In all fairness... How would that work? Not even just on Debian; in the general case, I don't see how to avoid that other than full filesystem snapshots or backups of some sort. Even on, say, a NixOS system where rolling back all the software and config (basically, /, /usr, and /etc) to exactly its old config is as easy as rebooting and picking the old generation, databases will still have migrated their on-disk format.
Indeed. Snapshots. And they are a breeze on operating systems where ZFS for everything is available. It's not like the Windows feature of the same name, which I suspect is in part what makes people wary of the idea. That works rather differently. A ZFS snapshot completes in seconds.
