Tried with lxd 5.21 and also 6.6 (purged and reinitialized in between). Brand new ZFS storage pool and lxdbr0 with IPv4 only. Unchanged snapcraft.yaml (based on core24) file which used to work.
Running inside a Ubuntu 22.04 VM with IPv4 only. My user has been in the lxd group since forever.
Hopefully relevant part of the log file after snapcraft pack fails:
2026-01-30 22:17:27.255 Creating an assert file for snap 'core24'
2026-01-30 22:17:27.256 Executing command on host: ['snap', 'known', 'account-key', 'public-key-sha3-384=BWDEoaqyr25nF5SNCvEv2v7QnM9QsfCc0PBMYD_i2NGSQ32EF2d4D0hqUel3m8ul']
2026-01-30 22:17:27.302 Executing command on host: ['snap', 'known', 'snap-declaration', 'snap-name=core24']
2026-01-30 22:17:27.355 Executing command on host: ['snap', 'known', 'snap-revision', 'snap-revision=1267', 'snap-id=dwTAh7MZZ01zyriOZErqd1JynQLiOGvM']
2026-01-30 22:17:27.757 Executing command on host: ['snap', 'known', 'account', 'account-id=canonical']
2026-01-30 22:17:27.796 Executing in container: lxc --project snapcraft exec local:base-instance-snapcraft-buildd-base-v71--f02c2da881cfba9d7924 -- env CRAFT_MANAGED_MODE=1 SNAPCRAFT_DEBUG=False SNAPCRAFT_LXD_REMOTE=local SNAPCRAFT_LAUNCHPAD_INSTANCE=production DEBIAN_FRONTEND=noninteractive DEBCONF_NONINTERACTIVE_SEEN=true DEBIAN_PRIORITY=critical test -d /tmp
2026-01-30 22:17:27.911 Executing on host: lxc --project snapcraft file push /home/roadster/tmp1lzx3z1l.tmp-craft/tmphc4exqee local:base-instance-snapcraft-buildd-base-v71--f02c2da881cfba9d7924/tmp/core24.assert --gid=0 --uid=0
2026-01-30 22:17:27.985 Executing in container: lxc --project snapcraft exec local:base-instance-snapcraft-buildd-base-v71--f02c2da881cfba9d7924 -- env CRAFT_MANAGED_MODE=1 SNAPCRAFT_DEBUG=False SNAPCRAFT_LXD_REMOTE=local SNAPCRAFT_LAUNCHPAD_INSTANCE=production DEBIAN_FRONTEND=noninteractive DEBCONF_NONINTERACTIVE_SEEN=true DEBIAN_PRIORITY=critical snap ack /tmp/core24.
assert
2026-01-30 22:17:28.407 Executing in container: lxc --project snapcraft exec local:base-instance-snapcraft-buildd-base-v71--f02c2da881cfba9d7924 -- env CRAFT_MANAGED_MODE=1 SNAPCRAFT_DEBUG=False SNAPCRAFT_LXD_REMOTE=local SNAPCRAFT_LAUNCHPAD_INSTANCE=production DEBIAN_FRONTEND=noninteractive DEBCONF_NONINTERACTIVE_SEEN=true DEBIAN_PRIORITY=critical test -d /tmp
2026-01-30 22:17:28.522 Executing on host: lxc --project snapcraft file push /home/roadster/tmpcdrvmxnr.tmp-craft/core24.snap local:base-instance-snapcraft-buildd-base-v71--f02c2da881cfba9d7924/tmp/core24.snap --gid=0 --uid=0
2026-01-30 22:17:28.921 Executing in container: lxc --project snapcraft exec local:base-instance-snapcraft-buildd-base-v71--f02c2da881cfba9d7924 -- env CRAFT_MANAGED_MODE=1 SNAPCRAFT_DEBUG=False SNAPCRAFT_LXD_REMOTE=local SNAPCRAFT_LAUNCHPAD_INSTANCE=production DEBIAN_FRONTEND=noninteractive DEBCONF_NONINTERACTIVE_SEEN=true DEBIAN_PRIORITY=critical snap install /tmp/cor
e24.snap
2026-01-30 22:17:29.424 Executing on host: lxc --project snapcraft config set local:base-instance-snapcraft-buildd-base-v71--f02c2da881cfba9d7924 user.craft_providers.timer 2026-01-30T21:17:29.424292+00:00
2026-01-30 22:17:29.517 Set instance timer to '2026-01-30T21:17:29.424292+00:00'
2026-01-30 22:17:30.505 Executing in container: lxc --project snapcraft exec local:base-instance-snapcraft-buildd-base-v71--f02c2da881cfba9d7924 -- env CRAFT_MANAGED_MODE=1 SNAPCRAFT_DEBUG=False SNAPCRAFT_LXD_REMOTE=local SNAPCRAFT_LAUNCHPAD_INSTANCE=production DEBIAN_FRONTEND=noninteractive DEBCONF_NONINTERACTIVE_SEEN=true DEBIAN_PRIORITY=critical test -f /etc/craft-in
stance.conf
2026-01-30 22:17:30.620 Executing on host: lxc --project snapcraft file pull local:base-instance-snapcraft-buildd-base-v71--f02c2da881cfba9d7924/etc/craft-instance.conf /home/roadster/tmpor31j8ca.tmp-craft/tmppd3wifd_
2026-01-30 22:17:30.696 Executing on host: lxc --project snapcraft file push /tmp/tmpbnd0x84j local:base-instance-snapcraft-buildd-base-v71--f02c2da881cfba9d7924/etc/craft-instance.conf --mode=0644
2026-01-30 22:17:30.867 Executing in container: lxc --project snapcraft exec local:base-instance-snapcraft-buildd-base-v71--f02c2da881cfba9d7924 -- env CRAFT_MANAGED_MODE=1 SNAPCRAFT_DEBUG=False SNAPCRAFT_LXD_REMOTE=local SNAPCRAFT_LAUNCHPAD_INSTANCE=production DEBIAN_FRONTEND=noninteractive DEBCONF_NONINTERACTIVE_SEEN=true DEBIAN_PRIORITY=critical chown root:root /etc/
craft-instance.conf
2026-01-30 22:17:30.968 Executing in container: lxc --project snapcraft exec local:base-instance-snapcraft-buildd-base-v71--f02c2da881cfba9d7924 -- env CRAFT_MANAGED_MODE=1 SNAPCRAFT_DEBUG=False SNAPCRAFT_LXD_REMOTE=local SNAPCRAFT_LAUNCHPAD_INSTANCE=production DEBIAN_FRONTEND=noninteractive DEBCONF_NONINTERACTIVE_SEEN=true DEBIAN_PRIORITY=critical test -f /etc/craft-in
stance.conf
2026-01-30 22:17:31.086 Executing on host: lxc --project snapcraft file pull local:base-instance-snapcraft-buildd-base-v71--f02c2da881cfba9d7924/etc/craft-instance.conf /home/roadster/tmpmdy24cof.tmp-craft/tmpbcluh7yz
2026-01-30 22:17:31.142 Failed to read instance config in environment at /etc/craft-instance.conf
2026-01-30 22:17:31.152 Traceback (most recent call last):
2026-01-30 22:17:31.152 File "/snap/snapcraft/16570/lib/python3.12/site-packages/craft_providers/lxd/lxc.py", line 569, in file_pull
2026-01-30 22:17:31.152 self._run_lxc(command, capture_output=True, project=project)
2026-01-30 22:17:31.152 File "/snap/snapcraft/16570/lib/python3.12/site-packages/craft_providers/lxd/lxc.py", line 206, in _run_lxc
2026-01-30 22:17:31.152 return subprocess.run(
2026-01-30 22:17:31.152 ^^^^^^^^^^^^^^^
2026-01-30 22:17:31.152 File "/snap/snapcraft/current/usr/lib/python3.12/subprocess.py", line 571, in run
2026-01-30 22:17:31.152 raise CalledProcessError(retcode, process.args,
2026-01-30 22:17:31.152 subprocess.CalledProcessError: Command '['lxc', '--project', 'snapcraft', 'file', 'pull', 'local:base-instance-snapcraft-buildd-base-v71--f02c2da881cfba9d7924/etc/craft-instance.conf', '/home/roadster/tmpmdy24cof.tmp-craft/tmpbcluh7yz']' returned non-zero exit status 1.
2026-01-30 22:17:31.152
2026-01-30 22:17:31.152 The above exception was the direct cause of the following exception:
2026-01-30 22:17:31.152 Traceback (most recent call last):
2026-01-30 22:17:31.152 File "/snap/snapcraft/16570/lib/python3.12/site-packages/craft_providers/instance_config.py", line 120, in load
2026-01-30 22:17:31.152 executor.pull_file(source=config_path, destination=temp_config_file)
2026-01-30 22:17:31.152 File "/snap/snapcraft/16570/lib/python3.12/site-packages/craft_providers/lxd/lxd_instance.py", line 479, in pull_file
2026-01-30 22:17:31.152 self.lxc.file_pull(
2026-01-30 22:17:04.832 Set instance timer to '2026-01-30T21:17:04.711901+00:00'
What’s also interesting: Trying to clean one of the parts always results in:
$ snapcraft clean webui
Failed to set config key 'user.craft_providers.status' to 'PREPARING' for instance 'base-instance-snapcraft-buildd-base-v71--f02c2da881cfba9d7924'.
Detailed information:
* Command that failed: 'lxc --project snapcraft config set local:base-instance-snapcraft-buildd-base-v71--f02c2da881cfba9d7924 user.craft_providers.status PREPARING'
* Command exit code: 1
* Command standard error output: b'cannot confirm that parent process is alive: Operation not permitted\ncannot send command 0 to helper process: Broken pipe\n'
Full execution log: '/home/roadster/.local/state/snapcraft/log/snapcraft-20260130-222859.715347.log'
Thanks for any help.