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

[Michael Chapman]

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).