apt-btrfs-snapshot blocks apt

[Mauro Miatello]

I've installed apt-btrfs-snapshot
then every apt operation shows:

Traceback (most recent call last):
  File "/usr/bin/apt-btrfs-snapshot", line 29, in <module>
    from apt_btrfs_snapshot import AptBtrfsSnapshot
  File "/usr/lib/python3/dist-packages/apt_btrfs_snapshot.py", line 28, in <module>
    from distutils.spawn import find_executable
ModuleNotFoundError: No module named 'distutils.spawn'

so I've installed python3-distutils, now apt doesn't work any more:

Supported
ERROR: Could not statfs: No such file or directory
E: Problem executing scripts DPkg::Pre-Invoke 'if [ -x /usr/bin/apt-btrfs-snapshot ] && apt-btrfs-snapshot supported; then apt-btrfs-snapshot snapshot; fi '
E: Sub-process returned an error code

also I can't remove packages
workaround is renaming /usr/bin/apt-btrfs-snapshot

[Mauro Miatello (mauro-miatello)]

same on kubuntu 20.04, but I didn't install python3-distutils so I have only warning
for now, I removed apt-btrfs-snapshot

[Launchpad Janitor (janitor)]

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

[Alan Walter Thomas (alazyworkaholic)]

I never had the python error above, but ever since I reverted to a snapshot for the first time I do get the ERROR: Could not statfs: No such file or directory.

I was able to keep apt-btrfs-snapshot's error from making apt unable to do anything by deleting /etc/apt/apt.conf.d/80-btrfs-snapshot, but that's really not a solution.

I have no idea what file it's looking for. Invoking it manually with --debug didn't yield any other information.

[Kent Ross (mumbleskates)]

i ran into this and figured out what it was.

apt-btrfs-snapshot makes several assumptions when it operates, not all of which are checked:

1. / is mounted from a btrfs device subvolume named /@
2. the btrfs filesystem on that device will mount the root filesystem, inside which @ resides.

1. is checked by "supported" by looking in fstab and ensuring that subvolid=@ is *explicitly* specified, 2. is not checked at all. if your volume root mounts @ as the default subvolume it's not gonna work!