External Drive Partition Table Messed up

Discussion in 'macOS' started by macnook, Oct 22, 2010.

  1. macnook macrumors newbie

    Joined:
    Oct 22, 2010
    #1
    Hi,
    I somehow messed up my 1TB external drive's partition table. I have mac os 10.6 and originally set up 3 partitions(1 mac, 2 NTFS). I am pretty sure that I still have all my data and partitions intact.

    here's what I get from pdisk:
    Partition map (with 512 byte blocks) on '/dev/rdisk1'
    #: type name length base ( size )
    1: Apple_Bootstrap Apple 63 @ 1
    2: Apple_Free Extra 262144 @ 64 (128.0M)
    3: Apple_HFS mac 980420872 @ 262208 (467.5G)
    4: Windows_NTFS windows1 490472584 @ 980683080 (233.9G)
    5: Apple_Free Extra 262144 @ 1471155664 (128.0M)
    6: Apple_HFS windows2 482107344 @ 1471417808 (229.9G)
    7: Apple_Free extra1 16 @ 1953525152

    Device block size=512, Number of Blocks=1953525168 (931.5G)
    DeviceType=0x0, DeviceId=0x0

    here's what I get from fdisk:
    fdisk /dev/rdisk1
    Disk: /dev/rdisk1 geometry: 121601/255/63 [1953525168 sectors]
    Signature: 0xAA55
    Starting Ending
    #: id cyl hd sec - cyl hd sec [ start - size]
    ------------------------------------------------------------------------
    1: 00 0 0 0 - 0 0 0 [ 0 - 0] unused
    2: 00 0 0 0 - 0 0 0 [ 0 - 0] unused
    3: 00 0 0 0 - 0 0 0 [ 0 - 0] unused
    4: 00 0 0 0 - 0 0 0 [ 0 - 0] unused

    why does pdisk show a partition table, but fdisk doesn't?

    Does it mean the boot0 boot block has problem?

    How can I rebuild the partition table?

    I really need to get my data back!

    Nook
     
  2. Rovingmonkey macrumors newbie

    Joined:
    May 29, 2010
    #2
    Hi Macnook,

    Im a bit rusty on such matters but as you haven't had a response yet ill have a go at your query - hopefully someone more knowledgable than me will be able to chip in!

    It would appear that your external HDD is formatted with a GUID scheme which pdisk will quite happily interpret.

    fdisk on the other hand, from your output, appears to be looking solely for a MPT (master partition table) which it will be looking for in the first sector of the disk (sector 0). A standard GUID partition table starts in sector 1.

    If the drive was bootable this would likely not be a problem as the GUID scheme would introduce a protective MBR to fool the OS into thinking there was a MPT.

    Due to the number of partitions described in your pdisk output; a MPT would not be able to cope with all of them! Unless you started playing about with extended within extended within extended. . .

    Hope that helps
    RM
     

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