NC 19->20 upgrade: error found (503 Service Unavailable)

Finally my 3rd NC-server got offered 19->20 upgrade, so I attempted it as usuall. All apps had updates too, so I started web-updater. To my surprise, it ended with not_much_saying message “error detected” and when I returned to front-page, all I see is “503 Service unavailable”. Web-server is definitely running, but NC apparently not.

What should I do now? I do not know what got screwed during update (there was no other message). How is it possible at all, that stable-to-stable upgrade (after NC20x has been released so long time ago) ends with hard-bricked NC-server? I believe backup of some sort has been created during web-updater running, but I do not know how to restore it without web-interface…

Not so funny thing is, two other NC-servers I take care of got updated to 20.x a few weeks ago without any problem…

The usual recommendation to narrow down the root cause of the problem is:

  • check the content of the Nextcloud server log file for any related messages.
  • check the content of the web server log file for any related messages.
  • use the search function of the forum to find possible solutions for your problem.

Of course I did it. I checked updater.log, nextcloud.log and access/error.log bud did not find any clue. I could re-install NC from scratch, but that’s not solution. It could happen agan…