Look very carefully. 99% of what happens in the upgrade happens under the title "Upgrading by install kernel". Literally, you just boot bsd.rd, smash return a few times, reboot, and you're done.
After that you're into the "final steps" territory. Which means running sysmerge to merge changes in config files. It's not called openbsd-update, but freebsd-update requires you to do the same thing.
Typically the only "manual" part is removing some files and users no longer needed by the new release. Now 5.6 has lots of these files, but it's not really representative -- most releases have a much shorter list of file removals. In any case, there are very good reasons for the system not to do this automatically for you. And, in any case, if you know you haven't done anything unusual so as to depend on these files, you can get away with copy pasting these instructions.
At this point you update your packages with pkg_add -u. Just as you would have to on freebsd...
> Literally, you just boot bsd.rd, smash return a few times, reboot, and you're done.
No, you're not done. You've merely dropped a new OS onto an old OS. It's now an exercise to the user to figure out how to remove all the files leftover from the old OpenBSD release. Leaving older libraries around is dangerous as programs could link against them long after they've been retired potentially exposing you to vulnerabilities that you didn't think you were exposed to anymore.
The correct way to upgrade OpenBSD is to do a clean install. Hopefully someday they'll support a tool like "freebsd-update" which handles all of this for the user.
What exercise? The upgrade guide tells you exactly how to remove what leftover files. You could copy and paste the rm commands mindlessly, not that I would suggest doing anything mindlessly.
If you're using the official OpenBSD packages, they would be linked to the correct libraries for that release, so there's no need to worry about linking to the wrong libraries. If you're compiling your own packages, you should be aware of anything you've done with any libraries that would require you pay any particular attention necessary to files being removed. Otherwise, it's not anything you would need be concerned about as a user.
Where do you get the idea that a clean install is the correct way to upgrade? Considering how conservative OpenBSD is, it would not provide an upgrade process if it wasn't something that was very well supported.
Removing files is included for completeness (because people kept asking for it), but it's hardly necessary. Just glancing at the list reveals half the files are old man pages; there's little harm in retaining them. Even libraries aren't a problem; the linker won't use old versions.
If you're custom building any software you could end up making a mistake though. Not everything a user may want to use is in packages/ports. I end up building several things manually because they're not in ports.
> It's now an exercise to the user to figure out how to remove all the files leftover from the old OpenBSD release.
No it's not. The upgrade guides for each release literally tell you exactly which files should be cleaned up, which packages are now part of base, which parts of base are now packages, etc. OpenBSD has a good reputation for having complete and thorough documentation on every last detail of its operation, and system upgrades are no exception.
having lost data on every single automatic Ubuntu update, I'm happy back on Debian using one partition for data, another for etc, and another for system. every upgrade i just format the system one, move the etc and then move back the files i care on the new etc. done.
After that you're into the "final steps" territory. Which means running sysmerge to merge changes in config files. It's not called openbsd-update, but freebsd-update requires you to do the same thing.
Typically the only "manual" part is removing some files and users no longer needed by the new release. Now 5.6 has lots of these files, but it's not really representative -- most releases have a much shorter list of file removals. In any case, there are very good reasons for the system not to do this automatically for you. And, in any case, if you know you haven't done anything unusual so as to depend on these files, you can get away with copy pasting these instructions.
At this point you update your packages with pkg_add -u. Just as you would have to on freebsd...