$ file data   

Linux rev 1.0 ext4 filesystem data, UUID=9f923f9d-2cbd-4a49-8b5c-6a3cece42509 (extents) (64bit) (large files) (huge files)

$ mount -t ext4 data /mnt/
mount: wrong fs type, bad option, bad superblock on /dev/loop2,
   missing codepage or helper program, or other error

   In some cases useful info is found in syslog - try
   dmesg | tail or so.
  • What are the messages in dmesg or /var/log/syslog when you attempt the mount? And do you know how the file data was created? Could it contain an entire disk, with separate partitions? – Xen2050 Nov 3 '15 at 2:19
  • I think this is a Docker volume. Still not sure how to access it (outside of Docker) though. – Keith Tyler Mar 24 '17 at 22:55

You cannot directly access the file (which is not a block device), you need to use a loop block device.

Assuming your kernel has loop device support,

losetup /dev/loop0 /path/to/data

mount /dev/loop0 /mnt

or directly

mount -o loop /path/to/data /mnt
  • 1
    From Sato's error "bad superblock on /dev/loop2" it sounds like mount might already be automatically using a loop device, but regardless your answer could only help – Xen2050 Nov 3 '15 at 2:19
  • You're right. I had not seen the "loop2". Possibly he was then mounting it to an improperly configured loop device. – LSerni Nov 3 '15 at 14:08

Definitely see dmesg or /var/log/syslog for more details on the error.

In case it was a problem with the filesystem itself, you may need to fsck it with fsck.ext4, these options should work (verbose, force check, preen or automatically repair). And assuming you've set up a loop device for the file like in lserni's answer with losetup /dev/loop8 /path/to/data )

fsck.ext4 -vfp /dev/loop8

And after it's fixed, try the mount again

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