Upgrade CentOS 7 to AlmaLinux 8+ with Leapp

This guide walks through upgrading CentOS 7 (EOL) to AlmaLinux 8 using the official Elevate/Leapp migration framework.

⚠️ Important Notes Before You Begin

• CentOS 7 reached End of Life in June 2024.
• Upgrade is in-place, but not risk-free.
• Backups are mandatory.
• Requires:
  • 2GB+ RAM (4GB recommended)
  • 5GB+ free disk space in /
  • Direct root or sudo access
  • No active control panels (cPanel is NOT supported for Leapp upgrades)

How to Upgrade CentOS 7 to AlmaLinux 8+ Using Leapp

To upgrade CentOS 7 to AlmaLinux 8+ using Leapp, follow the steps below:

1. Pre-Upgrade Preparation

   1. Update CentOS 7 fully

      yum clean all
      yum update -y
      reboot
      

      Verify version:

      cat /etc/centos-release
      

      Should show:

      CentOS Linux release 7.9.2009 (Core)
      

   2. Remove Unsupported Packages

      List 3rd-party packages:

      rpm -qa | grep -E "elrepo|epel|ius|remi"
      

      Disable or remove non-essential repos.

      Check for held packages:

      yum versionlock list
      

   3. Check Disk Space

      df -h
      

      Ensure / has at least 5GB free.

2. Install Elevate (Leapp Framework)

   The Elevate project allows migration between Enterprise Linux versions.

   Install repository:

   yum install -y https://repo.almalinux.org/elevate/elevate-release-latest-el7.noarch.rpm
   

   Install Leapp data for AlmaLinux 8:

   yum install -y leapp-upgrade leapp-data-almalinux
   

3. Run Pre-Upgrade Check

   This step analyzes your system and generates a report.

   leapp preupgrade
   

   Reports are generated at:

   /var/log/leapp/leapp-report.txt
   

   AND

   /var/log/leapp/leapp-report.json
   

   Resolve Inhibitors

   Common blockers:

   • Firewalld configuration issues
   • Old kernel modules
   • Deprecated authentication methods
   • Removed packages

   Example: remove deprecated PAM module:

   yum remove -y pam_pkcs11
   

   After fixing issues:

   leapp preupgrade
   

   Repeat until no inhibitors remain.

4. Start the Upgrade

   When clean:

   leapp upgrade
   

   This prepares the system and installs the new AlmaLinux 8 packages.

5. Reboot Into Upgrade Environment

   After completion:

   reboot
   

   GRUB will automatically boot into:

   Leapp Upgrade Initramfs
   

   Upgrade process runs automatically.

   This may take 10–30 minutes depending on system size.

6. Verify AlmaLinux 8

   After reboot:

   cat /etc/os-release
   

   You should see:

   AlmaLinux 8.x
   

   Verify kernel:

   uname -r
   

   Should show:

   4.18.x.el8
   

7. Post-Upgrade Cleanup

   Remove old CentOS 7 packages:

   rpm -qa | grep el7
   

   Remove leftovers:

   dnf remove -y $(rpm -qa | grep el7)
   

   Remove old kernels:

   dnf remove -y kernel-3.10.*
   

   Clean up:

   dnf autoremove -y
   dnf clean all
   

8. Re-enable Repositories

   Re-enable EPEL (EL8 version):

   dnf install -y epel-release
   

   Reinstall any required services.

9. SELinux Relabel (Recommended)

   touch /.autorelabel
   reboot
   

10. Validate Critical Services

    Check:

    systemctl status
    

    Verify:

    • Nginx / Apache
    • MariaDB
    • SSH
    • Firewall
    • Custom services (FreeIPA, Keycloak, FRR, etc.)

⚠️ Known Caveats

• Direct upgrade to AlmaLinux 9 is NOT supported from CentOS 7.
• Must go:
  • CentOS 7 → AlmaLinux 8
  • AlmaLinux 8 → AlmaLinux 9 (separate process)
• Control panels like cPanel are not supported for in-place upgrades.

Recommended Production Strategy

Safer method for production nodes:

1. Deploy fresh AlmaLinux 8 VPS
2. Migrate services manually
3. Test
4. Switch DNS / IP
5. Decommission CentOS 7

In-place upgrades are acceptable for:

• Internal nodes
• Monitoring servers
• Non-cPanel standalone services

Optional: Upgrade AlmaLinux 8 → AlmaLinux 9

After reaching AlmaLinux 8:

dnf install -y leapp-upgrade leapp-data-almalinux
leapp preupgrade
leapp upgrade
reboot

Final Checklist

• ✅ Full backup taken
• ✅ Preupgrade report clean
• ✅ No inhibitors
• ✅ Services validated
• ✅ SELinux relabeled
• ✅ Old kernels removed

Conclusion

You now know how to upgrade CentOS 7 to AlmaLinux 8+ with Leapp.

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