Best Practices for Upgrading RHEL

In order to remain current and keep your environment fully compatible with all the other components there comes a point where you will need to upgrade the OS on your system. In this case I’ll go oversome best practices for upgrading RHEL with an example of an upgrade going from RHEL 8 to RHEL 9

Prerequisites

There are various ways of upgrading the OS on your system. One way is to perform an in-place upgrade, and another is to do a complete rebuild from scratch after a fresh install of the newer OS. In this article we will discuss how to perform an in-place upgrade using leapp. Leapp utility is a tool that allows you to seamlessly perform an in-place upgrade of RHEL. In-place upgrades done using leapp are supported by Red Hat therefore if you have any issues during or after the upgrade Red Hat will provide assistance.

First let’s verify the version of RHEL that is currently installed

cat /etc/redhat-release

Enable the necessary repositories, in this case

subscription-manager repos --enable rhel-7-server-rpms --enable rhel-7-server-extras-rpms

Install Leapp

yum -y install leapp-upgrade

Verify leapp is installed. Version 15 is the latest at the time of writing this.

leapp --version

PreUpgrade Check

Let’s do a quick flight check. First, we need to make sure the system meets the requirements needed to be able to upgrade it. We do this by using the leapp utility by running

leapp --preupgrade --target 8.6

The precheck tool in leap does three things; assesses upgradability, collects data about the system and generates a pre-upgrade report.

If there is anything that inhibits the upgrade from being successful, the leapp utility will report it. If all checks pass you should see something like this.

Now we can stage the upgrade

leapp --upgrade --target 8.6

This will stage the upgrade, scheduling it for the next reboot of the system.

Reboot the system

reboot

Once it is back on, we can verify that the OS has been upgraded

cat /etc/release