I need to find (all) subvolume directories. I know, btrfs subvolumes root directories have inode #256, but a "find / -inum 256" is horrible slow!
Next idea: "btrfs subvolume list /" is really fast, but its output is not always direct usable to find the subvolume directory. Example output on a SUSE system: root@trulla:~# btrfs subvolume list / ID 257 gen 2280099 top level 5 path @ ID 258 gen 2280769 top level 257 path @/home ID 259 gen 2280947 top level 257 path @/opt ID 260 gen 2280098 top level 257 path @/srv ID 261 gen 2280954 top level 257 path @/tmp ID 262 gen 2280187 top level 257 path @/usr/local ID 263 gen 2280099 top level 257 path @/var/crash ID 264 gen 2280949 top level 257 path @/var/log ID 265 gen 2280099 top level 257 path @/var/opt ID 266 gen 2280954 top level 257 path @/var/spool ID 267 gen 2280947 top level 257 path @/var/tmp ID 270 gen 2280222 top level 257 path @/.snapshots ID 453 gen 2280954 top level 270 path @/.snapshots/128/snapshot ID 1235 gen 2280099 top level 257 path @/var/lib/machines ID 12392 gen 2123118 top level 270 path @/.snapshots/1065/snapshot ID 12393 gen 2123120 top level 270 path @/.snapshots/1066/snapshot ID 13273 gen 2176640 top level 270 path @/.snapshots/1089/snapshot ID 13274 gen 2176651 top level 270 path @/.snapshots/1090/snapshot ID 13553 gen 2203681 top level 270 path @/.snapshots/1103/snapshot There is no /@/ directory in the default filesystem because of: root@trulla:/# stat /@/.snapshots/128/snapshot stat: cannot stat '/@/.snapshots/128/snapshot': No such file or directory root@trulla:~# btrfs subvolume get-default / ID 453 gen 2280954 top level 270 path @/.snapshots/128/snapshot root@trulla:/# mount | grep " / " /dev/sda2 on / type btrfs (rw,relatime,space_cache,subvolid=453,subvol=/@/.snapshots/128/snapshot) On this particular system I could remove "@" from the subvolume path to get the subvolume directory: root@trulla:/# stat /.snapshots/128/snapshot File: '/.snapshots/128/snapshot' Size: 198 Blocks: 0 IO Block: 4096 directory Device: 27h/39d Inode: 256 Links: 1 Access: (0755/drwxr-xr-x) Uid: ( 0/ root) Gid: ( 0/ root) Access: 2019-07-13 01:03:08.543830085 +0200 Modify: 2019-07-13 01:03:37.336445461 +0200 Change: 2019-07-13 01:03:37.336445461 +0200 Birth: - But what if a btrfs filesystem does not have a toplevel /@/ directory, but anything else, like /this/is/my/top/directory ? Will be the first output line of "btrfs subvolume list /" always look like ID 257 gen 2280099 top level 5 path this/is/my/top/directory ? -- Ullrich Horlacher Server und Virtualisierung Rechenzentrum TIK Universitaet Stuttgart E-Mail: horlac...@tik.uni-stuttgart.de Allmandring 30a Tel: ++49-711-68565868 70569 Stuttgart (Germany) WWW: http://www.tik.uni-stuttgart.de/ REF:<20190712231705.ga16...@tik.uni-stuttgart.de>
