jLuger.de - hustior on Ubuntu 24.04

After updating to Ubuntu 24.04 hustior broke and wouldn't start. It turned that they have restricted the creation of unprivileged user namespaces. To work around this you need to save https://github.com/de-jluger/hustior/blob/master/hustior.apparmor.template as /etc/apparmor.d/hustior and change the /path/to/hustior to the correct path.

That was the short version of the story. Getting there wasn't as easy as it sounds because hustior failed to mount the root filesystem after it had restarted in a new namespace. Some tests later I've learned that even trying to access any file that doesn't belong to your user fails. So I've tried some unshare commands from Owncloud in a container: container and namespaces but they failed too. This failing led me to https://github.com/canonical/lxd/issues/12882 and the following workaround:

echo 0 > /proc/sys/kernel/apparmor_restrict_unprivileged_userns

echo 0 > /proc/sys/kernel/apparmor_restrict_unprivileged_unconfined

After this hustior worked again.
Searching for apparmor_restrict_unprivileged_userns brought me back to the article about the restriction of the unprivileged user namespaces. I've had it found previously but as I was able to start hustior in a new namespace I thought it didn't apply here. Turned out I was wrong about this.
As I didn't want to disable security features I've read the article again and found out that the simple template is all that is needed. Now hustior works with Ubuntu 24.04 too.