Setting `AutoUpdate=registry` will tell Podman to automatically fetch
an updated container image from its corresponding registry and restart
the container. The `podman-auto-update.timer` systemd unit needs to be
active for this to happen on a schedule.
The only privilege NUT needs is access to the USB device nodes. Using a
device CGroup rule to allow this is significantly better than disabling
all restrictions. Especially since I discovered that `--privileged`
implies `--security-opt label=disable`, effectively disabling SELinux
confinement of the container.
NUT needs some udev rules in order to set the proper permissions on USB
etc. devices so it can run as an otherwise unprivileged user. Since
udev rules can only be processed on the host, these rules need to be
copied out of the container and evaluated before the NUT server starts.
To enable this, the *nut-server* container image copies the rules it
contains to `/etc/udev/rules.d` if that directory is a mount point. By
bind mounting a directory on the host at that path, we can get a copy of
the rules files outside the container. Then, using a systemd path unit,
we can tell the udev daemon to reload and reevaluate its rules.
SELinux prevents processes in containers from writing to
`/etc/udev/rules.d` directly, so we have to use an intermediate location
and then copy the rules files to their final destination.
Dustin