[systemd-devel] sigpwr.target - intended usage?

[Michael Biebl]

2016-07-18 15:02 GMT+02:00 Lennart Poettering <lennart at poettering.net>:
> On Mon, 18.07.16 14:41, Michael Biebl (mbiebl at gmail.com) wrote:
>
>> 2016-07-18 14:00 GMT+02:00 Michael Biebl <mbiebl at gmail.com>:
>> > 2016-07-18 13:54 GMT+02:00 Lennart Poettering <lennart at poettering.net>:
>> >> On Mon, 18.07.16 13:37, Michael Biebl (mbiebl at gmail.com) wrote:
>> >>
>> >>> Apparently SIGPWR is used by lxc-stop to shut down LXC containers.
>> >>> What interface would you recommend instead?
>> >>>
>> >>> https://lists.linuxcontainers.org/pipermail/lxc-users/2015-May/009279.html
>> >>
>> >> Is that actually really used? I mean, upstart is pretty much dead
>> >> afaics...
>> >>
>> >> systemd since day one shuts down cleanly on SIGRTMIN+4, and it's
>> >> probably what a container manager should use (it is what machined
>> >> uses). See the "Signals" section in systemd(1).
>> >
>> > lxc containers require sigpwr.target to be hooked up properly,
>> > otherwise lxc-stop does not shutdown the container.
>>
>> SIGPWR is wired up in sysvinit and upstart by default to initiate a
>> shutdown. Afaics both do not react on SIGRTMIN+4.
>
> Well, many sysvinit distros where set up to log something about
> "IMPENDING POWER FAILURE" on SIGPWR... It sounds really wrong to
> trigger this in a container just to shut it down...

I do not really disagreeing here. I'm just trying to understand the
current situation.


>> So the problem here is that lxc doesn't know what runs inside the
>> container: could be an older version of Debian (using syvinit), and
>> older version of Ubuntu (using upstart) or systemd.
> Well, if they don't want to make SIGRTMIN+4 the default because they
> think sysvinit/Upstart is more relevant than systemd, then that's
> their right. But I think making the kill signal configurable per
> container would probably be a good idea. That's what we do in nspawn,
> where SIGRTMIN+3 is the default, but you can override it with
> --kill-signal= on the cmdline (or KillSignal= in .nspawn files), for
> compat with sysv.

I was told that this is already configurable in lxc via lxc.haltsignal.
So afaics, lxc-create would just need to make sure to set this
accordingly on distros which use systemd by default.

Michael

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