From f4dbb183f84dffd69e0aadaeeca91656196b2de2 Mon Sep 17 00:00:00 2001 From: DarkSun Date: Wed, 16 Aug 2023 12:17:59 +0800 Subject: [PATCH] =?UTF-8?q?=E9=80=89=E9=A2=98[tech]:=2020230816=20How=20to?= =?UTF-8?q?=20Change=20the=20default=20kernel=20in=20RHEL=208=20and=209?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit sources/tech/20230816 How to Change the default kernel in RHEL 8 and 9.md --- ...ange the default kernel in RHEL 8 and 9.md | 173 ++++++++++++++++++ 1 file changed, 173 insertions(+) create mode 100644 sources/tech/20230816 How to Change the default kernel in RHEL 8 and 9.md diff --git a/sources/tech/20230816 How to Change the default kernel in RHEL 8 and 9.md b/sources/tech/20230816 How to Change the default kernel in RHEL 8 and 9.md new file mode 100644 index 0000000000..466f370abf --- /dev/null +++ b/sources/tech/20230816 How to Change the default kernel in RHEL 8 and 9.md @@ -0,0 +1,173 @@ +[#]: subject: "How to Change the default kernel in RHEL 8 and 9" +[#]: via: "https://www.2daygeek.com/changing-default-kernel-rhel-8-rhel-9/" +[#]: author: "Rasool Cool https://www.2daygeek.com/author/rasool/" +[#]: collector: "lujun9972" +[#]: translator: " " +[#]: reviewer: " " +[#]: publisher: " " +[#]: url: " " + +How to Change the default kernel in RHEL 8 and 9 +====== + +Usually a Linux system boots with the latest installed kernel, which is set by default. It keeps maximum 3 recent versions of Linux Kernel boot entries. + +Let’s say you’ve done the yum update, and a new kernel is installed as part of this update. This prevents the application from starting as this kernel is incompatible with the application. + +To temporarily fix this problem, you should continue to boot the system into an older kernel. + +In this article, we’ll show you how to set old kernel version as default on RHEL 8 and RHEL 9 systems using grubby utility. + + * [**How to Upgrade from RHEL 7 to RHEL 8**][1] + + + +### What is grubby + +grubby is a command line tool used for updating and displaying information about the boot loaders configuration files across multiple architectures. + +### Checking currently booted kernel + +You can check booted/loaded kernel using **uname command** as shown below. + +``` + + uname -r + + 4.18.0-477.13.1.el8_8.x86_64 + +``` + +### Listing the Default Kernel + +To verify the default kernel version using grubby, run: + +``` + + grubby --default-kernel + + /boot/vmlinuz-4.18.0-477.13.1.el8_8.x86_64 + +``` + +To obtain the index number of the current default kernel, run: + +``` + + grubby --default-index + 0 + +``` + +### Checking installed kernels + +To check list of installed kernels, run: + +Let’s explain the below output. The latest kernel installed will have the **entry-index** of **`0`** , the next **older kernel** version will get **`1`** , second older kernel version will get **`2`** , and the **rescue kernel** will get an entry-index of **`3`**. + +``` + + grubby --info=ALL | egrep -i 'index|title' + + index=0 + title="Red Hat Enterprise Linux (4.18.0-477.13.1.el8_8.x86_64) 8.8 (Ootpa)" + index=1 + title="Red Hat Enterprise Linux (4.18.0-425.19.2.el8_7.x86_64) 8.7 (Ootpa)" + index=2 + title="Red Hat Enterprise Linux (4.18.0-425.13.1.el8_7.x86_64) 8.7 (Ootpa)" + index=3 + title="Red Hat Enterprise Linux (0-rescue-13iu76884ec5490puc67j8789s249b0c) 8.2 (Ootpa)" + +``` + +### Changing default kernel Boot entry + +This can be done in two ways either using **`'kernel filename'`** or **`'kernel entry-index'`**. We will be going to set ‘ **index=1 (4.18.0-425.19.2.el8_7.x86_64)** ‘ as default kernel due to application dependency. + +``` + + Syntax: + grubby --set-default [kernel-filename] + +``` + +``` + + grubby --set-default /boot/vmlinuz-4.18.0-425.19.2.el8_7.x86_64 + OR + grubby --set-default vmlinuz-4.18.0-425.19.2.el8_7.x86_64 + +``` + +To change the default kernel boot entry using kernel entry-index: + +``` + + Syntax: + grubby --set-default-index=[kernel-entry-index] + +``` + +``` + + grubby --set-default-index=1 + +``` + +### Rebooting the system + +Reboot the system to check whether the old kernel is persistent or not. + +``` + + reboot + or + init 6 + +``` + +### Verifying the Changes + +Let’s check if the kernel added in the previous step has taken effect or not. Yes, it booted with older kernel **`'N-1'`** as expected. + +``` + + uname -r + 4.18.0-425.19.2.el8_7.x86_64 + + grubby --default-kernel + /boot/vmlinuz-4.18.0-425.19.2.el8_7.x86_64 + +``` + +To check detailed information of all kernel, run: + +``` + + grubby --info=ALL + +``` + +![][2] + +##### Wrapping Up + +In this tutorial, we’ve shown you how to set old kernel version as default on RHEL 8 and RHEL 9 systems using grubby utility. + +If you have any questions or feedback, feel free to comment below. + +-------------------------------------------------------------------------------- + +via: https://www.2daygeek.com/changing-default-kernel-rhel-8-rhel-9/ + +作者：[Rasool Cool][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/rasool/ +[b]: https://github.com/lujun9972 +[1]: https://www.2daygeek.com/upgrading-from-rhel-7-to-rhel-8/ +[2]: https://www.2daygeek.com/wp-content/uploads/2023/06/changing-default-kernel-rhel-8-rhel-9-1024x494.jpg