How to convert from CentOS 8 to AlmaLinux 8

Introduction

CentOS 8 and other EL8 servers can be converted to use CloudLinux's fork of RHEL, AlmaLinux. CentOS 8 is currently slated for End-of-Life status on December 31, 2021.

Procedure

Note: CentOS 8 repositories have been vaulted by Redhat. The repository URL will need to be updated to connect to the package update system. To do this, edit the repo config file:

/etc/yum.repos.d/CentOS-Linux-BaseOS.repo 

Modify the following line from mirrorlist.centos.org to vault.centos.org and save the file.

mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=BaseOS&infra=$infra

Ensure the server has the latest packages available:

# dnf clean all
# dnf -y update

We also suggest rebooting the server to ensure that the latest kernel is loaded. This step can be skipped if the loaded kernel is verified to be the latest one.

# reboot

Download the almalinux-deploy script:

# curl -O https://raw.githubusercontent.com/AlmaLinux/almalinux-deploy/master/almalinux-deploy.sh

Run the script:

# bash almalinux-deploy.sh

Wait for the process to complete, check for errors:

Complete!
Run dnf distro-sync -y OK
Restoring of alternatives is done OK
Generating grub configuration file ...
done
All Secure Boot related packages which were released by not AlmaLinux are reinstalled OK

Migration to AlmaLinux is completed

Verify that the installation is complete:

Check release file

# cat /etc/redhat-release 
AlmaLinux release 8.4 (Electric Cheetah)

Check that the system boots AlmaLinux kernel by default

# grubby --info DEFAULT | grep AlmaLinux
title="AlmaLinux (4.18.0-305.el8.x86_64) 8.4"

More information about the conversion script is available in the AlmaLinux GitHub here:

almalinux-deploy