You’re making a good choice to upgrade. There are multiple critical security vulnerabilities in your current Jenkins version. You should also upgrade your operating system, since Red Hat Enterprise Linux 8.10 is the currently released version of Red Hat Enterprise Linux 8.
That’s a very large change in Jenkins versions. The Jenkins project recommends that users upgrade LTS versions every month. You’ve not upgraded in 32 months. You should plan to spend time evaluating and testing the upgrade in a copy of your environment before you attempt it on the production installation. You’re paying 32 months of upgrade debt.
Here are some of the answers that have been previously given. Refer to them for more details
The Jenkins LTS upgrade guides describe the changes from your current version to the most recent Jenkins LTS. Read the upgrade guides to identify areas that may be important to your installation.
Some of the key changes between those two versions include:
- Uses Java 17 or Java 21 instead of Java 8
- Fixes for critical security vulnerabilities
- Includes multiple user interface improvements
- Removes multiple outdated components
The Jenkins LTS changelog describes the details of each of the releases between your current release and the most recent release. Read the changelogs for each of the intervening releases and identify areas that may be important to your organization.
@mwp565733 shared an upgrade experience in a Jenkins blog post. Read the blog post:
Yes, you’ll need to install the most recent version of the plugins you currently have installed. This is also a time to remove deprecated plugins and to remove plugins with known security vulnerabilities.
The Jenkins plugins site now includes a plugin health score for each plugin. This is a good time to evaluate if there are plugins that should be removed because they are not being maintained or because they are no longer being used.
If multiple product teams are using the system, then I assume they care very much that the upgrade runs smoothly with very little downtime. If so, then follow the recommendations in the mentioned posts by creating a backup of the current installation and performing the upgrade on that backup. Confirm the upgrade works on the backup in all the cases that are important to your organization.