snap restore breaks sudo snap commands

[Natalia Litvinova]

I was following these instructions https://maas.io/docs/how-to-back-up-maas for MAAS backup and restore. And after the snapshot restore MAAS becomes unavailable. When I try running:

sudo maas config --show --show-database-password
cannot create user data directory: /root/snap/maas/25850: No such file or directory

But at the same time this command works:

sudo snap run --shell maas -c true; echo $?
cannot create user data directory: /root/snap/maas/25850: No such file or directory
1

The folder does exist:
sudo ls -l /root/snap/maas
total 8
drwxr-xr-x 2 root root 4096 Mar 16 09:45 25850
drwxr-xr-x 2 root root 4096 Mar 14 18:50 common
lrwxrwxrwx 1 root root 5 Feb 27 09:31 current -> 25850

This command hangs indefinitely:

sudo apparmor_parser

journalctl output is here: https://pastebin.canonical.com/p/KNYCnKFC48/
maas.cli apparmor profile: https://pastebin.canonical.com/p/d2NHvgsvwW/
maas.maas apparmor profile: https://pastebin.canonical.com/p/n9SkTxNBJN/
maas.supervisor apparmor profile: https://pastebin.canonical.com/p/4fDwZYrYWW/

Workaround:
After rebooting the MAAS machine it becomes alive and the command runs:
$ sudo maas config --show --show-database-password
Mode: region+rack
Settings:
maas_url=http://localhost:5240/MAAS/
database_host=localhost
database_port=None
database_name=maas
database_user=<REDACTED>
database_pass=<REDACTED>

Steps to reproduce:

sudo -u postgres pg_dumpall -c > ~/dump.sql
sudo systemctl stop postgresql.service
sudo snap save maas
sudo snap remove --purge maas
sudo systemctl start postgresql.service
sudo -u postgres psql -f dump.sql postgres
sudo snap restore <snapshot-id>
sudo maas config --show --show-database-password

[Michael Vogt (mvo)]

Uh, super sorry about the slow reply and also about the incorrect "apparmor_parsr" question - this should have been "apparmor_status".

[Chengen Du (chengendu)]

The issue and a potential fix are detailed in: https://github.com/snapcore/snapd/pull/13303