Cannot umount /var/cache?

smartyin · 2025-12-20 03:16:52

When I shutdown my laptop today, the log said failed to umount /var/cache. It worked fine yesterday, is it because systemd updated?

I have reboot the system 3 times, and the error always show up.

the disk format is btrfs, and /var/cache is on the subvolume named @cache.

/var/cache      btrfs           rw,noatime,compress=zstd:3,ssd,discard=async,space_cache=v2,subvol=/@cache    0 0
/var/log        btrfs           rw,noatime,compress=zstd:3,ssd,discard=async,space_cache=v2,subvol=/@log      0 0

systemd[1]: Failed unmounting /var/cache.

Last edited by smartyin (2025-12-20 03:17:30)

seth · 2025-12-20 08:49:07

is it because systemd updated?

Most likely, same as https://bbs.archlinux.org/viewtopic.php … 4#p2278914 ?

smartyin · 2025-12-20 09:17:45

I add the workaround line in sd-shutdown, but still have the problem.

systemd[1]: Unmounting /.snapshots...
systemd[1]: Unmounting /boot...
systemd[1]: Unmounting /home...
systemd[1]: Unmounting Temporary Directory /tmp...
systemd[1]: Unmounting /var/cache...
systemd[1]: Unmounting /var/tmp...
systemd[1]: Stopping Flush Journal to Persistent Storage...
systemd[1]: systemd-backlight@backlight:intel_backlight.service: Deactivated su>
systemd[1]: Stopped Load/Save Screen Backlight Brightness of backlight:intel_ba>
systemd[1]: Finished Virtual Console Setup.
umount[1866]: umount: /var/cache: target is busy.
systemd[1]: \x2esnapshots.mount: Deactivated successfully.
systemd[1]: Unmounted /.snapshots.
systemd[1]: boot.mount: Deactivated successfully.
systemd[1]: Unmounted /boot.
systemd[1]: home.mount: Deactivated successfully.
systemd[1]: Unmounted /home.
systemd[1]: tmp.mount: Deactivated successfully.

seth · 2025-12-21 08:48:58

umount[1866]: umount: /var/cache: target is busy.

What does the rest of the journal look like? Apparently some process (refused to die?) is still using the cache.

smartyin · 2025-12-21 14:24:10

seth wrote:

umount[1866]: umount: /var/cache: target is busy.
What does the rest of the journal look like? Apparently some process (refused to die?) is still using the cache.

I don't know how to find out the process, can you tell me?

seth · 2025-12-21 14:29:53

https://man.archlinux.org/man/ps.1

But /that/ process is by now gone - you'll have to wait until this happens again.

smartyin · 2025-12-22 04:16:15

I cannot find any clue about this problem. It is so weird.

seth · 2025-12-22 09:03:07

Oh, sorry - I confused this w/ another thread in my last post.
Please post your complete system journal for the last boot where this happened, eg.

sudo journalctl -b -1 | curl -F 'file=@-' 0x0.st

for the previous one.

smartyin · 2025-12-22 12:55:11

seth wrote:

Oh, sorry - I confused this w/ another thread in my last post.
Please post your complete system journal for the last boot where this happened, eg.
sudo journalctl -b -1 | curl -F 'file=@-' 0x0.st
for the previous one.

thanks.
I reinstall the system and packages and config everything step by step, want to find out what's wrong.
Till now, everything works fine only without the splash plymouth. But I donnot now why.

seth · 2025-12-22 15:57:18

Since you destroyed all evidence, you'll have to wait and see whether this re-emerges, then update the thread w/ the journal.

smartyin · 2025-12-23 05:10:44

I have just comfirmed the problem reason is installing the package named plymouth.
When I install the package, and use it in mkinitcpio.conf like this:

HOOKS=(base udev plymouth autodetect microcode modconf kms keyboard keymap consolefont block filesystems resume fsck)

with the theme like this:

[Daemon]
Theme=script

then the /var/cache will be busy when shutdown and cannot be unmounted. After uninstall that package, everything works fine.

seth · 2025-12-23 10:27:25

Do you have the problem w/ any other plymouth theme?
https://wiki.archlinux.org/title/Plymou … _the_theme

smartyin · 2025-12-23 23:27:34

seth wrote:

Do you have the problem w/ any other plymouth theme?
https://wiki.archlinux.org/title/Plymou … _the_theme

Yes, even using the default theme.

seth · 2025-12-24 09:16:47

https://gitlab.freedesktop.org/plymouth … h/-/issues
Is this a regression w/ systemd 259 or has it always been like that?

smartyin · 2025-12-24 10:38:16

I am not sure. Plymouth works fine, only find the failure when press esc key to show the log.

seth · 2025-12-24 16:20:00

It might be an artifact of the cache not being on the root partition - if it doesn't cause notable delays or other issues you could report it to the plymouth developers but otherwise just ignore it.

Arch Linux

#1 2025-12-20 03:16:52

Cannot umount /var/cache?

#2 2025-12-20 08:49:07

Re: Cannot umount /var/cache?

#3 2025-12-20 09:17:45

Re: Cannot umount /var/cache?

#4 2025-12-21 08:48:58

Re: Cannot umount /var/cache?

#5 2025-12-21 14:24:10

Re: Cannot umount /var/cache?

#6 2025-12-21 14:29:53

Re: Cannot umount /var/cache?

#7 2025-12-22 04:16:15

Re: Cannot umount /var/cache?

#8 2025-12-22 09:03:07

Re: Cannot umount /var/cache?

#9 2025-12-22 12:55:11

Re: Cannot umount /var/cache?

#10 2025-12-22 15:57:18

Re: Cannot umount /var/cache?

#11 2025-12-23 05:10:44

Re: Cannot umount /var/cache?

#12 2025-12-23 10:27:25

Re: Cannot umount /var/cache?

#13 2025-12-23 23:27:34

Re: Cannot umount /var/cache?

#14 2025-12-24 09:16:47

Re: Cannot umount /var/cache?

#15 2025-12-24 10:38:16

Re: Cannot umount /var/cache?

#16 2025-12-24 16:20:00

Re: Cannot umount /var/cache?

Board footer