We're trying to mount a disk, but even though the mount command finishes successfully, the disk isn't mounted

bart@test:/$ sudo mount -v /data
mount: /dev/sdc1 mounted on /data.
bart@test:/$ df -h
Filesystem      Size  Used Avail Use% Mounted on
udev            3.4G     0  3.4G   0% /dev
tmpfs           697M  688K  697M   1% /run
/dev/sda1        29G  3.0G   26G  11% /
tmpfs           3.5G     0  3.5G   0% /dev/shm
tmpfs           5.0M     0  5.0M   0% /run/lock
tmpfs           3.5G     0  3.5G   0% /sys/fs/cgroup
/dev/sda15      105M  3.4M  102M   4% /boot/efi
/dev/sdb1        14G   41M   13G   1% /mnt
tmpfs           697M     0  697M   0% /run/user/1000

Here is the relevant line in /etc/fstab:

UUID=f7c675d9-6b7c-4f96-a26f-5991df9b7cac    /data   ext4   defaults 1   2

Any idea what we could be missing?

/data is an empty folder with root permissions.

Output of blkid:

/dev/sdb1: UUID="7e15008f-4654-4f1d-8aec-1f233c68e5ea" TYPE="ext4" PARTUUID="3dbf34a8-01"
/dev/sda1: LABEL="cloudimg-rootfs" UUID="21b294f1-25bd-4265-9c4e-d6e4aeb57e97" TYPE="ext4" PARTUUID="bcf3ccb8-bce6-4498-93fb-1b9bd59fc81c"
/dev/sda15: LABEL="UEFI" UUID="5CC4-10AB" TYPE="vfat" PARTUUID="ee783a1a-c5d0-42d9-b874-71796971f49b"
/dev/sda14: PARTUUID="2081abbc-a4ba-496a-b391-07952095f65d"
/dev/sdc1: UUID="f7c675d9-6b7c-4f96-a26f-5991df9b7cac" TYPE="ext4" PARTUUID="54aa8864-01"

[Solved]: So while we tried this very thing multiple times yesterday, we just executed a reboot, and now the device is there. It probably got fixed by changes we made by pointers in this post. I don't know why it required a reboot, but all is good now.

  • 1
    What happens if you remove nofail from the fstab line? – Stephen Kitt Oct 11 '18 at 7:32
  • Could you paste output of blkid ? – mrc02_kr Oct 11 '18 at 7:36
  • @StephenKitt that doesn't make a difference unfortunately – Bart van den Burg Oct 11 '18 at 7:37
  • @mrc02_kr I've added the output to the post – Bart van den Burg Oct 11 '18 at 7:38
  • 1
    you could try checking journalctl -b. if systemd thinks the device does not exist / is removed, it has a mis-feature where it will unmount the disk. i guess you could also check systemctl list-units *.device and see if there is a systemd device unit for /dev/sdc1. – sourcejedi Oct 11 '18 at 7:43

The most likely reason is that file system is mounted, as the mount commands reports, but then systemd thinks it knows better and unmounts it before you can see it.

You could use another directory as a mount point, or find out from the logs why it is unmounted.

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