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

[Zbigniew Jędrzejewski-Szmek]

On Wed, Apr 17, 2013 at 05:20:52PM +0200, Lennart Poettering wrote:
> On Wed, 17.04.13 17:09, Lennart Poettering (lennart at poettering.net) wrote:
> 
> > 
> > On Tue, 16.04.13 09:11, Koen Kooi (koen at dominion.thruhere.net) 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.
> > 
> > timedatectl is just a frontend to timedated. So, without running
> > timedated inside of the container this is not going to be easy to do.
> 
> Ah, I missed that you'd actually be OK with booting up the whole thing
> for this command... You'd just need a nice way to run something after
> boot-up is complete, and that immeidately shuts down the container
> afterwards, right?
> 
> Hmm, here's an idea:
> 
> we could add a generator to systemd which looks for "systemd.run=" or so
> on the kernel cmdline and simply generates throw-away unit files from
> that, that runs the specified command(s) and triggers a shutdown
> afterwards... Would that work for you?
> 
> i.e. you'd then call:
> 
> systemd-nspawn -bD /srv/foobar \
>                systemd.run='/usr/bin/timedatectl set-timezone Europe/Paris' \
>                systemd.run='/usr/bin/timedatectl set-hostname BeagleBoneBlack'
> 
> and so on...
> 
> I think that would be reasonably pretty?
An alternative idea: let's a tool which waits until startup is finished.
(Unless I'm mistaken, there's dbus support with StartupFinished, but
not a ready tool which waits.)

Then one would inject into the container, wait for it to return,
and then inject other commands.

The advantage would be in better error handling and scriptability.

Zbyszek