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Upgrading CentOS 7 to Rocky Linux 8 ​

Introduction ​

Welcome to our Storage How-to Guides—a curated set of clear, step-by-step tutorials designed to simplify storage and system management tasks in Linux environments. This guide walks you through upgrading a CentOS 7 system to Rocky Linux 8 using the leapp tool. Whether you’re modernizing your OS or preparing for new software requirements, this tutorial provides practical steps to ensure a smooth transition. No deep expertise is needed—just follow along for reliable results.

Environment ​

  • Operating System: CentOS 7.
  • Target OS: Rocky Linux 8.
  • Tools: leapp, elevate-release, leapp-data-rocky.

Prerequisites ​

  • Backup: Back up all critical data and configurations to prevent data loss.
  • System Requirements: Ensure the system meets Rocky Linux 8 requirements (e.g., 2 GB RAM, 20 GB disk space).
  • Internet Access: Required for downloading packages and repositories.
  • Root Access: Run commands as root or with sudo.

Steps ​

Step 1 - Update CentOS 7 Packages ​

Before upgrading, ensure all CentOS 7 packages are up to date:

bash
sudo yum upgrade -y
  • -y: Automatically confirms package updates.

Step 2 - Reboot the System ​

Reboot to apply any kernel or system updates:

bash
sudo reboot

Step 3 - Update Packages Again ​

After rebooting, run another update to catch any remaining packages:

bash
sudo yum update -y

Step 4 - Reboot Again ​

Perform a second reboot to ensure the system is fully updated:

bash
sudo reboot

Step 5 - Verify OS and Kernel Version ​

Check the current CentOS version and kernel:

bash
cat /etc/centos-release
uname -r

Example output:

CentOS Linux release 7.9.2009 (Core)
3.10.0-1160.el7.x86_64
  • This confirms you’re running CentOS 7 with the latest updates.

Step 6 - Install the Elevate Repository ​

Install the elevate-release package to enable the repository for the upgrade:

bash
sudo yum install -y http://repo.almalinux.org/elevate/elevate-release-latest-el$(rpm --eval %rhel).noarch.rpm
  • This sets up the repository for Enterprise Linux 7 (EL7).

Step 7 - Install Leapp and Rocky Data Packages ​

Install the leapp-upgrade tool and the leapp-data-rocky package for Rocky Linux migration:

bash
sudo yum install -y leapp-upgrade leapp-data-rocky

Step 8 - Run the First Pre-Upgrade Check ​

Perform an initial pre-upgrade check to assess the system’s readiness:

bash
sudo leapp preupgrade
  • This analyzes packages, repositories, and system configuration for compatibility with Rocky Linux 8.
  • Check the generated report for issues:
    • /var/log/leapp/leapp-report.txt: Lists potential problems and remediation steps.
    • /var/log/leapp/answerfile: Records pre-upgrade prompts and responses.

Step 9 - Configure SSH and Leapp Settings ​

To address common issues during the upgrade:

  1. Enable root login in SSH (required by leapp):
    bash
    echo "PermitRootLogin yes" | sudo tee -a /etc/ssh/sshd_config
sudo systemctl restart sshd
  2. Answer specific leapp checks to bypass known issues:
    bash
    leapp answer --section authselect_check.confirm=True
leapp answer --section remove_pam_pkcs11_module_check.confirm=True

Step 10 - Run the Second Pre-Upgrade Check ​

Repeat the pre-upgrade check to ensure all issues are resolved:

bash
sudo leapp preupgrade
  • Review /var/log/leapp/leapp-report.txt again for any remaining issues.
  • Follow remediation steps if errors are reported (e.g., removing conflicting packages).

Note: Thoroughly inspect /var/log/leapp/leapp-report.txt and /var/log/leapp/answerfile to understand and resolve any issues before proceeding.

Step 11 - Perform the Upgrade ​

Initiate the OS upgrade to Rocky Linux 8:

bash
sudo leapp upgrade
  • This prepares the system for the upgrade, creating a special boot entry.

Step 12 - Reboot to Complete the Upgrade ​

Reboot the system to start the upgrade process:

bash
sudo reboot
  • During reboot, the system will use a temporary kernel to perform the upgrade from CentOS 7 to Rocky Linux 8.
  • The VM may be temporarily inaccessible during this process as the upgrade modifies core system components.

Step 13 - Verify the Upgrade ​

After the reboot, confirm the new OS version:

bash
cat /etc/rocky-release
uname -r

Example output:

Rocky Linux release 8.10 (Green Obsidian)
4.18.0-553.el8.x86_64
  • This confirms the system is now running Rocky Linux 8 with an updated kernel.

Notes ​

  • Check Logs: If issues arise, review /var/log/leapp/leapp-report.txt for detailed remediation steps.
  • Firewall and SELinux: Adjust settings post-upgrade if needed for your environment.
  • Post-Upgrade: Run sudo dnf update -y to ensure all Rocky Linux packages are current.
  • Backup: Always have a full backup before upgrading, as the process is complex and risks data loss.
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