tmpfiles.d: change all subvolumes to use quota Let's make sure the subvolumes we create fit into a sensible definition of a quota tree.

tmpfiles: automatically remove old machine snapshots at boot Remove old temporary snapshots, but only at boot. Ideally we'd have "self-destroying" btrfs snapshots that go away if the last last reference to it does. To mimic a scheme like this at least remove the old snapshots on fresh boots, where we know they cannot be referenced anymore. Note that we actually remove all temporary files in /var/lib/machines/ at boot, which should be safe since the directory has defined semantics. In the root directory (where systemd-nspawn --ephemeral places snapshots) we are more strict, to avoid removing unrelated temporary files. This also splits out nspawn/container related tmpfiles bits into a new tmpfiles snippet to systemd-nspawn.conf