[systemd-devel] Antw: [EXT] Re: [systemd‑devel] systemctl log verbosity

[Ulrich Windl]

>>> Michael Chapman <mike at very.puzzling.org> schrieb am 18.08.2021 um 08:38 in
Nachricht <f3d742a-53ca-85c7-32eb-adf8e682c3d1 at very.puzzling.org>:
> On Wed, 18 Aug 2021, Ulrich Windl wrote:
>> >>> Michael Chapman <mike at very.puzzling.org> schrieb am 17.08.2021 um 02:52
in
>> Nachricht <885331af-bb7-41d0-e8-26c92023bb77 at very.puzzling.org>:
>> > On Tue, 17 Aug 2021, Dave Close wrote:
>> >> I'm trying to run "systemctl show" in a cron script. It works but I get
>> >> a huge number of extra lines in my log for each run. Why? Can this be
>> >> suppressed. I don't want to overfill the log.
>> >> 
>> >> There is nothing in the man page (that I noticed) indicating that
"show"
>> >> causes anything to be logged. But here's an example of what I see.
>> >> 
>> >> >Aug 16 16:10:01 svcs systemd[1]: Created slice User Slice of UID 0.
>> >> >Aug 16 16:10:01 svcs systemd[1]: Starting User Runtime Directory 
>> > /run/user/0...
>> >> >Aug 16 16:10:01 svcs systemd[1]: Finished User Runtime Directory 
>> > /run/user/0.
>> >> >Aug 16 16:10:01 svcs systemd[1]: Starting User Manager for UID 0...
>> >> >Aug 16 16:10:01 svcs systemd[80491]: Queued start job for default
target 
>> > Main User Target.
>> >> >Aug 16 16:10:01 svcs systemd[80491]: Created slice User Application
>> Slice.
>> >> >Aug 16 16:10:01 svcs systemd[80491]: Condition check resulted in Mark
boot
>> 
>> > as successful after the 
>> >> user session has run 2 minutes being skipped.
>> >> >Aug 16 16:10:01 svcs systemd[80491]: Started Daily Cleanup of User's 
>> > Temporary Directories.
>> >> >Aug 16 16:10:01 svcs systemd[80491]: Reached target Paths.
>> >> >Aug 16 16:10:01 svcs systemd[80491]: Reached target Timers.
>> >> >Aug 16 16:10:01 svcs systemd[80491]: Starting D‑Bus User Message Bus
>> Socket.
>> >> >Aug 16 16:10:01 svcs systemd[80491]: Condition check resulted in
PipeWire
>> 
>> > PulseAudio being skipped.
>> >> >Aug 16 16:10:01 svcs systemd[80491]: Listening on Multimedia System.
>> >> >Aug 16 16:10:01 svcs systemd[80491]: Starting Create User's Volatile
Files
>> 
>> > and Directories...
>> >> >Aug 16 16:10:01 svcs systemd[80491]: Finished Create User's Volatile
Files
>> 
>> > and Directories.
>> >> >Aug 16 16:10:01 svcs systemd[80491]: Listening on D‑Bus User Message
Bus 
>> > Socket.
>> >> >Aug 16 16:10:01 svcs systemd[80491]: Reached target Sockets.
>> >> >Aug 16 16:10:01 svcs systemd[80491]: Reached target Basic System.
>> >> >Aug 16 16:10:01 svcs systemd[80491]: Reached target Main User Target.
>> >> >Aug 16 16:10:01 svcs systemd[80491]: Startup finished in 151ms.
>> >> >Aug 16 16:10:01 svcs systemd[1]: Started User Manager for UID 0.
>> >> >Aug 16 16:10:01 svcs systemd[1]: Started Session 72 of User root.
>> >> >Aug 16 16:10:01 svcs root[80504]: ## logger output from cron script ##
>> >> >Aug 16 16:10:01 svcs systemd[1]: session‑72.scope: Deactivated
>> successfully.
>> >> 
>> >> I see these additional 23 lines (plus the one‑line script output) every
>> >> time the script runs. That seems excessively verbose to me.
>> >> 
>> >> The system is Fedora 34 x86_64.
>> > 
>> > Cron jobs are run with pam_systemd, so they are run within a logind 
>> > session. If there is no other sessions for root at that time, root's own

>> > systemd manager is started when the Cron job launches, and is stopped
when 
>> > the Cron job terminates. All of these log messages are related to this.
>> > 
>> > You may instead want to make root a lingering user:
>> > 
>> >     loginctl enable‑linger root
>> > 
>> > This setting is persistent. You can use disable‑linger at a later time to

>> > turn it off if necessary.
>> > 
>> > With root configured as a lingering user, its systemd manager remains 
>> > running all the time.
>> 
>> After reading the manual page I wonder: Is tha tsetting persistent, i.e.:
>> Where is that setting stored?
> 
> Yes, it is persistent.
> 
> Lingering users are just represented as files under 
> /var/lib/systemd/linger/ (though this is an implementation detail, of 
> course).

Of course, but the manual page of systemd-logind.service could state that
settings are saved persistently "somewhere".
Currently it does not even mention "linger", but the binary has the string
"Failed to open /var/lib/systemd/linger/: %m" inside.

Regards,
Ulrich