Drive fails to unmount during shutdown

narcissus256 · 03-19-2022, 05:36 AM

Hi,

I've got a luks encrypted msata drive which I automount using crypttab and fstab:

Code:

# /etc/crypttab
msata   UUID=<drive-uuid>  /path/to/keyfile   nofail,luks

Code:

# /etc/fstab
UUID=<decrypted-volume-uuid> /mnt/msata ext4 defaults,nofail 0 2

Whenever I shut the laptop down, the following errors appear in journalctl:

Code:

Mar 10 15:42:29 thinkpad systemd[1]: Failed unmounting /mnt/msata. 
░░ Subject: A stop job for unit mnt-msata.mount has finished 
░░ Defined-By: systemd 
░░ Support: https://lists.freedesktop.org/mailman/listinfo/systemd-devel 
░░ 
░░ A stop job for unit mnt-msata.mount has finished. 
░░ 
░░ The job identifier is 4061 and the job result is failed. 
Mar 10 15:42:29 thinkpad systemd-cryptsetup[6272]: Device msata is still in use. 
Mar 10 15:42:29 thinkpad systemd-cryptsetup[6272]: Failed to deactivate: Device or resource busy

I wondered if it's bad and may perhaps damage the drive overtime. If so, is there a solution?

I run Arch (5.16.15-arch1-1), I have asked on the Arch Forum, but nobody has answered for a week.

Thank you!

suramya · 03-19-2022, 01:06 PM

It won't physically damage the drive, but there is a possibility of data loss when the system is rebooted without unmounting the partition. Some process is writing to the disk/using the disk that is preventing it from being unmounted. Check the output of iotop and search for the processes accessing /mnt/msata, that should show you the processes that are using that partition. Then you can investigate the programs found to see why they are not terminating when rebooting.

ondoho · 03-20-2022, 06:12 AM

Code:

Failed to deactivate: Device or resource busy

That message is very clear.

narcissus256 · 03-21-2022, 12:57 AM

Thanks! So I have figured out that "Device or resource busy" is because mpd is not giving up access to music on my msata drive.

I've got a user systemd unit starting mpd on startup.

Code:

# $HOME/.config/systemd/user/default.target.wants/mpd.service
[Unit]
Description=Music Player Daemon
Documentation=man:mpd(1) man:mpd.conf(5)
After=network.target sound.target

[Service]
Type=notify
ExecStart=/usr/bin/mpd --systemd

LimitRTPRIO=40
LimitRTTIME=infinity
LimitMEMLOCK=64M
ProtectSystem=yes

NoNewPrivileges=yes
ProtectKernelTunables=yes
ProtectControlGroups=yes
RestrictAddressFamilies=AF_INET AF_INET6 AF_UNIX AF_NETLINK
RestrictNamespaces=yes

[Install]
WantedBy=default.target

So I somehow have to stop this service just before shutdown. I admit I am not an expert on systemd, I have tried this:

Code:

# $HOME/.config/systemd/user/stop_mpd.service[Unit]
Description=Stop mpd before shutdown
DefaultDependencies=no
Before=shutdown.target

[Service]
Type=oneshot
ExecStart=systemctl --user stop mpd.service
TimeoutStartSec=0

[Install]
WantedBy=shutdown.target

But somehow it always fails:

Code:

Mar 20 21:31:25 thinkpad systemd[1]: Failed to start Stop mpd before shutdown.
░░ Subject: A start job for unit stop_mpd.service has failed
░░ Defined-By: systemd
░░ Support: https://lists.freedesktop.org/mailman/listinfo/systemd-devel
░░
░░ A start job for unit stop_mpd.service has finished with a failure.
░░
░░ The job identifier is 3883 and the job result is failed.

and anyway stop_mpd.service runs only after the error "Failed to deactivate: Device or resource busy".

So how would you write a user systemd service which gets run just before shutdown and which stops mpd.service? Or can one even specify that within mpd.service and not bother with stop_mpd.service?

Thank you!

ondoho · 03-21-2022, 11:55 PM

I have the exact same mpd.service, and no such problems.
It accesses an NFS mount on a different computer on the same network, so not quite your situation.
I never see problems with mpd when shutting down.
I don't think you can write a systemd.service to stop another systemd.service; IDK, it just feels wrong.
I also don't use crypttab; I forgot the details but I set my encrypted partitions up with the ArchWiki's help.

So maybe you have to
a) tell systemd to NOT auto(un)mount that partition, and write your own service for that <= the tricky part
b) tell it to unmount after mpd <= that part should be easy