btrfs: a mysterious snapshot consuming my space

English Install/Boot/Login
1

so, have been desperately watching my disk space reduce for no obvious reason. After a little investigation i notice there is a snapshot (844) not listed by snapper

output of snapper:

sudo snapper list
Type   | #   | Pre # | Date                          | User | Cleanup | Description           | Userdata      
-------+-----+-------+-------------------------------+------+---------+-----------------------+--------------
single | 0   |       |                               | root |         | current               |               
single | 1   |       | Thu 23 Jun 2016 10:07:00 CEST | root |         | first root filesystem |               
pre    | 893 |       | Fri 12 Jan 2018 19:43:21 CET  | root | number  | zypp(zypper)          | important=yes
post   | 894 | 893   | Fri 12 Jan 2018 20:00:26 CET  | root | number  |                       | important=yes
pre    | 895 |       | Sun 14 Jan 2018 14:45:32 CET  | root | number  | zypp(zypper)          | important=no  
post   | 896 | 895   | Sun 14 Jan 2018 14:45:44 CET  | root | number  |                       | important=no

output (trimmed) of btrfs:

sudo btrfs subvolume list /
..snip..
ID 2270 gen 490343 top level 258 path @/.snapshots/844/snapshot
ID 2335 gen 495322 top level 258 path @/.snapshots/893/snapshot
ID 2337 gen 495359 top level 258 path @/.snapshots/894/snapshot
ID 2352 gen 496131 top level 258 path @/.snapshots/895/snapshot
ID 2353 gen 496132 top level 258 path @/.snapshots/896/snapshot

qgroup scan shows its quite large

2270 gen 490343 top level 258 path @/.snapshots/844/snapshot       2270  10.06GB  6.52GB    
2335 gen 495322 top level 258 path @/.snapshots/893/snapshot       2335  10.31GB  1.58GB    
2337 gen 495359 top level 258 path @/.snapshots/894/snapshot       2337  10.73GB  138.55MB  
2352 gen 496131 top level 258 path @/.snapshots/895/snapshot       2352  10.30GB  1.90MB    
2353 gen 496132 top level 258 path @/.snapshots/896/snapshot       2353  10.37GB  2.62MB

other info

sudo btrfs subvolume get-default /
ID 259 gen 497548 top level 258 path @/.snapshots/1/snapshot

am i reading this correct that this is a ‘lost’ snapshot? if so should i just nuke it (using btrfs)? are there any checks i should do first or a more cautious approach e.g. rename. advice welcome.

2

I’d say if snapper does not see it removing it should not do any harm. You will need to remove both snapshot (/.snapshots/844/snapshot) and directory itself (/.snapshots/844).

3

so i assume this would be sudo btrfs subvolume delete /.snapshots/844/snapshot and sudo btrfs subvolume delete /.snapshots/844. In that order? If things dont go well can anyone comment on how to backup (rsync?) and then recreate the FS before restoring? would all subvolumes have to be manually recreated?

4

so… happy ending, a simple

sudo btrfs sub delete /.snapshots/844/snapshot

the snapshot has gone and have recovered 6.5GB of space

i dont know how this ‘rouge’ snapshot could have occurred, but perhaps something to check for if your root starts to inexplicably fill up.