[systemd-devel] How to run *ctl command using systemd-nspawn

[Zbigniew Jędrzejewski-Szmek]

On Tue, Apr 16, 2013 at 09:11:51AM +0200, Koen Kooi wrote:
> Hi,
> 
> To help with flashing the onboard eMMC of a 100000 boards I'm using systemd-nspawn to run package postinstall scripts that generate UUIDs and some other things and it's working great for that! Every board now has a unique value in /etc/machine-id instead it being empty and systemd randomizing it on startup.
> 
> What doesn't work however is something like this:
> 
> 	systemd-nspawn -D ${PART2MOUNT} /usr/bin/timedatectl set-timezone Europe/Paris
> 
> or this:
> 
> 	systemd-nspawn -D ${PART2MOUNT} /usr/bin/hostnamectl set-hostname BeagleBoneBlack
> 
> I know I can run the lowlevel 'ln -sf <zoneinfo> /etc/timezone' or echo the name into /etc/hostname, but I'd like to use the *ctl commands because they work and have error handling built-in. 
> it looks like I would need -b to get the *ctl commands to work, but -b doesn't support running single commands and exiting.
> 
> My goal is to be able to drop in a rootfs tarball and change timezone and hostname settings in a config file for the flasher script and avoid generating N different tarballs. For use in the office lab I use something like [1] to generate the hostnames based on board revision and serial number.
> 
> So, is there a way to *ctl command using systemd-nspawn in a rootfs that wasn't specially prepared (e.g. helper units/targets) for that?

With very recent systemd just run:

PID=$(head -n1 /sys/fs/cgroup/systemd/machine/$NAME/system/tasks)
nsenter -m -u -i -n -p -t $PID /usr/bin/timedatectl set-timezone Europe/Paris
...
nsenter -m -u -i -n -p -t $PID systemctl halt

where NAME is either speicified with -M or the name of the tree root.

Zbyszek