Docker Containers can not be stopped or removed - permission denied Error
I installed Docker from the snap package and after a while I decided to move to apt repository installation.
I was facing the same problem and using sudo aa-remove-unknown worked for me.
So no reinstallation of Apparmor was needed.
For anyone that does not wish to completely purge AppArmor.
Check status: sudo aa-status
Shutdown and prevent it from restarting: sudo systemctl disable apparmor.service --now
Unload AppArmor profiles: sudo service apparmor teardown
Check status: sudo aa-status
You should now be able to stop/kill containers.
I was able to fix the issue. Apparmor service in ubuntu was not working normally due to some unknown issue. The problem was similar to the issue reported in moby project https://github.com/moby/moby/issues/20554.
The /etc/apparmor.d/tunables folder was empty, and https://github.com/mlaventure suggested to purge/reinstall apparmor to get it to the initial state.
So I reinstalled apparmor, and after restarting the problem was solved.
Hope this helps.