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My Debian 8 vm has lots of systemd logs like this:

Apr 28 23:02:09 foo systemd[22305]: Starting Shutdown.
Apr 28 23:02:09 foo systemd[22305]: Reached target Shutdown.
Apr 28 23:02:09 foo systemd[22305]: Starting Exit the Session...
Apr 28 23:02:09 foo systemd[22305]: Received SIGRTMIN+24 from PID 22461 (kill).
Apr 28 23:02:10 foo systemd[22469]: Starting Paths.
Apr 28 23:02:10 foo systemd[22469]: Reached target Paths.
Apr 28 23:02:10 foo systemd[22469]: Starting Timers.

i.e. lots of Starting Shutdown lines and SIGRTMIN+24.

The docs say:

SIGRTMIN+24: Immediately exits the manager (only available for --user instances).

What does 'Shutdown' mean here? I don't think it means shutting down the whole machine - no signs of a reboot happening. So is it just a restart of systemd for some reason? What would cause that?

Confused!

artfulrobot
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1 Answers1

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Starting with some recent (not sure exactly) versions of systemd, a user systemd (systemd --user) instance is started (one per user) when a user is logging in. The systemd user instance can then start processes for the user.

When the user closes his last session, that user instance of systemd is killed by the user systemd-exit service (/usr/lib/systemd/user/systemd-exit.service).

So the shutdown sequence here is the shutdown of the systemd --user process

Bigon
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  • If a user logs out with some background processes still running, will systemd wait for the processes to end, or is there some timeout so that systemd will kill them after some time? – L. Levrel Feb 01 '19 at 17:09
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    I **think** that if they are started by systemd itself (via a .service file) they will be killed when the last session of the user has been closed. If they are not started by systemd, it depends of the `KillUserProcesses=` option defined in `/etc/systemd/logind.conf` https://www.freedesktop.org/software/systemd/man/logind.conf.html#KillUserProcesses= – Bigon Feb 01 '19 at 17:49