The Kernel is the brain for an operating system. It’s like the core element of every OS. Speaking of Linux, the Linux kernel – created by Linus Torvalds – is a monolithic, Unix-like kernel. Some popular OSs that use the Linux kernel are Ubuntu, CentOS, and Debian.
In this tutorial, I will show you how to upgrade CentOS 7 kernel to the latest version, and we will be using the kernel from ELRepo repository. CentOS 7 is using 3.10 as the default kernel version. And in this guide, we will install the latest stable version 5.2.0.
How to Upgrade Kernel on CentOS 7
What is ELRepo?
ELRepo is a community-based repository for Enterprise Linux and offers support for RedHat Enterprise (RHEL) and other distribution based on it (CentOS, Scientific, Fedora etc).
ELRepo is focused on the packages related to hardware, including filesystem drivers, graphic drivers, network drivers, sound card drivers, webcam, and others.
Update and upgrade CentOS 7
The first thing we must do before upgrading the kernel is to upgrade all packages to the latest version. Update the repository and all packages to latest versions with the yum command below.
yum -y update
Now install the following package to make installation and updating process fast.
yum -y install yum-plugin-fastestmirror
Checking kernel version
In this tutorial, we will use CentOS 7.6 with default kernel 3.10. Check your CentOS version with the following commands.
cat /etc/centos-release
You will get the system info as shown below.
For checking the kernel version, you can use the uname command.
uname -msr
The output will show your machine’s Linux kernel version as well system architecture.
Add ELRepo Repository
Before installing new kernel version, we need to add new repository ELRepo repository. That’s because we want to use the kernel version from the ELRepo community.
Add ELRepo gpg key to the system.
rpm --import https://www.elrepo.org/RPM-GPG-KEY-elrepo.org
- To install ELRepo for RHEL-7, SL-7 or CentOS-7:
yum install https://www.elrepo.org/elrepo-release-7.0-3.el7.elrepo.noarch.rpm
- To install ELRepo for RHEL-6, SL-6 or CentOS-6:
yum install https://www.elrepo.org/elrepo-release-6-8.el6.elrepo.noarch.rpm
Next, check all repositories enabled on the system, and make sure ELRepo is on the list.
yum repolist
ELRepo repository has been added to the CentOS 7 server.
Install new Kernel version
In this step, we will install latest kernel version (5.2.0 – the Latest stable version on kernel.org) from the ELRepo repository.
Use the following yum command for this.
yum --enablerepo=elrepo-kernel install kernel-ml
–enablerepo is an option to enable specific repository on CentOS system. By default, ‘elrepo’ repository is enabled, but for our case, we needed ‘elrepo-kernel’.
Configure Grub2
At last step, we’ve already installed a new kernel 5.2.0 to the system. Now we will show you how to make it the default kernel version that will load when the system is starting.
Check all available kernel versions with the awk command below.
awk -F\' '$1=="menuentry " {print i++ " : " $2}' /etc/grub2.cfg
In the output, you’ll see that we’ve four kernel versions.
We want to use kernel 5.2.0 as our default, so you can use the following command to make this happen.
grub2-set-default 0
0 – it’s from the awk command on the top. Kernel 5.2.0 = 0, and Kernel 3.10 = 1. When you want to revert back to the old kernel, you can change the value of the grub2-set-default command to 1.
Next, generate the grub2 config with ‘gurb2-mkconfig’ command, and then reboot the server.
grub2-mkconfig -o /boot/grub2/grub.cfg
reboot
Please login to the server again, and check currently used kernel.
uname -msr
Remove old kernel (optional)
This is an optional step that we think you need in order to get more free space. In this step, we will show you how to remove an old kernel from your CentOS 7 system. This can be done when you have several kernel versions installed on the server.
For this purpose, we need to install the yum-utils utility from the repository.
yum install yum-utils
Now clean your old kernel with the following command.
package-cleanup --oldkernels
f you get the result below.
That means you’ve only 2 or 3 versions of kernel installed. If you have more than 3 version installed, the command will automatically remove old kernel from your system.
CentOS 7 Kernel has been updated to the latest stable using ELRepo kernel version.
