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Thread: clarification of mbr and part table

  1. #1
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    clarification of mbr and part table

    I'm questioning the possibility that I've deleted my partition table using:

    dd if=/dev/zero of=/dev/sda1 bs=446 count=1

    ...trying to remove a grub that may or may not have been there. This is an advanced format disk, but I was under the impression that the partition table followed bs 446 (I did this on 3 drives with no problem on the others)

    Neither windows or linux recognizes the drive as formatted. Any clarification would be helpful...I can't loose the data, but I hope there is a more simple solution that I am unaware of. I'm assuming window's restore does nothing for mbr. Thanks

  2. #2
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    Re: clarification of mbr and part table

    As it just occured to me, This drive has only one partition, and was formatted by windows...

    EDIT: I have boot access to widows7 and linux distros
    Last edited by OlorinIWas; February 20th, 2013 at 01:31 AM.

  3. #3
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    Re: clarification of mbr and part table

    Quote Originally Posted by OlorinIWas View Post
    I'm questioning the possibility that I've deleted my partition table using:

    dd if=/dev/zero of=/dev/sda1 bs=446 count=1

    ...trying to remove a grub that may or may not have been there. This is an advanced format disk, but I was under the impression that the partition table followed bs 446 (I did this on 3 drives with no problem on the others)

    Neither windows or linux recognizes the drive as formatted. Any clarification would be helpful...I can't loose the data, but I hope there is a more simple solution that I am unaware of. I'm assuming window's restore does nothing for mbr. Thanks
    hi
    as i know is the MBR not on /dev/sda1 it is on /dev/sda - and that isn't the same disk-address.
    ciao
    "What is the robbing of a bank compared to the FOUNDING of a bank?" Berthold Brecht

  4. #4
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    Re: clarification of mbr and part table

    The MBR should be on /dev/sda, so you didn't overwrite the MBR, but you probably did overwrite the first 446 bytes of the /dev/sda1 partition, so it has lost the information about the internal stuff of the partition. Depending on what type the partition was (FAT, NTFS...), this information can be reconstructed from backups that are stored within the partition itself. You should be able to do it with TestDisk.

    If the partition is not too big and you have enough space, it would be safer to make an image of the pratition with dd command and then work on that image with TestDisk to see if everything goes OK.


    EDIT: I just saw you've said it is an advanced format disk. I'm not sure if TestDisk can work with this...
    Last edited by Laobi; February 20th, 2013 at 02:47 PM.

  5. #5
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    Re: clarification of mbr and part table

    Quote Originally Posted by Laobi View Post
    The MBR should be on /dev/sda, so you didn't overwrite the MBR, but you probably did overwrite the first 446 bytes of the /dev/sda1 partition, so it has lost the information about the internal stuff of the partition. Depending on what type the partition was (FAT, NTFS...), this information can be reconstructed from backups that are stored within the partition itself. You should be able to do it with TestDisk.

    If the partition is not too big and you have enough space, it would be safer to make an image of the pratition with dd command and then work on that image with TestDisk to see if everything goes OK.


    EDIT: I just saw you've said it is an advanced format disk. I'm not sure if TestDisk can work with this...
    Ok that makes sense. Am I to assume that manual retrieval is my only real option then? testdisk seems like a bad idea 2 me...the format is ntfs at 2 TB...
    Anyone know if data retrieval is likely possible at this pt?

  6. #6
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    Re: clarification of mbr and part table

    Quote Originally Posted by OlorinIWas View Post
    Ok that makes sense. Am I to assume that manual retrieval is my only real option then? testdisk seems like a bad idea 2 me...the format is ntfs at 2 TB...
    Anyone know if data retrieval is likely possible at this pt?
    well after messing with testdisk all night...I got around to trying the boot recovery...which worked, and I have all my data available..

    so I'm not sure exactly what I did...what I deleted, but the advanced testdisk functions (the scan was way off) were very helpful on this advanced format disk

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