Super User is a question and answer site for computer enthusiasts and power users. It's 100% free, no registration required.

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I have rescued my 2gb usb stick in nearly two days onto an 100gb blank reiserfs partition with these two commands:

ddrescue -f -n /dev/sda /dev/sdb8 logfile

ddrescue -d -f -r3 /dev/sda /dev/sdb8 logfile

since I did not know what to do next, I tried mounting /dev/sdb8 to look what's inside. But mount: you must specify the filesystem type. Before that I was able to mount the blank reiserfs partition before ddrescue wrote on it. Is there a way to read the rescued data now?


share|improve this question

you copied a disk to a partition - this is why there is a difference
if you wanted to mount the partition by itself to mount normally you should have used /dev/sda1 as the input file

you need to carve the partition out of the disk-file or use offsets for mounting tutorial:

you should also be able to easily see the contents with autopsy/sleuthkit available via apt-get or as rpm from

typically i copy a disk or partition to a's just easier to work with that way. then if i copied a disk to a file a carve the partitions into individual files or mount them like in the previously stated tutorial. last i have partition files i can mount and cp -pR to new partitions.

share|improve this answer

Most USB sticks use the PC partitioning format, and have a single partition. That means the first sector (512 bytes) of the disk contains a partition table (and optionally a bootloader), and the rest of the disk contains the partition.

You could have rescued just the partition with

ddrescue -f -n /dev/sda1 /dev/sdb8 logfile
ddrescue -d -f -r3 /dev/sda1 /dev/sdb8 logfile

But now that you have the whole disk, you can get at its partition.

losetup -o 512 /dev/loop0 /dev/sdb8
mount -r /dev/loop0 /mnt

If /dev/loop0 is already in use, you may have to choose another number. The command losetup -f will return the number of a free loop device.

However, manipulating partitions on a live system is error-prone, so rather than do this, I recommend moving the data from the USB stick to an ordinary file. Either copy the whole disk, then use losetup on the disk image (16M × 130 is calculated to be larger than the size of the USB stick):

dd bs=16M count=130 </dev/sdb8 >/var/tmp/usb-stick.disk

Or copy just the partition, and mount the partition image directly:

tail -c +513 </dev/sdb8 | dd bs=16M count=130 >/var/tmp/usb-stick.partition
mount -o loop,ro /var/tmp/usb-stick.partition /mnt

And for future reference, you might as well have passed an output file, rather than an output partition, to ddrescue in the first place.

share|improve this answer
hi! Cannot mount -r /dev/loop0 /mnt mount: you must specify the filesystem type so I gave mount -r -t usbfs /dev/loop0 /mnt a try and it worked, but the content was weired...four folders 001 002 003 004 and a textfile 'devices' ? – panny Nov 13 '10 at 22:21
@panny: usbfs is a pseudo-filesystem (like proc and sysfs); it ignores the device. What you have is probably a vfat filesystem, but if mount didn't figure out the filesystem automatically, there's probably something wrong elsewhere. How exactly did you create the loop device? What does file - </dev/loop0 show? What about file - </what/you/ran/losetup/on? – Gilles Nov 13 '10 at 22:29
file - </dev/loop0 shows /dev/stdin: DOS executable (device driver) and file - </dev/sdb8 shows /dev/stdin: DOS executable (device driver). I would ddrescue the whole 2gb again with proper arguments etc., but it took - don't know why - nearly two days to finish :/ – panny Nov 13 '10 at 22:40
#parted /dev/sdb8 unit B print Warning: GNU Parted has detected libreiserfs interface version mismatch. Found 1-1, required 0. ReiserFS support will be disabled. Error: /dev/sdb8: unrecognised disk label – panny Nov 13 '10 at 22:42
I created the loop filesystem like: losetup -o 512 /dev/loop0 /dev/sdb8 – panny Nov 13 '10 at 22:45

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.