[systemd-devel] idle home NFS gets unmounted although user is still logged in

[Dan Nicholson]

On Tue, May 16, 2023 at 5:54 AM Frank Steiner
<fsteiner-mail1 at bio.ifi.lmu.de> wrote:
>
> I changed the idle-time to 1 minute for debugging. What I can see
> 20 seconds before the umount happens:
>
> bioserver3 /etc/systemd# lsof /home/b
> COMMAND     PID    USER   FD   TYPE DEVICE SIZE/OFF      NODE NAME
> jupyterhu 14150 biouser  cwd    DIR  0,107     4096 134348997 /home/b/biouser (<server>:/b)
> jupyterhu 14150 biouser   10u   REG  0,107    16384 151474490 /home/b/biouser/.local/share/jupyter/nbsignatures.db (<server>:/b)
> python3.1 14195 biouser  cwd    DIR  0,107     4096 134348997 /home/b/biouser (<server>:/b)
> python3.1 14195 biouser   45u   REG  0,107    28672 134367744 /home/b/biouser/.ipython/profile_default/history.sqlite (<server>:/b)
> python3.1 14195 biouser   47u   REG  0,107    28672 134367744 /home/b/biouser/.ipython/profile_default/history.sqlite (<server>:/b)
> R         14198 biouser  cwd    DIR  0,107     4096 134348997 /home/b/biouser (<server>:/b)
> R         14198 biouser    3u   REG  0,107       18 134945871 /home/b/biouser/tmp/.nfs00000000080b1c4f000000c2 (<server>:/b)
>
> So, that's very far from the nfs mount being idle, but 20 seconds later
> the mount gets removed.
>
> When I chdir (as root) into /home/b, the mount stays and the user's
> jupyterhub session keeps running (tested for 30 minutes). When I chdir
> away from /home/b, the mount is removed a minute later.

I strongly suspect you're dealing with
https://bugzilla.redhat.com/show_bug.cgi?id=2056090. I.e., autofs
doesn't handle mount namespaces. Since systemd uses lots of mount
namespaces, the idle timeout essentially doesn't work. The only
workaround I'm aware of is to run something in the root namespace that
keeps the mount active. Having an active process with its current
directory in the mount would do it.

--
Dan