This is impossible. Debian packages are stateful: They have maintainer scripts that can do stuff, they are inherently non-transactional by design. Even if you

This is impossible. Debian packages are stateful: They have maintainer scripts that can do stuff, they are inherently non-transactional by design. Even if you can rollback updates, a lot of the time that's no help - your user data format was upgraded, rendering your data useless (especially for web browsers, which you can't really downgrade). That said, it's trivial to use file system snapshots. Ubuntu has apt-btrfs-snapshot to do this automatically, but it was never provided in Debian AFAICT. But even with snapshots, you also need to snapshot user state, not just the installation, otherwise you end up with upgraded incompatible data again.