Lost all clients after server update (with "apt upgrade")

After upgrading the server to the latest version, all clients disappeared from the server admin page.

The following message appears:

This server has discovered clients which are currently not configured to use this server. See here for details on how this can happen.

Everything else is empty too: backups, logs, statistics, settings…

Looks like some config files are not found.

Any way to restore them without losing backups?

Should only happen if you run a “purge” install with apt. You can restore the UrBackup database from backup if you have one. See 8.1.12 Automatically backup UrBackup database. Copy those files back to /var/urbackup.

Wow, you saved my day!
Thank you so much :kissing_heart:

BTW: Is it recommended to rebuild the database after restoring /var/urbackup?
Because theoretically the database could mismatch the actual files, no?