How to migrate a CentOS 8 to Rocky Linux 8.10

Migrating a CentOS 8 Docker Container to Rocky Linux 8.10

With the end of life for CentOS Linux 8 and its shift towards CentOS Stream, many users are opting to switch to stable alternatives like Rocky Linux. If you're running a CentOS 8 Docker container and want to migrate it to Rocky Linux 8.10, this guide will walk you through the process.

In this post, we'll go over how to perform an in-place migration of a CentOS 8 Docker container to Rocky Linux 8.10. This process involves replacing CentOS packages with their Rocky Linux equivalents while retaining your current container's configurations and data.

Why Migrate from CentOS to Rocky Linux?

Rocky Linux is a community-driven project designed to be 100% bug-for-bug compatible with Red Hat Enterprise Linux (RHEL). After the CentOS Project announced its focus shift towards CentOS Stream, Rocky Linux became a preferred choice for users looking for a stable, production-grade Linux distribution compatible with RHEL.

Prerequisites

Before we begin, make sure:

You have a running CentOS 8 Docker container.
You can run administrative commands (e.g., sudo) inside your container.
Your Docker setup is properly configured.

Steps to Migrate CentOS 8 Docker Container to Rocky Linux 8.10

1. Back Up Your Container

Before making any changes, it's highly recommended to create a backup of your Docker container. This way, if something goes wrong during the migration, you can restore your container to its previous state.

Run the following command on your host machine (outside the container):

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docker commit <container_id> backup-centos-container

Replace <container_id> with your actual container ID or container name.

This command saves the current state of your CentOS container as a new Docker image (backup-centos-container).

2. Update CentOS Packages (Optional)

It's a good practice to make sure that your CentOS system is fully up-to-date before starting the migration process. Inside the running container, execute:

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sudo yum update -y

This will update all existing packages to their latest versions.

3. Install the Rocky Linux Migration Script

The Rocky Linux community provides an official migration script called migrate2rocky, which automates the process of switching from CentOS to Rocky Linux.

To download and install the script inside the container, run:

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curl -O https://raw.githubusercontent.com/rocky-linux/rocky-tools/main/migrate2rocky/migrate2rocky.sh
chmod +x migrate2rocky.sh

4. Run the Migration Script

Once the script is downloaded and made executable, you can proceed with the migration by running the following command:

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sudo ./migrate2rocky.sh -r

The -r flag stands for "reboot," and it will automatically reboot the container at the end of the migration process. This script will replace CentOS packages with Rocky Linux packages.

5. Verify the Migration

After the script finishes running, verify that your system is now running Rocky Linux by checking the /etc/os-release file:

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cat /etc/os-release

You should see output indicating that the system is now Rocky Linux 8.10, similar to this:

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NAME="Rocky Linux"
VERSION="8.10 (Green Obsidian)"
ID="rocky"
...

6. Restart the Docker Container

If the container doesn't automatically reboot, you can manually restart it from the host machine:

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docker restart <container_id>

This ensures that all changes take effect after the migration.

7. Clean Up

Once the migration is complete, you might want to clean up old package metadata to free up space and avoid confusion in future package management operations:

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sudo dnf clean all

Conclusion

By following these steps, you should have successfully migrated your CentOS 8 Docker container to Rocky Linux 8.10. This process replaces CentOS packages with Rocky Linux packages while preserving your container's data and configurations. Rocky Linux offers long-term support and stability, making it a suitable replacement for users who relied on CentOS.

If you're looking to move away from CentOS and need a RHEL-compatible distribution, Rocky Linux is an excellent choice for your Docker-based workloads.

Key Commands Summary:

Back up your container : docker commit <container_id> backup-centos-container
Update CentOS packages : sudo yum update -y

Download migration script :

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curl -O https://raw.githubusercontent.com/rocky-linux/rocky-tools/main/migrate2rocky/migrate2rocky.sh
chmod +x migrate2rocky.sh

Run migration script : sudo ./migrate2rocky.sh -r
Verify migration : cat /etc/os-release
Restart container : docker restart <container_id>
Clean up package metadata : sudo dnf clean all