Upgrade the Clients
Clients use the versioning system of their underlying operating system. For clients using SUSE operating systems, you can perform upgrades within the Uyuni Web UI.
To upgrade clients running SLE 12 to SLE 15, the upgrade is automated, but you will need to do some preparation steps before you begin.
For supported SUSE Linux Enterprise 15 upgrade paths, see https://documentation.suse.com/sles/15-SP1/html/SLES-all/cha-upgrade-paths.html