Seamlessly Migrating from CentOS to RHEL: A Step-by-Step Practical Guide

Forget reinventing the wheel—here's how to repurpose your existing CentOS infrastructure efficiently as you migrate to RHEL, avoiding costly downtime and hidden pitfalls.

With CentOS shifting focus away from traditional long-term support releases, many businesses face urgent decisions to keep their Linux environments stable and supported. Migration may sound daunting, but transitioning from CentOS to Red Hat Enterprise Linux (RHEL) can be a straightforward process when planned carefully.

This guide walks you through a practical, hands-on approach to migrating your CentOS systems to RHEL, ensuring you preserve uptime, maintain configurations, and avoid unexpected surprises.

Why Migrate from CentOS to RHEL?

CentOS users trusted the platform for its binary compatibility with RHEL without licensing costs. However, the recent shift of CentOS Stream as a rolling-release model means traditional CentOS versions won’t get the usual maintenance and updates anymore.

RHEL offers:

• Certified and stable enterprise support
• Security patches and compliance updates
• Access to Red Hat’s extensive knowledge base and ecosystem
• Predictable lifecycle and maintenance schedules

Transitioning means preserving your workflows while gaining peace of mind over stability and compliance.

Prerequisites Before Starting the Migration

1. Backup Everything. Start by backing up all critical data, configurations, and databases. Use tools like rsync, tar, or enterprise backup solutions.
2. Document Your Environment. Know what services run on each machine:
   • Installed packages (rpm -qa)
   • Custom configurations (/etc/ contents)
   • Network setup
3. Check Subscription Requirements. Prepare for RHEL subscriptions:
   • Decide between Red Hat Enterprise Linux Server or other variants.
   • Purchase or apply for evaluation subscriptions via Red Hat Customer Portal.
4. Verify System Compatibility. Make sure your hardware meets Red Hat’s supported platforms.
5. Test in Non-Production Environments First. Avoid surprises by testing migration steps on staging servers.

Step 1: Prepare Your CentOS System

Before migrating, ensure your system is fully updated:

sudo yum clean all
sudo yum update -y

Check the current OS version:

cat /etc/redhat-release

Example output:

CentOS Linux release 7.9.2009 (Core)

You must be running CentOS 7.x since migration procedures vary.

Step 2: Remove Conflicting Packages

Remove any packages that might conflict with RHEL repos:

sudo yum remove centos-release -y

You can also remove some legacy packages specific to CentOS if needed.

Step 3: Register Your System with Red Hat Subscription Manager

1. Install subscription-manager if missing:

sudo yum install subscription-manager -y

1. Register your system:

sudo subscription-manager register --username=YOUR_RH_USERNAME --password=YOUR_RH_PASSWORD

If using an activation key instead:

sudo subscription-manager register --activationkey=YOUR_ACTIVATION_KEY --org=YOUR_ORG_ID

1. Attach appropriate subscriptions:

sudo subscription-manager attach --auto

1. Enable required repositories:

For example, enable base repositories:

sudo subscription-manager repos --enable=rhel-7-server-rpms
sudo subscription-manager repos --enable=rhel-7-server-extras-rpms
sudo subscription-manager repos --enable=rhel-7-server-optional-rpms

Step 4: Replace CentOS Repositories with RHEL Repositories

Once registered, remove any .repo files referencing CentOS repositories located under /etc/yum.repos.d/.

Alternatively, back them up first:

sudo mkdir /etc/yum.repos.d/backup/
sudo mv /etc/yum.repos.d/*.repo /etc/yum.repos.d/backup/

Then ensure only the RHEL repo files managed by subscription-manager exist.

Step 5: Clean Yum Cache and Update System Packages

Clean cache to avoid conflicts:

sudo yum clean all
sudo yum repolist

Update the system so all packages come from RHEL repos:

sudo yum update -y

This may upgrade critical core libraries like glibc, kernel, etc., aligning your OS fully with RHEL versions.

After update completes, reboot:

sudo reboot

Upon reboot, confirm release info:

cat /etc/redhat-release

# Expected output example:
# Red Hat Enterprise Linux Server release 7.9 (Maipo)

Step 6: Verify Critical Services & Configurations Post-Migration

1. Check that key services like httpd, mysqld, or custom applications are still running smoothly.
2. Review logs (/var/log/messages, /var/log/syslog) for errors.
3. Confirm network settings remain intact.
4. Validate installed package versions as needed.

If any package is missing that was present previously, re-install from appropriate RHEL repos.

Optional: Use Third-party Tools for Automated Migration (CentOS 7 Only)

Red Hat provides a tool called convert2rhel designed for automating this migration on CentOS 7.x systems.

How to use convert2rhel?

1. Enable required repos as shown in previous steps.
2. Install convert2rhel tool:

sudo yum install convert2rhel -y 

1. Run conversion command with debugging logs saved if desired:

sudo convert2rhel --username=YOUR_RH_USERNAME --password=YOUR_RH_PASSWORD --auto-reboot --log=/root/convert2rhel.log 

This utility handles repository swaps and package transitions automatically but always test first in a staging environment!

For details see official doc: https://access.redhat.com/articles/6754371

Final Tips to Ensure a Smooth Migration

• Plan Maintenance Windows: Perform migrations during low usage times.
• Monitor Systems Closely: Use monitoring tools like Nagios or Prometheus immediately post-migration.
• Keep Backup Plans Ready: In case rollback is needed.
• Leverage Red Hat Support: If you experience issues after migration.
• Automate Where Possible: Use Ansible playbooks to standardize these procedures across fleets of servers.

Conclusion

Migrating from CentOS to RHEL doesn’t require tearing down your existing infrastructure or rebuilding from scratch — in fact, it’s about smartly repurposing what you already have while gaining long-term support and stability guarantees from Red Hat.

With careful preparation, backup discipline, and following this step-by-step guide, technical leaders can navigate this transition confidently — maintaining uptime and business continuity without painful disruption.

If you’ve already migrated or are planning yours soon – share your experiences or questions below!

Happy migrating! 🚀