Snapper

Snapper was written by Arvin Schnell at SUSE around 2011 and is what makes openSUSE unusually forgiving. On a Btrfs filesystem the tool automatically takes a snapshot before and after every zypper transaction and every YaST change, using the filesystem's copy-on-write subvolumes — nearly free in both time and space.

If an update goes wrong, you can pick an earlier, read-only snapshot straight from the GRUB menu, boot into it and roll the system back to before the breakage. Snapper also handles LVM thin volumes and can diff what changed between two snapshots. It is transactional undo at the operating-system level, something most other distributions long lacked an equally smooth equivalent for.