Bug#1042015: reboot/poweroff throw errors if dbus/systemd-logind is not running

[MichaIng]

Package: systemd
Version: 252.12-1

Since Debian Bookworm (systemd 252), the reboot, poweroff and "shutdown 
now" commands throw the following error if the dbus service is not running:

-------
Failed to connect to bus: No such file or directory
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and if dbus is running, but systemd-logind is not:

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Failed to set wall message, ignoring: Unit 
dbus-org.freedesktop.login1.service failed to load properly, please 
adjust/correct and reload service manager: File exists
Call to Reboot failed: Unit dbus-org.freedesktop.login1.service failed 
to load properly, please adjust/correct and reload service manager: File 
exists
-------

The action however finishes properly. I know that systemd-logind is 
required for scheduled shutdowns/reboots, but it is not for immediate 
ones. I am not sure if those were ever supposed to send a wall message, 
as the possible purpose is minimal if the action is performed 
immediately. However, the "wall" command works perfectly fine without 
the two services and until Debian Bullseye, those errors were not thrown.

The "--no-wall" flag, which is supposed to suppress wall messages sent 
by those commands, has no effect on the dbus/systemd-logind contact 
attempt/error messages. Also I could not find any setting in 
/etc/systemd to change this new behaviour. "reboot -f" works, but it has 
unwanted implications, most notably no "sync" and unclean/no umounts.

The motivation to solve these errors without installing dbus and 
enabling systemd-logind is that both are not required on most server 
systems. systemd-logind is used for desktop sessions and by some GUI 
applications, and for mentioned scheduled shutdowns/reboots, but for a 
single admin server system it is usually not needed/used. For embedded 
systems with low power/RAM it can hence make sense to have 
systemd-logind masked and dbus uninstalled, to free up some resources, 
cleanup the process tree, logs etc.

I guess it is an upstream question/issue, but I wanted to be sure about 
this first. Hopefully someone can give more insights.

Best regards,

Micha