How to Upgrade Linux Kernel in CentOS 8

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In this article, you will learn how to upgrade Linux Kernel in CentOS 8 to the latest stable version. #centlinux #linux #linuxkernel

What is Linux Kernel?

Kernel is the most important component of any Linux operating system. A Linux kernel is works as the interpreter or mediator between computer hardware and software processes.

The Linux Kernel performs following tasks.

Process Management
Memory Management
Device Drivers
System Calls and Security

Each Linux distribution is shipped with a stable version of Linux Kernel and the supported software and drivers. But the shipped Kernel may not be the the latest one.

One needs to upgrade the whole operating system to move to another major version of Linux Kernel.

But there are some methods by using them, you can upgrade your operating system to latest Linux kernel.

The Kernel source is provided by the The Linux Kernel Archives. Based on the available source code two editions of Linux has been compiled and distributed through ELRepo yum repository.

kernel-lt is compiled by using the source code in “longterm” branch, whereas kernel-ml is compiled by using the source code in “mainline” branch.

Linux Server Specification

We are using a minimal CentOS 8 KVM machine with following specification.

CPU – 3.4 Ghz (2 cores)
Memory – 2 GB
Storage – 20 GB
Operating System – CentOS 8.2
Hostname – centos-8.centlinux.com
IP Address – 192.168.116.206 /24

Recommended Online Training: Learn Bash Shell in Linux for Beginners

Update Linux Software Packages

Connect with centos-8.centlinux.com server as root user by using a SSH tool.

Upgrade existing software packages in CentOS 8 machine by using the dnf command.

# dnf update -y
Last metadata expiration check: 0:02:03 ago on Sun 05 Jul 2020 12:20:54 AM PKT.
Dependencies resolved.
=============================================================================
 Package          Arch      Version                          Repo       Size
=============================================================================
Upgrading:
 gnutls           x86_64    3.6.8-11.el8_2                   BaseOS    915 k
 libnghttp2       x86_64    1.33.0-3.el8_2.1                 BaseOS     77 k
 microcode_ctl    x86_64    4:20191115-4.20200609.1.el8_2    BaseOS    2.7 M

Transaction Summary
=============================================================================
Upgrade  3 Packages

Total download size: 3.7 M
Downloading Packages:
(1/3): libnghttp2-1.33.0-3.el8_2.1.x86_64.rp  55 kB/s |  77 kB     00:01
(2/3): gnutls-3.6.8-11.el8_2.x86_64.rpm       96 kB/s | 915 kB     00:09
(3/3): microcode_ctl-20191115-4.20200609.1.e 204 kB/s | 2.7 MB     00:13
-----------------------------------------------------------------------------
Total                                        230 kB/s | 3.7 MB     00:16
Running transaction check
Transaction check succeeded.
Running transaction test
Transaction test succeeded.
Running transaction
  Preparing        :                                                     1/1
  Running scriptlet: microcode_ctl-4:20191115-4.20200609.1.el8_2.x86_6   1/1
  Upgrading        : microcode_ctl-4:20191115-4.20200609.1.el8_2.x86_6   1/6
  Running scriptlet: microcode_ctl-4:20191115-4.20200609.1.el8_2.x86_6   1/6
  Upgrading        : libnghttp2-1.33.0-3.el8_2.1.x86_64                  2/6
  Upgrading        : gnutls-3.6.8-11.el8_2.x86_64                        3/6
  Running scriptlet: microcode_ctl-4:20191115-4.20200602.2.el8_2.x86_6   4/6
  Cleanup          : microcode_ctl-4:20191115-4.20200602.2.el8_2.x86_6   4/6
  Running scriptlet: microcode_ctl-4:20191115-4.20200602.2.el8_2.x86_6   4/6
  Cleanup          : libnghttp2-1.33.0-1.el8_0.1.x86_64                  5/6
  Cleanup          : gnutls-3.6.8-10.el8_2.x86_64                        6/6
  Running scriptlet: microcode_ctl-4:20191115-4.20200609.1.el8_2.x86_6   6/6
  Running scriptlet: gnutls-3.6.8-10.el8_2.x86_64                        6/6
  Verifying        : gnutls-3.6.8-11.el8_2.x86_64                        1/6
  Verifying        : gnutls-3.6.8-10.el8_2.x86_64                        2/6
  Verifying        : libnghttp2-1.33.0-3.el8_2.1.x86_64                  3/6
  Verifying        : libnghttp2-1.33.0-1.el8_0.1.x86_64                  4/6
  Verifying        : microcode_ctl-4:20191115-4.20200609.1.el8_2.x86_6   5/6
  Verifying        : microcode_ctl-4:20191115-4.20200602.2.el8_2.x86_6   6/6

Upgraded:
  gnutls-3.6.8-11.el8_2.x86_64
  libnghttp2-1.33.0-3.el8_2.1.x86_64
  microcode_ctl-4:20191115-4.20200609.1.el8_2.x86_64

Complete!

Verify the Kernel version of CentOS 8 operating system.

# uname -r
4.18.0-193.6.3.el8_2.x86_64

Install ELRepo Yum Repository

The latest Linux kernels are available through ELRepo yum repository. Therefore, we are installing the ELRepo repository using following dnf command.

# dnf install -y https://www.elrepo.org/elrepo-release-8.el8.elrepo.noarch.rpm
Last metadata expiration check: 0:02:29 ago on Sun 05 Jul 2020 12:28:31 AM PKT.
elrepo-release-8.el8.elrepo.noarch.rpm        10 kB/s |  13 kB     00:01
Dependencies resolved.
=============================================================================
 Package            Arch       Version                Repository        Size
=============================================================================
Installing:
 elrepo-release     noarch     8.2-1.el8.elrepo       @commandline      13 k

Transaction Summary
=============================================================================
Install  1 Package

Total size: 13 k
Installed size: 5.0 k
Downloading Packages:
Running transaction check
Transaction check succeeded.
Running transaction test
Transaction test succeeded.
Running transaction
  Preparing        :                                                     1/1
  Installing       : elrepo-release-8.2-1.el8.elrepo.noarch              1/1
  Verifying        : elrepo-release-8.2-1.el8.elrepo.noarch              1/1

Installed:
  elrepo-release-8.2-1.el8.elrepo.noarch

Complete!

Import the GPG Key of ELRepo repository into the system.

# rpm --import https://www.elrepo.org/RPM-GPG-KEY-elrepo.org

Build cache for newly installed yum repositories.

# dnf makecache
CentOS-8 - AppStream                         5.6 kB/s | 4.3 kB     00:00
CentOS-8 - Base                               10 kB/s | 3.9 kB     00:00
CentOS-8 - Extras                            785  B/s | 1.5 kB     00:01
ELRepo.org Community Enterprise Linux Reposi 2.9 kB/s | 2.9 kB     00:01
Metadata cache created.

Install Latest Linux Kernel in CentOS 8

ELRepo repository contains elrepo-kernel channel that provides the Long Term Supported kernels (kernel-lt) and Main-Line Stable Kernels (kernel-ml) for Red Hat Enterprise Linux based distributions. Both of these Kernel packages are built from the sources available from The Linux Kernel Archives.

Currently, there isn’t any Long Term Supported kernel is available in this channel. But the Main-Line kernel based on latest stable release of Linux Kernel 5.7 is available.

Search the elrepo-kernel channel to list down the kernel-ml related packages.

# dnf --disablerepo="*" --enablerepo="elrepo-kernel" list available | grep kernel-ml
kernel-ml.x86_64                         5.7.7-1.el8.elrepo        elrepo-kernel
kernel-ml-core.x86_64                    5.7.7-1.el8.elrepo        elrepo-kernel
kernel-ml-devel.x86_64                   5.7.7-1.el8.elrepo        elrepo-kernel
kernel-ml-doc.noarch                     5.7.7-1.el8.elrepo        elrepo-kernel
kernel-ml-headers.x86_64                 5.7.7-1.el8.elrepo        elrepo-kernel
kernel-ml-modules.x86_64                 5.7.7-1.el8.elrepo        elrepo-kernel
kernel-ml-modules-extra.x86_64           5.7.7-1.el8.elrepo        elrepo-kernel
kernel-ml-tools.x86_64                   5.7.7-1.el8.elrepo        elrepo-kernel
kernel-ml-tools-libs.x86_64              5.7.7-1.el8.elrepo        elrepo-kernel
kernel-ml-tools-libs-devel.x86_64        5.7.7-1.el8.elrepo        elrepo-kernel

Install the kernel-ml package by using the following command. You can also install any other kernel-ml-* package according to your requirement.

# dnf --enablerepo="elrepo-kernel" install -y kernel-ml
Last metadata expiration check: 0:05:46 ago on Sun 05 Jul 2020 12:33:14 AM PKT.
Dependencies resolved.
================================================================================
 Package              Arch      Version                  Repository        Size
================================================================================
Installing:
 kernel-ml            x86_64    5.7.7-1.el8.elrepo       elrepo-kernel     32 k
Installing dependencies:
 kernel-ml-core       x86_64    5.7.7-1.el8.elrepo       elrepo-kernel     28 M
 kernel-ml-modules    x86_64    5.7.7-1.el8.elrepo       elrepo-kernel     23 M

Transaction Summary
================================================================================
Install  3 Packages

Total download size: 51 M
Installed size: 87 M
Downloading Packages:
(1/3): kernel-ml-5.7.7-1.el8.elrepo.x86_64.rpm   51 kB/s |  32 kB     00:00
(2/3): kernel-ml-modules-5.7.7-1.el8.elrepo.x86 115 kB/s |  23 MB     03:24
(3/3): kernel-ml-core-5.7.7-1.el8.elrepo.x86_64 109 kB/s |  28 MB     04:25
--------------------------------------------------------------------------------
Total                                           196 kB/s |  51 MB     04:28
Running transaction check
Transaction check succeeded.
Running transaction test
Transaction test succeeded.
Running transaction
  Preparing        :                                                        1/1
  Installing       : kernel-ml-core-5.7.7-1.el8.elrepo.x86_64               1/3
  Running scriptlet: kernel-ml-core-5.7.7-1.el8.elrepo.x86_64               1/3
  Installing       : kernel-ml-modules-5.7.7-1.el8.elrepo.x86_64            2/3
  Running scriptlet: kernel-ml-modules-5.7.7-1.el8.elrepo.x86_64            2/3
  Installing       : kernel-ml-5.7.7-1.el8.elrepo.x86_64                    3/3
  Running scriptlet: kernel-ml-core-5.7.7-1.el8.elrepo.x86_64               3/3
  Running scriptlet: kernel-ml-5.7.7-1.el8.elrepo.x86_64                    3/3
  Verifying        : kernel-ml-modules-5.7.7-1.el8.elrepo.x86_64            1/3
  Verifying        : kernel-ml-core-5.7.7-1.el8.elrepo.x86_64               2/3
  Verifying        : kernel-ml-5.7.7-1.el8.elrepo.x86_64                    3/3

Installed:
  kernel-ml-5.7.7-1.el8.elrepo.x86_64
  kernel-ml-core-5.7.7-1.el8.elrepo.x86_64
  kernel-ml-modules-5.7.7-1.el8.elrepo.x86_64

Complete!

Linux Kernel 5.7 has been installed on our CentOS 8 server.

To load the new Linux kernel we need to restart the CentOS 8 machine.

# systemctl reboot

After reboot, the newly installed Linux Kernel 5.7 has been added to the GRUB boot menu.

Do not confuse with the long list of kernels in following screenshot. It is because, we have experimented with the different versions of Linux kernels. In your case, there will be only two boot menu entries.

Start the CentOS 8 operating system with Linux Kernel 5.7.

After CentOS 8 startup, execute the following command at Linux CLI to verify the active Kernel version.

# uname -r
5.7.7-1.el8.elrepo.x86_64

We have successfully upgrade Linux Kernel to latest version i.e. 5.7 on CentOS 8.

Uninstall Old Linux Kernel

Uninstall process of Linux Kernel 5.7 is very straight forward, But we have included it in this article for the sake of completeness.

Restart your CentOS 8 machine.

# systemctl reboot

Start the Linux operating system with a previous version of Linux Kernel.

After successful startup, verify the active kernel version by executing the following command at Linux CLI.

# uname -r
4.18.0-193.6.3.el8_2.x86_64

Our CentOS 8 operating system is now using our previous Linux kernel.

Use dnf command to uninstall Linux Kernel 5.7 as follows.

# dnf remove -y kernel-ml
Dependencies resolved.
================================================================================
 Package              Arch      Version                 Repository         Size
================================================================================
Removing:
 kernel-ml            x86_64    5.7.7-1.el8.elrepo      @elrepo-kernel      0
Removing unused dependencies:
 kernel-ml-core       x86_64    5.7.7-1.el8.elrepo      @elrepo-kernel     64 M
 kernel-ml-modules    x86_64    5.7.7-1.el8.elrepo      @elrepo-kernel     23 M

Transaction Summary
================================================================================
Remove  3 Packages

Freed space: 87 M
Running transaction check
Transaction check succeeded.
Running transaction test
Transaction test succeeded.
Running transaction
  Preparing        :                                                        1/1
  Erasing          : kernel-ml-5.7.7-1.el8.elrepo.x86_64                    1/3
  Erasing          : kernel-ml-modules-5.7.7-1.el8.elrepo.x86_64            2/3
  Running scriptlet: kernel-ml-modules-5.7.7-1.el8.elrepo.x86_64            2/3
  Running scriptlet: kernel-ml-core-5.7.7-1.el8.elrepo.x86_64               3/3
  Erasing          : kernel-ml-core-5.7.7-1.el8.elrepo.x86_64               3/3
  Running scriptlet: kernel-ml-core-5.7.7-1.el8.elrepo.x86_64               3/3
  Verifying        : kernel-ml-5.7.7-1.el8.elrepo.x86_64                    1/3
  Verifying        : kernel-ml-core-5.7.7-1.el8.elrepo.x86_64               2/3
  Verifying        : kernel-ml-modules-5.7.7-1.el8.elrepo.x86_64            3/3

Removed:
  kernel-ml-5.7.7-1.el8.elrepo.x86_64
  kernel-ml-core-5.7.7-1.el8.elrepo.x86_64
  kernel-ml-modules-5.7.7-1.el8.elrepo.x86_64

Complete!

Restart the CentOS 8 machine again.

# systemctl reboot

You can see that the Linux Kernel 5.7 has been removed from the GRUB boot menu. Linux Kernel 5.7 has been uninstalled now.

Conclusion – Upgrade Linux Kernel

We have successfully demonstrate how to upgrade Linux Kernel in CentOS 8. There is a good book for those who want to explore Linux operating system in detail. The book title is How Linux Works, 2nd Edition: What Every Superuser Should Know Second Edition (PAID LINK) and it is written by Brian Ward.

2 thoughts on “How to Upgrade Linux Kernel in CentOS 8”

Anonymous
November 14, 2022 at 4:25 pm
Is it ok to apply the above procedure to upgrade the kernel from Cent OS 7 to Cent OS 8?
Log in to Reply
Ahmer M
November 14, 2022 at 4:27 pm
No. But you can apply following procedure to upgrade CentOS 7 to CentOS 8.
https://www.centlinux.com/2020/01/how-to-upgrade-centos-7-to-8-server.html
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