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20140714-2 选题
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DeadFire
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Fix No Sound In Ubuntu 14.04 As HDMI Enabled BY Default
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================================================================================
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Sound problem is not new in Ubuntu. I have previously written on various ways to [fix “no sound” issue in Ubuntu][1]. But the soud issue I am going to discuss here is different than those mentioned in the other article.
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So I installed Ubuntu 14.04, actually re-installed it. As always, I did all those [things to do after a fresh install of Ubuntu 14.04][2]. And than I realized that the system had no sound. While investigating the issue I found one strange thing. I checked [alsamixer][3] and it was in a weird state:
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As you can see, **HDMI is set by default in alsamixer**. Which means by default HDMI output has been selected instead of the built in speakers. This is why I get no sound from the built in speakers in my system.
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Use the following command to check the state of alsamixer:
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alsamixer
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If alsamixer is set by default to HDMI or some other audio output, continue this article to see how can we fix it.
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### Fixing no sound in Ubuntu when HDMI is set as default ###
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Now to force Ubuntu to use analog output instead of HDMI by default, we need a little information. Open a terminal and use the following command:
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aplay -l
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This will list the devices, card number etc. Note down the card and device number for analog output. For me the output was like this:
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Once you have the required card and device number, make a new configuration file like this:
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sudo gedit /etc/asound.conf
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The above command will also open the file. Add the following lines to it, replacing with your card and device number of course:
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defaults.pcm.card 1
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defaults.pcm.device 0
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Save the file and restart the computer. You should hear the sound now. Just to mention, this will work for all the Linux distributions such as Linux Mint, Elementary OS, Fedora, Arch Linux etc. As I said previously, this “no sound fix” only works with the case where HDMI is set by default. For other cases, you can read [this article about fixing no sound issue in Ubuntu and Linux Mint][4].
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Feel free to use the comment section to let me know if it worked or not or if you have some better trick to handle this such issue. Ciao 
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----------
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About Abhishek
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I am Abhishek Prakash, 'creator' of It's F.O.S.S. I have a Masters in Communication System Engineering. I am an avid Linux lover and Open Source enthusiast. I use Ubuntu and believe in sharing knowledge. Apart from Linux, I love classic detective mystery. Huge fan of Agatha Christie work. Feel free to circle me on [Google Plus][g] and Follow [@abhishek_pc][t]
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--------------------------------------------------------------------------------
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via: http://itsfoss.com/fix-sound-ubuntu-1404/
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译者：[译者ID](https://github.com/译者ID) 校对：[校对者ID](https://github.com/校对者ID)
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本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译，[Linux中国](http://linux.cn/) 荣誉推出
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[1]:http://itsfoss.com/fix-sound-ubuntu-1304-quick-tip/
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[2]:http://itsfoss.com/things-to-do-after-installing-ubuntu-14-04/
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[3]:http://en.wikipedia.org/wiki/Alsamixer
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[4]:http://itsfoss.com/fix-sound-ubuntu-1304-quick-tip/
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[g]:https://plus.google.com/u/0/110180944531110746460
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[t]:https://twitter.com/abhishek_pc
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[Quick Tip] Set Default Browser on Debian/Ubuntu Using Terminal
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================================================================================
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Hey Guys,
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In this post, we are going to use the terminal to make a browser default.
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Even though, this can easily be done using the browser’s main interface, is handy sometimes if you need to do this remotely.
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To do this you simply open up the terminal and run the line of code below:
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Enter the number beside the browser you wish to make default and you are done.
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sudo update-alternatives --config x-www-browser
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Enjoy!
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--------------------------------------------------------------------------------
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via: http://www.unixmen.com/quick-tip-set-default-browser-debianubuntu-using-terminal/
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译者：[译者ID](https://github.com/译者ID) 校对：[校对者ID](https://github.com/校对者ID)
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本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译，[Linux中国](http://linux.cn/) 荣誉推出
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Test read/write speed of usb and ssd drives with dd command on Linux
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================================================================================
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### Drive speed ###
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The speed of a drive is measured in terms of how much data it can read or write in unit time. The dd command is a simple command line tool that can be used to read and write arbitrary blocks of data to a drive and measure the speed at which the data transfer took place.
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In this post we shall use the dd command to test and read and write speed of usb and ssd drives using the dd command.
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The data transfer speed does not depend solely on the drive, but also on the interface it is connected to. For example a usb 2.0 port has a maximum operational speed limit of 35 Mbytes/s, so even if you were to plug a high speed usb 3 pen drive into a usb 2 port, the speed would be capped to the lower limit.
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The same applies to SSD. SSD connect via SATA ports which have different versions. Sata 2.0 has a maximum theoretical speed limit of 3Gbits/s which is roughly 375 Mbytes/s. Whereas Sata 3.0 supports twice that speed.
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### Test Method ###
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Mount the drive and navigate into it from the terminal. Then use the dd command to first write a file using fixed sized blocks. Then read the same file out using the same block site.
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The general syntax of the dd command looks like this
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dd if=path/to/input_file of=/path/to/output_file bs=block_size count=number_of_blocks
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When writing to the drive, we simply read from /dev/zero which is a source of infinite useless bytes. And when read from the drive, we read the file written earlier and send it to /dev/null which is nowhere. In the whole process, dd keeps track of the speed with which the transfer takes place and reports it.
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### SSD ###
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The SSD that we are using is a "Samsung Evo 120GB" ssd. It is a beginner level ssd that comes within a decent budget and is also my first SSD. It is also one of the best performing ssds, in the market.
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In this test the ssd is connected to a sata 2.0 port.
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#### Write speed ####
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Lets first write to the ssd
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$ dd if=/dev/zero of=./largefile bs=1M count=1024
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1024+0 records in
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1024+0 records out
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1073741824 bytes (1.1 GB) copied, 4.82364 s, 223 MB/s
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Block size is actually quite large. You can try with smaller sizes like 64k or even 4k.
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#### Read speed ####
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Now read back the same file. However, first clear the memory cache to ensure that the file is actually read from drive.
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Run the following command to clear the memory cache
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$ sudo sh -c "sync && echo 3 > /proc/sys/vm/drop_caches"
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Now read the file
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$ dd if=./largefile of=/dev/null bs=4k
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165118+0 records in
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165118+0 records out
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676323328 bytes (676 MB) copied, 3.0114 s, 225 MB/s
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The Arch Linux wiki has a page full of information about the read/write speed of various SSDs from different vendors like Intel, Samsung, Sandisk etc. Check it out at the following url.
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[https://wiki.archlinux.org/index.php/SSD_Benchmarking][1]
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### USB ###
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In this test we shall measure the read and write speed of ordinary usb/pen drives. The drives are plugged to standard usb 2 ports. The first one is a sony 4gb usb drive and the second is a strontium 16gb drive.
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First plug the drive into the port and mount it, so that it is readable. Then navigate into the mount directory from the command line.
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#### Sony 4GB - Write ####
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In this test, the dd command is used to write 10,000 chunks of 8 Kbyte each to a single file on the drive.
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# dd if=/dev/zero of=./largefile bs=8k count=10000
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10000+0 records in
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10000+0 records out
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81920000 bytes (82 MB) copied, 11.0626 s, 7.4 MB/s
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So the write speed is around 7.5 MBytes/s. This is a low figure.
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#### Sony 4GB - Read ####
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The same file is read back to test the read speed. Run the following command to clear the memory cache
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$ sudo sh -c "sync && echo 3 > /proc/sys/vm/drop_caches"
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Now read the file using the dd command
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# dd if=./largefile of=/dev/null bs=8k
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8000+0 records in
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8000+0 records out
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65536000 bytes (66 MB) copied, 2.65218 s, 24.7 MB/s
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The read speed comes out around 25 Mbytes/s which is a more or less the standard for cheap usb drives.
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> USB 2.0 has a theoretical maximum signaling rate of 480 Mbits/s or 60 Mbytes/s. However due to various constraints the maximum throughput is restricted to around 280 Mbit/s or 35 Mbytes/s. Beyond this the actual speed achieved depends on the quality of the pen drives and other factors too.
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And the above usb drive was plugged inside a USB 2.0 port and it achieved a read speed of 24.7 Mbytes/s which is not very bad. But the write speed lags much behind
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Now lets do the same test with a Strontium 16gb drive. Strontium is another very cheapy brand, although usb drives are reliable.
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#### Strontium 16gb write speed ####
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# dd if=/dev/zero of=./largefile bs=64k count=1000
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1000+0 records in
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1000+0 records out
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65536000 bytes (66 MB) copied, 8.3834 s, 7.8 MB/s
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Strontium 16gb read speed
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# sudo sh -c "sync && echo 3 > /proc/sys/vm/drop_caches"
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# dd if=./largefile of=/dev/null bs=8k
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8000+0 records in
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8000+0 records out
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65536000 bytes (66 MB) copied, 2.90366 s, 22.6 MB/s
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The read speed is lower than the Sony drive.
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### Resources ###
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- [http://en.wikipedia.org/wiki/USB][2]
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- [https://wiki.archlinux.org/index.php/SSD_Benchmarking][1]
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----------
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About Silver Moon
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Php developer, blogger and Linux enthusiast. He can be reached at [m00n.silv3r@gmail.com][e]. Or find him on [Google+][g]
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--------------------------------------------------------------------------------
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via: http://www.binarytides.com/linux-test-drive-speed/
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译者：[译者ID](https://github.com/译者ID) 校对：[校对者ID](https://github.com/校对者ID)
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本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译，[Linux中国](http://linux.cn/) 荣誉推出
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[1]:http://wiki.archlinux.org/index.php/SSD_Benchmarking
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[2]:http://en.wikipedia.org/wiki/USB
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[e]:m00n.silv3r@gmail.com
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[g]:http://plus.google.com/117145272367995638274/posts
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