[systemd-devel] Shutdown a specific service in systemd shutdown

[Lennart Poettering]

On Sun, 22.05.16 15:24, Andrei Borzenkov (arvidjaar at gmail.com) wrote:

> 19.05.2016 11:57, Martin Pitt пишет:
> > Hello Bao,
> > 
> > Bao Nguyen [2016-05-19 15:52 +0700]:
> >> When the system is shutdown, systemd will terminate all services in
> >> parallel manner, could you let me know if there is any ways to tell systemd
> >> to shutdown a specific service first, then shutdown all remaining services?
> > 
> > The concept of "first"/"last" has no well-defined meaning in any
> > non-serial init systems (not even SysV init with insserv, only with
> > classic SysV init with manually set priorities). I've heard requests
> > like "but this needs to be started as the last thing" a lot in the
> > recent years, and there's no way all the services can simultaneously
> > be "last" :-)
> 
> Well, the very good example of service that has to be started/stopped
> before/after anything else is splash screen (plymouth or anything). It
> really must appear as soon as user hit ENTER in "systemctl reboot". As
> it stands now, there is no way to ensure it.

Well, shutting down is asynchronous anyway. Hence, yes, it should be shown
pretty quickly, but strict, enforced ordering here is not necessary.

This is a different story if you want a smooth transition between some
graphical login thingy (such as gdm) and the ply shutdown screen, but
in that case there should really be a direct hand-over so that gdm
only releases the DRM when it knows that py has taken over. Such logic
needs to happen directly between ply and gdm however, and in fact does
already.

> > You should put sufficient After= properties into your service, so that
> > it gets started after and stopped before the ones you specify. 
> 
> Do you suggest adding dependency on plymouth to *every* service?

No, I'd suggest that you are using the wrong tool here and should use
something else...

Lennart

-- 
Lennart Poettering, Red Hat