Upgrading the CentOS kernel to the latest version

This guide explains how to install a newer kernel on CentOS 7 using the ELRepo repository.

If you are still running CentOS 7, consider migrating to AlmaLinux 8 using the Elevate tool.

Choose a kernel variant

ELRepo provides two kernel variants:

kernel-ml installs the mainline kernel, which follows the latest upstream Linux releases. It receives new features and improvements quickly but may introduce compatibility issues with drivers or production workloads.

kernel-lt installs a long-term support kernel, which prioritizes stability over new features. This is the recommended option for production servers.

Update the system and install ELRepo

Update the installed packages:

yum -y update

Import the ELRepo GPG key and install the repository:

rpm --import https://www.elrepo.org/RPM-GPG-KEY-elrepo.org
rpm -Uvh https://www.elrepo.org/elrepo-release-7.el7.elrepo.noarch.rpm

Verify that the repository was added successfully:

yum repolist | grep elrepo

Clear the yum cache:

yum clean all

Install the new kernel

To install the long-term support kernel (recommended for production):

yum --enablerepo=elrepo-kernel install kernel-lt kernel-lt-headers 
kernel-lt-tools kernel-lt-tools-libs

To install the mainline kernel instead:

yum --enablerepo=elrepo-kernel install kernel-ml kernel-ml-headers 
kernel-ml-tools kernel-ml-tools-libs

Verify that the kernel packages were installed:

rpm -qa | grep '^kernel-'

Set the new kernel as default

List all installed kernels with their boot order:

grubby --info=ALL | grep -E 'title|kernel'

The newest kernel is usually assigned index 0, but verify the order before setting it as default. Set the default by index:

grubby --set-default=0

Or by the full kernel path for reliability:

grubby --set-default /boot/vmlinuz-<version>

Replace <version> with the actual version string from the grubby --info=ALL output.

Verify the default kernel:

grubby --default-kernel
grub2-editenv list

Reboot and verify

Reboot the server:

reboot

After the system comes back up, verify the running kernel version:

uname -r

Remove old kernels

Once the new kernel is confirmed working, remove older versions to free disk space. The --count=2 option keeps the two most recent kernels as a fallback:

yum install -y yum-utils
package-cleanup --oldkernels --count=2

Emergency rollback

If the new kernel does not boot, select the previous kernel from the GRUB menu during startup. After booting into the old kernel, restore it as default:

grubby --set-default=1
reboot

Replace 1 with the index of the working kernel from grubby --info=ALL.