Bug#887343: systemd-timesyncd does not start with DynamicUser=yes

[Guido Günther]

Package: systemd
Version: 236-3
Severity: normal
File: systemd-timesyncd.service

Hi,
on a newly installed (without installing recommends) system¹ systemd-timesyncd fails to start like

$ systemctl status systemd-timesyncd 
● systemd-timesyncd.service - Network Time Synchronization
   Loaded: loaded (/lib/systemd/system/systemd-timesyncd.service; enabled; vendor preset: enabled)
   Active: failed (Result: exit-code) since Mon 2018-01-15 08:58:10 UTC; 8min ago
     Docs: man:systemd-timesyncd.service(8)
  Process: 563 ExecStart=/lib/systemd/systemd-timesyncd (code=exited, status=1/FAILURE)
 Main PID: 563 (code=exited, status=1/FAILURE)
   Status: "Shutting down..."

Jan 15 08:58:10 foo systemd[1]: systemd-timesyncd.service: Service has no hold-off time, scheduling restart.
Jan 15 08:58:10 foo systemd[1]: systemd-timesyncd.service: Scheduled restart job, restart counter is at 5.
Jan 15 08:58:10 foo systemd[1]: Stopped Network Time Synchronization.
Jan 15 08:58:10 foo systemd[1]: systemd-timesyncd.service: Start request repeated too quickly.
Jan 15 08:58:10 foo systemd[1]: systemd-timesyncd.service: Failed with result 'exit-code'.
Jan 15 08:58:10 foo systemd[1]: Failed to start Network Time Synchronization.

and the log has

Jan 15 08:58:09 foo systemd-timesyncd[563]: Cannot resolve user name systemd-timesync: No such process
Jan 15 08:58:10 foo systemd[1]: systemd-timesyncd.service: Main process exited, code=exited, status=1/FAILURE
Jan 15 08:58:10 foo systemd[1]: systemd-timesyncd.service: Failed with result 'exit-code'.
Jan 15 08:58:10 foo systemd[1]: Failed to start Network Time Synchronization.

This seems to be caused by the fact that libnss-systemd is not a hard
dependency of systemd. I'm not sure what the best solution is? Having a
service that is enabled by fails to start looks weird though. Maybe
providing a static user isn't that bad?

This might be the same as:

    https://lists.debian.org/msgid-search/CAO6P2QQX7zghFxgPdPqfZcASNZ2Wv+B0rnTFhkvrXTfbFp76_A@mail.gmail.com

Cheers,
 -- Guido