[systemd-devel] Failure to umount /var at shutdown

[Daniele Nicolodi]

Hello,

I have a Debian sid system where there is a problem with the unmonting
of the /var filesystem that causes a delay in the shutdown process:

> ott 21 10:08:46 nautilus virtualbox[28559]: Stopping VirtualBox kernel modules.
> ott 21 10:08:46 nautilus systemd[2086]: Received SIGRTMIN+24 from PID 28503 (kill).
> ott 21 10:08:46 nautilus systemd[1186]: Received SIGRTMIN+24 from PID 28500 (kill).
> ott 21 10:08:46 nautilus systemd[2087]: pam_unix(systemd-user:session): session closed for user lele
> ott 21 10:08:46 nautilus systemd[1192]: pam_unix(systemd-user:session): session closed for user lightdm
> ott 21 10:10:16 nautilus systemd[1]: user at 117.service stop-sigterm timed out. Killing.
> ott 21 10:10:16 nautilus systemd[1]: Unit user at 117.service entered failed state.
> ott 21 10:10:16 nautilus systemd-udevd[294]: Network interface NamePolicy= disabled on kernel commandline, ignoring.
> ott 21 10:10:16 nautilus networking[28622]: Deconfiguring network interfaces...done.
> ott 21 10:10:16 nautilus lvm[28706]: 5 logical volume(s) in volume group "system" unmonitored
> ott 21 10:10:16 nautilus umount[28721]: umount: /var: target is busy
> ott 21 10:10:16 nautilus umount[28721]: (In some cases useful info about processes that
> ott 21 10:10:16 nautilus umount[28721]: use the device is found by lsof(8) or fuser(1).)
> ott 21 10:10:16 nautilus systemd[1]: var.mount mount process exited, code=exited status=32
> ott 21 10:10:16 nautilus systemd[1]: Failed unmounting /var.
> ott 21 10:10:17 nautilus systemd[1]: Shutting down.
> ott 21 10:10:17 nautilus systemd-journal[267]: Journal stopped

As you can see, the umount for /var fails because the filesystem is in
use and this apparently makes systemd to wait for what seems to be a 90
seconds timeout before proceeding with the shutdown.

First, how can I debug what is going on, namely how can I see which
process is keeping /var busy?  Second, where does the 90 seconds timeout
come from?  Does it make sense to wait for a timeout if the un-mounting
of a partition fails a shutdown?

Thank you!

Cheers,
Daniele