How to delete btrfs subvolumes with <FS_TREE> in their name

Question

I have a bunch of btrfs snapshots like so:

20:17:37 [root@galaxy /]$ btrfs subvolume list -a / |grep apt
ID 271 gen 348 top level 5 path <FS_TREE>/@apt-snapshot-2013-04-17_21:44:30
ID 272 gen 352 top level 5 path <FS_TREE>/@apt-snapshot-2013-04-17_21:46:25
ID 273 gen 361 top level 5 path <FS_TREE>/@apt-snapshot-2013-04-17_21:51:13
... # lots more

I would like to get rid of them. So I tried

20:21:31 [root@galaxy ~]$ btrfs subvolume delete '/<FS_TREE>/@apt-snapshot-2013-04-17_21:44:30'
ERROR: error accessing '/<FS_TREE>/@apt-snapshot-2013-04-17_21:44:30'
20:21:36 [root@galaxy ~]$ btrfs subvolume delete '<FS_TREE>/@apt-snapshot-2013-04-17_21:44:30'
ERROR: error accessing '<FS_TREE>/@apt-snapshot-2013-04-17_21:44:30'
20:21:43 [root@galaxy ~]$ btrfs subvolume delete '/@apt-snapshot-2013-04-17_21:44:30'
ERROR: error accessing '/@apt-snapshot-2013-04-17_21:44:30'
20:21:47 [root@galaxy ~]$ btrfs subvolume delete '@apt-snapshot-2013-04-17_21:44:30'
ERROR: error accessing '@apt-snapshot-2013-04-17_21:44:30'

What's the correct syntax to delete these snapshots?

Answer 1

I was able to delete these snapshots by first mounting the whole btrfs volume (not the @ subvolume) and then working from there:

# mount /dev/mapper/whatever /mnt -o subvol=/
# ls /mnt
@
@apt-snapshot-2013-04-17_21:44:30
...

So at this point, all subvolumes (including the funky apt-snapshot ones) are visible in /mnt, so we can delete them:

# btrfs subvol delete /mnt/@apt-snapshot-2013-04-17_21:44:30
# umount /mnt

Answer 2

The easiest way to do this is to use the built in apt-btrfs-snapshot commands:

Unlike normal snapshot deletion, you do not need to mount the filesystem to delete snapshots.

First, list the available apt-btrfs-snapshot snapshots using the following command:

sudo apt-btrfs-snapshot list

Here is an example of the output from that command:

@apt-snapshot-old-root-2015-10-19_20:20:10
@apt-snapshot-2015-10-28_19:00:46
@apt-snapshot-2015-10-28_19:09:14
@apt-snapshot-2015-10-29_04:40:07
@apt-snapshot-2015-10-29_06:35:57
@apt-snapshot-2015-10-29_07:03:39
@apt-snapshot-2015-10-30_03:49:05
@apt-snapshot-2015-10-30_17:53:59

To delete the snapshot @apt-snapshot-2015-10-30_17:53:59, run:

sudo apt-btrfs-snapshot delete @apt-snapshot-2015-10-30_17:53:59

You can also delete a number of snapshots by date. Here is an example of a command that would delete all snapshots that are older than 0 days.

sudo apt-btrfs-snapshot delete-older-than 0d   

Here is an example of the output from that command:

Delete subvolume (no-commit): '/tmp/apt-btrfs-snapshot-mp-odfe0o4g/@apt-snapshot-old-root-2015-10-19_20:20:10'
ERROR: cannot delete '/tmp/apt-btrfs-snapshot-mp-odfe0o4g/@apt-snapshot-old-root-2015-10-19_20:20:10' - Directory not empty
Delete subvolume (no-commit): '/tmp/apt-btrfs-snapshot-mp-b2zv18qr/@apt-snapshot-2015-10-28_19:00:46'
Delete subvolume (no-commit): '/tmp/apt-btrfs-snapshot-mp-zjglvefe/@apt-snapshot-2015-10-28_19:09:14'
Delete subvolume (no-commit): '/tmp/apt-btrfs-snapshot-mp-lj3v74qa/@apt-snapshot-2015-10-29_04:40:07'
Delete subvolume (no-commit): '/tmp/apt-btrfs-snapshot-mp-vztc82zr/@apt-snapshot-2015-10-29_06:35:57'
Delete subvolume (no-commit): '/tmp/apt-btrfs-snapshot-mp-q0ou8e24/@apt-snapshot-2015-10-29_07:03:39'
Delete subvolume (no-commit): '/tmp/apt-btrfs-snapshot-mp-dw8eq0vv/@apt-snapshot-2015-10-30_03:49:05'
Delete subvolume (no-commit): '/tmp/apt-btrfs-snapshot-mp-vgo2yuf2/@apt-snapshot-2015-10-30_17:53:59'

As you can see, the available snapshots were deleted. However, the oldest snapshot "old-root" was not deleted and can still be used to roll back even though it is much older than 0 days.

Run the following command for a full list of features:

apt-btrfs-snapshot --help