internal mSATA non-destructive conversion from GUID to APM, possible?

Discussion in 'MacBook Pro' started by tillkrueger, Mar 11, 2018.

  1. tillkrueger macrumors newbie


    Dec 1, 2013
    Hi, I just upgraded my mid-2012 Retina MacBook Pro from its internal 500GB SSD "card" to a 1TB Samsung EVO 850 mSATA card (using an adapter) the past, I had done so with the OWC upgrade kit, without issue, but since this is more of a "home-made" solution, using a readily available and much less expensive mSATA card, it didn't go so smoothly.

    Long story short, the mSATA card was refusing to be partitioned or formatted until I figured out how to force a different partitioning map (GUID) on the card, which was using MBR, apparently, and was finally able to restore my system partition backup to it...when I reboot now, however, I boot into a black screen. Only when I hold down the Option key do I get the option of booting into either my System or the Recovery partition.

    My question: is there a way that I can non-destructively convert from my GUID partition map to the Apple Partition Map, so that I can boot automatically, as I was before this upgrade? I know that the gdisk command can do all sorts of magic, and I had to use it extensively to get to this point, so the answer probably lies in a particular gdisk command with the correct parameters to do this conversion.

    This is where I currently stand:

    rMBP-Till:~ till$ diskutil list
    /dev/disk0 (internal, physical):
    0: GUID_partition_scheme *1.0 TB disk0
    1: EFI EFI 209.7 MB disk0s1
    2: Apple_HFS macOS-1TB 999.2 GB disk0s2
    3: Apple_Boot Recovery HD 650.0 MB disk0s3

    rMBP-Till:~ till$ sudo gdisk /dev/disk0
    GPT fdisk (gdisk) version 1.0.3

    Warning: Devices opened with shared lock will not have their
    partition table automatically reloaded!
    Partition table scan:
    MBR: protective
    BSD: not present
    APM: not present
    GPT: present

    Found valid GPT with protective MBR; using GPT.
  2. chabig macrumors 603

    Sep 6, 2002
    GUID is the correct partition type for Macs. Apple Partition Map was deprecated in 2006 when Apple switched from PowerPC to Intel.

    You probably made a mistake somewhere when you cloned your old drive to the new drive. How did you do it? Downloading and running the latest macOS installer might fix it.
  3. tillkrueger thread starter macrumors newbie


    Dec 1, 2013
    Ah, that's good to know...keeps me from walking down the wrong path.

    good question...I spent 2 days trying a dozen different ways to clone my smaller SSD to the new mSATA, so I am not entirely sure anymore what made me end up with the current situation. Maybe you're right and booting into recovery and running the "Install macOS" option will fix it...I'll try that next.
  4. tillkrueger thread starter macrumors newbie


    Dec 1, 2013
    it was indeed that simple, chabig...thank you so much for pointing out the obvious!

    I ran the macOS install from Recovery, after it finished I did a reboot and watched it go straight into my macOS volume.

    it looks like after 3 days of head scratching and many failures, I finally upgraded my trusty old rMBP to a 1TB mSATA "drive". :)

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3 March 11, 2018