Migrating to CentOS Stream is generally straightforward using the official swap and distro-sync approach. The key is thorough preparation (backups, updates) and post-migration validation to ensure your applications continue functioning properly.

• If you run production workloads, always test upgrades in a staging environment first.
• Decide whether CentOS Stream 8 or 9 is best for your needs.
• Maintain a regular update schedule to stay on top of the rolling-release changes.

Why Migrate to CentOS Stream?

• Longer Support Window – while CentOS Linux 8 reached EOL (End of Life) on December 31, 2021, CentOS Stream 8 continues to receive updates. Moving to CentOS Stream is a supported path if you want to stay close to the RHEL ecosystem without paying for a RHEL subscription.

• Rolling-Release Model – centOS Stream provides a rolling-release distribution that sits between Fedora (upstream) and Red Hat Enterprise Linux (RHEL) (downstream). This means you get more frequent package updates and a preview of what will eventually land in future RHEL releases.

Preliminary Steps

• Make sure you’re actually running CentOS Linux (not already on CentOS Stream)

cat /etc/centos-release

If it says CentOS Linux release 8.x, you’re on CentOS Linux 8. If it says CentOS Stream release 8.x, you’re already on CentOS Stream 8.

• Perform a Full System Backup
  • If your system is running on a virtual machine or cloud, take a snapshot. For physical machines, use tools like rsync, tar, or disk imaging solutions to back up important data.
  • Once the backup is complete, check it to ensure everything is restorable by verifying the backup integrity.
• Update your current CentOS Linux 8 system to the latest packages:

sudo dnf update -y 
sudo dnf clean all 

• Reboot if any kernel or system-critical packages were updated:

Migration Steps

The official CentOS Swap Method is the simplest official method to migrate from CentOS Linux 8 to CentOS Stream 8. To install the CentOS Stream repository package, swap your CentOS Linux repos for CentOS Stream repos, and perform a distro-sync:

# 1. Install CentOS Stream repository
sudo dnf install centos-release-stream -y

# 2. Swap the existing CentOS Linux repositories with CentOS Stream repositories
sudo dnf swap centos-{linux,stream}-repos -y

# 3. Synchronize packages with the new repos
sudo dnf distro-sync -y

Post-Migration Tasks

After the dnf distro-sync completes, reboot:

sudo reboot

Once the system restarts:

cat /etc/centos-release

You should see something similar to CentOS Stream release 8

• Check for Additional Updates

sudo dnf update -y

This ensures you’re fully synchronized with the CentOS Stream repository.

• Review Custom Repositories or Third-Party Packages
  • If you use EPEL or other repositories, ensure they have CentOS Stream–compatible branches.
  • Some repositories or software may need adjusting if they only targeted CentOS Linux. The EPEL repositories generally work fine with CentOS Stream, but it’s always good practice to confirm.

• Security and SELinux
  • Confirm SELinux it’s enabled and set to your desired enforcing level.
  • Verify that your Firewalld / iptables configuration persists after migration.

• Application Validation
  • If you run services like Apache, NGINX, or database servers (MySQL, PostgreSQL, MariaDB), do a quick functional check.
  • Look for any package downgrades or version mismatches. Tools like rpmconf can help resolve configuration file conflicts.

Considering CentOS Stream 9

CentOS Stream 9 is based on RHEL 9 sources. If you need newer features or want a longer supported timeline, you could consider migrating directly to CentOS Stream 9.

However, there isn’t an official direct upgrade path from CentOS Stream 8 to Stream 9 (nor from CentOS Linux 8 to Stream 9). This typically involves a fresh installation or a more manual migration process.

If you’re comfortable with reinstallation or you have a robust configuration management system (like Ansible, Puppet, or Chef), migrating to Stream 9 might be worth considering, especially if you want to stay supported longer.

Troubleshooting & Best Practices

• DNF Cleanups if you run into package conflicts:

sudo dnf clean all
sudo dnf --refresh update

• Check Fallback Options by keeping your system backup or VM snapshot for a rollback if needed.
• Monitor Logs by checking /var/log/dnf.log for any migration-related issues.
• Keep an eye on the CentOS Stream release notes and community forums for known issues or updates.

Additional Resources:

• CentOS Stream Official Documentation
• EPEL Repositories
• RHEL to CentOS Stream FAQs