Re: btrfs subvolume list for not mounted filesystem?

2017-12-18 Thread Andrei Borzenkov
18.12.2017 19:49, Ulli Horlacher пишет:
> I want to mount an alternative subvolume of a btrfs filesystem.
> I can list the subvolumes when the filesystem is mounted, but how do I
> know them, when the filesystem is not mounted? Is there a query command?
> 
> root@xerus:~# mount | grep /test
> /dev/sdd4 on /test type btrfs 
> (rw,relatime,space_cache,user_subvol_rm_allowed,subvolid=5,subvol=/)
> 
> root@xerus:~# btrfs subvolume list /test
> ID 258 gen 156 top level 5 path tux/zz
> ID 259 gen 156 top level 5 path tux/z1
> ID 260 gen 156 top level 5 path tmp/zz
> ID 261 gen 19 top level 260 path tmp/zz/z1
> ID 269 gen 156 top level 5 path tux/test
> ID 271 gen 129 top level 269 path tux/test/.snapshot/2017-12-02_1341.test
> 
> root@xerus:~# umount /test
> 
> root@xerus:~# btrfs subvolume list /dev/sdd4
> ERROR: not a btrfs filesystem: /dev/sdd4
> ERROR: can't access '/dev/sdd4'
> 
> 
> 

btrfs-debug-tree -r /dev/sdd4

(or in more recent btrfs-progs, "btrfs inspect-internal dump-tree") will
show subvolume IDs (as ROOT_ITEM); I'm not sure of there is simple way
to resolve subvolume path names on unmounted device.
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btrfs subvolume list for not mounted filesystem?

2017-12-18 Thread Ulli Horlacher
I want to mount an alternative subvolume of a btrfs filesystem.
I can list the subvolumes when the filesystem is mounted, but how do I
know them, when the filesystem is not mounted? Is there a query command?

root@xerus:~# mount | grep /test
/dev/sdd4 on /test type btrfs 
(rw,relatime,space_cache,user_subvol_rm_allowed,subvolid=5,subvol=/)

root@xerus:~# btrfs subvolume list /test
ID 258 gen 156 top level 5 path tux/zz
ID 259 gen 156 top level 5 path tux/z1
ID 260 gen 156 top level 5 path tmp/zz
ID 261 gen 19 top level 260 path tmp/zz/z1
ID 269 gen 156 top level 5 path tux/test
ID 271 gen 129 top level 269 path tux/test/.snapshot/2017-12-02_1341.test

root@xerus:~# umount /test

root@xerus:~# btrfs subvolume list /dev/sdd4
ERROR: not a btrfs filesystem: /dev/sdd4
ERROR: can't access '/dev/sdd4'



-- 
Ullrich Horlacher  Server und Virtualisierung
Rechenzentrum TIK 
Universitaet Stuttgart E-Mail: horlac...@tik.uni-stuttgart.de
Allmandring 30aTel:++49-711-68565868
70569 Stuttgart (Germany)  WWW:http://www.tik.uni-stuttgart.de/
REF:<20171218164941.ga22...@rus.uni-stuttgart.de>
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