systemd keeps unmounting a removable drive

Question

I have following line in /etc/fstab:

UUID=E0FD-F7F5 /mnt/zeno vfat noauto,utf8,user,rw,uid=1000,gid=1000,fmask=0113,dmask=0002 0 0

The partition is freshly created by gnome-disks under the respective user, and spans the whole card.

Now: Running mount /mnt/zeno as user (1000) succeeds, but right after that I find out that it's actually not mounted: following umount /mnt/zeno fails with umount: /mnt/zeno: not mounted. When watching journalctl -f, I can see following messages appear when mounting:

[...] kernel: SELinux: initialized (dev mmcblk0p1, type vfat), uses genfs_contexts
[...] systemd[1]: Unit mnt-zeno.mount is bound to inactive service. Stopping, too.
[...] systemd[1]: Unmounting /mnt/zeno...
[...] systemd[1]: Unmounted /mnt/zeno.

So it seems that systemd indeed keeps unmounting the drive, but I can't find out why. I don't remember creating any custom ".mount" files. I tried to find something in /etc/systemd and in my home folder but did not find anything.

So what is this "mnt-zeno.mount" file and how can I review it? And most importantly, how can I mount the drive?

Answer 1

mnt-zeno.mount was created by systemd-fstab-generator. According to Jonathan de Boyne Pollard's explanation on debian-user mailing list:

[systemd-fstab-generator is] a program that reads /etc/fstab at boot time and generates units that translate fstab records to the systemd way of doing things [.....]

The systemd way of doing things is mount and device units, per the systemd.mount(5) and systemd.device(5) manual pages. In the raw systemd way of doing things, there's a device unit named "dev-sde1.device" which is a base requirement for a mount unit named "media-lumix\x2dphotos.mount".

After altering fstab one should either run systemctl daemon-reload (this makes systemd to reparse /etc/fstab and pick up the changes) or reboot.

Answer 2

For people who come here via a google search (like me), the developers have known about this problem for almost 5(!) years as of writing this and still nobody tries to fix it. https://github.com/systemd/systemd/issues/1741

Workaround: Often, restarting the systemd daemon via systemctl daemon-reload solves the problem.

Answer 3

systemd: Unmounting /boot

One of the Redhat 7 Linux VM running on Azure platform. recently. i have restored the data from old backup with the help of below mentioned URL Azure KB article.

https://docs.microsoft.com/en-us/azure/backup/backup-azure-restore-files-from-vm

Post restoration activity Azure unmounted the disk automatically from the linux VM.

After that i dont see /boot filesystem on the server and it's unmounted automatically.

below is the error message starting seeing in the /var/log/messages

Dec 14 15:04:00 rhellinuxdbprodserver systemd: Unmounting /boot...
Dec 14 15:04:00 rhellinuxdbprodserver kernel: XFS (sda1): Unmounting Filesystem
Dec 14 15:04:00 rhellinuxdbprodserver systemd: Unmounted /boot.

To fix the issue i just reparse the "systemctl daemon-reload" post that /boot filesystem mounted properly.

Pre-Artifact

[root@rhellinuxdbprodserver boot]# df -Th | grep -v tmpfs
Filesystem     Type      Size  Used Avail Use% Mounted on
/dev/sda2      xfs        64G   51G   14G  79% /
/dev/sdb1      ext4      111G   17G   89G  16% /mnt/resource

[root@rhellinuxdbprodserver boot]# systemctl daemon-reload

[root@rhellinuxdbprodserver boot]# mount -a

Post-Artifact

[root@rhellinuxdbprodserver boot]# df -Th | grep -v tmpfs
Filesystem     Type      Size  Used Avail Use% Mounted on
/dev/sda2      xfs        64G   51G   14G  79% /
/dev/sdb1      ext4      111G   17G   89G  16% /mnt/resource
/dev/sda1      xfs       497M  203M  294M  41% /boot