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  1. #1

    Using dd_rescue on Knoppix Live CD

    Hi all, my apologies in advance if my question has been asked to death or is otherwise inappropriate for this forum, but searching for linux help, Google pointed me here. I registered in the hope some here may have advice or tips for a hard drive problem I have. I will try to sum up the problem as best as I'm able.

    I have a Buffalo TeraStation NAS, and thru it, had attached a 500gb USB HDD, formatted as XFS. A handful of days ago, all the contents of the drive disappeared, but were not deleted and the HDD still reported the space of the data as being used. I guessed from this that the file table had become corrupted. "Partition Table Doctor" (a WinXP program that's served me well in the past) wasn't able to repair it, and while I'm petrified that my tinkering with PTD *may* have done something to my data, I *think* it's still in tact (and believe that the only corruption is to the "table of contents").

    After trawling the web (as you do) I found many forum posts discussing miracles performed with dd_rescue. I eventually tracked down and burned Knoppix CD (I think 5.1 2007-01-04), and purchased a new 500gb HDD to try and recover the data onto. Plugging in both drives via USB I (think I) identified the two drives as sda1 (new) and sdb1 (corrupt). The steps I've taken are:

    - Use TeraStation to format new drive as XFS
    - Boot Knoppix CD
    - Change root password to blank
    - Run "Root Terminal"
    - Typed: dd_rescue /dev/sdb1 /dev/sda1

    Now the window is scrolling at ludicrous speed. I took a screenshot as follows:

    Am I on the right track? I fear dd_rescue may also copy any corrupt boot sector/file table or whatever the problem with the first drive is, across to the new one. Is this likely? Does the screenshot above indicate that it's working? I tried opening sda1 but it shows as empty in the Konquerer window. While I'm very skilled with sorting Windows problems, my knowledge of Linux is very limited, and the latter four steps above took me an age to figure out I would be most grateful for any and all help with this, particularly so if it saves my data! With many thanks in advance.

    David Y

  2. #2
    I *think* I have (since posting the above) sussed out a (possible) workaround. I eventually figured out doing: mount -o ro,norecovery /dev/sdb1 seems to forcefully mount the corrupt drive, bypassing whatever is preventing it from mounting correctly ("Can't read superblock"?). I can now see the files/folders on the duff drive and am trying to rescue what I can...but it keeps unmounting itself, which doesn't help matters any

    I also realised that the above screenshot only occurs after this drive has unmounted (or more, disappeared from being detected by the OS entirely). dd_rescue showed a different screen prior to this happening.

  3. #3
    Linux User
    Join Date
    Dec 2007
    Idaho USA
    I guessed from this that the file table had become corrupted.
    I will assume you mean the Volume Boot Record on a Windows System , or the Superblock for linux. You can try TESTDISK (on the knoppix live cd, or TestDisk - CGSecurity) or read
    Mounting with an alternative superblock .

    It does not look like you will have a good copy with the errors from the screen shot, but then again I have never used dd_rescue so can not be sure.

  4. $spacer_open

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