On 10/17/2016 06:53 PM, Andrei Borzenkov wrote: > I try to understand how to build a tree of snapshots (i.e. - which > subvolume was used to snapshot/clone other subvolume). What is the > correct way to determine it? In particular, "btrfs sub list -p" always > prints something for "parent snapshot", while btrfs sub list -q" only > prints parent_uuid for actual snapshots (i.e. for subvolumes I know are > snapshots). Are "parent" and "parent_uuid" related to each other? Of > not, what do they mean?
It's confusing because there are two different things, which both are called a parent. * parent is the subvolume another subvolume is placed in * parent_uuid is the uuid of a subvolume that this is a snapshot from So: -# btrfs sub create foo Create subvolume './foo' -# btrfs sub list -p -q . ID 3486 gen 3368 parent 5 top level 5 parent_uuid - path foo foo has parent 5, because I created it at the top of the filesystem, and the top level subvolume (the fs itself) has id 5 -# btrfs sub create bar Create subvolume './bar' -# btrfs sub list -p -q . ID 3486 gen 3368 parent 5 top level 5 parent_uuid - path foo ID 3487 gen 3369 parent 5 top level 5 parent_uuid - path bar now I have a second one... -# mv foo bar/ -# btrfs sub list -p -q . ID 3486 gen 3368 parent 3487 top level 3487 parent_uuid - path bar/foo ID 3487 gen 3369 parent 5 top level 5 parent_uuid - path bar if I move the foo subvolume *into* the bar subvolume, it gets the bar as parent -# btrfs sub snap -r bar bar-snap Create a readonly snapshot of 'bar' in './bar-snap' -# btrfs sub list -p -q . ID 3486 gen 3368 parent 3487 top level 3487 parent_uuid - path bar/foo ID 3487 gen 3370 parent 5 top level 5 parent_uuid - path bar ID 3488 gen 3370 parent 5 top level 5 parent_uuid 8de7ab74-4654-e542-a29b-169848ee73b3 path bar-snap and there's the parent_uuid... -- Hans van Kranenburg -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
