apt-btrfs-snapshot creates nested snapshots that cannot be deleted easily

[Sanjeev Gupta]

Hi,

This is on a precise, with seperate / and /home , both fresh btrfs.

I have NO previous btrfs experience.

Some snapshots created automatically by apt-get upgrade cannot be deleted, others can.

See:
root@precise-X201:~# apt-btrfs-snapshot list
Available snapshots:
@apt-snapshot-2012-02-06_10:57:25
@apt-snapshot-2012-02-06_10:57:26
@apt-snapshot-2012-02-07_10:39:29
@apt-snapshot-2012-02-21_11:31:14
@apt-snapshot-2012-04-23_14:12:51
@apt-snapshot-2012-05-02_12:56:59
@apt-snapshot-2012-05-09_23:46:30
@apt-snapshot-2012-05-10_18:13:32
@apt-snapshot-2012-05-10_21:42:52
@apt-snapshot-2012-05-10_21:44:23
@apt-snapshot-2012-05-11_14:05:17

root@precise-X201:~# apt-btrfs-snapshot delete-older-than 1d
Delete subvolume '/tmp/apt-btrfs-snapshot-mp-AtGJCL/@apt-snapshot-2012-02-06_10:57:25'
ERROR: cannot delete '/tmp/apt-btrfs-snapshot-mp-AtGJCL/@apt-snapshot-2012-02-06_10:57:25'
Delete subvolume '/tmp/apt-btrfs-snapshot-mp-G7ba5C/@apt-snapshot-2012-02-06_10:57:26'
ERROR: cannot delete '/tmp/apt-btrfs-snapshot-mp-G7ba5C/@apt-snapshot-2012-02-06_10:57:26'
Delete subvolume '/tmp/apt-btrfs-snapshot-mp-rJFoU7/@apt-snapshot-2012-02-07_10:39:29'
ERROR: cannot delete '/tmp/apt-btrfs-snapshot-mp-rJFoU7/@apt-snapshot-2012-02-07_10:39:29'
Delete subvolume '/tmp/apt-btrfs-snapshot-mp-l0O8Tc/@apt-snapshot-2012-02-21_11:31:14'
ERROR: cannot delete '/tmp/apt-btrfs-snapshot-mp-l0O8Tc/@apt-snapshot-2012-02-21_11:31:14'
Delete subvolume '/tmp/apt-btrfs-snapshot-mp-NxuzYR/@apt-snapshot-2012-04-23_14:12:51'
ERROR: cannot delete '/tmp/apt-btrfs-snapshot-mp-NxuzYR/@apt-snapshot-2012-04-23_14:12:51'
Delete subvolume '/tmp/apt-btrfs-snapshot-mp-qTWNui/@apt-snapshot-2012-05-02_12:56:59'
ERROR: cannot delete '/tmp/apt-btrfs-snapshot-mp-qTWNui/@apt-snapshot-2012-05-02_12:56:59'
Delete subvolume '/tmp/apt-btrfs-snapshot-mp-C6mvol/@apt-snapshot-2012-05-09_23:46:30'
Delete subvolume '/tmp/apt-btrfs-snapshot-mp-WKrgPg/@apt-snapshot-2012-05-10_18:13:32'
Delete subvolume '/tmp/apt-btrfs-snapshot-mp-nSMmvC/@apt-snapshot-2012-05-10_21:42:52'
Delete subvolume '/tmp/apt-btrfs-snapshot-mp-H0UnbV/@apt-snapshot-2012-05-10_21:44:23'

root@precise-X201:~# apt-btrfs-snapshot list
Available snapshots:
@apt-snapshot-2012-02-06_10:57:25
@apt-snapshot-2012-02-06_10:57:26
@apt-snapshot-2012-02-07_10:39:29
@apt-snapshot-2012-02-21_11:31:14
@apt-snapshot-2012-04-23_14:12:51
@apt-snapshot-2012-05-02_12:56:59
@apt-snapshot-2012-05-11_14:05:17

I update daily, and cannot spot a pattern when and why some are "special".

--
Sanjeev Gupta

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: apt-btrfs-snapshot 0.2.1build1
ProcVersionSignature: Ubuntu 3.2.0-24.37-generic 3.2.14
Uname: Linux 3.2.0-24-generic x86_64
ApportVersion: 2.0.1-0ubuntu7
Architecture: amd64
Date: Fri May 11 14:04:41 2012
InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Alpha amd64 (20111129.1)
PackageArchitecture: all
ProcEnviron:
 LANGUAGE=en_SG:en
 TERM=xterm
 PATH=(custom, no user)
 LANG=en_SG.UTF-8
 SHELL=/bin/bash
SourcePackage: apt-btrfs-snapshot
UpgradeStatus: No upgrade log present (probably fresh install)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Sanjeev Gupta (ghane)]

Please see comment by MatthewHawn (steamraven) on Bug #852458

That describes this behaviour perfectly.

[Sanjeev Gupta (ghane)]

Hi,

Please see
  http://www.ogre.com/node/413
for a work-around.

[Robert C. (fuzxxl)]

As a possible workaround, you can attempt to delete those "inner" snapshots first. This worked for me to delete all apt-snapshots:

    for i in /@apt-* ; sudo btrfs sub del $i/@ ; sudo btrfs sub del $i

[Jacek Nykis (jacekn)]

Robert is rith in #6, here is what I did on my system to get rid of the snapshots:
mount /dev/sda1 /mnt/tmp #Mounted the same volume for the second time on a running system, can be done online
cd /mnt/tmp
btrfs subvolume list /mnt/tmp/
btrfs subvolume delete /mnt/tmp/@apt-snapshot-2013-01-01_12:42:41/@
btrfs subvolume delete /mnt/tmp/@apt-snapshot-2013-01-01_12:42:41

and repeated for all the other snapshots which would not disappear

[Andrew Stubbs (ams-codesourcery)]

The problem appear to be caused by multiple snapshots taken within the same second. See #852458.

[Michael (auslands-kv)]

I find it a pity that this long standing bug is still unassigned.

It is still not working correctly even under Ubuntu 14.04 :-(

I am wondering why we report bugs at all ...

[Jonathan (jjcf89)]

Creation of @ snapshot:

 $ sudo apt-btrfs-snapshot snapshot; sudo apt-btrfs-snapshot snapshot
Create a snapshot of '/tmp/apt-btrfs-snapshot-mp-r4lbis5q/@' in '/tmp/apt-btrfs-snapshot-mp-r4lbis5q/@apt-snapshot-2016-01-04_09:55:08'
Create a snapshot of '/tmp/apt-btrfs-snapshot-mp-vszwto5y/@' in '/tmp/apt-btrfs-snapshot-mp-vszwto5y/@apt-snapshot-2016-01-04_09:55:08/@'

Possible fix, not sure about name root_snapshot_dir though:

 $ diff /usr/lib/python3/dist-packages/apt_btrfs_snapshot.py.orig /usr/lib/python3/dist-packages/apt_btrfs_snapshot.py -u3
--- /usr/lib/python3/dist-packages/apt_btrfs_snapshot.py.orig 2016-01-04 09:48:53.632890479 -0500
+++ /usr/lib/python3/dist-packages/apt_btrfs_snapshot.py 2016-01-04 09:53:30.168895671 -0500
@@ -260,7 +260,15 @@

     def delete_snapshot(self, snapshot_name):
         mp = self.mount_btrfs_root_volume()
+ snapshot_dir = os.path.join(mp, snapshot_name)
+ # Check for @ snapshot inside snapshot. Need to delete this
+ # snapshot first if exists
+ root_snapshot_dir = os.path.join(snapshot_dir, "@")
+ if os.path.isdir(root_snapshot_dir):
+ res = self.commands.btrfs_delete_snapshot(
+ root_snapshot_dir)
+
         res = self.commands.btrfs_delete_snapshot(
- os.path.join(mp, snapshot_name))
+ snapshot_dir)
         self.umount_btrfs_root_volume()
         return res

 $ sudo apt-btrfs-snapshot delete @apt-snapshot-2016-01-04_09:55:08
Delete subvolume '/tmp/apt-btrfs-snapshot-mp-4g4167i8/@apt-snapshot-2016-01-04_09:55:08/@'
Delete subvolume '/tmp/apt-btrfs-snapshot-mp-4g4167i8/@apt-snapshot-2016-01-04_09:55:08'

Also create_btrfs_root_snapshot() could check for an existing snapshot and not create another one or add milliseconds to snapshot name.

[Ubuntu Foundations Team Bug Bot (crichton)]

The attachment "apt_btrfs_snapshot_fix_delete_snapshot.patch" seems to be a patch. If it isn't, please remove the "patch" flag from the attachment, remove the "patch" tag, and if you are a member of the ~ubuntu-reviewers, unsubscribe the team.

[This is an automated message performed by a Launchpad user owned by ~brian-murray, for any issues please contact him.]