTSP Server][19]. The KIWI-LTSP Server is a flexible, cost effective solution aimed at empowering schools, businesses, and organizations all over the world to easily install and deploy desktop workstations. Although this might not directly aid the student to be more productive, it certainly enables educational institutions be more productive in deploying desktops for students to use. For more information on setting up KIWI-LTSP, check out the openSUSE [KIWI-LTSP quick start guide][20]. + +Learn more about Linux through the free ["Introduction to Linux" ][21]course from The Linux Foundation and edX. + +-------------------------------------------------------------------------------- + +via: https://www.linux.com/blog/learn/2019/1/top-5-linux-distributions-productivity + +作者：[Jack Wallen][a] +选题：[lujun9972][b] +译者：[译者ID](https://github.com/译者ID) +校对：[校对者ID](https://github.com/校对者ID) + +本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 + +[a]: https://www.linux.com/users/jlwallen +[b]: https://github.com/lujun9972 +[1]: https://www.ubuntu.com/ +[2]: /files/images/productivity1jpg +[3]: https://www.linux.com/sites/lcom/files/styles/rendered_file/public/productivity_1.jpg?itok=yxez3X1w (GNOME Clipboard) +[4]: /licenses/category/used-permission +[5]: https://labs.fedoraproject.org/en/design-suite/ +[6]: https://fedoraproject.org/wiki/Design_Suite/Tutorials +[7]: /files/images/productivity2jpg +[8]: https://www.linux.com/sites/lcom/files/styles/rendered_file/public/productivity_2.jpg?itok=ke0b8qyH (Fedora Design Suite Favorites) +[9]: https://system76.com/ +[10]: https://system76.com/pop +[11]: /files/images/productivity3jpg-0 +[12]: https://www.linux.com/sites/lcom/files/styles/rendered_file/public/productivity_3_0.jpg?itok=8UkCUfsD (Pop!_OS) +[13]: https://www.debian.org/ +[14]: /files/images/productivity4jpg +[15]: https://www.linux.com/sites/lcom/files/styles/rendered_file/public/productivity_4.jpg?itok=c9yD3Xw2 (Debian) +[16]: https://en.opensuse.org/openSUSE:Education-Li-f-e +[17]: /files/images/productivity5jpg +[18]: https://www.linux.com/sites/lcom/files/styles/rendered_file/public/productivity_5.jpg?itok=oAFtV8nT (Education) +[19]: https://en.opensuse.org/Portal:KIWI-LTSP +[20]: https://en.opensuse.org/SDB:KIWI-LTSP_quick_start +[21]: https://training.linuxfoundation.org/linux-courses/system-administration-training/introduction-to-linux diff --git a/sources/tech/20190113 Editing Subtitles in Linux.md b/sources/tech/20190113 Editing Subtitles in Linux.md new file mode 100644 index 0000000000..1eaa6a68fd --- /dev/null +++ b/sources/tech/20190113 Editing Subtitles in Linux.md @@ -0,0 +1,168 @@ +[#]: collector: (lujun9972) +[#]: translator: ( ) +[#]: reviewer: ( ) +[#]: publisher: ( ) +[#]: url: ( ) +[#]: subject: (Editing Subtitles in Linux) +[#]: via: (https://itsfoss.com/editing-subtitles) +[#]: author: (Shirish https://itsfoss.com/author/shirish/) + +Editing Subtitles in Linux +====== + +I have been a world movie and regional movies lover for decades. Subtitles are the essential tool that have enabled me to enjoy the best movies in various languages and from various countries. + +If you enjoy watching movies with subtitles, you might have noticed that sometimes the subtitles are not synced or not correct. + +Did you know that you can edit subtitles and make them better? Let me show you some basic subtitle editing in Linux. + +![Editing subtitles in Linux][1] + +### Extracting subtitles from closed captions data + +Around 2012, 2013 I came to know of a tool called [CCEextractor.][2] As time passed, it has become one of the vital tools for me, especially if I come across a media file which has the subtitle embedded in it. + +CCExtractor analyzes video files and produces independent subtitle files from the closed captions data. + +CCExtractor is a cross-platform, free and open source tool. The tool has matured quite a bit from its formative years and has been part of [GSOC][3] and Google Code-in now and [then.][4] + +The tool, to put it simply, is more or less a set of scripts which work one after another in a serialized order to give you an extracted subtitle. + +You can follow the installation instructions for CCExtractor on [this page][5]. + +After installing when you want to extract subtitles from a media file, do the following: + +``` +ccextractor +``` + +The output of the command will be something like this: + +It basically scans the media file. In this case, it found that the media file is in malyalam and that the media container is an [.mkv][6] container. It extracted the subtitle file with the same name as the video file adding _eng to it. + +CCExtractor is a wonderful tool which can be used to enhance subtitles along with Subtitle Edit which I will share in the next section. + +``` +Interesting Read: There is an interesting synopsis of subtitles at [vicaps][7] which tells and shares why subtitles are important to us. It goes into quite a bit of detail of movie-making as well for those interested in such topics. +``` + +### Editing subtitles with SubtitleEditor Tool + +You probably are aware that most subtitles are in [.srt format][8] . The beautiful thing about this format is and was you could load it in your text editor and do little fixes in it. + +A srt file looks something like this when launched into a simple text-editor: + +The excerpt subtitle I have shared is from a pretty Old German Movie called [The Cabinet of Dr. Caligari (1920)][9] + +Subtitleeditor is a wonderful tool when it comes to editing subtitles. Subtitle Editor is and can be used to manipulate time duration, frame-rate of the subtitle file to be in sync with the media file, duration of breaks in-between and much more. I’ll share some of the basic subtitle editing here. + +![][10] + +First install subtitleeditor the same way you installed ccextractor, using your favorite installation method. In Debian, you can use this command: + +``` +sudo apt install subtitleeditor +``` + +When you have it installed, let’s see some of the common scenarios where you need to edit a subtitle. + +#### Manipulating Frame-rates to sync with Media file + +If you find that the subtitles are not synced with the video, one of the reasons could be the difference between the frame rates of the video file and the subtitle file. + +How do you know the frame rates of these files, then? + +To get the frame rate of a video file, you can use the mediainfo tool. You may need to install it first using your distribution’s package manager. + +Using mediainfo is simple: + +``` +$ mediainfo somefile.mkv | grep Frame + Format settings : CABAC / 4 Ref Frames + Format settings, ReFrames : 4 frames + Frame rate mode : Constant + Frame rate : 25.000 FPS + Bits/(Pixel*Frame) : 0.082 + Frame rate : 46.875 FPS (1024 SPF) +``` + +Now you can see that framerate of the video file is 25.000 FPS. The other Frame-rate we see is for the audio. While I can share why particular fps are used in Video-encoding, Audio-encoding etc. it would be a different subject matter. There is a lot of history associated with it. + +Next is to find out the frame rate of the subtitle file and this is a slightly complicated. + +Usually, most subtitles are in a zipped format. Unzipping the .zip archive along with the subtitle file which ends in something.srt. Along with it, there is usually also a .info file with the same name which sometime may have the frame rate of the subtitle. + +If not, then it usually is a good idea to go some site and download the subtitle from a site which has that frame rate information. For this specific German file, I will be using [Opensubtitle.org][11] + +As you can see in the link, the frame rate of the subtitle is 23.976 FPS. Quite obviously, it won’t play well with my video file with frame rate 25.000 FPS. + +In such cases, you can change the frame rate of the subtitle file using the Subtitle Editor tool: + +Select all the contents from the subtitle file by doing CTRL+A. Go to Timings -> Change Framerate and change frame rates from 23.976 fps to 25.000 fps or whatever it is that is desired. Save the changed file. + +![synchronize frame rates of subtitles in Linux][12] + +#### Changing the Starting position of a subtitle file + +Sometimes the above method may be enough, sometimes though it will not be enough. + +You might find some cases when the start of the subtitle file is different from that in the movie or a media file while the frame rate is the same. + +In such cases, do the following: + +Select all the contents from the subtitle file by doing CTRL+A. Go to Timings -> Select Move Subtitle. + +![Move subtitles using Subtitle Editor on Linux][13] + +Change the new Starting position of the subtitle file. Save the changed file. + +![Move subtitles using Subtitle Editor in Linux][14] + +If you wanna be more accurate, then use [mpv][15] to see the movie or media file and click on the timing, if you click on the timing bar which shows how much the movie or the media file has elapsed, clicking on it will also reveal the microsecond. + +I usually like to be accurate so I try to be as precise as possible. It is very difficult in MPV as human reaction time is imprecise. If I wanna be super accurate then I use something like [Audacity][16] but then that is another ball-game altogether as you can do so much more with it. That may be something to explore in a future blog post as well. + +#### Manipulating Duration + +Sometimes even doing both is not enough and you even have to shrink or add the duration to make it sync with the media file. This is one of the more tedious works as you have to individually fix the duration of each sentence. This can happen especially if you have variable frame rates in the media file (nowadays rare but you still get such files). + +In such a scenario, you may have to edit the duration manually and automation is not possible. The best way is either to fix the video file (not possible without degrading the video quality) or getting video from another source at a higher quality and then [transcode][17] it with the settings you prefer. This again, while a major undertaking I could shed some light on in some future blog post. + +### Conclusion + +What I have shared in above is more or less on improving on existing subtitle files. If you were to start a scratch you need loads of time. I haven’t shared that at all because a movie or any video material of say an hour can easily take anywhere from 4-6 hours or even more depending upon skills of the subtitler, patience, context, jargon, accents, native English speaker, translator etc. all of which makes a difference to the quality of the subtitle. + +I hope you find this interesting and from now onward, you’ll handle your subtitles slightly better. If you have any suggestions to add, please leave a comment below. + + +-------------------------------------------------------------------------------- + +via: https://itsfoss.com/editing-subtitles + +作者：[Shirish][a] +选题：[lujun9972][b] +译者：[译者ID](https://github.com/译者ID) +校对：[校对者ID](https://github.com/校对者ID) + +本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 + +[a]: https://itsfoss.com/author/shirish/ +[b]: https://github.com/lujun9972 +[1]: https://i0.wp.com/itsfoss.com/wp-content/uploads/2019/01/editing-subtitles-in-linux.jpeg?resize=800%2C450&ssl=1 +[2]: https://www.ccextractor.org/ +[3]: https://itsfoss.com/best-open-source-internships/ +[4]: https://www.ccextractor.org/public:codein:google_code-in_2018 +[5]: https://github.com/CCExtractor/ccextractor/wiki/Installation +[6]: https://en.wikipedia.org/wiki/Matroska +[7]: https://www.vicaps.com/blog/history-of-silent-movies-and-subtitles/ +[8]: https://en.wikipedia.org/wiki/SubRip#SubRip_text_file_format +[9]: https://www.imdb.com/title/tt0010323/ +[10]: https://i1.wp.com/itsfoss.com/wp-content/uploads/2018/12/subtitleeditor.jpg?ssl=1 +[11]: https://www.opensubtitles.org/en/search/sublanguageid-eng/idmovie-4105 +[12]: https://i1.wp.com/itsfoss.com/wp-content/uploads/2019/01/subtitleeditor-frame-rate-sync.jpg?resize=800%2C450&ssl=1 +[13]: https://i0.wp.com/itsfoss.com/wp-content/uploads/2019/01/Move-subtitles-Caligiri.jpg?resize=800%2C450&ssl=1 +[14]: https://i2.wp.com/itsfoss.com/wp-content/uploads/2019/01/move-subtitles.jpg?ssl=1 +[15]: https://itsfoss.com/mpv-video-player/ +[16]: https://www.audacityteam.org/ +[17]: https://en.wikipedia.org/wiki/Transcoding +[18]: https://i0.wp.com/itsfoss.com/wp-content/uploads/2019/01/editing-subtitles-in-linux.jpeg?fit=800%2C450&ssl=1 diff --git a/sources/tech/20190115 Linux Desktop Setup - HookRace Blog.md b/sources/tech/20190115 Linux Desktop Setup - HookRace Blog.md new file mode 100644 index 0000000000..29d5f63d2a --- /dev/null +++ b/sources/tech/20190115 Linux Desktop Setup - HookRace Blog.md @@ -0,0 +1,514 @@ +[#]: collector: (lujun9972) +[#]: translator: ( ) +[#]: reviewer: ( ) +[#]: publisher: ( ) +[#]: url: ( ) +[#]: subject: (Linux Desktop Setup · HookRace Blog) +[#]: via: (https://hookrace.net/blog/linux-desktop-setup/) +[#]: author: (Dennis Felsing http://felsin9.de/nnis/) + +Linux Desktop Setup +====== + + +My software setup has been surprisingly constant over the last decade, after a few years of experimentation since I initially switched to Linux in 2006. It might be interesting to look back in another 10 years and see what changed. A quick overview of what’s running as I’m writing this post: + +[![htop overview][1]][2] + +### Motivation + +My software priorities are, in no specific order: + + * Programs should run on my local system so that I’m in control of them, this excludes cloud solutions. + * Programs should run in the terminal, so that they can be used consistently from anywhere, including weak computers or a phone. + * Keyboard focused is nearly automatic by using terminal software. I prefer to use the mouse where it makes sense only, reaching for the mouse all the time during typing feels like a waste of time. Occasionally it took me an hour to notice that the mouse wasn’t even plugged in. + * Ideally use fast and efficient software, I don’t like hearing the fan and feeling the room heat up. I can also keep running older hardware for much longer, my 10 year old Thinkpad x200s is still fine for all the software I use. + * Be composable. I don’t want to do every step manually, instead automate more when it makes sense. This naturally favors the shell. + + + +### Operating Systems + +I had a hard start with Linux 12 years ago by removing Windows, armed with just the [Gentoo Linux][3] installation CD and a printed manual to get a functioning Linux system. It took me a few days of compiling and tinkering, but in the end I felt like I had learnt a lot. + +I haven’t looked back to Windows since then, but I switched to [Arch Linux][4] on my laptop after having the fan fail from the constant compilation stress. Later I also switched all my other computers and private servers to Arch Linux. As a rolling release distribution you get package upgrades all the time, but the most important breakages are nicely reported in the [Arch Linux News][5]. + +One annoyance though is that Arch Linux removes the old kernel modules once you upgrade it. I usually notice that once I try plugging in a USB flash drive and the kernel fails to load the relevant module. Instead you’re supposed to reboot after each kernel upgrade. There are a few [hacks][6] around to get around the problem, but I haven’t been bothered enough to actually use them. + +Similar problems happen with other programs, commonly Firefox, cron or Samba requiring a restart after an upgrade, but annoyingly not warning you that that’s the case. [SUSE][7], which I use at work, nicely warns about such cases. + +For the [DDNet][8] production servers I prefer [Debian][9] over Arch Linux, so that I have a lower chance of breakage on each upgrade. For my firewall and router I used [OpenBSD][10] for its clean system, documentation and great [pf firewall][11], but right now I don’t have a need for a separate router anymore. + +### Window Manager + +Since I started out with Gentoo I quickly noticed the huge compile time of KDE, which made it a no-go for me. I looked around for more minimal solutions, and used [Openbox][12] and [Fluxbox][13] initially. At some point I jumped on the tiling window manager train in order to be more keyboard-focused and picked up [dwm][14] and [awesome][15] close to their initial releases. + +In the end I settled on [xmonad][16] thanks to its flexibility, extendability and being written and configured in pure [Haskell][17], a great functional programming language. One example of this is that at home I run a single 40” 4K screen, but often split it up into four virtual screens, each displaying a workspace on which my windows are automatically arranged. Of course xmonad has a [module][18] for that. + +[dzen][19] and [conky][20] function as a simple enough status bar for me. My entire conky config looks like this: + +``` +out_to_console yes +update_interval 1 +total_run_times 0 + +TEXT +${downspeed eth0} ${upspeed eth0} | $cpu% ${loadavg 1} ${loadavg 2} ${loadavg 3} $mem/$memmax | ${time %F %T} +``` + +And gets piped straight into dzen2 with `conky | dzen2 -fn '-xos4-terminus-medium-r-normal-*-12-*-*-*-*-*-*-*' -bg '#000000' -fg '#ffffff' -p -e '' -x 1000 -w 920 -xs 1 -ta r`. + +One important feature for me is to make the terminal emit a beep sound once a job is done. This is done simply by adding a `\a` character to the `PR_TITLEBAR` variable in zsh, which is shown whenever a job is done. Of course I disable the actual beep sound by blacklisting the `pcspkr` kernel module with `echo "blacklist pcspkr" > /etc/modprobe.d/nobeep.conf`. Instead the sound gets turned into an urgency by urxvt’s `URxvt.urgentOnBell: true` setting. Then xmonad has an urgency hook to capture this and I can automatically focus the currently urgent window with a key combination. In dzen I get the urgent windowspaces displayed with a nice and bright `#ff0000`. + +The final result in all its glory on my Laptop: + +[![Laptop screenshot][21]][22] + +I hear that [i3][23] has become quite popular in the last years, but it requires more manual window alignment instead of specifying automated methods to do it. + +I realize that there are also terminal multiplexers like [tmux][24], but I still require a few graphical applications, so in the end I never used them productively. + +### Terminal Persistency + +In order to keep terminals alive I use [dtach][25], which is just the detach feature of screen. In order to make every terminal on my computer detachable I wrote a [small wrapper script][26]. This means that even if I had to restart my X server I could keep all my terminals running just fine, both local and remote. + +### Shell & Programming + +Instead of [bash][27] I use [zsh][28] as my shell for its huge number of features. + +As a terminal emulator I found [urxvt][29] to be simple enough, support Unicode and 256 colors and has great performance. Another great feature is being able to run the urxvt client and daemon separately, so that even a large number of terminals barely takes up any memory (except for the scrollback buffer). + +There is only one font that looks absolutely clean and perfect to me: [Terminus][30]. Since i’s a bitmap font everything is pixel perfect and renders extremely fast and at low CPU usage. In order to switch fonts on-demand in each terminal with `CTRL-WIN-[1-7]` my ~/.Xdefaults contains: + +``` +URxvt.font: -xos4-terminus-medium-r-normal-*-14-*-*-*-*-*-*-* +dzen2.font: -xos4-terminus-medium-r-normal-*-14-*-*-*-*-*-*-* + +URxvt.keysym.C-M-1: command:\033]50;-xos4-terminus-medium-r-normal-*-12-*-*-*-*-*-*-*\007 +URxvt.keysym.C-M-2: command:\033]50;-xos4-terminus-medium-r-normal-*-14-*-*-*-*-*-*-*\007 +URxvt.keysym.C-M-3: command:\033]50;-xos4-terminus-medium-r-normal-*-18-*-*-*-*-*-*-*\007 +URxvt.keysym.C-M-4: command:\033]50;-xos4-terminus-medium-r-normal-*-22-*-*-*-*-*-*-*\007 +URxvt.keysym.C-M-5: command:\033]50;-xos4-terminus-medium-r-normal-*-24-*-*-*-*-*-*-*\007 +URxvt.keysym.C-M-6: command:\033]50;-xos4-terminus-medium-r-normal-*-28-*-*-*-*-*-*-*\007 +URxvt.keysym.C-M-7: command:\033]50;-xos4-terminus-medium-r-normal-*-32-*-*-*-*-*-*-*\007 + +URxvt.keysym.C-M-n: command:\033]10;#ffffff\007\033]11;#000000\007\033]12;#ffffff\007\033]706;#00ffff\007\033]707;#ffff00\007 +URxvt.keysym.C-M-b: command:\033]10;#000000\007\033]11;#ffffff\007\033]12;#000000\007\033]706;#0000ff\007\033]707;#ff0000\007 +``` + +For programming and writing I use [Vim][31] with syntax highlighting and [ctags][32] for indexing, as well as a few terminal windows with grep, sed and the other usual suspects for search and manipulation. This is probably not at the same level of comfort as an IDE, but allows me more automation. + +One problem with Vim is that you get so used to its key mappings that you’ll want to use them everywhere. + +[Python][33] and [Nim][34] do well as scripting languages where the shell is not powerful enough. + +### System Monitoring + +[htop][35] (look at the background of that site, it’s a live view of the server that’s hosting it) works great for getting a quick overview of what the software is currently doing. [lm_sensors][36] allows monitoring the hardware temperatures, fans and voltages. [powertop][37] is a great little tool by Intel to find power savings. [ncdu][38] lets you analyze disk usage interactively. + +[nmap][39], iptraf-ng, [tcpdump][40] and [Wireshark][41] are essential tools for analyzing network problems. + +There are of course many more great tools. + +### Mails & Synchronization + +On my home server I have a [fetchmail][42] daemon running for each email acccount that I have. Fetchmail just retrieves the incoming emails and invokes [procmail][43]: + +``` +#!/bin/sh +for i in /home/deen/.fetchmail/*; do + FETCHMAILHOME=$i /usr/bin/fetchmail -m 'procmail -d %T' -d 60 +done +``` + +The configuration is as simple as it could be and waits for the server to inform us of fresh emails: + +``` +poll imap.1und1.de protocol imap timeout 120 user "dennis@felsin9.de" password "XXX" folders INBOX keep ssl idle +``` + +My `.procmailrc` config contains a few rules to backup all mails and sort them into the correct directories, for example based on the mailing list id or from field in the mail header: + +``` +MAILDIR=/home/deen/shared/Maildir +LOGFILE=$HOME/.procmaillog +LOGABSTRACT=no +VERBOSE=off +FORMAIL=/usr/bin/formail +NL=" +" + +:0wc +* ! ? test -d /media/mailarchive/`date +%Y` +| mkdir -p /media/mailarchive/`date +%Y` + +# Make backups of all mail received in format YYYY/YYYY-MM +:0c +/media/mailarchive/`date +%Y`/`date +%Y-%m` + +:0 +* ^From: .*(.*@.*.kit.edu|.*@.*.uka.de|.*@.*.uni-karlsruhe.de) +$MAILDIR/.uni/ + +:0 +* ^list-Id:.*lists.kit.edu +$MAILDIR/.uni-ml/ + +[...] +``` + +To send emails I use [msmtp][44], which is also great to configure: + +``` +account default +host smtp.1und1.de +tls on +tls_trust_file /etc/ssl/certs/ca-certificates.crt +auth on +from dennis@felsin9.de +user dennis@felsin9.de +password XXX + +[...] +``` + +But so far the emails are still on the server. My documents are all stored in a directory that I synchronize between all computers using [Unison][45]. Think of Unison as a bidirectional interactive [rsync][46]. My emails are part of this documents directory and thus they end up on my desktop computers. + +This also means that while the emails reach my server immediately, I only fetch them on deman instead of getting instant notifications when an email comes in. + +From there I read the mails with [mutt][47], using the sidebar plugin to display my mail directories. The `/etc/mailcap` file is essential to display non-plaintext mails containing HTML, Word or PDF: + +``` +text/html;w3m -I %{charset} -T text/html; copiousoutput +application/msword; antiword %s; copiousoutput +application/pdf; pdftotext -layout /dev/stdin -; copiousoutput +``` + +### News & Communication + +[Newsboat][48] is a nice little RSS/Atom feed reader in the terminal. I have it running on the server in a `tach` session with about 150 feeds. Filtering feeds locally is also possible, for example: + +``` +ignore-article "https://forum.ddnet.tw/feed.php" "title =~ \"Map Testing •\" or title =~ \"Old maps •\" or title =~ \"Map Bugs •\" or title =~ \"Archive •\" or title =~ \"Waiting for mapper •\" or title =~ \"Other mods •\" or title =~ \"Fixes •\"" +``` + +I use [Irssi][49] the same way for communication via IRC. + +### Calendar + +[remind][50] is a calendar that can be used from the command line. Setting new reminders is done by editing the `rem` files: + +``` +# One time events +REM 2019-01-20 +90 Flight to China %b + +# Recurring Holidays +REM 1 May +90 Holiday "Tag der Arbeit" %b +REM [trigger(easterdate(year(today()))-2)] +90 Holiday "Karfreitag" %b + +# Time Change +REM Nov Sunday 1 --7 +90 Time Change (03:00 -> 02:00) %b +REM Apr Sunday 1 --7 +90 Time Change (02:00 -> 03:00) %b + +# Birthdays +FSET birthday(x) "'s " + ord(year(trigdate())-x) + " birthday is %b" +REM 16 Apr +90 MSG Andreas[birthday(1994)] + +# Sun +SET $LatDeg 49 +SET $LatMin 19 +SET $LatSec 49 +SET $LongDeg -8 +SET $LongMin -40 +SET $LongSec -24 + +MSG Sun from [sunrise(trigdate())] to [sunset(trigdate())] +[...] +``` + +Unfortunately there is no Chinese Lunar calendar function in remind yet, so Chinese holidays can’t be calculated easily. + +I use two aliases for remind: + +``` +rem -m -b1 -q -g +``` + +to see a list of the next events in chronological order and + +``` +rem -m -b1 -q -cuc12 -w$(($(tput cols)+1)) | sed -e "s/\f//g" | less +``` + +to show a calendar fitting just the width of my terminal: + +![remcal][51] + +### Dictionary + +[rdictcc][52] is a little known dictionary tool that uses the excellent dictionary files from [dict.cc][53] and turns them into a local database: + +``` +$ rdictcc rasch +====================[ A => B ]==================== +rasch: + - apace + - brisk [speedy] + - cursory + - in a timely manner + - quick + - quickly + - rapid + - rapidly + - sharpish [Br.] [coll.] + - speedily + - speedy + - swift + - swiftly +rasch [gehen]: + - smartly [quickly] +Rasch {n} [Zittergras-Segge]: + - Alpine grass [Carex brizoides] + - quaking grass sedge [Carex brizoides] +Rasch {m} [regional] [Putzrasch]: + - scouring pad +====================[ B => A ]==================== +Rasch model: + - Rasch-Modell {n} +``` + +### Writing and Reading + +I have a simple todo file containing my tasks, that is basically always sitting open in a Vim session. For work I also use the todo file as a “done” file so that I can later check what tasks I finished on each day. + +For writing documents, letters and presentations I use [LaTeX][54] for its superior typesetting. A simple letter in German format can be set like this for example: + +``` +\documentclass[paper = a4, fromalign = right]{scrlttr2} +\usepackage{german} +\usepackage{eurosym} +\usepackage[utf8]{inputenc} +\setlength{\parskip}{6pt} +\setlength{\parindent}{0pt} + +\setkomavar{fromname}{Dennis Felsing} +\setkomavar{fromaddress}{Meine Str. 1\\69181 Leimen} +\setkomavar{subject}{Titel} + +\setkomavar*{enclseparator}{Anlagen} + +\makeatletter +\@setplength{refvpos}{89mm} +\makeatother + +\begin{document} +\begin{letter} {Herr Soundso\\Deine Str. 2\\69121 Heidelberg} +\opening{Sehr geehrter Herr Soundso,} + +Sie haben bei mir seit dem Bla Bla Bla. + +Ich fordere Sie hiermit zu Bla Bla Bla auf. + +\closing{Mit freundlichen Grüßen} + +\end{letter} +\end{document} +``` + +Further example documents and presentations can be found over at [my private site][55]. + +To read PDFs [Zathura][56] is fast, has Vim-like controls and even supports two different PDF backends: Poppler and MuPDF. [Evince][57] on the other hand is more full-featured for the cases where I encounter documents that Zathura doesn’t like. + +### Graphical Editing + +[GIMP][58] and [Inkscape][59] are easy choices for photo editing and interactive vector graphics respectively. + +In some cases [Imagemagick][60] is good enough though and can be used straight from the command line and thus automated to edit images. Similarly [Graphviz][61] and [TikZ][62] can be used to draw graphs and other diagrams. + +### Web Browsing + +As a web browser I’ve always used [Firefox][63] for its extensibility and low resource usage compared to Chrome. + +Unfortunately the [Pentadactyl][64] extension development stopped after Firefox switched to Chrome-style extensions entirely, so I don’t have satisfying Vim-like controls in my browser anymore. + +### Media Players + +[mpv][65] with hardware decoding allows watching videos at 5% CPU load using the `vo=gpu` and `hwdec=vaapi` config settings. `audio-channels=2` in mpv seems to give me clearer downmixing to my stereo speakers / headphones than what PulseAudio does by default. A great little feature is exiting with `Shift-Q` instead of just `Q` to save the playback location. When watching with someone with another native tongue you can use `--secondary-sid=` to show two subtitles at once, the primary at the bottom, the secondary at the top of the screen + +My wirelss mouse can easily be made into a remote control with mpv with a small `~/.config/mpv/input.conf`: + +``` +MOUSE_BTN5 run "mixer" "pcm" "-2" +MOUSE_BTN6 run "mixer" "pcm" "+2" +MOUSE_BTN1 cycle sub-visibility +MOUSE_BTN7 add chapter -1 +MOUSE_BTN8 add chapter 1 +``` + +[youtube-dl][66] works great for watching videos hosted online, best quality can be achieved with `-f bestvideo+bestaudio/best --all-subs --embed-subs`. + +As a music player [MOC][67] hasn’t been actively developed for a while, but it’s still a simple player that plays every format conceivable, including the strangest Chiptune formats. In the AUR there is a [patch][68] adding PulseAudio support as well. Even with the CPU clocked down to 800 MHz MOC barely uses 1-2% of a single CPU core. + +![moc][69] + +My music collection sits on my home server so that I can access it from anywhere. It is mounted using [SSHFS][70] and automount in the `/etc/fstab/`: + +``` +root@server:/media/media /mnt/media fuse.sshfs noauto,x-systemd.automount,idmap=user,IdentityFile=/root/.ssh/id_rsa,allow_other,reconnect 0 0 +``` + +### Cross-Platform Building + +Linux is great to build packages for any major operating system except Linux itself! In the beginning I used [QEMU][71] to with an old Debian, Windows and Mac OS X VM to build for these platforms. + +Nowadays I switched to using chroot for the old Debian distribution (for maximum Linux compatibility), [MinGW][72] to cross-compile for Windows and [OSXCross][73] to cross-compile for Mac OS X. + +The script used to [build DDNet][74] as well as the [instructions for updating library builds][75] are based on this. + +### Backups + +As usual, we nearly forgot about backups. Even if this is the last chapter, it should not be an afterthought. + +I wrote [rrb][76] (reverse rsync backup) 10 years ago to wrap rsync so that I only need to give the backup server root SSH rights to the computers that it is backing up. Surprisingly rrb needed 0 changes in the last 10 years, even though I kept using it the entire time. + +The backups are stored straight on the filesystem. Incremental backups are implemented using hard links (`--link-dest`). A simple [config][77] defines how long backups are kept, which defaults to: + +``` +KEEP_RULES=( \ + 7 7 \ # One backup a day for the last 7 days + 31 8 \ # 8 more backups for the last month + 365 11 \ # 11 more backups for the last year +1825 4 \ # 4 more backups for the last 5 years +) +``` + +Since some of my computers don’t have a static IP / DNS entry and I still want to back them up using rrb I use a reverse SSH tunnel (as a systemd service) for them: + +``` +[Unit] +Description=Reverse SSH Tunnel +After=network.target + +[Service] +ExecStart=/usr/bin/ssh -N -R 27276:localhost:22 -o "ExitOnForwardFailure yes" server +KillMode=process +Restart=always + +[Install] +WantedBy=multi-user.target +``` + +Now the server can reach the client through `ssh -p 27276 localhost` while the tunnel is running to perform the backup, or in `.ssh/config` format: + +``` +Host cr-remote + HostName localhost + Port 27276 +``` + +While talking about SSH hacks, sometimes a server is not easily reachable thanks to some bad routing. In that case you can route the SSH connection through another server to get better routing, in this case going through the USA to reach my Chinese server which had not been reliably reachable from Germany for a few weeks: + +``` +Host chn.ddnet.tw + ProxyCommand ssh -q usa.ddnet.tw nc -q0 chn.ddnet.tw 22 + Port 22 +``` + +### Final Remarks + +Thanks for reading my random collection of tools. I probably forgot many programs that I use so naturally every day that I don’t even think about them anymore. Let’s see how stable my software setup stays in the next years. If you have any questions, feel free to get in touch with me at [dennis@felsin9.de][78]. + +Comments on [Hacker News][79]. + +-------------------------------------------------------------------------------- + +via: https://hookrace.net/blog/linux-desktop-setup/ + +作者：[Dennis Felsing][a] +选题：[lujun9972][b] +译者：[译者ID](https://github.com/译者ID) +校对：[校对者ID](https://github.com/校对者ID) + +本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 + +[a]: http://felsin9.de/nnis/ +[b]: https://github.com/lujun9972 +[1]: https://hookrace.net/public/linux-desktop/htop_small.png +[2]: https://hookrace.net/public/linux-desktop/htop.png +[3]: https://gentoo.org/ +[4]: https://www.archlinux.org/ +[5]: https://www.archlinux.org/news/ +[6]: https://www.reddit.com/r/archlinux/comments/4zrsc3/keep_your_system_fully_functional_after_a_kernel/ +[7]: https://www.suse.com/ +[8]: https://ddnet.tw/ +[9]: https://www.debian.org/ +[10]: https://www.openbsd.org/ +[11]: https://www.openbsd.org/faq/pf/ +[12]: http://openbox.org/wiki/Main_Page +[13]: http://fluxbox.org/ +[14]: https://dwm.suckless.org/ +[15]: https://awesomewm.org/ +[16]: https://xmonad.org/ +[17]: https://www.haskell.org/ +[18]: http://hackage.haskell.org/package/xmonad-contrib-0.15/docs/XMonad-Layout-LayoutScreens.html +[19]: http://robm.github.io/dzen/ +[20]: https://github.com/brndnmtthws/conky +[21]: https://hookrace.net/public/linux-desktop/laptop_small.png +[22]: https://hookrace.net/public/linux-desktop/laptop.png +[23]: https://i3wm.org/ +[24]: https://github.com/tmux/tmux/wiki +[25]: http://dtach.sourceforge.net/ +[26]: https://github.com/def-/tach/blob/master/tach +[27]: https://www.gnu.org/software/bash/ +[28]: http://www.zsh.org/ +[29]: http://software.schmorp.de/pkg/rxvt-unicode.html +[30]: http://terminus-font.sourceforge.net/ +[31]: https://www.vim.org/ +[32]: http://ctags.sourceforge.net/ +[33]: https://www.python.org/ +[34]: https://nim-lang.org/ +[35]: https://hisham.hm/htop/ +[36]: http://lm-sensors.org/ +[37]: https://01.org/powertop/ +[38]: https://dev.yorhel.nl/ncdu +[39]: https://nmap.org/ +[40]: https://www.tcpdump.org/ +[41]: https://www.wireshark.org/ +[42]: http://www.fetchmail.info/ +[43]: http://www.procmail.org/ +[44]: https://marlam.de/msmtp/ +[45]: https://www.cis.upenn.edu/~bcpierce/unison/ +[46]: https://rsync.samba.org/ +[47]: http://www.mutt.org/ +[48]: https://newsboat.org/ +[49]: https://irssi.org/ +[50]: https://www.roaringpenguin.com/products/remind +[51]: https://hookrace.net/public/linux-desktop/remcal.png +[52]: https://github.com/tsdh/rdictcc +[53]: https://www.dict.cc/ +[54]: https://www.latex-project.org/ +[55]: http://felsin9.de/nnis/research/ +[56]: https://pwmt.org/projects/zathura/ +[57]: https://wiki.gnome.org/Apps/Evince +[58]: https://www.gimp.org/ +[59]: https://inkscape.org/ +[60]: https://imagemagick.org/Usage/ +[61]: https://www.graphviz.org/ +[62]: https://sourceforge.net/projects/pgf/ +[63]: https://www.mozilla.org/en-US/firefox/new/ +[64]: https://github.com/5digits/dactyl +[65]: https://mpv.io/ +[66]: https://rg3.github.io/youtube-dl/ +[67]: http://moc.daper.net/ +[68]: https://aur.archlinux.org/packages/moc-pulse/ +[69]: https://hookrace.net/public/linux-desktop/moc.png +[70]: https://github.com/libfuse/sshfs +[71]: https://www.qemu.org/ +[72]: http://www.mingw.org/ +[73]: https://github.com/tpoechtrager/osxcross +[74]: https://github.com/ddnet/ddnet-scripts/blob/master/ddnet-release.sh +[75]: https://github.com/ddnet/ddnet-scripts/blob/master/ddnet-lib-update.sh +[76]: https://github.com/def-/rrb/blob/master/rrb +[77]: https://github.com/def-/rrb/blob/master/config.example +[78]: mailto:dennis@felsin9.de +[79]: https://news.ycombinator.com/item?id=18979731 diff --git a/sources/tech/20190116 Best Audio Editors For Linux.md b/sources/tech/20190116 Best Audio Editors For Linux.md new file mode 100644 index 0000000000..d588c886e2 --- /dev/null +++ b/sources/tech/20190116 Best Audio Editors For Linux.md @@ -0,0 +1,156 @@ +[#]: collector: (lujun9972) +[#]: translator: ( ) +[#]: reviewer: ( ) +[#]: publisher: ( ) +[#]: url: ( ) +[#]: subject: (Best Audio Editors For Linux) +[#]: via: (https://itsfoss.com/best-audio-editors-linux) +[#]: author: (Ankush Das https://itsfoss.com/author/ankush/) + +Best Audio Editors For Linux +====== + +You’ve got a lot of choices when it comes to audio editors for Linux. No matter whether you are a professional music producer or just learning to create awesome music, the audio editors will always come in handy. + +Well, for professional-grade usage, a [DAW][1] (Digital Audio Workstation) is always recommended. However, not everyone needs all the functionalities, so you should know about some of the most simple audio editors as well. + +In this article, we will talk about a couple of DAWs and basic audio editors which are available as **free and open source** solutions for Linux and (probably) for other operating systems. + +### Top Audio Editors for Linux + +![Best audio editors and DAW for Linux][2] + +We will not be focusing on all the functionalities that DAWs offer – but the basic audio editing capabilities. You may still consider this as the list of best DAW for Linux. + +**Installation instruction:** You will find all the mentioned audio editors or DAWs in your AppCenter or Software center. In case, you do not find them listed, please head to their official website for more information. + +#### 1\. Audacity + +![audacity audio editor][3] + +Audacity is one of the most basic yet a capable audio editor available for Linux. It is a free and open-source cross-platform tool. A lot of you must be already knowing about it. + +It has improved a lot when compared to the time when it started trending. I do recall that I utilized it to “try” making karaokes by removing the voice from an audio file. Well, you can still do it – but it depends. + +**Features:** + +It also supports plug-ins that include VST effects. Of course, you should not expect it to support VST Instruments. + + * Live audio recording through a microphone or a mixer + * Export/Import capability supporting multiple formats and multiple files at the same time + * Plugin support: LADSPA, LV2, Nyquist, VST and Audio Unit effect plug-ins + * Easy editing with cut, paste, delete and copy functions. + * Spectogram view mode for analyzing frequencies + + + +#### 2\. LMMS + +![][4] + +LMMS is a free and open source (cross-platform) digital audio workstation. It includes all the basic audio editing functionalities along with a lot of advanced features. + +You can mix sounds, arrange them, or create them using VST instruments. It does support them. Also, it comes baked in with some samples, presets, VST Instruments, and effects to get started. In addition, you also get a spectrum analyzer for some advanced audio editing. + +**Features:** + + * Note playback via MIDI + * VST Instrument support + * Native multi-sample support + * Built-in compressor, limiter, delay, reverb, distortion and bass enhancer + + + +#### 3\. Ardour + +![Ardour audio editor][5] + +Ardour is yet another free and open source digital audio workstation. If you have an audio interface, Ardour will support it. Of course, you can add unlimited multichannel tracks. The multichannel tracks can also be routed to different mixer tapes for the ease of editing and recording. + +You can also import a video to it and edit the audio to export the whole thing. It comes with a lot of built-in plugins and supports VST plugins as well. + +**Features:** + + * Non-linear editing + * Vertical window stacking for easy navigation + * Strip silence, push-pull trimming, Rhythm Ferret for transient and note onset-based editing + + + +#### 4\. Cecilia + +![cecilia audio editor][6] + +Cecilia is not an ordinary audio editor application. It is meant to be used by sound designers or if you are just in the process of becoming one. It is technically an audio signal processing environment. It lets you create ear-bending sound out of them. + +You get in-build modules and plugins for sound effects and synthesis. It is tailored for a specific use – if that is what you were looking for – look no further! + +**Features:** + + * Modules to achieve more (UltimateGrainer – A state-of-the-art granulation processing, RandomAccumulator – Variable speed recording accumulator, +UpDistoRes – Distortion with upsampling and resonant lowpass filter) + * Automatic Saving of modulations + + + +#### 5\. Mixxx + +![Mixxx audio DJ ][7] + +If you want to mix and record something while being able to have a virtual DJ tool, [Mixxx][8] would be a perfect tool. You get to know the BPM, key, and utilize the master sync feature to match the tempo and beats of a song. Also, do not forget that it is yet another free and open source application for Linux! + +It supports custom DJ equipment as well. So, if you have one or a MIDI – you can record your live mixes using this tool. + +**Features** + + * Broadcast and record DJ Mixes of your song + * Ability to connect your equipment and perform live + * Key detection and BPM detection + + + +#### 6\. Rosegarden + +![rosegarden audio editor][9] + +Rosegarden is yet another impressive audio editor for Linux which is free and open source. It is neither a fully featured DAW nor a basic audio editing tool. It is a mixture of both with some scaled down functionalities. + +I wouldn’t recommend this for professionals but if you have a home studio or just want to experiment, this would be one of the best audio editors for Linux to have installed. + +**Features:** + + * Music notation editing + * Recording, Mixing, and samples + + + +### Wrapping Up + +These are some of the best audio editors you could find out there for Linux. No matter whether you need a DAW, a cut-paste editing tool, or a basic mixing/recording audio editor, the above-mentioned tools should help you out. + +Did we miss any of your favorite? Let us know about it in the comments below. + + +-------------------------------------------------------------------------------- + +via: https://itsfoss.com/best-audio-editors-linux + +作者：[Ankush Das][a] +选题：[lujun9972][b] +译者：[译者ID](https://github.com/译者ID) +校对：[校对者ID](https://github.com/校对者ID) + +本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 + +[a]: https://itsfoss.com/author/ankush/ +[b]: https://github.com/lujun9972 +[1]: https://en.wikipedia.org/wiki/Digital_audio_workstation +[2]: https://i1.wp.com/itsfoss.com/wp-content/uploads/2019/01/linux-audio-editors-800x450.jpeg?resize=800%2C450&ssl=1 +[3]: https://i2.wp.com/itsfoss.com/wp-content/uploads/2019/01/audacity-audio-editor.jpg?fit=800%2C591&ssl=1 +[4]: https://i2.wp.com/itsfoss.com/wp-content/uploads/2019/01/lmms-daw.jpg?fit=800%2C472&ssl=1 +[5]: https://i2.wp.com/itsfoss.com/wp-content/uploads/2019/01/ardour-audio-editor.jpg?fit=800%2C639&ssl=1 +[6]: https://i1.wp.com/itsfoss.com/wp-content/uploads/2019/01/cecilia.jpg?fit=800%2C510&ssl=1 +[7]: https://i0.wp.com/itsfoss.com/wp-content/uploads/2019/01/mixxx.jpg?fit=800%2C486&ssl=1 +[8]: https://itsfoss.com/dj-mixxx-2/ +[9]: https://i2.wp.com/itsfoss.com/wp-content/uploads/2019/01/rosegarden.jpg?fit=800%2C391&ssl=1 +[10]: https://i2.wp.com/itsfoss.com/wp-content/uploads/2019/01/linux-audio-editors.jpeg?fit=800%2C450&ssl=1 diff --git a/sources/tech/20190116 GameHub - An Unified Library To Put All Games Under One Roof.md b/sources/tech/20190116 GameHub - An Unified Library To Put All Games Under One Roof.md new file mode 100644 index 0000000000..bdaae74b43 --- /dev/null +++ b/sources/tech/20190116 GameHub - An Unified Library To Put All Games Under One Roof.md @@ -0,0 +1,139 @@ +[#]: collector: (lujun9972) +[#]: translator: ( ) +[#]: reviewer: ( ) +[#]: publisher: ( ) +[#]: url: ( ) +[#]: subject: (GameHub – An Unified Library To Put All Games Under One Roof) +[#]: via: (https://www.ostechnix.com/gamehub-an-unified-library-to-put-all-games-under-one-roof/) +[#]: author: (SK https://www.ostechnix.com/author/sk/) + +GameHub – An Unified Library To Put All Games Under One Roof +====== + + + +**GameHub** is an unified gaming library that allows you to view, install, run and remove games on GNU/Linux operating system. It supports both native and non-native games from various sources including Steam, GOG, Humble Bundle, and Humble Trove etc. The non-native games are supported by [Wine][1], Proton, [DOSBox][2], ScummVM and RetroArch. It also allows you to add custom emulators and download bonus content and DLCs for GOG games. Simply put, Gamehub is a frontend for Steam/GoG/Humblebundle/Retroarch. It can use steam technologies like Proton to run windows gog games. GameHub is free, open source gaming platform written in **Vala** using **GTK+3**. If you’re looking for a way to manage all games under one roof, GameHub might be a good choice. + +### Installing GameHub + +The author of GameHub has designed it specifically for elementary OS. So, you can install it on Debian, Ubuntu, elementary OS and other Ubuntu-derivatives using GameHub PPA. + +``` +$ sudo apt install --no-install-recommends software-properties-common +$ sudo add-apt-repository ppa:tkashkin/gamehub +$ sudo apt update +$ sudo apt install com.github.tkashkin.gamehub +``` + +GameHub is available in [**AUR**][3], so just install it on Arch Linux and its variants using any AUR helpers, for example [**YaY**][4]. + +``` +$ yay -S gamehub-git +``` + +It is also available as **AppImage** and **Flatpak** packages in [**releases page**][5]. + +If you prefer AppImage package, do the following: + +``` +$ wget https://github.com/tkashkin/GameHub/releases/download/0.12.1-91-dev/GameHub-bionic-0.12.1-91-dev-cd55bb5-x86_64.AppImage -O gamehub +``` + +Make it executable: + +``` +$ chmod +x gamehub +``` + +And, run GameHub using command: + +``` +$ ./gamehub +``` + +If you want to use Flatpak installer, run the following commands one by one. + +``` +$ git clone https://github.com/tkashkin/GameHub.git +$ cd GameHub +$ scripts/build.sh build_flatpak +``` + +### Put All Games Under One Roof + +Launch GameHub from menu or application launcher. At first launch, you will see the following welcome screen. + + + +As you can see in the above screenshot, you need to login to the given sources namely Steam, GoG or Humble Bundle. If you don’t have Steam client on your Linux system, you need to install it first to access your steam account. For GoG and Humble bundle sources, click on the icon to log in to the respective source. + +Once you logged in to your account(s), all games from the all sources can be visible on GameHub dashboard. + + + +You will see list of logged-in sources on the top left corner. To view the games from each source, just click on the respective icon. + +You can also switch between list view or grid view, sort the games by applying the filters and search games from the list in GameHub dashboard. + +#### Installing a game + +Click on the game of your choice from the list and click Install button. If the game is non-native, GameHub will automatically choose the compatibility layer (E.g Wine) that suits to run the game and install the selected game. As you see in the below screenshot, Indiana Jones game is not available for Linux platform. + + + +If it is a native game (i.e supports Linux), simply press the Install button. + +![][7] + +If you don’t want to install the game, just hit the **Download** button to save it in your games directory. It is also possible to add locally installed games to GameHub using the **Import** option. + + + +#### GameHub Settings + +GameHub Settings window can be launched by clicking on the four straight lines on top right corner. + +From Settings section, we can enable, disable and set various settings such as, + + * Switch between light/dark themes. + * Use Symbolic icons instead of colored icons for games. + * Switch to compact list. + * Enable/disable merging games from different sources. + * Enable/disable compatibility layers. + * Set games collection directory. The default directory for storing the collection is **$HOME/Games/_Collection**. + * Set games directories for each source. + * Add/remove emulators, + * And many. + + + +For more details, refer the project links given at the end of this guide. + +**Related read:** + +And, that’s all for now. Hope this helps. I will be soon here with another guide. Until then, stay tuned with OSTechNix. + +Cheers! + + + +-------------------------------------------------------------------------------- + +via: https://www.ostechnix.com/gamehub-an-unified-library-to-put-all-games-under-one-roof/ + +作者：[SK][a] +选题：[lujun9972][b] +译者：[译者ID](https://github.com/译者ID) +校对：[校对者ID](https://github.com/校对者ID) + +本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 + +[a]: https://www.ostechnix.com/author/sk/ +[b]: https://github.com/lujun9972 +[1]: https://www.ostechnix.com/run-windows-games-softwares-ubuntu-16-04/ +[2]: https://www.ostechnix.com/how-to-run-ms-dos-games-and-programs-in-linux/ +[3]: https://aur.archlinux.org/packages/gamehub-git/ +[4]: https://www.ostechnix.com/yay-found-yet-another-reliable-aur-helper/ +[5]: https://github.com/tkashkin/GameHub/releases +[6]: data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7 +[7]: http://www.ostechnix.com/wp-content/uploads/2019/01/gamehub4.png diff --git a/sources/tech/20190116 Zipping files on Linux- the many variations and how to use them.md b/sources/tech/20190116 Zipping files on Linux- the many variations and how to use them.md new file mode 100644 index 0000000000..fb98f78b06 --- /dev/null +++ b/sources/tech/20190116 Zipping files on Linux- the many variations and how to use them.md @@ -0,0 +1,324 @@ +[#]: collector: (lujun9972) +[#]: translator: ( ) +[#]: reviewer: ( ) +[#]: publisher: ( ) +[#]: url: ( ) +[#]: subject: (Zipping files on Linux: the many variations and how to use them) +[#]: via: (https://www.networkworld.com/article/3333640/linux/zipping-files-on-linux-the-many-variations-and-how-to-use-them.html) +[#]: author: (Sandra Henry-Stocker https://www.networkworld.com/author/Sandra-Henry_Stocker/) + +Zipping files on Linux: the many variations and how to use them +====== + + +Some of us have been zipping files on Unix and Linux systems for many decades — to save some disk space and package files together for archiving. Even so, there are some interesting variations on zipping that not all of us have tried. So, in this post, we’re going to look at standard zipping and unzipping as well as some other interesting zipping options. + +### The basic zip command + +First, let’s look at the basic **zip** command. It uses what is essentially the same compression algorithm as **gzip** , but there are a couple important differences. For one thing, the gzip command is used only for compressing a single file where zip can both compress files and join them together into an archive. For another, the gzip command zips “in place”. In other words, it leaves a compressed file — not the original file alongside the compressed copy. Here's an example of gzip at work: + +``` +$ gzip onefile +$ ls -l +-rw-rw-r-- 1 shs shs 10514 Jan 15 13:13 onefile.gz +``` + +And here's zip. Notice how this command requires that a name be provided for the zipped archive where gzip simply uses the original file name and adds the .gz extension. + +``` +$ zip twofiles.zip file* + adding: file1 (deflated 82%) + adding: file2 (deflated 82%) +$ ls -l +-rw-rw-r-- 1 shs shs 58021 Jan 15 13:25 file1 +-rw-rw-r-- 1 shs shs 58933 Jan 15 13:34 file2 +-rw-rw-r-- 1 shs shs 21289 Jan 15 13:35 twofiles.zip +``` + +Notice also that the original files are still sitting there. + +The amount of disk space that is saved (i.e., the degree of compression obtained) will depend on the content of each file. The variation in the example below is considerable. + +``` +$ zip mybin.zip ~/bin/* + adding: bin/1 (deflated 26%) + adding: bin/append (deflated 64%) + adding: bin/BoD_meeting (deflated 18%) + adding: bin/cpuhog1 (deflated 14%) + adding: bin/cpuhog2 (stored 0%) + adding: bin/ff (deflated 32%) + adding: bin/file.0 (deflated 1%) + adding: bin/loop (deflated 14%) + adding: bin/notes (deflated 23%) + adding: bin/patterns (stored 0%) + adding: bin/runme (stored 0%) + adding: bin/tryme (deflated 13%) + adding: bin/tt (deflated 6%) +``` + +### The unzip command + +The **unzip** command will recover the contents from a zip file and, as you'd likely suspect, leave the zip file intact, whereas a similar gunzip command would leave only the uncompressed file. + +``` +$ unzip twofiles.zip +Archive: twofiles.zip + inflating: file1 + inflating: file2 +$ ls -l +-rw-rw-r-- 1 shs shs 58021 Jan 15 13:25 file1 +-rw-rw-r-- 1 shs shs 58933 Jan 15 13:34 file2 +-rw-rw-r-- 1 shs shs 21289 Jan 15 13:35 twofiles.zip +``` + +### The zipcloak command + +The **zipcloak** command encrypts a zip file, prompting you to enter a password twice (to help ensure you don't "fat finger" it) and leaves the file in place. You can expect the file size to vary a little from the original. + +``` +$ zipcloak twofiles.zip +Enter password: +Verify password: +encrypting: file1 +encrypting: file2 +$ ls -l +total 204 +-rw-rw-r-- 1 shs shs 58021 Jan 15 13:25 file1 +-rw-rw-r-- 1 shs shs 58933 Jan 15 13:34 file2 +-rw-rw-r-- 1 shs shs 21313 Jan 15 13:46 twofiles.zip <== slightly larger than + unencrypted version +``` + +Keep in mind that the original files are still sitting there unencrypted. + +### The zipdetails command + +The **zipdetails** command is going to show you details — a _lot_ of details about a zipped file, likely a lot more than you care to absorb. Even though we're looking at an encrypted file, zipdetails does display the file names along with file modification dates, user and group information, file length data, etc. Keep in mind that this is all "metadata." We don't see the contents of the files. + +``` +$ zipdetails twofiles.zip + +0000 LOCAL HEADER #1 04034B50 +0004 Extract Zip Spec 14 '2.0' +0005 Extract OS 00 'MS-DOS' +0006 General Purpose Flag 0001 + [Bit 0] 1 'Encryption' + [Bits 1-2] 1 'Maximum Compression' +0008 Compression Method 0008 'Deflated' +000A Last Mod Time 4E2F6B24 'Tue Jan 15 13:25:08 2019' +000E CRC F1B115BD +0012 Compressed Length 00002904 +0016 Uncompressed Length 0000E2A5 +001A Filename Length 0005 +001C Extra Length 001C +001E Filename 'file1' +0023 Extra ID #0001 5455 'UT: Extended Timestamp' +0025 Length 0009 +0027 Flags '03 mod access' +0028 Mod Time 5C3E2584 'Tue Jan 15 13:25:08 2019' +002C Access Time 5C3E27BB 'Tue Jan 15 13:34:35 2019' +0030 Extra ID #0002 7875 'ux: Unix Extra Type 3' +0032 Length 000B +0034 Version 01 +0035 UID Size 04 +0036 UID 000003E8 +003A GID Size 04 +003B GID 000003E8 +003F PAYLOAD + +2943 LOCAL HEADER #2 04034B50 +2947 Extract Zip Spec 14 '2.0' +2948 Extract OS 00 'MS-DOS' +2949 General Purpose Flag 0001 + [Bit 0] 1 'Encryption' + [Bits 1-2] 1 'Maximum Compression' +294B Compression Method 0008 'Deflated' +294D Last Mod Time 4E2F6C56 'Tue Jan 15 13:34:44 2019' +2951 CRC EC214569 +2955 Compressed Length 00002913 +2959 Uncompressed Length 0000E635 +295D Filename Length 0005 +295F Extra Length 001C +2961 Filename 'file2' +2966 Extra ID #0001 5455 'UT: Extended Timestamp' +2968 Length 0009 +296A Flags '03 mod access' +296B Mod Time 5C3E27C4 'Tue Jan 15 13:34:44 2019' +296F Access Time 5C3E27BD 'Tue Jan 15 13:34:37 2019' +2973 Extra ID #0002 7875 'ux: Unix Extra Type 3' +2975 Length 000B +2977 Version 01 +2978 UID Size 04 +2979 UID 000003E8 +297D GID Size 04 +297E GID 000003E8 +2982 PAYLOAD + +5295 CENTRAL HEADER #1 02014B50 +5299 Created Zip Spec 1E '3.0' +529A Created OS 03 'Unix' +529B Extract Zip Spec 14 '2.0' +529C Extract OS 00 'MS-DOS' +529D General Purpose Flag 0001 + [Bit 0] 1 'Encryption' + [Bits 1-2] 1 'Maximum Compression' +529F Compression Method 0008 'Deflated' +52A1 Last Mod Time 4E2F6B24 'Tue Jan 15 13:25:08 2019' +52A5 CRC F1B115BD +52A9 Compressed Length 00002904 +52AD Uncompressed Length 0000E2A5 +52B1 Filename Length 0005 +52B3 Extra Length 0018 +52B5 Comment Length 0000 +52B7 Disk Start 0000 +52B9 Int File Attributes 0001 + [Bit 0] 1 Text Data +52BB Ext File Attributes 81B40000 +52BF Local Header Offset 00000000 +52C3 Filename 'file1' +52C8 Extra ID #0001 5455 'UT: Extended Timestamp' +52CA Length 0005 +52CC Flags '03 mod access' +52CD Mod Time 5C3E2584 'Tue Jan 15 13:25:08 2019' +52D1 Extra ID #0002 7875 'ux: Unix Extra Type 3' +52D3 Length 000B +52D5 Version 01 +52D6 UID Size 04 +52D7 UID 000003E8 +52DB GID Size 04 +52DC GID 000003E8 + +52E0 CENTRAL HEADER #2 02014B50 +52E4 Created Zip Spec 1E '3.0' +52E5 Created OS 03 'Unix' +52E6 Extract Zip Spec 14 '2.0' +52E7 Extract OS 00 'MS-DOS' +52E8 General Purpose Flag 0001 + [Bit 0] 1 'Encryption' + [Bits 1-2] 1 'Maximum Compression' +52EA Compression Method 0008 'Deflated' +52EC Last Mod Time 4E2F6C56 'Tue Jan 15 13:34:44 2019' +52F0 CRC EC214569 +52F4 Compressed Length 00002913 +52F8 Uncompressed Length 0000E635 +52FC Filename Length 0005 +52FE Extra Length 0018 +5300 Comment Length 0000 +5302 Disk Start 0000 +5304 Int File Attributes 0001 + [Bit 0] 1 Text Data +5306 Ext File Attributes 81B40000 +530A Local Header Offset 00002943 +530E Filename 'file2' +5313 Extra ID #0001 5455 'UT: Extended Timestamp' +5315 Length 0005 +5317 Flags '03 mod access' +5318 Mod Time 5C3E27C4 'Tue Jan 15 13:34:44 2019' +531C Extra ID #0002 7875 'ux: Unix Extra Type 3' +531E Length 000B +5320 Version 01 +5321 UID Size 04 +5322 UID 000003E8 +5326 GID Size 04 +5327 GID 000003E8 + +532B END CENTRAL HEADER 06054B50 +532F Number of this disk 0000 +5331 Central Dir Disk no 0000 +5333 Entries in this disk 0002 +5335 Total Entries 0002 +5337 Size of Central Dir 00000096 +533B Offset to Central Dir 00005295 +533F Comment Length 0000 +Done +``` + +### The zipgrep command + +The **zipgrep** command is going to use a grep-type feature to locate particular content in your zipped files. If the file is encrypted, you will need to enter the password provided for the encryption for each file you want to examine. If you only want to check the contents of a single file from the archive, add its name to the end of the zipgrep command as shown below. + +``` +$ zipgrep hazard twofiles.zip file1 +[twofiles.zip] file1 password: +Certain pesticides should be banned since they are hazardous to the environment. +``` + +### The zipinfo command + +The **zipinfo** command provides information on the contents of a zipped file whether encrypted or not. This includes the file names, sizes, dates and permissions. + +``` +$ zipinfo twofiles.zip +Archive: twofiles.zip +Zip file size: 21313 bytes, number of entries: 2 +-rw-rw-r-- 3.0 unx 58021 Tx defN 19-Jan-15 13:25 file1 +-rw-rw-r-- 3.0 unx 58933 Tx defN 19-Jan-15 13:34 file2 +2 files, 116954 bytes uncompressed, 20991 bytes compressed: 82.1% +``` + +### The zipnote command + +The **zipnote** command can be used to extract comments from zip archives or add them. To display comments, just preface the name of the archive with the command. If no comments have been added previously, you will see something like this: + +``` +$ zipnote twofiles.zip +@ file1 +@ (comment above this line) +@ file2 +@ (comment above this line) +@ (zip file comment below this line) +``` + +If you want to add comments, write the output from the zipnote command to a file: + +``` +$ zipnote twofiles.zip > comments +``` + +Next, edit the file you've just created, inserting your comments above the **(comment above this line)** lines. Then add the comments using a zipnote command like this one: + +``` +$ zipnote -w twofiles.zip < comments +``` + +### The zipsplit command + +The **zipsplit** command can be used to break a zip archive into multiple zip archives when the original file is too large — maybe because you're trying to add one of the files to a small thumb drive. The easiest way to do this seems to be to specify the max size for each of the zipped file portions. This size must be large enough to accomodate the largest included file. + +``` +$ zipsplit -n 12000 twofiles.zip +2 zip files will be made (100% efficiency) +creating: twofile1.zip +creating: twofile2.zip +$ ls twofile*.zip +-rw-rw-r-- 1 shs shs 10697 Jan 15 14:52 twofile1.zip +-rw-rw-r-- 1 shs shs 10702 Jan 15 14:52 twofile2.zip +-rw-rw-r-- 1 shs shs 21377 Jan 15 14:27 twofiles.zip +``` + +Notice how the extracted files are sequentially named "twofile1" and "twofile2". + +### Wrap-up + +The **zip** command, along with some of its zipping compatriots, provide a lot of control over how you generate and work with compressed file archives. + +**[ Also see:[Invaluable tips and tricks for troubleshooting Linux][1] ]** + +Join the Network World communities on [Facebook][2] and [LinkedIn][3] to comment on topics that are top of mind. + +-------------------------------------------------------------------------------- + +via: https://www.networkworld.com/article/3333640/linux/zipping-files-on-linux-the-many-variations-and-how-to-use-them.html + +作者：[Sandra Henry-Stocker][a] +选题：[lujun9972][b] +译者：[译者ID](https://github.com/译者ID) +校对：[校对者ID](https://github.com/校对者ID) + +本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 + +[a]: https://www.networkworld.com/author/Sandra-Henry_Stocker/ +[b]: https://github.com/lujun9972 +[1]: https://www.networkworld.com/article/3242170/linux/invaluable-tips-and-tricks-for-troubleshooting-linux.html +[2]: https://www.facebook.com/NetworkWorld/ +[3]: https://www.linkedin.com/company/network-world diff --git a/sources/tech/20190117 Pyvoc - A Command line Dictionary And Vocabulary Building Tool.md b/sources/tech/20190117 Pyvoc - A Command line Dictionary And Vocabulary Building Tool.md new file mode 100644 index 0000000000..b0aa45d618 --- /dev/null +++ b/sources/tech/20190117 Pyvoc - A Command line Dictionary And Vocabulary Building Tool.md @@ -0,0 +1,239 @@ +[#]: collector: (lujun9972) +[#]: translator: ( ) +[#]: reviewer: ( ) +[#]: publisher: ( ) +[#]: url: ( ) +[#]: subject: (Pyvoc – A Command line Dictionary And Vocabulary Building Tool) +[#]: via: (https://www.ostechnix.com/pyvoc-a-command-line-dictionary-and-vocabulary-building-tool/) +[#]: author: (SK https://www.ostechnix.com/author/sk/) + +Pyvoc – A Command line Dictionary And Vocabulary Building Tool +====== + + + +Howdy! I have a good news for non-native English speakers. Now, you can improve your English vocabulary and find the meaning of English words, right from your Terminal. Say hello to **Pyvoc** , a cross-platform, open source, command line dictionary and vocabulary building tool written in **Python** programming language. Using this tool, you can brush up some English words meanings, test or improve your vocabulary skill or simply use it as a CLI dictionary on Unix-like operating systems. + +### Installing Pyvoc + +Since Pyvoc is written using Python language, you can install it using [**Pip3**][1] package manager. + +``` +$ pip3 install pyvoc +``` + +Once installed, run the following command to automatically create necessary configuration files in your $HOME directory. + +``` +$ pyvoc word +``` + +Sample output: + +``` +|Creating necessary config files +/getting api keys. please handle with care! +| + +word +Noun: single meaningful element of speech or writing +example: I don't like the word ‘unofficial’ + +Verb: express something spoken or written +example: he words his request in a particularly ironic way + +Interjection: used to express agreement or affirmation +example: Word, that's a good record, man +``` + +Done! Let us go ahead and brush the English skills. + +### Use Pyvoc as a command line Dictionary tool + +Pyvoc fetches the word meaning from **Oxford Dictionary API**. + +Let us say, you want to find the meaning of a word **‘digression’**. To do so, run: + +``` +$ pyvoc digression +``` + + + +See? Pyvoc not only displays the meaning of word **‘digression’** , but also an example sentence which shows how to use that word in practical. + +Let us see an another example. + +``` +$ pyvoc subterfuge +| + +subterfuge +Noun: deceit used in order to achieve one's goal +example: he had to use subterfuge and bluff on many occasions +``` + +It also shows the word classes as well. As you already know, English has four major **word classes** : + + 1. Nouns, + + 2. Verbs, + + 3. Adjectives, + + 4. Adverbs. + + + + +Take a look at the following example. + +``` +$ pyvoc welcome + / + +welcome +Noun: instance or manner of greeting someone +example: you will receive a warm welcome + +Interjection: used to greet someone in polite or friendly way +example: welcome to the Wildlife Park + +Verb: greet someone arriving in polite or friendly way +example: hotels should welcome guests in their own language + +Adjective: gladly received +example: I'm pleased to see you, lad—you're welcome +``` + +As you see in the above output, the word ‘welcome’ can be used as a verb, noun, adjective and interjection. Pyvoc has given example for each class. + +If you misspell a word, it will inform you to check the spelling of the given word. + +``` +$ pyvoc wlecome +\ +No definition found. Please check the spelling!! +``` + +Useful, isn’t it? + +### Create vocabulary groups + +A vocabulary group is nothing but a collection words added by the user. You can later revise or take quiz from these groups. 100 groups of 60 words are **reserved** for the user. + +To add a word (E.g **sporadic** ) to a group, just run: + +``` +$ pyvoc sporadic -a +- + +sporadic +Adjective: occurring at irregular intervals or only in few places +example: sporadic fighting broke out + + +writing to vocabulary group... +word added to group number 51 +``` + +As you can see, I didn’t provide any group number and pyvoc displayed the meaning of given word and automatically added that word to group number **51**. If you don’t provide the group number, Pyvoc will **incrementally add words** to groups **51-100**. + +Pyvoc also allows you to specify a group number if you want to. You can specify a group from 1-50 using **-g** option. For example, I am going to add a word to Vocabulary group 20 using the following command. + +``` +$ pyvoc discrete -a -g 20 + / + +discrete +Adjective: individually separate and distinct +example: speech sounds are produced as a continuous sound signal rather + than discrete units + +creating group Number 20... +writing to vocabulary group... +word added to group number 20 +``` + +See? The above command displays the meaning of ‘discrete’ word and adds it to the vocabulary group 20. If the group doesn’t exists, Pyvoc will create it and add the word. + +By default, Pyvoc includes three predefined vocabulary groups (101, 102, and 103). These custom groups has 800 words of each. All words in these groups are taken from **GRE** and **SAT** preparation websites. + +To view the user-generated groups, simply run: + +``` +$ pyvoc word -l + - + +word +Noun: single meaningful element of speech or writing +example: I don't like the word ‘unofficial’ + +Verb: express something spoken or written +example: he words his request in a particularly ironic way + +Interjection: used to express agreement or affirmation +example: Word, that's a good record, man + + +USER GROUPS +Group no. No. of words +20 1 + +DEFAULT GROUP +Group no. No. of words +51 1 +``` +``` + +``` + +As you see, I have created one group (20) including the default group (51). + +### Test and improve English vocabulary + +As I already said, you can use the Vocabulary groups to revise or take quiz from them. + +For instance, to revise the group no. **101** , use **-r** option like below. + +``` +$ pyvoc 101 -r +``` + +You can now revise the meaning of all words in the Vocabulary group 101 in random order. Just hit ENTER to go through next questions. Once done, hit **CTRL+C** to exit. + + + +Also, you take quiz from the existing groups to brush up your vocabulary. To do so, use **-q** option like below. + +``` +$ pyvoc 103 -q 50 +``` + +This command allows you to take quiz of 50 questions from vocabulary group 103. Choose the correct answer from the list by entering the appropriate number. You will get 1 point for every correct answer. The more you score the more your vocabulary skill will be. + + + +Pyvoc is in the early-development stage. I hope the developer will improve it and add more features in the days to come. + +As a non-native English speaker, I personally find it useful to test and learn new word meanings in my free time. If you’re a heavy command line user and wanted to quickly check the meaning of a word, Pyvoc is the right tool. You can also test your English Vocabulary at your free time to memorize and improve your English language skill. Give it a try. You won’t be disappointed. + +And, that’s all for now. Hope this was useful. More good stuffs to come. Stay tuned! + +Cheers! + + +-------------------------------------------------------------------------------- + +via: https://www.ostechnix.com/pyvoc-a-command-line-dictionary-and-vocabulary-building-tool/ + +作者：[SK][a] +选题：[lujun9972][b] +译者：[译者ID](https://github.com/译者ID) +校对：[校对者ID](https://github.com/校对者ID) + +本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 + +[a]: https://www.ostechnix.com/author/sk/ +[b]: https://github.com/lujun9972 +[1]: https://www.ostechnix.com/manage-python-packages-using-pip/ diff --git a/sources/tech/20190121 How to Resize OpenStack Instance (Virtual Machine) from Command line.md b/sources/tech/20190121 How to Resize OpenStack Instance (Virtual Machine) from Command line.md new file mode 100644 index 0000000000..e235cabdbf --- /dev/null +++ b/sources/tech/20190121 How to Resize OpenStack Instance (Virtual Machine) from Command line.md @@ -0,0 +1,149 @@ +[#]: collector: (lujun9972) +[#]: translator: ( ) +[#]: reviewer: ( ) +[#]: publisher: ( ) +[#]: url: ( ) +[#]: subject: (How to Resize OpenStack Instance (Virtual Machine) from Command line) +[#]: via: (https://www.linuxtechi.com/resize-openstack-instance-command-line/) +[#]: author: (Pradeep Kumar http://www.linuxtechi.com/author/pradeep/) + +How to Resize OpenStack Instance (Virtual Machine) from Command line +====== + +Being a Cloud administrator, resizing or changing resources of an instance or virtual machine is one of the most common tasks. + + + +In Openstack environment, there are some scenarios where cloud user has spin a vm using some flavor( like m1.smalll) where root partition disk size is 20 GB, but at some point of time user wants to extends the root partition size to 40 GB. So resizing of vm’s root partition can be accomplished by using the resize option in nova command. During the resize, we need to specify the new flavor that will include disk size as 40 GB. + +**Note:** Once you extend the instance resources like RAM, CPU and disk using resize option in openstack then you can’t reduce it. + +**Read More on** : [**How to Create and Delete Virtual Machine(VM) from Command line in OpenStack**][1] + +In this tutorial I will demonstrate how to resize an openstack instance from command line. Let’s assume I have an existing instance named “ **test_resize_vm** ” and it’s associated flavor is “m1.small” and root partition disk size is 20 GB. + +Execute the below command from controller node to check on which compute host our vm “test_resize_vm” is provisioned and its flavor details + +``` +:~# openstack server show test_resize_vm | grep -E "flavor|hypervisor" +| OS-EXT-SRV-ATTR:hypervisor_hostname | compute-57 | +| flavor | m1.small (2) | +:~# +``` + +Login to VM as well and check the root partition size, + +``` +[[email protected] ~]# df -Th +Filesystem Type Size Used Avail Use% Mounted on +/dev/vda1 xfs 20G 885M 20G 5% / +devtmpfs devtmpfs 900M 0 900M 0% /dev +tmpfs tmpfs 920M 0 920M 0% /dev/shm +tmpfs tmpfs 920M 8.4M 912M 1% /run +tmpfs tmpfs 920M 0 920M 0% /sys/fs/cgroup +tmpfs tmpfs 184M 0 184M 0% /run/user/1000 +[[email protected] ~]# echo "test file for resize operation" > demofile +[[email protected] ~]# cat demofile +test file for resize operation +[[email protected] ~]# +``` + +Get the available flavor list using below command, + +``` +:~# openstack flavor list ++--------------------------------------|-----------------|-------|------|-----------|-------|-----------+ +| ID | Name | RAM | Disk | Ephemeral | VCPUs | Is Public | ++--------------------------------------|-----------------|-------|------|-----------|-------|-----------+ +| 2 | m1.small | 2048 | 20 | 0 | 1 | True | +| 3 | m1.medium | 4096 | 40 | 0 | 2 | True | +| 4 | m1.large | 8192 | 80 | 0 | 4 | True | +| 5 | m1.xlarge | 16384 | 160 | 0 | 8 | True | ++--------------------------------------|-----------------|-------|------|-----------|-------|-----------+ +``` + +So we will be using the flavor “m1.medium” for resize operation, Run the beneath nova command to resize “test_resize_vm”, + +Syntax: # nova resize {VM_Name} {flavor_id} —poll + +``` +:~# nova resize test_resize_vm 3 --poll +Server resizing... 100% complete +Finished +:~# +``` + +Now confirm the resize operation using “ **openstack server –confirm”** command, + +``` +~# openstack server list | grep -i test_resize_vm +| 1d56f37f-94bd-4eef-9ff7-3dccb4682ce0 | test_resize_vm | VERIFY_RESIZE |private-net=10.20.10.51 | +:~# +``` + +As we can see in the above command output the current status of the vm is “ **verify_resize** “, execute below command to confirm resize, + +``` +~# openstack server resize --confirm 1d56f37f-94bd-4eef-9ff7-3dccb4682ce0 +~# +``` + +After the resize confirmation, status of VM will become active, now re-verify hypervisor and flavor details for the vm + +``` +:~# openstack server show test_resize_vm | grep -E "flavor|hypervisor" +| OS-EXT-SRV-ATTR:hypervisor_hostname | compute-58 | +| flavor | m1.medium (3)| +``` + +Login to your VM now and verify the root partition size + +``` +[[email protected] ~]# df -Th +Filesystem Type Size Used Avail Use% Mounted on +/dev/vda1 xfs 40G 887M 40G 3% / +devtmpfs devtmpfs 1.9G 0 1.9G 0% /dev +tmpfs tmpfs 1.9G 0 1.9G 0% /dev/shm +tmpfs tmpfs 1.9G 8.4M 1.9G 1% /run +tmpfs tmpfs 1.9G 0 1.9G 0% /sys/fs/cgroup +tmpfs tmpfs 380M 0 380M 0% /run/user/1000 +[[email protected] ~]# cat demofile +test file for resize operation +[[email protected] ~]# +``` + +This confirm that VM root partition has been resized successfully. + +**Note:** Due to some reason if resize operation was not successful and you want to revert the vm back to previous state, then run the following command, + +``` +# openstack server resize --revert {instance_uuid} +``` + +If have noticed “ **openstack server show** ” commands output, VM is migrated from compute-57 to compute-58 after resize. This is the default behavior of “nova resize” command ( i.e nova resize command will migrate the instance to another compute & then resize it based on the flavor details) + +In case if you have only one compute node then nova resize will not work, but we can make it work by changing the below parameter in nova.conf file on compute node, + +Login to compute node, verify the parameter value + +If “ **allow_resize_to_same_host** ” is set as False then change it to True and restart the nova compute service. + +**Read More on** [**OpenStack Deployment using Devstack on CentOS 7 / RHEL 7 System**][2] + +That’s all from this tutorial, in case it helps you technically then please do share your feedback and comments. + +-------------------------------------------------------------------------------- + +via: https://www.linuxtechi.com/resize-openstack-instance-command-line/ + +作者：[Pradeep Kumar][a] +选题：[lujun9972][b] +译者：[译者ID](https://github.com/译者ID) +校对：[校对者ID](https://github.com/校对者ID) + +本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 + +[a]: http://www.linuxtechi.com/author/pradeep/ +[b]: https://github.com/lujun9972 +[1]: https://www.linuxtechi.com/create-delete-virtual-machine-command-line-openstack/ +[2]: https://www.linuxtechi.com/openstack-deployment-devstack-centos-7-rhel-7/ diff --git a/sources/tech/20190123 Dockter- A container image builder for researchers.md b/sources/tech/20190123 Dockter- A container image builder for researchers.md new file mode 100644 index 0000000000..359d0c1d1e --- /dev/null +++ b/sources/tech/20190123 Dockter- A container image builder for researchers.md @@ -0,0 +1,121 @@ +[#]: collector: (lujun9972) +[#]: translator: ( ) +[#]: reviewer: ( ) +[#]: publisher: ( ) +[#]: url: ( ) +[#]: subject: (Dockter: A container image builder for researchers) +[#]: via: (https://opensource.com/article/19/1/dockter-image-builder-researchers) +[#]: author: (Nokome Bentley https://opensource.com/users/nokome) + +Dockter: A container image builder for researchers +====== +Dockter supports the specific requirements of researchers doing data analysis, including those using R. + + + +Dependency hell is ubiquitous in the world of software for research, and this affects research transparency and reproducibility. Containerization is one solution to this problem, but it creates new challenges for researchers. Docker is gaining popularity in the research community—but using it efficiently requires solid Dockerfile writing skills. + +As a part of the [Stencila][1] project, which is a platform for creating, collaborating on, and sharing data-driven content, we are developing [Dockter][2], an open source tool that makes it easier for researchers to create Docker images for their projects. Dockter scans a research project's source code, generates a Dockerfile, and builds a Docker image. It has a range of features that allow flexibility and can help researchers learn more about working with Docker. + +Dockter also generates a JSON file with information about the software environment (based on [CodeMeta][3] and [Schema.org][4]) to enable further processing and interoperability with other tools. + +Several other projects create Docker images from source code and/or requirements files, including: [alibaba/derrick][5], [jupyter/repo2docker][6], [Gueils/whales][7], [o2r-project/containerit][8]; [openshift/source-to-image][9], and [ViDA-NYU/reprozip][10]. Dockter is similar to repo2docker, containerit, and ReproZip in that it is aimed at researchers doing data analysis (and supports R), whereas most other tools are aimed at software developers (and don't support R). + +Dockter differs from these projects principally in that it: + + * Performs static code analysis for multiple languages to determine package requirements + * Uses package databases to determine package system dependencies and generate linked metadata (containerit does this for R) + * Installs language package dependencies quicker (which can be useful during research projects where dependencies often change) + * By default but optionally, installs Stencila packages so that Stencila client interfaces can execute code in the container + + + +### Dockter's features + +Following are some of the ways researchers can use Dockter. + +#### Generating Docker images from code + +Dockter scans a research project folder and builds a Docker image for it. If the folder already has a Dockerfile, Dockter will build the image from that. If not, Dockter will scan the source code files in the folder and generate one. Dockter currently handles R, Python, and Node.js source code. The .dockerfile (with the dot at the beginning) it generates is fully editable so users can take over from Dockter and carry on with editing the file as they see fit. + +If the folder contains an R package [DESCRIPTION][11] file, Dockter will install the R packages listed under Imports into the image. If the folder does not contain a DESCRIPTION file, Dockter will scan all the R files in the folder for package import or usage statements and create a .DESCRIPTION file. + +If the folder contains a [requirements.txt][12] file for Python, Dockter will copy it into the Docker image and use [pip][13] to install the specified packages. If the folder does not contain either of those files, Dockter will scan all the folder's .py files for import statements and create a .requirements.txt file. + +If the folder contains a [package.json][14] file, Dockter will copy it into the Docker image and use npm to install the specified packages. If the folder does not contain a package.json file, Dockter will scan all the folder's .js files for require calls and create a .package.json file. + +#### Capturing system requirements automatically + +One of the headaches researchers face when hand-writing Dockerfiles is figuring out which system dependencies their project needs. Often this involves a lot of trial and error. Dockter automatically checks if any dependencies (or dependencies of dependencies, or dependencies of…) require system packages and installs those into the image. No more trial and error cycles of build, fail, add dependency, repeat… + +#### Reinstalling language packages faster + +If you have ever built a Docker image, you know it can be frustrating waiting for all your project's dependencies to reinstall when you add or remove just one. + +This happens because of Docker's layered filesystem: When you update a requirements file, Docker throws away all the subsequent layers—including the one where you previously installed your dependencies. That means all the packages have to be reinstalled. + +Dockter takes a different approach. It leaves the installation of language packages to the language package managers: Python's pip, Node.js's npm, and R's install.packages. These package managers are good at the job they were designed for: checking which packages need to be updated and updating only them. The result is much faster rebuilds, especially for R packages, which often involve compilation. + +Dockter does this by looking for a special **# dockter** comment in a Dockerfile. Instead of throwing away layers, it executes all instructions after this comment in the same layer—thereby reusing packages that were previously installed. + +#### Generating structured metadata for a project + +Dockter uses [JSON-LD][15] as its internal data structure. When it parses a project's source code, it generates a JSON-LD tree using vocabularies from schema.org and CodeMeta. + +Dockter also fetches metadata on a project's dependencies, which could be used to generate a complete software citation for the project. + +### Easy to pick up, easy to throw away + +Dockter is designed to make it easier to get started creating Docker images for your project. But it's also designed to not get in your way or restrict you from using bare Docker. You can easily and individually override any of the steps Dockter takes to build an image. + + * **Code analysis:** To stop Dockter from doing code analysis and specify your project's package dependencies, just remove the leading **.** (dot) from the .DESCRIPTION, .requirements.txt, or .package.json files. + + * **Dockerfile generation:** Dockter aims to generate readable Dockerfiles that conform to best practices. They include comments on what each section does and are a good way to start learning how to write your own Dockerfiles. To stop Dockter from generating a .Dockerfile and start editing it yourself, just rename it Dockerfile (without the leading dot). + + + + +### Install Dockter + +[Dockter is available][16] as pre-compiled, standalone command line tool or as a Node.js package. Click [here][17] for a demo. + +We welcome and encourage all [contributions][18]! + +A longer version of this article is available on the project's [GitHub page][19]. + +Aleksandra Pawlik will present [Building reproducible computing environments: a workshop for non-experts][20] at [linux.conf.au][21], January 21-25 in Christchurch, New Zealand. + +-------------------------------------------------------------------------------- + +via: https://opensource.com/article/19/1/dockter-image-builder-researchers + +作者：[Nokome Bentley][a] +选题：[lujun9972][b] +译者：[译者ID](https://github.com/译者ID) +校对：[校对者ID](https://github.com/校对者ID) + +本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 + +[a]: https://opensource.com/users/nokome +[b]: https://github.com/lujun9972 +[1]: https://stenci.la/ +[2]: https://stencila.github.io/dockter/ +[3]: https://codemeta.github.io/index.html +[4]: http://Schema.org +[5]: https://github.com/alibaba/derrick +[6]: https://github.com/jupyter/repo2docker +[7]: https://github.com/Gueils/whales +[8]: https://github.com/o2r-project/containerit +[9]: https://github.com/openshift/source-to-image +[10]: https://github.com/ViDA-NYU/reprozip +[11]: http://r-pkgs.had.co.nz/description.html +[12]: https://pip.readthedocs.io/en/1.1/requirements.html +[13]: https://pypi.org/project/pip/ +[14]: https://docs.npmjs.com/files/package.json +[15]: https://json-ld.org/ +[16]: https://github.com/stencila/dockter/releases/ +[17]: https://asciinema.org/a/pOHpxUqIVkGdA1dqu7bENyxZk?size=medium&cols=120&autoplay=1 +[18]: https://github.com/stencila/dockter/blob/master/CONTRIBUTING.md +[19]: https://github.com/stencila/dockter +[20]: https://2019.linux.conf.au/schedule/presentation/185/ +[21]: https://linux.conf.au/ diff --git a/sources/tech/20190123 GStreamer WebRTC- A flexible solution to web-based media.md b/sources/tech/20190123 GStreamer WebRTC- A flexible solution to web-based media.md new file mode 100644 index 0000000000..bb7e129ff3 --- /dev/null +++ b/sources/tech/20190123 GStreamer WebRTC- A flexible solution to web-based media.md @@ -0,0 +1,108 @@ +[#]: collector: (lujun9972) +[#]: translator: ( ) +[#]: reviewer: ( ) +[#]: publisher: ( ) +[#]: url: ( ) +[#]: subject: (GStreamer WebRTC: A flexible solution to web-based media) +[#]: via: (https://opensource.com/article/19/1/gstreamer) +[#]: author: (Nirbheek Chauhan https://opensource.com/users/nirbheek) + +GStreamer WebRTC: A flexible solution to web-based media +====== +GStreamer's WebRTC implementation eliminates some of the shortcomings of using WebRTC in native apps, server applications, and IoT devices. + + + +Currently, [WebRTC.org][1] is the most popular and feature-rich WebRTC implementation. It is used in Chrome and Firefox and works well for browsers, but the Native API and implementation have several shortcomings that make it a less-than-ideal choice for uses outside of browsers, including native apps, server applications, and internet of things (IoT) devices. + +Last year, our company ([Centricular][2]) made an independent implementation of a Native WebRTC API available in GStreamer 1.14. This implementation is much easier to use and more flexible than the WebRTC.org Native API, is transparently compatible with WebRTC.org, has been tested with all browsers, and is already in production use. + +### What are GStreamer and WebRTC? + +[GStreamer][3] is an open source, cross-platform multimedia framework and one of the easiest and most flexible ways to implement any application that needs to play, record, or transform media-like data across a diverse scale of devices and products, including embedded (IoT, in-vehicle infotainment, phones, TVs, etc.), desktop (video/music players, video recording, non-linear editing, video conferencing, [VoIP][4] clients, browsers, etc.), servers (encode/transcode farms, video/voice conferencing servers, etc.), and [more][5]. + +The main feature that makes GStreamer the go-to multimedia framework for many people is its pipeline-based model, which solves one of the hardest problems in API design: catering to applications of varying complexity; from the simplest one-liners and quick solutions to those that need several hundreds of thousands of lines of code to implement their full feature set. If you want to learn how to use GStreamer, [Jan Schmidt's tutorial][6] from [LCA 2018][7] is a good place to start. + +[WebRTC][8] is a set of draft specifications that build upon existing [RTP][9], [RTCP][10], [SDP][11], [DTLS][12], [ICE][13], and other real-time communication (RTC) specifications and define an API for making them accessible using browser JavaScript (JS) APIs. + +People have been doing real-time communication over [IP][14] for [decades][15] with the protocols WebRTC builds upon. WebRTC's real innovation was creating a bridge between native applications and web apps by defining a standard yet flexible API that browsers can expose to untrusted JavaScript code. + +These specifications are [constantly being improved][16], which, combined with the ubiquitous nature of browsers, means WebRTC is fast becoming the standard choice for video conferencing on all platforms and for most applications. + +### **Everything is great, let's build amazing apps!** + +Not so fast, there's more to the story! For web apps, the [PeerConnection API][17] is [everywhere][18]. There are some browser-specific quirks, and the API keeps changing, but the [WebRTC JS adapter][19] handles most of that. Overall, the web app experience is mostly 👍. + +Unfortunately, for native code or applications that need more flexibility than a sandboxed JavaScript app can achieve, there haven't been a lot of great options. + +[Libwebrtc][20] (Google's implementation), [Janus][21], [Kurento][22], and [OpenWebRTC][23] have traditionally been the main contenders, but each implementation has its own inflexibilities, shortcomings, and constraints. + +Libwebrtc is still the most mature implementation, but it is also the most difficult to work with. Since it's embedded inside Chrome, it's a moving target and the project [is quite difficult to build and integrate][24]. These are all obstacles for native or server app developers trying to quickly prototype and experiment with things. + +Also, WebRTC was not built for multimedia, so the lower layers get in the way of non-browser use cases and applications. It is quite painful to do anything other than the default "set raw media, transmit" and "receive from remote, get raw media." This means if you want to use your own filters or hardware-specific codecs or sinks/sources, you end up having to fork libwebrtc. + +[**OpenWebRTC**][23] by Ericsson was the first attempt to rectify this situation. It was built on top of GStreamer. Its target audience was app developers, and it fit the bill quite well as a proof of concept—even though it used a custom API and some of the architectural decisions made it quite inflexible for most other uses. However, after an initial flurry of activity around the project, momentum petered out, the project failed to gather a community, and it is now effectively dead. Full disclosure: Centricular worked with Ericsson to polish some of the rough edges around the project immediately prior to its public release. + +### WebRTC in GStreamer + +GStreamer's WebRTC implementation gives you full control, as it does with any other [GStreamer pipeline][25]. + +As we said, the WebRTC standards build upon existing standards and protocols that serve similar purposes. GStreamer has supported almost all of them for a while now because they were being used for real-time communication, live streaming, and many other IP-based applications. This led Ericsson to choose GStreamer as the base for its OpenWebRTC project. + +Combined with the [SRTP][26] and DTLS plugins that were written during OpenWebRTC's development, it means that the implementation is built upon a solid and well-tested base, and implementing WebRTC features does not involve as much code-from-scratch work as one might presume. However, WebRTC is a large collection of standards, and reaching feature-parity with libwebrtc is an ongoing task. + +Due to decisions made while architecting WebRTCbin's internals, the API follows the PeerConnection specification quite closely. Therefore, almost all its missing features involve writing code that would plug into clearly defined sockets. For instance, since the GStreamer 1.14 release, the following features have been added to the WebRTC implementation and will be available in the next release of the GStreamer WebRTC: + + * Forward error correction + * RTP retransmission (RTX) + * RTP BUNDLE + * Data channels over SCTP + + + +We believe GStreamer's API is the most flexible, versatile, and easy to use WebRTC implementation out there, and it will only get better as time goes by. Bringing the power of pipeline-based multimedia manipulation to WebRTC opens new doors for interesting, unique, and highly efficient applications. If you'd like to demo the technology and play with the code, build and run [these demos][27], which include C, Rust, Python, and C# examples. + +Matthew Waters will present [GStreamer WebRTC—The flexible solution to web-based media][28] at [linux.conf.au][29], January 21-25 in Christchurch, New Zealand. + +-------------------------------------------------------------------------------- + +via: https://opensource.com/article/19/1/gstreamer + +作者：[Nirbheek Chauhan][a] +选题：[lujun9972][b] +译者：[译者ID](https://github.com/译者ID) +校对：[校对者ID](https://github.com/校对者ID) + +本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 + +[a]: https://opensource.com/users/nirbheek +[b]: https://github.com/lujun9972 +[1]: http://webrtc.org/ +[2]: https://www.centricular.com/ +[3]: https://gstreamer.freedesktop.org/documentation/application-development/introduction/gstreamer.html +[4]: https://en.wikipedia.org/wiki/Voice_over_IP +[5]: https://wiki.ligo.org/DASWG/GstLAL +[6]: https://www.youtube.com/watch?v=ZphadMGufY8 +[7]: http://lca2018.linux.org.au/ +[8]: https://en.wikipedia.org/wiki/WebRTC +[9]: https://en.wikipedia.org/wiki/Real-time_Transport_Protocol +[10]: https://en.wikipedia.org/wiki/RTP_Control_Protocol +[11]: https://en.wikipedia.org/wiki/Session_Description_Protocol +[12]: https://en.wikipedia.org/wiki/Datagram_Transport_Layer_Security +[13]: https://en.wikipedia.org/wiki/Interactive_Connectivity_Establishment +[14]: https://en.wikipedia.org/wiki/Internet_Protocol +[15]: https://en.wikipedia.org/wiki/Session_Initiation_Protocol +[16]: https://datatracker.ietf.org/wg/rtcweb/documents/ +[17]: https://developer.mozilla.org/en-US/docs/Web/API/RTCPeerConnection +[18]: https://caniuse.com/#feat=rtcpeerconnection +[19]: https://github.com/webrtc/adapter +[20]: https://github.com/aisouard/libwebrtc +[21]: https://janus.conf.meetecho.com/ +[22]: https://www.kurento.org/kurento-architecture +[23]: https://en.wikipedia.org/wiki/OpenWebRTC +[24]: https://webrtchacks.com/building-webrtc-from-source/ +[25]: https://gstreamer.freedesktop.org/documentation/application-development/introduction/basics.html +[26]: https://en.wikipedia.org/wiki/Secure_Real-time_Transport_Protocol +[27]: https://github.com/centricular/gstwebrtc-demos/ +[28]: https://linux.conf.au/schedule/presentation/143/ +[29]: https://linux.conf.au/ diff --git a/sources/tech/20190124 Orpie- A command-line reverse Polish notation calculator.md b/sources/tech/20190124 Orpie- A command-line reverse Polish notation calculator.md new file mode 100644 index 0000000000..10e666f625 --- /dev/null +++ b/sources/tech/20190124 Orpie- A command-line reverse Polish notation calculator.md @@ -0,0 +1,128 @@ +[#]: collector: (lujun9972) +[#]: translator: ( ) +[#]: reviewer: ( ) +[#]: publisher: ( ) +[#]: url: ( ) +[#]: subject: (Orpie: A command-line reverse Polish notation calculator) +[#]: via: (https://opensource.com/article/19/1/orpie) +[#]: author: (Peter Faller https://opensource.com/users/peterfaller) + +Orpie: A command-line reverse Polish notation calculator +====== +Orpie is a scientific calculator that functions much like early, well-loved HP calculators. + +Orpie is a text-mode [reverse Polish notation][1] (RPN) calculator for the Linux console. It works very much like the early, well-loved Hewlett-Packard calculators. + +### Installing Orpie + +RPM and DEB packages are available for most distributions, so installation is just a matter of using either: + +``` +$ sudo apt install orpie +``` + +or + +``` +$ sudo yum install orpie +``` + +Orpie has a comprehensive man page; new users may want to have it open in another terminal window as they get started. Orpie can be customized for each user by editing the **~/.orpierc** configuration file. The [orpierc(5)][2] man page describes the contents of this file, and **/etc/orpierc** describes the default configuration. + +### Starting up + +Start Orpie by typing **orpie** at the command line. The main screen shows context-sensitive help on the left and the stack on the right. The cursor, where you enter numbers you want to calculate, is at the bottom-right corner. + + + +### Example calculation + +For a simple example, let's calculate the factorial of **5 (2 core.md Dict.md lctt2014.md lctt2016.md lctt2018.md LICENSE published README.md scripts sources translated 3 core.md Dict.md lctt2014.md lctt2016.md lctt2018.md LICENSE published README.md scripts sources translated 4 core.md Dict.md lctt2014.md lctt2016.md lctt2018.md LICENSE published README.md scripts sources translated 5)**. First the long way: + +| Keys | Result | +| --------- | --------- | +| 2 | Push 2 onto the stack | +| 3 | Push 3 onto the stack | +| * | Multiply to get 6 | +| 4 | Push 4 onto the stack | +| * | Multiply to get 24 | +| 5 | Push 5 onto the stack | +| * | Multiply to get 120 | + +Note that the multiplication happens as soon as you type *****. If you hit **< enter>** after ***** , Orpie will duplicate the value at position 1 on the stack. (If this happens, you can drop the duplicate with **\**.) + +Equivalent sequences are: + +| Keys | Result | +| ------------- | ------------- | +| 2 3 * 4 * 5 * | Faster! | +| 2 3 4 5 * * * | Same result | +| 5 ' fact | Fastest: Use the built-in function | + +Observe that when you enter **'** , the left pane changes to show matching functions as you type. In the example above, typing **fa** is enough to get the **fact** function. Orpie offers many functions—experiment by typing **'** and a few letters to see what's available. + + + +Note that each operation replaces one or more values on the stack. If you want to store the value at position 1 in the stack, key in (for example) **@factot ** and **S'**. To retrieve the value, key in (for example) **@factot ** then **;** (if you want to see it; otherwise just leave **@factot** as the value for the next calculation). + +### Constants and units + +Orpie understands units and predefines many useful scientific constants. For example, to calculate the energy in a blue light photon at 400nm, calculate **E=hc/(400nm)**. The key sequences are: + +| Keys | Result | +| -------------- | -------------- | +| C c | Get the speed of light in m/s | +| C h | Get Planck's constant in Js | +| * | Calculate h*c | +| 400 9 n _ m | Input 4 _ 10^-9 m | +| / | Do the division and get the result: 4.966 _ 10^-19 J | + +Like choosing functions after typing **'** , typing **C** shows matching constants based on what you type. + + + +### Matrices + +Orpie can also do operations with matrices. For example, to multiply two 2x2 matrices: + +| Keys | Result | +| -------- | -------- | +| [ 1 , 2 [ 3 , 4 | Stack contains the matrix [[ 1, 2 ][ 3, 4 ]] | +| [ 1 , 0 [ 1 , 1 | Push the multiplier matrix onto the stack | +| * | The result is: [[ 3, 2 ][ 7, 4 ]] | + +Note that the **]** characters are automatically inserted—entering **[** starts a new row. + +### Complex numbers + +Orpie can also calculate with complex numbers. They can be entered or displayed in either polar or rectangular form. You can toggle between the polar and rectangular display using the **p** key, and between degrees and radians using the **r** key. For example, to multiply **3 + 4i** by **4 + 4i** : + +| Keys | Result | +| -------- | -------- | +| ( 3 , 4 | The stack contains (3, 4) | +| ( 4 , 4 | Push (4, 4) | +| * | Get the result: (-4, 28) | + +Note that as you go, the results are kept on the stack so you can observe intermediate results in a lengthy calculation. + + + +### Quitting Orpie + +You can exit from Orpie by typing **Q**. Your state is saved, so the next time you start Orpie, you'll find the stack as you left it. + +-------------------------------------------------------------------------------- + +via: https://opensource.com/article/19/1/orpie + +作者：[Peter Faller][a] +选题：[lujun9972][b] +译者：[译者ID](https://github.com/译者ID) +校对：[校对者ID](https://github.com/校对者ID) + +本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 + +[a]: https://opensource.com/users/peterfaller +[b]: https://github.com/lujun9972 +[1]: https://en.wikipedia.org/wiki/Reverse_Polish_notation +[2]: https://github.com/pelzlpj/orpie/blob/master/doc/orpierc.5 diff --git a/sources/tech/20190124 ffsend - Easily And Securely Share Files From Linux Command Line Using Firefox Send Client.md b/sources/tech/20190124 ffsend - Easily And Securely Share Files From Linux Command Line Using Firefox Send Client.md new file mode 100644 index 0000000000..fcbdd3c5c7 --- /dev/null +++ b/sources/tech/20190124 ffsend - Easily And Securely Share Files From Linux Command Line Using Firefox Send Client.md @@ -0,0 +1,330 @@ +[#]: collector: (lujun9972) +[#]: translator: ( ) +[#]: reviewer: ( ) +[#]: publisher: ( ) +[#]: url: ( ) +[#]: subject: (ffsend – Easily And Securely Share Files From Linux Command Line Using Firefox Send Client) +[#]: via: (https://www.2daygeek.com/ffsend-securely-share-files-folders-from-linux-command-line-using-firefox-send-client/) +[#]: author: (Vinoth Kumar https://www.2daygeek.com/author/vinoth/) + +ffsend – Easily And Securely Share Files From Linux Command Line Using Firefox Send Client +====== + +Linux users were preferred to go with scp or rsync for files or folders copy. + +However, so many new options are coming to Linux because it’s a opensource. + +Anyone can develop a secure software for Linux. + +We had written multiple articles in our site in the past about this topic. + +Even, today we are going to discuss the same kind of topic called ffsend. + +Those are **[OnionShare][1]** , **[Magic Wormhole][2]** , **[Transfer.sh][3]** and **[Dcp – Dat Copy][4]**. + +### What’s ffsend? + +[ffsend][5] is a command line Firefox Send client that allow users to transfer and receive files and folders through command line. + +It allow us to easily and securely share files and directories from the command line through a safe, private and encrypted link using a single simple command. + +Files are shared using the Send service and the allowed file size is up to 2GB. + +Others are able to download these files with this tool, or through their web browser. + +All files are always encrypted on the client, and secrets are never shared with the remote host. + +Additionally you can add a password for the file upload. + +The uploaded files will be removed after the download (default count is 1 up to 10) or after 24 hours. This will make sure that your files does not remain online forever. + +This tool is currently in the alpha phase. Use at your own risk. Also, only limited installation options are available right now. + +### ffsend Features: + + * Fully featured and friendly command line tool + * Upload and download files and directories securely + * Always encrypted on the client + * Additional password protection, generation and configurable download limits + * Built-in file and directory archiving and extraction + * History tracking your files for easy management + * Ability to use your own Send host + * Inspect or delete shared files + * Accurate error reporting + * Low memory footprint, due to encryption and download/upload streaming + * Intended to be used in scripts without interaction + + + +### How To Install ffsend in Linux? + +There is no package for each distributions except Debian and Arch Linux systems. However, we can easily get this utility by downloading the prebuilt appropriate binaries file based on the operating system and architecture. + +Run the below command to download the latest available version for your operating system. + +``` +$ wget https://github.com/timvisee/ffsend/releases/download/v0.1.2/ffsend-v0.1.2-linux-x64.tar.gz +``` + +Extract the tar archive using the following command. + +``` +$ tar -xvf ffsend-v0.1.2-linux-x64.tar.gz +``` + +Run the following command to identify your path variable. + +``` +$ echo $PATH +/home/daygeek/.cargo/bin:/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/lib/jvm/default/bin:/usr/bin/site_perl:/usr/bin/vendor_perl:/usr/bin/core_perl +``` + +As i told previously, just move the executable file to your path directory. + +``` +$ sudo mv ffsend /usr/local/sbin +``` + +Run the `ffsend` command alone to get the basic usage information. + +``` +$ ffsend +ffsend 0.1.2 +Usage: ffsend [FLAGS] ... + +Easily and securely share files from the command line. +A fully featured Firefox Send client. + +Missing subcommand. Here are the most used: + ffsend upload ... + ffsend download ... + +To show all subcommands, features and other help: + ffsend help [SUBCOMMAND] +``` + +For Arch Linux based users can easily install it with help of **[AUR Helper][6]** , as this package is available in AUR repository. + +``` +$ yay -S ffsend +``` + +For **`Debian/Ubuntu`** systems, use **[DPKG Command][7]** to install ffsend. + +``` +$ wget https://github.com/timvisee/ffsend/releases/download/v0.1.2/ffsend_0.1.2_amd64.deb +$ sudo dpkg -i ffsend_0.1.2_amd64.deb +``` + +### How To Send A File Using ffsend? + +It’s not complicated. We can easily send a file using simple syntax. + +**Syntax:** + +``` +$ ffsend upload [/Path/to/the/file/name] +``` + +In the following example, we are going to upload a file called `passwd-up1.sh`. Once you upload the file then you will be getting the unique URL. + +``` +$ ffsend upload passwd-up1.sh --copy +Upload complete +Share link: https://send.firefox.com/download/a4062553f4/#yy2_VyPaUMG5HwXZzYRmpQ +``` + +![][9] + +Just download the above unique URL to get the file in any remote system. + +**Syntax:** + +``` +$ ffsend download [Generated URL] +``` + +Output for the above command. + +``` +$ ffsend download https://send.firefox.com/download/a4062553f4/#yy2_VyPaUMG5HwXZzYRmpQ +Download complete +``` + +![][10] + +Use the following syntax format for directory upload. + +``` +$ ffsend upload [/Path/to/the/Directory] --copy +``` + +In this example, we are going to upload `2g` directory. + +``` +$ ffsend upload /home/daygeek/2g --copy +You've selected a directory, only a single file may be uploaded. +Archive the directory into a single file? [Y/n]: y +Archiving... +Upload complete +Share link: https://send.firefox.com/download/90aa5cfe67/#hrwu6oXZRG2DNh8vOc3BGg +``` + +Just download the above generated the unique URL to get a folder in any remote system. + +``` +$ ffsend download https://send.firefox.com/download/90aa5cfe67/#hrwu6oXZRG2DNh8vOc3BGg +You're downloading an archive, extract it into the selected directory? [Y/n]: y +Extracting... +Download complete +``` + +As this already send files through a safe, private, and encrypted link. However, if you would like to add a additional security at your level. Yes, you can add a password for a file. + +``` +$ ffsend upload file-copy-rsync.sh --copy --password +Password: +Upload complete +Share link: https://send.firefox.com/download/0742d24515/#P7gcNiwZJ87vF8cumU71zA +``` + +It will prompt you to update a password when you are trying to download a file in the remote system. + +``` +$ ffsend download https://send.firefox.com/download/0742d24515/#P7gcNiwZJ87vF8cumU71zA +This file is protected with a password. +Password: +Download complete +``` + +Alternatively you can limit a download speed by providing the download speed while uploading a file. + +``` +$ ffsend upload file-copy-scp.sh --copy --downloads 10 +Upload complete +Share link: https://send.firefox.com/download/23cb923c4e/#LVg6K0CIb7Y9KfJRNZDQGw +``` + +Just download the above unique URL to get a file in any remote system. + +``` +ffsend download https://send.firefox.com/download/23cb923c4e/#LVg6K0CIb7Y9KfJRNZDQGw +Download complete +``` + +If you want to see more details about the file, use the following format. It will shows you the file name, file size, Download counts and when it will going to expire. + +**Syntax:** + +``` +$ ffsend info [Generated URL] + +$ ffsend info https://send.firefox.com/download/23cb923c4e/#LVg6K0CIb7Y9KfJRNZDQGw +ID: 23cb923c4e +Name: file-copy-scp.sh +Size: 115 B +MIME: application/x-sh +Downloads: 3 of 10 +Expiry: 23h58m (86280s) +``` + +You can view your transaction history using the following format. + +``` +$ ffsend history +# LINK EXPIRY +1 https://send.firefox.com/download/23cb923c4e/#LVg6K0CIb7Y9KfJRNZDQGw 23h57m +2 https://send.firefox.com/download/0742d24515/#P7gcNiwZJ87vF8cumU71zA 23h55m +3 https://send.firefox.com/download/90aa5cfe67/#hrwu6oXZRG2DNh8vOc3BGg 23h52m +4 https://send.firefox.com/download/a4062553f4/#yy2_VyPaUMG5HwXZzYRmpQ 23h46m +5 https://send.firefox.com/download/74ff30e43e/#NYfDOUp_Ai-RKg5g0fCZXw 23h44m +6 https://send.firefox.com/download/69afaab1f9/#5z51_94jtxcUCJNNvf6RcA 23h43m +``` + +If you don’t want the link anymore then we can delete it. + +**Syntax:** + +``` +$ ffsend delete [Generated URL] + +$ ffsend delete https://send.firefox.com/download/69afaab1f9/#5z51_94jtxcUCJNNvf6RcA +File deleted +``` + +Alternatively this can be done using firefox browser by opening the page + +``` + +You can define multiple responses and, if you want, you could use an event or a service call inside the request to determine which response you may want to use. I opted for a response of type "view." A view is a rendered response; other types are request-redirects, forwards, and alike. The system comes with various renderers and allows you to determine the output later; to do so, add the following: + +``` + ++ + +``` + +Replace **my-component** with your own component name. Then you can define your very first screen by adding the following inside the tags within the **widget/CommonScreens.xml** file: + +``` + + + + ++ +
- ` 和 `
` 元素那样定义 `
- ` 元素的宽度。这是因为 `
- ` 是 `
` 的子节点，`
` 已经被约束到 550px，所以 `
- ` 不会超出这个范围。
+
+让我们保存文件并刷新浏览器以查看结果：
+
+
+
+你会立即注意到在每个列表项之前显示了重点标志。我们现在不需要在每个列表项之前写 “-”。
+
+经过仔细检查，你会注意到最后一行超出 550px 宽度。这是为什么？因为 HTML 不允许 `
- ` 元素出现在 `
` 元素中。让我们将第一行和最后一行放在单独的 `
` 元素中： + +``` +
+ After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you. +
+``` + +``` ++ You complete my darkness with your light. I love: +
+``` + +``` +-
+
+ I have learned a lot from you. You have occupied a special place in my heart over the time. +
+``` + +保存并刷新。 + +注意，这次我们还定义了 `- ` 元素的宽度。那是因为我们现在已经将 `
- ` 元素放在了 `
` 元素之外。 + +定义情书中所有元素的宽度会变得很麻烦。我们有一个特定的元素用于此目的：`
` 元素。一个 `
` 元素就是一个通用容器，用于对内容进行分组，以便轻松设置样式。
+
+让我们用 `
` 元素包装整个情书，并为其赋予宽度：550px 。
+
+```
+`、`
+
+```
+
+棒极了，我们的代码现在看起来简洁多了。
+
+### HTML 中的标题
+
+到目前为止，蝙蝠侠对结果很高兴，他希望在情书上标题。他想写一个标题： “Bat Letter”。当然，你已经看到这个名字了，不是吗？:D
+
+你可以使用 `+ After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you. +
++ You complete my darkness with your light. I love: +
+-
+
+ I have learned a lot from you. You have occupied a special place in my heart over the time. +
+`、``、``、``、`` 和 `` 标签来添加标题，`` 是最大的标题和最主要的标题，`` 是最小的标题。
+
+
+
+让我们在第二段之前使用 `` 做主标题和一个副标题：
+
+```
+
+ Bat Letter
+
+ After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you.
+
+```
+
+```
+ You are the light of my life
+
+ You complete my darkness with your light. I love:
+
+
+
+
+ I have learned a lot from you. You have occupied a special place in my heart over the time.
+
+
+```
+
+保存，刷新。
+
+
+
+### HTML 中的图像
+
+我们的情书尚未完成，但在继续之前，缺少一件大事：蝙蝠侠标志。你见过是蝙蝠侠的东西但没有蝙蝠侠的标志吗？
+
+并没有。
+
+所以，让我们在情书中添加一个蝙蝠侠标志。
+
+在 HTML 中包含图像就像在一个 Word 文件中包含图像一样。在 MS Word 中，你到 “菜单 -> 插入 -> 图像 -> 然后导航到图像位置为止 -> 选择图像 -> 单击插入”。
+
+在 HTML 中，我们使用 `![]()
` 标签让浏览器知道我们需要加载的图像，而不是单击菜单。我们在 `src` 属性中写入文件的位置和名称。如果图像在项目根目录中，我们可以简单地在 `src` 属性中写入图像文件的名称。
+
+在我们深入编码之前，从[这里][3]下载蝙蝠侠标志。你可能希望裁剪图像中的额外空白区域。复制项目根目录中的图像并将其重命名为 “bat-logo.jpeg”。
+
+```
+
+ Bat Letter
+
+
+ After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you.
+
+```
+
+```
+You are the light of my life
+
+ You complete my darkness with your light. I love:
+
+
+
+
+ I have learned a lot from you. You have occupied a special place in my heart over the time.
+
+
+```
+
+我们在第 3 行包含了 `![]()
` 标签。这个标签也是一个自闭合的标签，所以我们不需要写 ``。在 `src` 属性中，我们给出了图像文件的名称。这个名称应与图像名称完全相同，包括扩展名（.jpeg）及其大小写。
+
+保存并刷新，查看结果。
+
+
+
+该死的！刚刚发生了什么？
+
+当使用 `![]()
` 标签包含图像时，默认情况下，图像将以其原始分辨率显示。在我们的例子中，图像比 550px 宽得多。让我们使用 `style` 属性定义它的宽度：
+
+
+```
+
+ Bat Letter
+
+
+ After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you.
+
+```
+
+```
+You are the light of my life
+
+ You complete my darkness with your light. I love:
+
+
+
+
+ I have learned a lot from you. You have occupied a special place in my heart over the time.
+
+
+```
+
+你会注意到，这次我们定义宽度使用了 “%” 而不是 “px”。当我们在 “%” 中定义宽度时，它将占据父元素宽度的百分比。因此，100% 的 550px 将为我们提供 550px。
+
+保存并刷新，查看结果。
+
+
+
+太棒了！这让蝙蝠侠的脸露出了羞涩的微笑 :)。
+
+### HTML 中的粗体和斜体
+
+现在蝙蝠侠想在最后几段中承认他的爱。他有以下文本供你用 HTML 编写：
+
+“I have a confession to make
+
+It feels like my chest _does_ have a heart. You make my heart beat. Your smile brings a smile to my face, your pain brings pain to my heart.
+
+I don’t show my emotions, but I think this man behind the mask is falling for you.”
+
+当阅读到这里时，你会问蝙蝠侠：“等等，这是给谁的？”蝙蝠侠说：
+
+“这是给超人的。”
+
+
+
+你说：哦！我还以为是给神奇女侠的呢。
+
+蝙蝠侠说：不，这是给超人的，请在最后写上 “I love you Superman.”。
+
+好的，我们来写：
+
+
+```
+
+ Bat Letter
+
+
+ After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you.
+
+```
+
+```
+You are the light of my life
+
+ You complete my darkness with your light. I love:
+
+
+
+
+ I have learned a lot from you. You have occupied a special place in my heart over the time.
+
+ I have a confession to make
+
+ It feels like my chest does have a heart. You make my heart beat. Your smile brings smile on my face, your pain brings pain to my heart.
+
+
+ I don't show my emotions, but I think this man behind the mask is falling for you.
+
+ I love you Superman.
+
+ Your not-so-secret-lover,
+ Batman
+
+
+```
+
+这封信差不多完成了，蝙蝠侠另外想再做两次改变。蝙蝠侠希望在最后段落的第一句中的 “does” 一词是斜体，而 “I love you Superman” 这句话是粗体的。
+
+我们使用 `` 和 `` 以斜体和粗体显示文本。让我们来更新这些更改：
+
+```
+
+ Bat Letter
+
+
+ After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you.
+
+```
+
+```
+ You are the light of my life
+
+ You complete my darkness with your light. I love:
+
+
+
+
+ I have learned a lot from you. You have occupied a special place in my heart over the time.
+
+ I have a confession to make
+
+ It feels like my chest does have a heart. You make my heart beat. Your smile brings smile on my face, your pain brings pain to my heart.
+
+
+ I don't show my emotions, but I think this man behind the mask is falling for you.
+
+ I love you Superman.
+
+ Your not-so-secret-lover,
+ Batman
+
+
+```
+
+
+
+### HTML 中的样式
+
+你可以通过三种方式设置样式或定义 HTML 元素的外观：
+
+* 内联样式：我们使用元素的 `style` 属性来编写样式。这是我们迄今为止使用的，但这不是一个好的实践。
+* 嵌入式样式：我们在由 `` 包裹的 “style” 元素中编写所有样式。
+* 链接样式表：我们在具有 .css 扩展名的单独文件中编写所有元素的样式。此文件称为样式表。
+
+让我们来看看如何定义 `` 的内联样式：
+
+```
+
+```
+
+我们可以在 `` 里面写同样的样式：
+
+```
+div{
+ width:550px;
+}
+```
+
+在嵌入式样式中，我们编写的样式是与元素分开的。所以我们需要一种方法来关联元素及其样式。第一个单词 “div” 就做了这样的活。它让浏览器知道花括号 `{...}` 里面的所有样式都属于 “div” 元素。由于这种语法确定要应用样式的元素，因此它称为一个选择器。
+
+我们编写样式的方式保持不变：属性（`width`）和值（`550px`）用冒号（`:`）分隔，以分号（`;`）结束。
+
+让我们从 `` 和 `![]()
` 元素中删除内联样式，将其写入 `
+```
+
+```
+
+ Bat Letter
+
+
+ After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you.
+
+```
+
+```
+ You are the light of my life
+
+ You complete my darkness with your light. I love:
+
+
+
+
+ I have learned a lot from you. You have occupied a special place in my heart over the time.
+
+ I have a confession to make
+
+ It feels like my chest does have a heart. You make my heart beat. Your smile brings smile on my face, your pain brings pain to my heart.
+
+
+ I don't show my emotions, but I think this man behind the mask is falling for you.
+
+ I love you Superman.
+
+ Your not-so-secret-lover,
+ Batman
+
+
+```
+
+保存并刷新，结果应保持不变。
+
+但是有一个大问题，如果我们的 HTML 文件中有多个 `` 和 `![]()
` 元素该怎么办？这样我们在 `
+```
+
+```
+
+ Bat Letter
+
+
+ After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you.
+
+```
+
+```
+ You are the light of my life
+
+ You complete my darkness with your light. I love:
+
+
+
+
+ I have learned a lot from you. You have occupied a special place in my heart over the time.
+
+ I have a confession to make
+
+ It feels like my chest does have a heart. You make my heart beat. Your smile brings smile on my face, your pain brings pain to my heart.
+
+
+ I don't show my emotions, but I think this man behind the mask is falling for you.
+
+ I love you Superman.
+
+ Your not-so-secret-lover,
+ Batman
+
+
+```
+
+HTML 已经准备好了嵌入式样式。
+
+但是，你可以看到，随着我们包含越来越多的样式，`` 将变得很大。这可能很快会混乱我们的主 HTML 文件。
+
+因此，让我们更进一步，通过将 ``。
+
+我们需要使用 HTML 文件中的 `` 标签来将新创建的 CSS 文件链接到 HTML 文件。以下是我们如何做到这一点：
+
+```
+
+```
+
+我们使用 `` 元素在 HTML 文档中包含外部资源，它主要用于链接样式表。我们使用的三个属性是：
+
+* `rel`：关系。链接文件与文档的关系。具有 .css 扩展名的文件称为样式表，因此我们保留 rel=“stylesheet”。
+* `type`：链接文件的类型；对于一个 CSS 文件来说它是 “text/css”。
+* `href`：超文本参考。链接文件的位置。
+
+link 元素的结尾没有 ``。因此，`` 也是一个自闭合的标签。
+
+```
+
+```
+
+如果只是得到一个女朋友，那么很容易：D
+
+可惜没有那么简单，让我们继续前进。
+
+这是我们 “loveletter.html” 的内容：
+
+```
+
+
+ Bat Letter
+
+
+ After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you.
+
+ You are the light of my life
+
+ You complete my darkness with your light. I love:
+
+
+
+
+ I have learned a lot from you. You have occupied a special place in my heart over the time.
+
+ I have a confession to make
+
+ It feels like my chest does have a heart. You make my heart beat. Your smile brings smile on my face, your pain brings pain to my heart.
+
+
+ I don't show my emotions, but I think this man behind the mask is falling for you.
+
+ I love you Superman.
+
+ Your not-so-secret-lover,
+ Batman
+
+
+```
+
+“style.css” 内容：
+
+```
+#letter-container{
+ width:550px;
+}
+#header-bat-logo{
+ width:100%;
+}
+```
+
+保存文件并刷新，浏览器中的输出应保持不变。
+
+### 一些手续
+
+我们的情书已经准备好给蝙蝠侠，但还有一些正式的片段。
+
+与其他任何编程语言一样，HTML 自出生以来（1990 年）经历过许多版本，当前版本是 HTML5。
+
+那么，浏览器如何知道你使用哪个版本的 HTML 来编写页面呢？要告诉浏览器你正在使用 HTML5，你需要在页面顶部包含 ``。对于旧版本的 HTML，这行不同，但你不需要了解它们，因为我们不再使用它们了。
+
+此外，在之前的 HTML 版本中，我们曾经将整个文档封装在 `` 标签内。整个文件分为两个主要部分：头部在 `` 里面，主体在 `` 里面。这在 HTML5 中不是必须的，但由于兼容性原因，我们仍然这样做。让我们用 ``, ``、 `` 和 `` 更新我们的代码：
+
+```
+
+
+
+
+
+
+
+ Bat Letter
+
+
+ After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you.
+
+ You are the light of my life
+
+ You complete my darkness with your light. I love:
+
+
+
+
+ I have learned a lot from you. You have occupied a special place in my heart over the time.
+
+ I have a confession to make
+
+ It feels like my chest does have a heart. You make my heart beat. Your smile brings smile on my face, your pain brings pain to my heart.
+
+
+ I don't show my emotions, but I think this man behind the mask is falling for you.
+
+ I love you Superman.
+
+ Your not-so-secret-lover,
+ Batman
+
+
+
+
+```
+
+主要内容在 `` 里面，元信息在 `` 里面。所以我们把 `` 保存在 `` 里面并加载 `` 里面的样式表。
+
+保存并刷新，你的 HTML 页面应显示与之前相同的内容。
+
+### HTML 的标题
+
+我发誓，这是最后一次改变。
+
+你可能已经注意到选项卡的标题正在显示 HTML 文件的路径：
+
+
+
+我们可以使用 `` 标签来定义 HTML 文件的标题。标题标签也像链接标签一样在 `<head>` 内部。让我们我们在标题中加上 “Bat Letter”：
+
+```
+<!DOCTYPE html>
+<html>
+<head>
+ <title>Bat Letter
+
+
+
+
+ Bat Letter
+
+
+ After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you.
+
+ You are the light of my life
+
+ You complete my darkness with your light. I love:
+
+
+
+
+ I have learned a lot from you. You have occupied a special place in my heart over the time.
+
+ I have a confession to make
+
+ It feels like my chest does have a heart. You make my heart beat. Your smile brings smile on my face, your pain brings pain to my heart.
+
+
+ I don't show my emotions, but I think this man behind the mask is falling for you.
+
+ I love you Superman.
+
+ Your not-so-secret-lover,
+ Batman
+
+
+
+
+```
+
+保存并刷新，你将看到在选项卡上显示的是 “Bat Letter” 而不是文件路径。
+
+蝙蝠侠的情书现在已经完成。
+
+恭喜！你用 HTML 制作了蝙蝠侠的情书。
+
+
+
+### 我们学到了什么
+
+我们学习了以下新概念：
+
+ * 一个 HTML 文档的结构
+ * 在 HTML 中如何写元素（``）
+ * 如何使用 style 属性在元素内编写样式（这称为内联样式，尽可能避免这种情况）
+ * 如何在 `` 中编写元素的样式（这称为嵌入式样式）
+ * 在 HTML 中如何使用 `` 在单独的文件中编写样式并链接它（这称为链接样式表）
+ * 什么是标签名称，属性，开始标签和结束标签
+ * 如何使用 id 属性为一个元素赋予 id
+ * CSS 中的标签选择器和 id 选择器
+
+我们学习了以下 HTML 标签：
+
+ * ``：用于段落
+ * `
`：用于换行
+ * `
`、`
`、``、`` 和 `` 标签来添加标题，`` 是最大的标题和最主要的标题，`` 是最小的标题。
+
+
+
+让我们在第二段之前使用 `` 做主标题和一个副标题：
+
+```
+
+ Bat Letter
+
+ After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you.
+
+```
+
+```
+ You are the light of my life
+
+ You complete my darkness with your light. I love:
+
+
+
+
+ I have learned a lot from you. You have occupied a special place in my heart over the time.
+
+
+```
+
+保存，刷新。
+
+
+
+### HTML 中的图像
+
+我们的情书尚未完成，但在继续之前，缺少一件大事：蝙蝠侠标志。你见过是蝙蝠侠的东西但没有蝙蝠侠的标志吗？
+
+并没有。
+
+所以，让我们在情书中添加一个蝙蝠侠标志。
+
+在 HTML 中包含图像就像在一个 Word 文件中包含图像一样。在 MS Word 中，你到 “菜单 -> 插入 -> 图像 -> 然后导航到图像位置为止 -> 选择图像 -> 单击插入”。
+
+在 HTML 中，我们使用 `![]()
` 标签让浏览器知道我们需要加载的图像，而不是单击菜单。我们在 `src` 属性中写入文件的位置和名称。如果图像在项目根目录中，我们可以简单地在 `src` 属性中写入图像文件的名称。
+
+在我们深入编码之前，从[这里][3]下载蝙蝠侠标志。你可能希望裁剪图像中的额外空白区域。复制项目根目录中的图像并将其重命名为 “bat-logo.jpeg”。
+
+```
+
+ Bat Letter
+
+
+ After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you.
+
+```
+
+```
+You are the light of my life
+
+ You complete my darkness with your light. I love:
+
+
+
+
+ I have learned a lot from you. You have occupied a special place in my heart over the time.
+
+
+```
+
+我们在第 3 行包含了 `![]()
` 标签。这个标签也是一个自闭合的标签，所以我们不需要写 ``。在 `src` 属性中，我们给出了图像文件的名称。这个名称应与图像名称完全相同，包括扩展名（.jpeg）及其大小写。
+
+保存并刷新，查看结果。
+
+
+
+该死的！刚刚发生了什么？
+
+当使用 `![]()
` 标签包含图像时，默认情况下，图像将以其原始分辨率显示。在我们的例子中，图像比 550px 宽得多。让我们使用 `style` 属性定义它的宽度：
+
+
+```
+
+ Bat Letter
+
+
+ After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you.
+
+```
+
+```
+You are the light of my life
+
+ You complete my darkness with your light. I love:
+
+
+
+
+ I have learned a lot from you. You have occupied a special place in my heart over the time.
+
+
+```
+
+你会注意到，这次我们定义宽度使用了 “%” 而不是 “px”。当我们在 “%” 中定义宽度时，它将占据父元素宽度的百分比。因此，100% 的 550px 将为我们提供 550px。
+
+保存并刷新，查看结果。
+
+
+
+太棒了！这让蝙蝠侠的脸露出了羞涩的微笑 :)。
+
+### HTML 中的粗体和斜体
+
+现在蝙蝠侠想在最后几段中承认他的爱。他有以下文本供你用 HTML 编写：
+
+“I have a confession to make
+
+It feels like my chest _does_ have a heart. You make my heart beat. Your smile brings a smile to my face, your pain brings pain to my heart.
+
+I don’t show my emotions, but I think this man behind the mask is falling for you.”
+
+当阅读到这里时，你会问蝙蝠侠：“等等，这是给谁的？”蝙蝠侠说：
+
+“这是给超人的。”
+
+
+
+你说：哦！我还以为是给神奇女侠的呢。
+
+蝙蝠侠说：不，这是给超人的，请在最后写上 “I love you Superman.”。
+
+好的，我们来写：
+
+
+```
+
+ Bat Letter
+
+
+ After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you.
+
+```
+
+```
+You are the light of my life
+
+ You complete my darkness with your light. I love:
+
+
+
+
+ I have learned a lot from you. You have occupied a special place in my heart over the time.
+
+ I have a confession to make
+
+ It feels like my chest does have a heart. You make my heart beat. Your smile brings smile on my face, your pain brings pain to my heart.
+
+
+ I don't show my emotions, but I think this man behind the mask is falling for you.
+
+ I love you Superman.
+
+ Your not-so-secret-lover,
+ Batman
+
+
+```
+
+这封信差不多完成了，蝙蝠侠另外想再做两次改变。蝙蝠侠希望在最后段落的第一句中的 “does” 一词是斜体，而 “I love you Superman” 这句话是粗体的。
+
+我们使用 `` 和 `` 以斜体和粗体显示文本。让我们来更新这些更改：
+
+```
+
+ Bat Letter
+
+
+ After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you.
+
+```
+
+```
+ You are the light of my life
+
+ You complete my darkness with your light. I love:
+
+
+
+
+ I have learned a lot from you. You have occupied a special place in my heart over the time.
+
+ I have a confession to make
+
+ It feels like my chest does have a heart. You make my heart beat. Your smile brings smile on my face, your pain brings pain to my heart.
+
+
+ I don't show my emotions, but I think this man behind the mask is falling for you.
+
+ I love you Superman.
+
+ Your not-so-secret-lover,
+ Batman
+
+
+```
+
+
+
+### HTML 中的样式
+
+你可以通过三种方式设置样式或定义 HTML 元素的外观：
+
+* 内联样式：我们使用元素的 `style` 属性来编写样式。这是我们迄今为止使用的，但这不是一个好的实践。
+* 嵌入式样式：我们在由 `` 包裹的 “style” 元素中编写所有样式。
+* 链接样式表：我们在具有 .css 扩展名的单独文件中编写所有元素的样式。此文件称为样式表。
+
+让我们来看看如何定义 `` 的内联样式：
+
+```
+
+```
+
+我们可以在 `` 里面写同样的样式：
+
+```
+div{
+ width:550px;
+}
+```
+
+在嵌入式样式中，我们编写的样式是与元素分开的。所以我们需要一种方法来关联元素及其样式。第一个单词 “div” 就做了这样的活。它让浏览器知道花括号 `{...}` 里面的所有样式都属于 “div” 元素。由于这种语法确定要应用样式的元素，因此它称为一个选择器。
+
+我们编写样式的方式保持不变：属性（`width`）和值（`550px`）用冒号（`:`）分隔，以分号（`;`）结束。
+
+让我们从 `` 和 `![]()
` 元素中删除内联样式，将其写入 `
+```
+
+```
+
+ Bat Letter
+
+
+ After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you.
+
+```
+
+```
+ You are the light of my life
+
+ You complete my darkness with your light. I love:
+
+
+
+
+ I have learned a lot from you. You have occupied a special place in my heart over the time.
+
+ I have a confession to make
+
+ It feels like my chest does have a heart. You make my heart beat. Your smile brings smile on my face, your pain brings pain to my heart.
+
+
+ I don't show my emotions, but I think this man behind the mask is falling for you.
+
+ I love you Superman.
+
+ Your not-so-secret-lover,
+ Batman
+
+
+```
+
+保存并刷新，结果应保持不变。
+
+但是有一个大问题，如果我们的 HTML 文件中有多个 `` 和 `![]()
` 元素该怎么办？这样我们在 `
+```
+
+```
+
+ Bat Letter
+
+
+ After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you.
+
+```
+
+```
+ You are the light of my life
+
+ You complete my darkness with your light. I love:
+
+
+
+
+ I have learned a lot from you. You have occupied a special place in my heart over the time.
+
+ I have a confession to make
+
+ It feels like my chest does have a heart. You make my heart beat. Your smile brings smile on my face, your pain brings pain to my heart.
+
+
+ I don't show my emotions, but I think this man behind the mask is falling for you.
+
+ I love you Superman.
+
+ Your not-so-secret-lover,
+ Batman
+
+
+```
+
+HTML 已经准备好了嵌入式样式。
+
+但是，你可以看到，随着我们包含越来越多的样式，`` 将变得很大。这可能很快会混乱我们的主 HTML 文件。
+
+因此，让我们更进一步，通过将 ``。
+
+我们需要使用 HTML 文件中的 `` 标签来将新创建的 CSS 文件链接到 HTML 文件。以下是我们如何做到这一点：
+
+```
+
+```
+
+我们使用 `` 元素在 HTML 文档中包含外部资源，它主要用于链接样式表。我们使用的三个属性是：
+
+* `rel`：关系。链接文件与文档的关系。具有 .css 扩展名的文件称为样式表，因此我们保留 rel=“stylesheet”。
+* `type`：链接文件的类型；对于一个 CSS 文件来说它是 “text/css”。
+* `href`：超文本参考。链接文件的位置。
+
+link 元素的结尾没有 ``。因此，`` 也是一个自闭合的标签。
+
+```
+
+```
+
+如果只是得到一个女朋友，那么很容易：D
+
+可惜没有那么简单，让我们继续前进。
+
+这是我们 “loveletter.html” 的内容：
+
+```
+
+
+ Bat Letter
+
+
+ After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you.
+
+ You are the light of my life
+
+ You complete my darkness with your light. I love:
+
+
+
+
+ I have learned a lot from you. You have occupied a special place in my heart over the time.
+
+ I have a confession to make
+
+ It feels like my chest does have a heart. You make my heart beat. Your smile brings smile on my face, your pain brings pain to my heart.
+
+
+ I don't show my emotions, but I think this man behind the mask is falling for you.
+
+ I love you Superman.
+
+ Your not-so-secret-lover,
+ Batman
+
+
+```
+
+“style.css” 内容：
+
+```
+#letter-container{
+ width:550px;
+}
+#header-bat-logo{
+ width:100%;
+}
+```
+
+保存文件并刷新，浏览器中的输出应保持不变。
+
+### 一些手续
+
+我们的情书已经准备好给蝙蝠侠，但还有一些正式的片段。
+
+与其他任何编程语言一样，HTML 自出生以来（1990 年）经历过许多版本，当前版本是 HTML5。
+
+那么，浏览器如何知道你使用哪个版本的 HTML 来编写页面呢？要告诉浏览器你正在使用 HTML5，你需要在页面顶部包含 ``。对于旧版本的 HTML，这行不同，但你不需要了解它们，因为我们不再使用它们了。
+
+此外，在之前的 HTML 版本中，我们曾经将整个文档封装在 `` 标签内。整个文件分为两个主要部分：头部在 `` 里面，主体在 `` 里面。这在 HTML5 中不是必须的，但由于兼容性原因，我们仍然这样做。让我们用 ``, ``、 `` 和 `` 更新我们的代码：
+
+```
+
+
+
+
+
+
+
+ Bat Letter
+
+
+ After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you.
+
+ You are the light of my life
+
+ You complete my darkness with your light. I love:
+
+
+
+
+ I have learned a lot from you. You have occupied a special place in my heart over the time.
+
+ I have a confession to make
+
+ It feels like my chest does have a heart. You make my heart beat. Your smile brings smile on my face, your pain brings pain to my heart.
+
+
+ I don't show my emotions, but I think this man behind the mask is falling for you.
+
+ I love you Superman.
+
+ Your not-so-secret-lover,
+ Batman
+
+
+
+
+```
+
+主要内容在 `` 里面，元信息在 `` 里面。所以我们把 `` 保存在 `` 里面并加载 `` 里面的样式表。
+
+保存并刷新，你的 HTML 页面应显示与之前相同的内容。
+
+### HTML 的标题
+
+我发誓，这是最后一次改变。
+
+你可能已经注意到选项卡的标题正在显示 HTML 文件的路径：
+
+
+
+我们可以使用 `` 标签来定义 HTML 文件的标题。标题标签也像链接标签一样在 `<head>` 内部。让我们我们在标题中加上 “Bat Letter”：
+
+```
+<!DOCTYPE html>
+<html>
+<head>
+ <title>Bat Letter
+
+
+
+
+ Bat Letter
+
+
+ After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you.
+
+ You are the light of my life
+
+ You complete my darkness with your light. I love:
+
+
+
+
+ I have learned a lot from you. You have occupied a special place in my heart over the time.
+
+ I have a confession to make
+
+ It feels like my chest does have a heart. You make my heart beat. Your smile brings smile on my face, your pain brings pain to my heart.
+
+
+ I don't show my emotions, but I think this man behind the mask is falling for you.
+
+ I love you Superman.
+
+ Your not-so-secret-lover,
+ Batman
+
+
+
+
+```
+
+保存并刷新，你将看到在选项卡上显示的是 “Bat Letter” 而不是文件路径。
+
+蝙蝠侠的情书现在已经完成。
+
+恭喜！你用 HTML 制作了蝙蝠侠的情书。
+
+
+
+### 我们学到了什么
+
+我们学习了以下新概念：
+
+ * 一个 HTML 文档的结构
+ * 在 HTML 中如何写元素（``）
+ * 如何使用 style 属性在元素内编写样式（这称为内联样式，尽可能避免这种情况）
+ * 如何在 `` 中编写元素的样式（这称为嵌入式样式）
+ * 在 HTML 中如何使用 `` 在单独的文件中编写样式并链接它（这称为链接样式表）
+ * 什么是标签名称，属性，开始标签和结束标签
+ * 如何使用 id 属性为一个元素赋予 id
+ * CSS 中的标签选择器和 id 选择器
+
+我们学习了以下 HTML 标签：
+
+ * ``：用于段落
+ * `
`：用于换行
+ * `
`、`
` 和 `` 标签来添加标题，`` 是最大的标题和最主要的标题，`` 是最小的标题。
+
+
+
+让我们在第二段之前使用 `` 做主标题和一个副标题：
+
+```
+
+ Bat Letter
+
+ After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you.
+
+```
+
+```
+ You are the light of my life
+
+ You complete my darkness with your light. I love:
+
+
+
+
+ I have learned a lot from you. You have occupied a special place in my heart over the time.
+
+
+```
+
+保存，刷新。
+
+
+
+### HTML 中的图像
+
+我们的情书尚未完成，但在继续之前，缺少一件大事：蝙蝠侠标志。你见过是蝙蝠侠的东西但没有蝙蝠侠的标志吗？
+
+并没有。
+
+所以，让我们在情书中添加一个蝙蝠侠标志。
+
+在 HTML 中包含图像就像在一个 Word 文件中包含图像一样。在 MS Word 中，你到 “菜单 -> 插入 -> 图像 -> 然后导航到图像位置为止 -> 选择图像 -> 单击插入”。
+
+在 HTML 中，我们使用 `![]()
` 标签让浏览器知道我们需要加载的图像，而不是单击菜单。我们在 `src` 属性中写入文件的位置和名称。如果图像在项目根目录中，我们可以简单地在 `src` 属性中写入图像文件的名称。
+
+在我们深入编码之前，从[这里][3]下载蝙蝠侠标志。你可能希望裁剪图像中的额外空白区域。复制项目根目录中的图像并将其重命名为 “bat-logo.jpeg”。
+
+```
+
+ Bat Letter
+
+
+ After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you.
+
+```
+
+```
+You are the light of my life
+
+ You complete my darkness with your light. I love:
+
+
+
+
+ I have learned a lot from you. You have occupied a special place in my heart over the time.
+
+
+```
+
+我们在第 3 行包含了 `![]()
` 标签。这个标签也是一个自闭合的标签，所以我们不需要写 ``。在 `src` 属性中，我们给出了图像文件的名称。这个名称应与图像名称完全相同，包括扩展名（.jpeg）及其大小写。
+
+保存并刷新，查看结果。
+
+
+
+该死的！刚刚发生了什么？
+
+当使用 `![]()
` 标签包含图像时，默认情况下，图像将以其原始分辨率显示。在我们的例子中，图像比 550px 宽得多。让我们使用 `style` 属性定义它的宽度：
+
+
+```
+
+ Bat Letter
+
+
+ After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you.
+
+```
+
+```
+You are the light of my life
+
+ You complete my darkness with your light. I love:
+
+
+
+
+ I have learned a lot from you. You have occupied a special place in my heart over the time.
+
+
+```
+
+你会注意到，这次我们定义宽度使用了 “%” 而不是 “px”。当我们在 “%” 中定义宽度时，它将占据父元素宽度的百分比。因此，100% 的 550px 将为我们提供 550px。
+
+保存并刷新，查看结果。
+
+
+
+太棒了！这让蝙蝠侠的脸露出了羞涩的微笑 :)。
+
+### HTML 中的粗体和斜体
+
+现在蝙蝠侠想在最后几段中承认他的爱。他有以下文本供你用 HTML 编写：
+
+“I have a confession to make
+
+It feels like my chest _does_ have a heart. You make my heart beat. Your smile brings a smile to my face, your pain brings pain to my heart.
+
+I don’t show my emotions, but I think this man behind the mask is falling for you.”
+
+当阅读到这里时，你会问蝙蝠侠：“等等，这是给谁的？”蝙蝠侠说：
+
+“这是给超人的。”
+
+
+
+你说：哦！我还以为是给神奇女侠的呢。
+
+蝙蝠侠说：不，这是给超人的，请在最后写上 “I love you Superman.”。
+
+好的，我们来写：
+
+
+```
+
+ Bat Letter
+
+
+ After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you.
+
+```
+
+```
+You are the light of my life
+
+ You complete my darkness with your light. I love:
+
+
+
+
+ I have learned a lot from you. You have occupied a special place in my heart over the time.
+
+ I have a confession to make
+
+ It feels like my chest does have a heart. You make my heart beat. Your smile brings smile on my face, your pain brings pain to my heart.
+
+
+ I don't show my emotions, but I think this man behind the mask is falling for you.
+
+ I love you Superman.
+
+ Your not-so-secret-lover,
+ Batman
+
+
+```
+
+这封信差不多完成了，蝙蝠侠另外想再做两次改变。蝙蝠侠希望在最后段落的第一句中的 “does” 一词是斜体，而 “I love you Superman” 这句话是粗体的。
+
+我们使用 `` 和 `` 以斜体和粗体显示文本。让我们来更新这些更改：
+
+```
+
+ Bat Letter
+
+
+ After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you.
+
+```
+
+```
+ You are the light of my life
+
+ You complete my darkness with your light. I love:
+
+
+
+
+ I have learned a lot from you. You have occupied a special place in my heart over the time.
+
+ I have a confession to make
+
+ It feels like my chest does have a heart. You make my heart beat. Your smile brings smile on my face, your pain brings pain to my heart.
+
+
+ I don't show my emotions, but I think this man behind the mask is falling for you.
+
+ I love you Superman.
+
+ Your not-so-secret-lover,
+ Batman
+
+
+```
+
+
+
+### HTML 中的样式
+
+你可以通过三种方式设置样式或定义 HTML 元素的外观：
+
+* 内联样式：我们使用元素的 `style` 属性来编写样式。这是我们迄今为止使用的，但这不是一个好的实践。
+* 嵌入式样式：我们在由 `` 包裹的 “style” 元素中编写所有样式。
+* 链接样式表：我们在具有 .css 扩展名的单独文件中编写所有元素的样式。此文件称为样式表。
+
+让我们来看看如何定义 `` 的内联样式：
+
+```
+
+```
+
+我们可以在 `` 里面写同样的样式：
+
+```
+div{
+ width:550px;
+}
+```
+
+在嵌入式样式中，我们编写的样式是与元素分开的。所以我们需要一种方法来关联元素及其样式。第一个单词 “div” 就做了这样的活。它让浏览器知道花括号 `{...}` 里面的所有样式都属于 “div” 元素。由于这种语法确定要应用样式的元素，因此它称为一个选择器。
+
+我们编写样式的方式保持不变：属性（`width`）和值（`550px`）用冒号（`:`）分隔，以分号（`;`）结束。
+
+让我们从 `` 和 `![]()
` 元素中删除内联样式，将其写入 `
+```
+
+```
+
+ Bat Letter
+
+
+ After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you.
+
+```
+
+```
+ You are the light of my life
+
+ You complete my darkness with your light. I love:
+
+
+
+
+ I have learned a lot from you. You have occupied a special place in my heart over the time.
+
+ I have a confession to make
+
+ It feels like my chest does have a heart. You make my heart beat. Your smile brings smile on my face, your pain brings pain to my heart.
+
+
+ I don't show my emotions, but I think this man behind the mask is falling for you.
+
+ I love you Superman.
+
+ Your not-so-secret-lover,
+ Batman
+
+
+```
+
+保存并刷新，结果应保持不变。
+
+但是有一个大问题，如果我们的 HTML 文件中有多个 `` 和 `![]()
` 元素该怎么办？这样我们在 `
+```
+
+```
+
+ Bat Letter
+
+
+ After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you.
+
+```
+
+```
+ You are the light of my life
+
+ You complete my darkness with your light. I love:
+
+
+
+
+ I have learned a lot from you. You have occupied a special place in my heart over the time.
+
+ I have a confession to make
+
+ It feels like my chest does have a heart. You make my heart beat. Your smile brings smile on my face, your pain brings pain to my heart.
+
+
+ I don't show my emotions, but I think this man behind the mask is falling for you.
+
+ I love you Superman.
+
+ Your not-so-secret-lover,
+ Batman
+
+
+```
+
+HTML 已经准备好了嵌入式样式。
+
+但是，你可以看到，随着我们包含越来越多的样式，`` 将变得很大。这可能很快会混乱我们的主 HTML 文件。
+
+因此，让我们更进一步，通过将 ``。
+
+我们需要使用 HTML 文件中的 `` 标签来将新创建的 CSS 文件链接到 HTML 文件。以下是我们如何做到这一点：
+
+```
+
+```
+
+我们使用 `` 元素在 HTML 文档中包含外部资源，它主要用于链接样式表。我们使用的三个属性是：
+
+* `rel`：关系。链接文件与文档的关系。具有 .css 扩展名的文件称为样式表，因此我们保留 rel=“stylesheet”。
+* `type`：链接文件的类型；对于一个 CSS 文件来说它是 “text/css”。
+* `href`：超文本参考。链接文件的位置。
+
+link 元素的结尾没有 ``。因此，`` 也是一个自闭合的标签。
+
+```
+
+```
+
+如果只是得到一个女朋友，那么很容易：D
+
+可惜没有那么简单，让我们继续前进。
+
+这是我们 “loveletter.html” 的内容：
+
+```
+
+
+ Bat Letter
+
+
+ After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you.
+
+ You are the light of my life
+
+ You complete my darkness with your light. I love:
+
+
+
+
+ I have learned a lot from you. You have occupied a special place in my heart over the time.
+
+ I have a confession to make
+
+ It feels like my chest does have a heart. You make my heart beat. Your smile brings smile on my face, your pain brings pain to my heart.
+
+
+ I don't show my emotions, but I think this man behind the mask is falling for you.
+
+ I love you Superman.
+
+ Your not-so-secret-lover,
+ Batman
+
+
+```
+
+“style.css” 内容：
+
+```
+#letter-container{
+ width:550px;
+}
+#header-bat-logo{
+ width:100%;
+}
+```
+
+保存文件并刷新，浏览器中的输出应保持不变。
+
+### 一些手续
+
+我们的情书已经准备好给蝙蝠侠，但还有一些正式的片段。
+
+与其他任何编程语言一样，HTML 自出生以来（1990 年）经历过许多版本，当前版本是 HTML5。
+
+那么，浏览器如何知道你使用哪个版本的 HTML 来编写页面呢？要告诉浏览器你正在使用 HTML5，你需要在页面顶部包含 ``。对于旧版本的 HTML，这行不同，但你不需要了解它们，因为我们不再使用它们了。
+
+此外，在之前的 HTML 版本中，我们曾经将整个文档封装在 `` 标签内。整个文件分为两个主要部分：头部在 `` 里面，主体在 `` 里面。这在 HTML5 中不是必须的，但由于兼容性原因，我们仍然这样做。让我们用 ``, ``、 `` 和 `` 更新我们的代码：
+
+```
+
+
+
+
+
+
+
+ Bat Letter
+
+
+ After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you.
+
+ You are the light of my life
+
+ You complete my darkness with your light. I love:
+
+
+
+
+ I have learned a lot from you. You have occupied a special place in my heart over the time.
+
+ I have a confession to make
+
+ It feels like my chest does have a heart. You make my heart beat. Your smile brings smile on my face, your pain brings pain to my heart.
+
+
+ I don't show my emotions, but I think this man behind the mask is falling for you.
+
+ I love you Superman.
+
+ Your not-so-secret-lover,
+ Batman
+
+
+
+
+```
+
+主要内容在 `` 里面，元信息在 `` 里面。所以我们把 `` 保存在 `` 里面并加载 `` 里面的样式表。
+
+保存并刷新，你的 HTML 页面应显示与之前相同的内容。
+
+### HTML 的标题
+
+我发誓，这是最后一次改变。
+
+你可能已经注意到选项卡的标题正在显示 HTML 文件的路径：
+
+
+
+我们可以使用 `` 标签来定义 HTML 文件的标题。标题标签也像链接标签一样在 `<head>` 内部。让我们我们在标题中加上 “Bat Letter”：
+
+```
+<!DOCTYPE html>
+<html>
+<head>
+ <title>Bat Letter
+
+
+
+
+ Bat Letter
+
+
+ After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you.
+
+ You are the light of my life
+
+ You complete my darkness with your light. I love:
+
+
+
+
+ I have learned a lot from you. You have occupied a special place in my heart over the time.
+
+ I have a confession to make
+
+ It feels like my chest does have a heart. You make my heart beat. Your smile brings smile on my face, your pain brings pain to my heart.
+
+
+ I don't show my emotions, but I think this man behind the mask is falling for you.
+
+ I love you Superman.
+
+ Your not-so-secret-lover,
+ Batman
+
+
+
+
+```
+
+保存并刷新，你将看到在选项卡上显示的是 “Bat Letter” 而不是文件路径。
+
+蝙蝠侠的情书现在已经完成。
+
+恭喜！你用 HTML 制作了蝙蝠侠的情书。
+
+
+
+### 我们学到了什么
+
+我们学习了以下新概念：
+
+ * 一个 HTML 文档的结构
+ * 在 HTML 中如何写元素（``）
+ * 如何使用 style 属性在元素内编写样式（这称为内联样式，尽可能避免这种情况）
+ * 如何在 `` 中编写元素的样式（这称为嵌入式样式）
+ * 在 HTML 中如何使用 `` 在单独的文件中编写样式并链接它（这称为链接样式表）
+ * 什么是标签名称，属性，开始标签和结束标签
+ * 如何使用 id 属性为一个元素赋予 id
+ * CSS 中的标签选择器和 id 选择器
+
+我们学习了以下 HTML 标签：
+
+ * ``：用于段落
+ * `
`：用于换行
+ * `
`、`
` 是最大的标题和最主要的标题，`` 是最小的标题。
+
+
+
+让我们在第二段之前使用 `` 做主标题和一个副标题：
+
+```
+
+ Bat Letter
+
+ After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you.
+
+```
+
+```
+ You are the light of my life
+
+ You complete my darkness with your light. I love:
+
+
+
+
+ I have learned a lot from you. You have occupied a special place in my heart over the time.
+
+
+```
+
+保存，刷新。
+
+
+
+### HTML 中的图像
+
+我们的情书尚未完成，但在继续之前，缺少一件大事：蝙蝠侠标志。你见过是蝙蝠侠的东西但没有蝙蝠侠的标志吗？
+
+并没有。
+
+所以，让我们在情书中添加一个蝙蝠侠标志。
+
+在 HTML 中包含图像就像在一个 Word 文件中包含图像一样。在 MS Word 中，你到 “菜单 -> 插入 -> 图像 -> 然后导航到图像位置为止 -> 选择图像 -> 单击插入”。
+
+在 HTML 中，我们使用 `![]()
` 标签让浏览器知道我们需要加载的图像，而不是单击菜单。我们在 `src` 属性中写入文件的位置和名称。如果图像在项目根目录中，我们可以简单地在 `src` 属性中写入图像文件的名称。
+
+在我们深入编码之前，从[这里][3]下载蝙蝠侠标志。你可能希望裁剪图像中的额外空白区域。复制项目根目录中的图像并将其重命名为 “bat-logo.jpeg”。
+
+```
+
+ Bat Letter
+
+
+ After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you.
+
+```
+
+```
+You are the light of my life
+
+ You complete my darkness with your light. I love:
+
+
+
+
+ I have learned a lot from you. You have occupied a special place in my heart over the time.
+
+
+```
+
+我们在第 3 行包含了 `![]()
` 标签。这个标签也是一个自闭合的标签，所以我们不需要写 ``。在 `src` 属性中，我们给出了图像文件的名称。这个名称应与图像名称完全相同，包括扩展名（.jpeg）及其大小写。
+
+保存并刷新，查看结果。
+
+
+
+该死的！刚刚发生了什么？
+
+当使用 `![]()
` 标签包含图像时，默认情况下，图像将以其原始分辨率显示。在我们的例子中，图像比 550px 宽得多。让我们使用 `style` 属性定义它的宽度：
+
+
+```
+
+ Bat Letter
+
+
+ After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you.
+
+```
+
+```
+You are the light of my life
+
+ You complete my darkness with your light. I love:
+
+
+
+
+ I have learned a lot from you. You have occupied a special place in my heart over the time.
+
+
+```
+
+你会注意到，这次我们定义宽度使用了 “%” 而不是 “px”。当我们在 “%” 中定义宽度时，它将占据父元素宽度的百分比。因此，100% 的 550px 将为我们提供 550px。
+
+保存并刷新，查看结果。
+
+
+
+太棒了！这让蝙蝠侠的脸露出了羞涩的微笑 :)。
+
+### HTML 中的粗体和斜体
+
+现在蝙蝠侠想在最后几段中承认他的爱。他有以下文本供你用 HTML 编写：
+
+“I have a confession to make
+
+It feels like my chest _does_ have a heart. You make my heart beat. Your smile brings a smile to my face, your pain brings pain to my heart.
+
+I don’t show my emotions, but I think this man behind the mask is falling for you.”
+
+当阅读到这里时，你会问蝙蝠侠：“等等，这是给谁的？”蝙蝠侠说：
+
+“这是给超人的。”
+
+
+
+你说：哦！我还以为是给神奇女侠的呢。
+
+蝙蝠侠说：不，这是给超人的，请在最后写上 “I love you Superman.”。
+
+好的，我们来写：
+
+
+```
+
+ Bat Letter
+
+
+ After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you.
+
+```
+
+```
+You are the light of my life
+
+ You complete my darkness with your light. I love:
+
+
+
+
+ I have learned a lot from you. You have occupied a special place in my heart over the time.
+
+ I have a confession to make
+
+ It feels like my chest does have a heart. You make my heart beat. Your smile brings smile on my face, your pain brings pain to my heart.
+
+
+ I don't show my emotions, but I think this man behind the mask is falling for you.
+
+ I love you Superman.
+
+ Your not-so-secret-lover,
+ Batman
+
+
+```
+
+这封信差不多完成了，蝙蝠侠另外想再做两次改变。蝙蝠侠希望在最后段落的第一句中的 “does” 一词是斜体，而 “I love you Superman” 这句话是粗体的。
+
+我们使用 `` 和 `` 以斜体和粗体显示文本。让我们来更新这些更改：
+
+```
+
+ Bat Letter
+
+
+ After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you.
+
+```
+
+```
+ You are the light of my life
+
+ You complete my darkness with your light. I love:
+
+
+
+
+ I have learned a lot from you. You have occupied a special place in my heart over the time.
+
+ I have a confession to make
+
+ It feels like my chest does have a heart. You make my heart beat. Your smile brings smile on my face, your pain brings pain to my heart.
+
+
+ I don't show my emotions, but I think this man behind the mask is falling for you.
+
+ I love you Superman.
+
+ Your not-so-secret-lover,
+ Batman
+
+
+```
+
+
+
+### HTML 中的样式
+
+你可以通过三种方式设置样式或定义 HTML 元素的外观：
+
+* 内联样式：我们使用元素的 `style` 属性来编写样式。这是我们迄今为止使用的，但这不是一个好的实践。
+* 嵌入式样式：我们在由 `` 包裹的 “style” 元素中编写所有样式。
+* 链接样式表：我们在具有 .css 扩展名的单独文件中编写所有元素的样式。此文件称为样式表。
+
+让我们来看看如何定义 `` 的内联样式：
+
+```
+
+```
+
+我们可以在 `` 里面写同样的样式：
+
+```
+div{
+ width:550px;
+}
+```
+
+在嵌入式样式中，我们编写的样式是与元素分开的。所以我们需要一种方法来关联元素及其样式。第一个单词 “div” 就做了这样的活。它让浏览器知道花括号 `{...}` 里面的所有样式都属于 “div” 元素。由于这种语法确定要应用样式的元素，因此它称为一个选择器。
+
+我们编写样式的方式保持不变：属性（`width`）和值（`550px`）用冒号（`:`）分隔，以分号（`;`）结束。
+
+让我们从 `` 和 `![]()
` 元素中删除内联样式，将其写入 `
+```
+
+```
+
+ Bat Letter
+
+
+ After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you.
+
+```
+
+```
+ You are the light of my life
+
+ You complete my darkness with your light. I love:
+
+
+
+
+ I have learned a lot from you. You have occupied a special place in my heart over the time.
+
+ I have a confession to make
+
+ It feels like my chest does have a heart. You make my heart beat. Your smile brings smile on my face, your pain brings pain to my heart.
+
+
+ I don't show my emotions, but I think this man behind the mask is falling for you.
+
+ I love you Superman.
+
+ Your not-so-secret-lover,
+ Batman
+
+
+```
+
+保存并刷新，结果应保持不变。
+
+但是有一个大问题，如果我们的 HTML 文件中有多个 `` 和 `![]()
` 元素该怎么办？这样我们在 `
+```
+
+```
+
+ Bat Letter
+
+
+ After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you.
+
+```
+
+```
+ You are the light of my life
+
+ You complete my darkness with your light. I love:
+
+
+
+
+ I have learned a lot from you. You have occupied a special place in my heart over the time.
+
+ I have a confession to make
+
+ It feels like my chest does have a heart. You make my heart beat. Your smile brings smile on my face, your pain brings pain to my heart.
+
+
+ I don't show my emotions, but I think this man behind the mask is falling for you.
+
+ I love you Superman.
+
+ Your not-so-secret-lover,
+ Batman
+
+
+```
+
+HTML 已经准备好了嵌入式样式。
+
+但是，你可以看到，随着我们包含越来越多的样式，`` 将变得很大。这可能很快会混乱我们的主 HTML 文件。
+
+因此，让我们更进一步，通过将 ``。
+
+我们需要使用 HTML 文件中的 `` 标签来将新创建的 CSS 文件链接到 HTML 文件。以下是我们如何做到这一点：
+
+```
+
+```
+
+我们使用 `` 元素在 HTML 文档中包含外部资源，它主要用于链接样式表。我们使用的三个属性是：
+
+* `rel`：关系。链接文件与文档的关系。具有 .css 扩展名的文件称为样式表，因此我们保留 rel=“stylesheet”。
+* `type`：链接文件的类型；对于一个 CSS 文件来说它是 “text/css”。
+* `href`：超文本参考。链接文件的位置。
+
+link 元素的结尾没有 ``。因此，`` 也是一个自闭合的标签。
+
+```
+
+```
+
+如果只是得到一个女朋友，那么很容易：D
+
+可惜没有那么简单，让我们继续前进。
+
+这是我们 “loveletter.html” 的内容：
+
+```
+
+
+ Bat Letter
+
+
+ After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you.
+
+ You are the light of my life
+
+ You complete my darkness with your light. I love:
+
+
+
+
+ I have learned a lot from you. You have occupied a special place in my heart over the time.
+
+ I have a confession to make
+
+ It feels like my chest does have a heart. You make my heart beat. Your smile brings smile on my face, your pain brings pain to my heart.
+
+
+ I don't show my emotions, but I think this man behind the mask is falling for you.
+
+ I love you Superman.
+
+ Your not-so-secret-lover,
+ Batman
+
+
+```
+
+“style.css” 内容：
+
+```
+#letter-container{
+ width:550px;
+}
+#header-bat-logo{
+ width:100%;
+}
+```
+
+保存文件并刷新，浏览器中的输出应保持不变。
+
+### 一些手续
+
+我们的情书已经准备好给蝙蝠侠，但还有一些正式的片段。
+
+与其他任何编程语言一样，HTML 自出生以来（1990 年）经历过许多版本，当前版本是 HTML5。
+
+那么，浏览器如何知道你使用哪个版本的 HTML 来编写页面呢？要告诉浏览器你正在使用 HTML5，你需要在页面顶部包含 ``。对于旧版本的 HTML，这行不同，但你不需要了解它们，因为我们不再使用它们了。
+
+此外，在之前的 HTML 版本中，我们曾经将整个文档封装在 `` 标签内。整个文件分为两个主要部分：头部在 `` 里面，主体在 `` 里面。这在 HTML5 中不是必须的，但由于兼容性原因，我们仍然这样做。让我们用 ``, ``、 `` 和 `` 更新我们的代码：
+
+```
+
+
+
+
+
+
+
+ Bat Letter
+
+
+ After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you.
+
+ You are the light of my life
+
+ You complete my darkness with your light. I love:
+
+
+
+
+ I have learned a lot from you. You have occupied a special place in my heart over the time.
+
+ I have a confession to make
+
+ It feels like my chest does have a heart. You make my heart beat. Your smile brings smile on my face, your pain brings pain to my heart.
+
+
+ I don't show my emotions, but I think this man behind the mask is falling for you.
+
+ I love you Superman.
+
+ Your not-so-secret-lover,
+ Batman
+
+
+
+
+```
+
+主要内容在 `` 里面，元信息在 `` 里面。所以我们把 `` 保存在 `` 里面并加载 `` 里面的样式表。
+
+保存并刷新，你的 HTML 页面应显示与之前相同的内容。
+
+### HTML 的标题
+
+我发誓，这是最后一次改变。
+
+你可能已经注意到选项卡的标题正在显示 HTML 文件的路径：
+
+
+
+我们可以使用 `` 标签来定义 HTML 文件的标题。标题标签也像链接标签一样在 `<head>` 内部。让我们我们在标题中加上 “Bat Letter”：
+
+```
+<!DOCTYPE html>
+<html>
+<head>
+ <title>Bat Letter
+
+
+
+
+ Bat Letter
+
+
+ After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you.
+
+ You are the light of my life
+
+ You complete my darkness with your light. I love:
+
+
+
+
+ I have learned a lot from you. You have occupied a special place in my heart over the time.
+
+ I have a confession to make
+
+ It feels like my chest does have a heart. You make my heart beat. Your smile brings smile on my face, your pain brings pain to my heart.
+
+
+ I don't show my emotions, but I think this man behind the mask is falling for you.
+
+ I love you Superman.
+
+ Your not-so-secret-lover,
+ Batman
+
+
+
+
+```
+
+保存并刷新，你将看到在选项卡上显示的是 “Bat Letter” 而不是文件路径。
+
+蝙蝠侠的情书现在已经完成。
+
+恭喜！你用 HTML 制作了蝙蝠侠的情书。
+
+
+
+### 我们学到了什么
+
+我们学习了以下新概念：
+
+ * 一个 HTML 文档的结构
+ * 在 HTML 中如何写元素（``）
+ * 如何使用 style 属性在元素内编写样式（这称为内联样式，尽可能避免这种情况）
+ * 如何在 `` 中编写元素的样式（这称为嵌入式样式）
+ * 在 HTML 中如何使用 `` 在单独的文件中编写样式并链接它（这称为链接样式表）
+ * 什么是标签名称，属性，开始标签和结束标签
+ * 如何使用 id 属性为一个元素赋予 id
+ * CSS 中的标签选择器和 id 选择器
+
+我们学习了以下 HTML 标签：
+
+ * ``：用于段落
+ * `
`：用于换行
+ * `
`、`
` 做主标题和一个副标题：
+
+```
+
+ Bat Letter
+
+ After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you.
+
+```
+
+```
+ You are the light of my life
+
+ You complete my darkness with your light. I love:
+
+
+
+
+ I have learned a lot from you. You have occupied a special place in my heart over the time.
+
+
+```
+
+保存，刷新。
+
+
+
+### HTML 中的图像
+
+我们的情书尚未完成，但在继续之前，缺少一件大事：蝙蝠侠标志。你见过是蝙蝠侠的东西但没有蝙蝠侠的标志吗？
+
+并没有。
+
+所以，让我们在情书中添加一个蝙蝠侠标志。
+
+在 HTML 中包含图像就像在一个 Word 文件中包含图像一样。在 MS Word 中，你到 “菜单 -> 插入 -> 图像 -> 然后导航到图像位置为止 -> 选择图像 -> 单击插入”。
+
+在 HTML 中，我们使用 `![]()
` 标签让浏览器知道我们需要加载的图像，而不是单击菜单。我们在 `src` 属性中写入文件的位置和名称。如果图像在项目根目录中，我们可以简单地在 `src` 属性中写入图像文件的名称。
+
+在我们深入编码之前，从[这里][3]下载蝙蝠侠标志。你可能希望裁剪图像中的额外空白区域。复制项目根目录中的图像并将其重命名为 “bat-logo.jpeg”。
+
+```
+
+ Bat Letter
+
+
+ After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you.
+
+```
+
+```
+You are the light of my life
+
+ You complete my darkness with your light. I love:
+
+
+
+
+ I have learned a lot from you. You have occupied a special place in my heart over the time.
+
+
+```
+
+我们在第 3 行包含了 `![]()
` 标签。这个标签也是一个自闭合的标签，所以我们不需要写 ``。在 `src` 属性中，我们给出了图像文件的名称。这个名称应与图像名称完全相同，包括扩展名（.jpeg）及其大小写。
+
+保存并刷新，查看结果。
+
+
+
+该死的！刚刚发生了什么？
+
+当使用 `![]()
` 标签包含图像时，默认情况下，图像将以其原始分辨率显示。在我们的例子中，图像比 550px 宽得多。让我们使用 `style` 属性定义它的宽度：
+
+
+```
+
+ Bat Letter
+
+
+ After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you.
+
+```
+
+```
+You are the light of my life
+
+ You complete my darkness with your light. I love:
+
+
+
+
+ I have learned a lot from you. You have occupied a special place in my heart over the time.
+
+
+```
+
+你会注意到，这次我们定义宽度使用了 “%” 而不是 “px”。当我们在 “%” 中定义宽度时，它将占据父元素宽度的百分比。因此，100% 的 550px 将为我们提供 550px。
+
+保存并刷新，查看结果。
+
+
+
+太棒了！这让蝙蝠侠的脸露出了羞涩的微笑 :)。
+
+### HTML 中的粗体和斜体
+
+现在蝙蝠侠想在最后几段中承认他的爱。他有以下文本供你用 HTML 编写：
+
+“I have a confession to make
+
+It feels like my chest _does_ have a heart. You make my heart beat. Your smile brings a smile to my face, your pain brings pain to my heart.
+
+I don’t show my emotions, but I think this man behind the mask is falling for you.”
+
+当阅读到这里时，你会问蝙蝠侠：“等等，这是给谁的？”蝙蝠侠说：
+
+“这是给超人的。”
+
+
+
+你说：哦！我还以为是给神奇女侠的呢。
+
+蝙蝠侠说：不，这是给超人的，请在最后写上 “I love you Superman.”。
+
+好的，我们来写：
+
+
+```
+
+ Bat Letter
+
+
+ After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you.
+
+```
+
+```
+You are the light of my life
+
+ You complete my darkness with your light. I love:
+
+
+
+
+ I have learned a lot from you. You have occupied a special place in my heart over the time.
+
+ I have a confession to make
+
+ It feels like my chest does have a heart. You make my heart beat. Your smile brings smile on my face, your pain brings pain to my heart.
+
+
+ I don't show my emotions, but I think this man behind the mask is falling for you.
+
+ I love you Superman.
+
+ Your not-so-secret-lover,
+ Batman
+
+
+```
+
+这封信差不多完成了，蝙蝠侠另外想再做两次改变。蝙蝠侠希望在最后段落的第一句中的 “does” 一词是斜体，而 “I love you Superman” 这句话是粗体的。
+
+我们使用 `` 和 `` 以斜体和粗体显示文本。让我们来更新这些更改：
+
+```
+
+ Bat Letter
+
+
+ After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you.
+
+```
+
+```
+ You are the light of my life
+
+ You complete my darkness with your light. I love:
+
+
+
+
+ I have learned a lot from you. You have occupied a special place in my heart over the time.
+
+ I have a confession to make
+
+ It feels like my chest does have a heart. You make my heart beat. Your smile brings smile on my face, your pain brings pain to my heart.
+
+
+ I don't show my emotions, but I think this man behind the mask is falling for you.
+
+ I love you Superman.
+
+ Your not-so-secret-lover,
+ Batman
+
+
+```
+
+
+
+### HTML 中的样式
+
+你可以通过三种方式设置样式或定义 HTML 元素的外观：
+
+* 内联样式：我们使用元素的 `style` 属性来编写样式。这是我们迄今为止使用的，但这不是一个好的实践。
+* 嵌入式样式：我们在由 `` 包裹的 “style” 元素中编写所有样式。
+* 链接样式表：我们在具有 .css 扩展名的单独文件中编写所有元素的样式。此文件称为样式表。
+
+让我们来看看如何定义 `` 的内联样式：
+
+```
+
+```
+
+我们可以在 `` 里面写同样的样式：
+
+```
+div{
+ width:550px;
+}
+```
+
+在嵌入式样式中，我们编写的样式是与元素分开的。所以我们需要一种方法来关联元素及其样式。第一个单词 “div” 就做了这样的活。它让浏览器知道花括号 `{...}` 里面的所有样式都属于 “div” 元素。由于这种语法确定要应用样式的元素，因此它称为一个选择器。
+
+我们编写样式的方式保持不变：属性（`width`）和值（`550px`）用冒号（`:`）分隔，以分号（`;`）结束。
+
+让我们从 `` 和 `![]()
` 元素中删除内联样式，将其写入 `
+```
+
+```
+
+ Bat Letter
+
+
+ After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you.
+
+```
+
+```
+ You are the light of my life
+
+ You complete my darkness with your light. I love:
+
+
+
+
+ I have learned a lot from you. You have occupied a special place in my heart over the time.
+
+ I have a confession to make
+
+ It feels like my chest does have a heart. You make my heart beat. Your smile brings smile on my face, your pain brings pain to my heart.
+
+
+ I don't show my emotions, but I think this man behind the mask is falling for you.
+
+ I love you Superman.
+
+ Your not-so-secret-lover,
+ Batman
+
+
+```
+
+保存并刷新，结果应保持不变。
+
+但是有一个大问题，如果我们的 HTML 文件中有多个 `` 和 `![]()
` 元素该怎么办？这样我们在 `
+```
+
+```
+
+ Bat Letter
+
+
+ After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you.
+
+```
+
+```
+ You are the light of my life
+
+ You complete my darkness with your light. I love:
+
+
+
+
+ I have learned a lot from you. You have occupied a special place in my heart over the time.
+
+ I have a confession to make
+
+ It feels like my chest does have a heart. You make my heart beat. Your smile brings smile on my face, your pain brings pain to my heart.
+
+
+ I don't show my emotions, but I think this man behind the mask is falling for you.
+
+ I love you Superman.
+
+ Your not-so-secret-lover,
+ Batman
+
+
+```
+
+HTML 已经准备好了嵌入式样式。
+
+但是，你可以看到，随着我们包含越来越多的样式，`` 将变得很大。这可能很快会混乱我们的主 HTML 文件。
+
+因此，让我们更进一步，通过将 ``。
+
+我们需要使用 HTML 文件中的 `` 标签来将新创建的 CSS 文件链接到 HTML 文件。以下是我们如何做到这一点：
+
+```
+
+```
+
+我们使用 `` 元素在 HTML 文档中包含外部资源，它主要用于链接样式表。我们使用的三个属性是：
+
+* `rel`：关系。链接文件与文档的关系。具有 .css 扩展名的文件称为样式表，因此我们保留 rel=“stylesheet”。
+* `type`：链接文件的类型；对于一个 CSS 文件来说它是 “text/css”。
+* `href`：超文本参考。链接文件的位置。
+
+link 元素的结尾没有 ``。因此，`` 也是一个自闭合的标签。
+
+```
+
+```
+
+如果只是得到一个女朋友，那么很容易：D
+
+可惜没有那么简单，让我们继续前进。
+
+这是我们 “loveletter.html” 的内容：
+
+```
+
+
+ Bat Letter
+
+
+ After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you.
+
+ You are the light of my life
+
+ You complete my darkness with your light. I love:
+
+
+
+
+ I have learned a lot from you. You have occupied a special place in my heart over the time.
+
+ I have a confession to make
+
+ It feels like my chest does have a heart. You make my heart beat. Your smile brings smile on my face, your pain brings pain to my heart.
+
+
+ I don't show my emotions, but I think this man behind the mask is falling for you.
+
+ I love you Superman.
+
+ Your not-so-secret-lover,
+ Batman
+
+
+```
+
+“style.css” 内容：
+
+```
+#letter-container{
+ width:550px;
+}
+#header-bat-logo{
+ width:100%;
+}
+```
+
+保存文件并刷新，浏览器中的输出应保持不变。
+
+### 一些手续
+
+我们的情书已经准备好给蝙蝠侠，但还有一些正式的片段。
+
+与其他任何编程语言一样，HTML 自出生以来（1990 年）经历过许多版本，当前版本是 HTML5。
+
+那么，浏览器如何知道你使用哪个版本的 HTML 来编写页面呢？要告诉浏览器你正在使用 HTML5，你需要在页面顶部包含 ``。对于旧版本的 HTML，这行不同，但你不需要了解它们，因为我们不再使用它们了。
+
+此外，在之前的 HTML 版本中，我们曾经将整个文档封装在 `` 标签内。整个文件分为两个主要部分：头部在 `` 里面，主体在 `` 里面。这在 HTML5 中不是必须的，但由于兼容性原因，我们仍然这样做。让我们用 ``, ``、 `` 和 `` 更新我们的代码：
+
+```
+
+
+
+
+
+
+
+ Bat Letter
+
+
+ After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you.
+
+ You are the light of my life
+
+ You complete my darkness with your light. I love:
+
+
+
+
+ I have learned a lot from you. You have occupied a special place in my heart over the time.
+
+ I have a confession to make
+
+ It feels like my chest does have a heart. You make my heart beat. Your smile brings smile on my face, your pain brings pain to my heart.
+
+
+ I don't show my emotions, but I think this man behind the mask is falling for you.
+
+ I love you Superman.
+
+ Your not-so-secret-lover,
+ Batman
+
+
+
+
+```
+
+主要内容在 `` 里面，元信息在 `` 里面。所以我们把 `` 保存在 `` 里面并加载 `` 里面的样式表。
+
+保存并刷新，你的 HTML 页面应显示与之前相同的内容。
+
+### HTML 的标题
+
+我发誓，这是最后一次改变。
+
+你可能已经注意到选项卡的标题正在显示 HTML 文件的路径：
+
+
+
+我们可以使用 `` 标签来定义 HTML 文件的标题。标题标签也像链接标签一样在 `<head>` 内部。让我们我们在标题中加上 “Bat Letter”：
+
+```
+<!DOCTYPE html>
+<html>
+<head>
+ <title>Bat Letter
+
+
+
+
+ Bat Letter
+
+
+ After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you.
+
+ You are the light of my life
+
+ You complete my darkness with your light. I love:
+
+
+
+
+ I have learned a lot from you. You have occupied a special place in my heart over the time.
+
+ I have a confession to make
+
+ It feels like my chest does have a heart. You make my heart beat. Your smile brings smile on my face, your pain brings pain to my heart.
+
+
+ I don't show my emotions, but I think this man behind the mask is falling for you.
+
+ I love you Superman.
+
+ Your not-so-secret-lover,
+ Batman
+
+
+
+
+```
+
+保存并刷新，你将看到在选项卡上显示的是 “Bat Letter” 而不是文件路径。
+
+蝙蝠侠的情书现在已经完成。
+
+恭喜！你用 HTML 制作了蝙蝠侠的情书。
+
+
+
+### 我们学到了什么
+
+我们学习了以下新概念：
+
+ * 一个 HTML 文档的结构
+ * 在 HTML 中如何写元素（``）
+ * 如何使用 style 属性在元素内编写样式（这称为内联样式，尽可能避免这种情况）
+ * 如何在 `` 中编写元素的样式（这称为嵌入式样式）
+ * 在 HTML 中如何使用 `` 在单独的文件中编写样式并链接它（这称为链接样式表）
+ * 什么是标签名称，属性，开始标签和结束标签
+ * 如何使用 id 属性为一个元素赋予 id
+ * CSS 中的标签选择器和 id 选择器
+
+我们学习了以下 HTML 标签：
+
+ * ``：用于段落
+ * `
`：用于换行
+ * `
`、`
Bat Letter
++ After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you. +
+``` + +``` +You are the light of my life
++ You complete my darkness with your light. I love: +
+-
+
+ I have learned a lot from you. You have occupied a special place in my heart over the time. +
+Bat Letter
+
+ + After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you. +
+``` + +``` +You are the light of my life
++ You complete my darkness with your light. I love: +
+-
+
+ I have learned a lot from you. You have occupied a special place in my heart over the time. +
+Bat Letter
+
+ + After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you. +
+``` + +``` +You are the light of my life
++ You complete my darkness with your light. I love: +
+-
+
+ I have learned a lot from you. You have occupied a special place in my heart over the time. +
+Bat Letter
+
+ + After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you. +
+``` + +``` +You are the light of my life
++ You complete my darkness with your light. I love: +
+-
+
+ I have learned a lot from you. You have occupied a special place in my heart over the time. +
+I have a confession to make
++ It feels like my chest does have a heart. You make my heart beat. Your smile brings smile on my face, your pain brings pain to my heart. +
++ I don't show my emotions, but I think this man behind the mask is falling for you. +
+I love you Superman.
+
+ Your not-so-secret-lover,
+ Batman
+
Bat Letter
+
+ + After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you. +
+``` + +``` +You are the light of my life
++ You complete my darkness with your light. I love: +
+-
+
+ I have learned a lot from you. You have occupied a special place in my heart over the time. +
+I have a confession to make
++ It feels like my chest does have a heart. You make my heart beat. Your smile brings smile on my face, your pain brings pain to my heart. +
++ I don't show my emotions, but I think this man behind the mask is falling for you. +
+I love you Superman.
+
+ Your not-so-secret-lover,
+ Batman
+
+```
+
+我们可以在 `` 里面写同样的样式：
+
+```
+div{
+ width:550px;
+}
+```
+
+在嵌入式样式中，我们编写的样式是与元素分开的。所以我们需要一种方法来关联元素及其样式。第一个单词 “div” 就做了这样的活。它让浏览器知道花括号 `{...}` 里面的所有样式都属于 “div” 元素。由于这种语法确定要应用样式的元素，因此它称为一个选择器。
+
+我们编写样式的方式保持不变：属性（`width`）和值（`550px`）用冒号（`:`）分隔，以分号（`;`）结束。
+
+让我们从 `
` 和 `![]()
` 元素中删除内联样式，将其写入 `
+```
+
+```
+
+
+
+```
+
+保存并刷新，结果应保持不变。
+
+但是有一个大问题，如果我们的 HTML 文件中有多个 `Bat Letter
+
+ + After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you. +
+``` + +``` +You are the light of my life
++ You complete my darkness with your light. I love: +
+-
+
+ I have learned a lot from you. You have occupied a special place in my heart over the time. +
+I have a confession to make
++ It feels like my chest does have a heart. You make my heart beat. Your smile brings smile on my face, your pain brings pain to my heart. +
++ I don't show my emotions, but I think this man behind the mask is falling for you. +
+I love you Superman.
+
+ Your not-so-secret-lover,
+ Batman
+
` 和 `![]()
` 元素该怎么办？这样我们在 `
+```
+
+```
+`, ``、 `` 和 `` 更新我们的代码：
+
+```
+
+
+
+
+
+
+
+
+
+```
+
+HTML 已经准备好了嵌入式样式。
+
+但是，你可以看到，随着我们包含越来越多的样式，`` 将变得很大。这可能很快会混乱我们的主 HTML 文件。
+
+因此，让我们更进一步，通过将 ``。
+
+我们需要使用 HTML 文件中的 `` 标签来将新创建的 CSS 文件链接到 HTML 文件。以下是我们如何做到这一点：
+
+```
+
+```
+
+我们使用 `` 元素在 HTML 文档中包含外部资源，它主要用于链接样式表。我们使用的三个属性是：
+
+* `rel`：关系。链接文件与文档的关系。具有 .css 扩展名的文件称为样式表，因此我们保留 rel=“stylesheet”。
+* `type`：链接文件的类型；对于一个 CSS 文件来说它是 “text/css”。
+* `href`：超文本参考。链接文件的位置。
+
+link 元素的结尾没有 ``。因此，`` 也是一个自闭合的标签。
+
+```
+
+```
+
+如果只是得到一个女朋友，那么很容易：D
+
+可惜没有那么简单，让我们继续前进。
+
+这是我们 “loveletter.html” 的内容：
+
+```
+
+Bat Letter
+
+ + After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you. +
+``` + +``` +You are the light of my life
++ You complete my darkness with your light. I love: +
+-
+
+ I have learned a lot from you. You have occupied a special place in my heart over the time. +
+I have a confession to make
++ It feels like my chest does have a heart. You make my heart beat. Your smile brings smile on my face, your pain brings pain to my heart. +
++ I don't show my emotions, but I think this man behind the mask is falling for you. +
+I love you Superman.
+
+ Your not-so-secret-lover,
+ Batman
+
+
+
+```
+
+“style.css” 内容：
+
+```
+#letter-container{
+ width:550px;
+}
+#header-bat-logo{
+ width:100%;
+}
+```
+
+保存文件并刷新，浏览器中的输出应保持不变。
+
+### 一些手续
+
+我们的情书已经准备好给蝙蝠侠，但还有一些正式的片段。
+
+与其他任何编程语言一样，HTML 自出生以来（1990 年）经历过许多版本，当前版本是 HTML5。
+
+那么，浏览器如何知道你使用哪个版本的 HTML 来编写页面呢？要告诉浏览器你正在使用 HTML5，你需要在页面顶部包含 ``。对于旧版本的 HTML，这行不同，但你不需要了解它们，因为我们不再使用它们了。
+
+此外，在之前的 HTML 版本中，我们曾经将整个文档封装在 `` 标签内。整个文件分为两个主要部分：头部在 `` 里面，主体在 `` 里面。这在 HTML5 中不是必须的，但由于兼容性原因，我们仍然这样做。让我们用 `Bat Letter
+
+ + After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you. +
+You are the light of my life
++ You complete my darkness with your light. I love: +
+-
+
+ I have learned a lot from you. You have occupied a special place in my heart over the time. +
+I have a confession to make
++ It feels like my chest does have a heart. You make my heart beat. Your smile brings smile on my face, your pain brings pain to my heart. +
++ I don't show my emotions, but I think this man behind the mask is falling for you. +
+I love you Superman.
+
+ Your not-so-secret-lover,
+ Batman
+
+
+
+
+
+```
+
+主要内容在 `` 里面，元信息在 `` 里面。所以我们把 `Bat Letter
+
+ + After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you. +
+You are the light of my life
++ You complete my darkness with your light. I love: +
+-
+
+ I have learned a lot from you. You have occupied a special place in my heart over the time. +
+I have a confession to make
++ It feels like my chest does have a heart. You make my heart beat. Your smile brings smile on my face, your pain brings pain to my heart. +
++ I don't show my emotions, but I think this man behind the mask is falling for you. +
+I love you Superman.
+
+ Your not-so-secret-lover,
+ Batman
+
` 保存在 `` 里面并加载 `` 里面的样式表。
+
+保存并刷新，你的 HTML 页面应显示与之前相同的内容。
+
+### HTML 的标题
+
+我发誓，这是最后一次改变。
+
+你可能已经注意到选项卡的标题正在显示 HTML 文件的路径：
+
+
+
+我们可以使用 `` 标签来定义 HTML 文件的标题。标题标签也像链接标签一样在 `<head>` 内部。让我们我们在标题中加上 “Bat Letter”：
+
+```
+<!DOCTYPE html>
+<html>
+<head>
+ <title>Bat Letter
+
+
+
+
+
+
+
+
+```
+
+保存并刷新，你将看到在选项卡上显示的是 “Bat Letter” 而不是文件路径。
+
+蝙蝠侠的情书现在已经完成。
+
+恭喜！你用 HTML 制作了蝙蝠侠的情书。
+
+
+
+### 我们学到了什么
+
+我们学习了以下新概念：
+
+ * 一个 HTML 文档的结构
+ * 在 HTML 中如何写元素（``）
+ * 如何使用 style 属性在元素内编写样式（这称为内联样式，尽可能避免这种情况）
+ * 如何在 `` 中编写元素的样式（这称为嵌入式样式）
+ * 在 HTML 中如何使用 `` 在单独的文件中编写样式并链接它（这称为链接样式表）
+ * 什么是标签名称，属性，开始标签和结束标签
+ * 如何使用 id 属性为一个元素赋予 id
+ * CSS 中的标签选择器和 id 选择器
+
+我们学习了以下 HTML 标签：
+
+ * `Bat Letter
+
+ + After all the battles we faught together, after all the difficult times we saw together, after all the good and bad moments we've been through, I think it's time I let you know how I feel about you. +
+You are the light of my life
++ You complete my darkness with your light. I love: +
+-
+
+ I have learned a lot from you. You have occupied a special place in my heart over the time. +
+I have a confession to make
++ It feels like my chest does have a heart. You make my heart beat. Your smile brings smile on my face, your pain brings pain to my heart. +
++ I don't show my emotions, but I think this man behind the mask is falling for you. +
+I love you Superman.
+
+ Your not-so-secret-lover,
+ Batman
+
`：用于段落
+ * `
`：用于换行
+ * `
- `、`