[CentOS] systemd: Failed unmounting /var on reboot, should I worry about fs corruption?

In article <db155fbf-7c80-f89f-d401-fcc1097dfe76 at c4.cz>,
Ján Lalinský <lalinsky at c4.cz> wrote:
> Hi all,
> 
> I have Centos 8 installed on a physical machine (www6) with separate LVM
> volumes for /, /var, /var/lib/mysql etc.
> 
> System boot proceeds without a hiccup, in terminal systemctl status says
> everything is OK and running, journalctl says so as well - systemd
> mounts everything stated in fstab.
> 
> However, on reboot systemd echoes problems with filesystem on /var :
> 
> ...// unmounting all volumes
> 
> Nov 26 23:51:30 www6 systemd[1]: Unmounting /var...
> Nov 26 23:51:30 www6 umount[2118]: umount: /var: target is busy.
> Nov 26 23:51:30 www6 systemd[1]: Stopped target Swap.
> Nov 26 23:51:30 www6 systemd[1]: Deactivating swap
> /dev/disk/by-label/lv_swap...
> Nov 26 23:51:30 www6 systemd[1]: var.mount: Mount process exited,
> code=exited status=32
> Nov 26 23:51:30 www6 systemd[1]: Failed unmounting /var.
> 
> Then proceeds and reboots the machine. This occurs on every reboot.
> 
> Did anybody here encounter similar problems on reboot?
> 
> I found this bug
> 
> https://github.com/systemd/systemd/issues/867
> 
> which was closed without a definitive solution, the developer says the
> issue is hard to solve and just cosmetic since /var gets unmounted in
> the end anyway, which is strange because there is a log line about
> unmounting just about every other mountpoint and in the end of the
> journal, there are about 7 log lines about unmounting swap volume, but
> zilch about /var. If the system is getting down without proper unmount,
> data corruption can happen. I would feel much better if there were no
> such errors...

You need to un-hide and read the hidden comments on that bug. They give
a few different workarounds, but also indicate that the issue has indeed
been solved in a later version of systemd. But that was only in April of
this year; I don't know which version of upstream systemd was used in
RHEL/CentOS 8. Maybe the fixed version won't appear until 8.2? Some of
the workarounds such as lazy unmount for /var ought to work in the
meantime.

Cheers
Tony

-- 
Tony Mountifield
Work: tony at softins.co.uk - http://www.softins.co.uk
Play: tony at mountifield.org - http://tony.mountifield.org