[systemd-devel] Passing variables from udev to unit

[Peter Hutterer]

On Fri, Mar 14, 2014 at 06:27:26AM +0400, Andrey Borzenkov wrote:
> В Fri, 14 Mar 2014 08:53:45 +1000
> Peter Hutterer <peter.hutterer at who-t.net> пишет:
> 
> > Hey,
> > 
> > I have a service file wacom-inputattach at .service that is started from a udev
> > rule:
> > 
> >   SUBSYSTEM=="tty|pnp", KERNEL=="ttyS[0-9]*", ATTRS{id}=="WACf*",
> >   TAG+="systemd", ENV{SYSTEMD_WANTS}+="wacom-inputattach@%k.service"
> > 
> > and the service file then runs:
> > 
> >   ExecStart=/usr/bin/inputattach -w8001 /dev/%I
> > 
> > That works fine, but now I need to pass a second parameter into the service
> > file. Ideally I want to run something like:
> > 
> >   ExecStart=/usr/bin/inputattach --baud $BAUD -w8001 /dev/%I
> > 
> > I can set the baud rate based on ATTRS{id} in the udev rule, I just don't
> > know if there is a way to pass this to the service file. Is there a way to
> > do this or do I need to write a wrapper?
> 
> 
> One possibility would be to generate 
> /run/systemd/system/wacom-inputattach@%k.service.d/baud.conf that
> contains
> 
> [Service]
> BAUD=9600
> 
> But this requires systemd reload and may generate burst of reload
> requests if there are multiple devices. May be wrapper is simpler.

thanks, I'll look into that. there should only ever be one of these devices
and they're built-in, so that shouldn't matter too much (in fact it'd
probably be possible to generate this file only once, but that's too much
effort to figure out).

Cheers,
  Peter