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I have a usb stick which is unreadable for some reason. I want to make an image of it for storage purposes so I can try to retrieve the data from the image at a later date.

How would I go about creating such a bit identical image of a usb stick?

This is the error I get when using dd:

oshirowanen@desktop:~$ sudo dd if=/dev/sdd of=/USB_image
[sudo] password for oshirowanen: 
dd: reading `/dev/sdd': Input/output error
0+0 records in
0+0 records out
0 bytes (0 B) copied, 1.00783 s, 0.0 kB/s
oshirowanen@desktop:~$
oshirowanen
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5 Answers5

43

dd it!

Usage would be something like sudo dd if=/dev/sdb of=~/USB_image where /dev/sdb is your usb drive as listed by sudo fdisk -l and ~/USB_image is the image file where the copy will be made (a path where the image file will be created).

To restore the image to another USB drive just invert the process: sudo dd if=~/USB_image of=/dev/sdb will restore ~/USB_image to the device sdb. Just make sure that the new USB drive is as big or bigger than the original one.

You can also mount the image file you just created into a path without need to restore it first to another USB drive with mount ~/USB_image /mnt/USB_image -o loop.

Bruno Pereira
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12

Use ddrescue. It will continue after errors, where dd will simply fail.

Additionally, ddrescue is in the repos. On 13.04, I typed sudo apt-get install gddrescue to install.

Use sudo fdisk -l or dmesg to figure out the device location eg: /dev/sdb, then run a command such as 

ddrescue /dev/sdb /home/user/desktop/bkp.img

there are many options to ddrescue, and you may want to read the man pages. Also I'm not sure why your hardware is failing, and dumping dd. One bad block could make dd quit, but so could intermittent power failures. dmesg may tell you more about hardware failures you may be experiencing.

MAKE SURE the device is not mounted! when you try to do data recovery, imaging, etc. This may cause problems.

There is a lot of things that can go wrong in data recovery. Post back if you have problems. testdisk is a nice utility for doing data recovery once you have an image.

Just for clarity, is this a usb hard drive or usb (solid state memory) device?

I/O errors are typically indicative of hardware malfunctions rather than file-system corruptions.

Also try obtaining the SMART data analysis of the device, if it is available. This may tell you things like if the device his been over heating, powered on for a long time, has bad sectors, exposed to more than X no. of Gs etc.

Zanna
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j0h
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4

dd, as mentioned by a previous poster, is the native way to go. You'll want it to continue over errors, though, so you'd start it with:

dd if=<usb device> of=<new file on disk with enough space> bs=<should match your blocksize> conv=noerror,sync

The important part is the last one: conv=sync tells dd to pad all those blocks it could read only partially with zeroes, so the resulting image may have a few zeroes too many, but will structurally equal the flaky disk, minus its read errors. conv=noerror took care of those read errors, telling dd to continue with the next block. At this point, block size matters, for if it's larger than necessary to skip the error, readable data will be lost here. The Blocksize should always be a factor of two - if in doubt, 512k should do the trick.

Then I'd suggest to:

  • store an unmodified copy of that image somewhere safe
  • fsck a copy of the disk image
  • mount the disk image
  • check your files - they're readable without trouble now, but some may be missing or be truncated
  • If the device itself cannot be read at all, you may be out of luck. Also, if the device happens to contain some proprietary software, it may be setup to return read errors when accessed in the first blocks.

(Partially quoting myself from an article written back in 2010)

If you don't need to remain native, you could always try tools that are trying to ease the process somewhat, such as ddrescue (package gddrescue) and its companion ddrescueview (sourceforge) to visualize the errors.

Tatjana Heuser
  • 625
2

You can create an image of an USB stick (or another device) by using dd.

E.g.

dd if=<usb device> of=usb.img

You can add more parameters to dd to optimize the command (e.g. bs).

Uwe Plonus
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  • 4
  • 14
2

With regards to the second half of your question "This is the error I get when using dd": I can see a couple of possibilities.

  1. Note the difference in command you typed versus the accepted answer; you're missing a ~ in front of /USB_image. In other words, you're trying to output the root of your filesystem instead of to your home directory.
  2. /dev/sdd may not be the correct drive. Run sudo fdisk -l and compare the size of the drive to the known size of the USB stick. For instance, I know this is my USB stick because it's close to 16GB: Disk /dev/sdf: 15.8 GB, 15805186048 bytes.
MDMower
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