I need to upgrade a Leap 15.3 system that has become difficult to maintain due to the age of the OS. The reason why I have not completed upgrades before is, that I never succeeded to get Leap 15.4 to boot on any of my computers after the upgrade and always had to fall back. I had the same issues with Tumbleweed until about 2 months ago. There must have been a very deep bug in the installer/kernel that is now fixed. I know that I am not supposed to skip versions when upgrading, but I literally cannot go version by version. Has anybody successfully made a big upgrade step? I would like to avoid a clean and fresh update as many of my tools and configs have grown over years and every time I do a fresh install I have to restart chasing down bugs and settings until I have a well-running system.
How many computers did you have that failed to boot 15.4? Are they all the same? What CPUs and GPUs are in them? Have you attempted to boot the 15.6 installer, just to see what happens? It’s easily aborted.
I haven’t done a 3 version direct skip in over a year, but I had no problem with it when I did. Last skip I did was from 15.4. to 15.6. I can’t recall any significant problem in any case of zypper dup between Leap versions. TW’s continual duping has made the dup process well developed, highly competent. Keys to maximum success include kernel lockdown, existing initrd lockdown, and disabling or removing all non-default repos. I “remove” repos by changing the filename of each non-standard repo’s file in /etc/zypp/repos.d/ to not end with “o”. Non-default repos that continue to exist at the current version can be re-enabled after completion success using only standard repos. IME, successive Leap versions can continue to boot on prior version kernels. Locking of initrds, or readily and conveniently available backups of them, ensure they won’t be regenerated during the upgrade process into a possibly unusable state. I perform the task at every new kernel installation using chattr +i initrd<version>. Zypper lockdown of kernels means the upgrade process won’t remove them, providing extra insurance bootability is retained as the rest of the system is upgraded. New kernels are readily installed as a standalone process after dup is finished if the lock is kept enabled during dup. These things work pretty much the same as during routine duping in TW.
It doesn’t hurt to remove stale software prior to upgrade, and could help: sudo zypper pa --unneeded will list packages the system finds unnecessary. sudo zypper rm <package name(s)> will remove as many packages as you include on the rm command line. Wildcards are usable.
Upgrades do not change any personal settings, but may change things you have changed in /etc/.