How can i recreate my Partition Table

Discussion in 'Mac Basics and Help' started by steeelampe, Aug 28, 2014.

  1. steeelampe, Aug 28, 2014
    Last edited: Aug 28, 2014

    steeelampe macrumors newbie

    Aug 28, 2014
    What happened:

    I upgraded to the Yosemite public beta, which messed up my boot record (?) and rendered my bootcamp partition unbootable. In the process of trying to save my Win 8.1 partition i ended up with a completely empty partition table.

    The current situation: i can boot my mac into internet recovery but diskutil shows only one partition on my 500gb harddrive.

    the previous partitions were:

    1: mac partition - filevault, yosemite public beta (SHOULD BE RECOVERED):

    was ~320 GB in size and the standard mac partition at the beginning, which got shrinked at the end to fit the bootcamp win partition (2). the mac partition uses filevault and runs as mentioned the yosemite public beta.

    2: windows 8.1 bootcamp partition (CAN BE DELETED)

    the question:

    can i somehow recreate my partition table and make my mac partition bootable again? if the windows partition is lost, so be it, as long the mac one is saved.

    TestDisk looks promising as i assume i have to somehow scan my harddrive for partitions and recreate the partition table manually.

    How should i continue? if you need any additional information just ask! thanks in advance for any help!
  2. maflynn Moderator


    Staff Member

    May 3, 2009
    Are you looking to recover your partitions or just recreate them?

    If the latter, boot into the internet recovery, recreate the single partition, install OS X, then after restoring your backup, run boot camp assistant to create a new windows partition
  3. steeelampe thread starter macrumors newbie

    Aug 28, 2014
    i need to recover them, at least the mac partition.
    recreating and losing data is the last option.

    As it was the first partition on the harddrive my idea was to somehow restore the "default" table leaving me with one big mac partition.
  4. Weaselboy Moderator


    Staff Member

    Jan 23, 2005
    Go back to recovery and enter "diskutil cs list" without the quotes in Terminal and post up the output. You can find Terminal in the Utilities menu from recovery.
  5. steeelampe thread starter macrumors newbie

    Aug 28, 2014
    "no corestorage logial volume groups found"

    probably because there are no visible filvault partitions in the partition table?

    i'm currently scanning the drive with TestDrive for partitions from an osx on an external drive. I'll post the found partitions here when its finished.
    The plan is to recreate the table manually with the given sectors of the partions but i'd appreciate help with this one as i've no experience at all with this kind of stuff.

  6. steeelampe, Aug 28, 2014
    Last edited: Aug 28, 2014

    steeelampe thread starter macrumors newbie

    Aug 28, 2014
    So this is what TestDisk says to my current partition structure. When i boot and press alt there is still no partition visible.

    Partition 2 "Unknown" is the one to be saved!
    How should i proceed best? use gdisk to rewrite the table to contain partition 1 (EFI) and partition 2 (macintosh HD), and if yes, how is this done best? (remember, the partition used file vault)

    Attached Files:

  7. blueroom macrumors 603


    Feb 15, 2009
    Toronto, Canada
  8. steeelampe thread starter macrumors newbie

    Aug 28, 2014
    yes i do but i managed to boot the mac partition again like this:

    To find the hidden partition i created a bootable OSX Mavericks installation on an external harddrive on which i installed TestDisk.

    TestDisk scanned my builtin HDD for partitions and created the output seen above

    To restore the table gdisk with the given sectors gdisk was used.

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