WARNING: Think twice before applying the latest ML update.

Discussion in 'Windows, Linux & Others on the Mac' started by CountBrass, Aug 8, 2012.

  1. CountBrass, Aug 8, 2012
    Last edited: Aug 9, 2012

    CountBrass macrumors regular

    Mar 17, 2009
    Update: If you're having a similar problem, try leaving it on on the grey boot screen overnight (ie several hours). In my case that seemed to resolve the issue. What the issue was remains a mystery.

    As I , and others have discovered, the latest ML update completely messes up your hard drive layout to the point that Bootcamp/Windows will not start.

    To give you an idea how much it screws things up here is my disk layout *after* the update:

    gpt show: disk0: mediasize=751277983744; sectorsize=512; blocks=1467339812
    gpt show: disk0: Suspicious MBR at sector 0
    gpt show: disk0: Pri GPT at sector 1
    gpt show: disk0: Sec GPT at sector 1467339811
    start size index contents
    0 1 MBR
    1 1 Pri GPT header
    2 32 Pri GPT table
    34 6
    40 409600 1 GPT part - C12A7328-F81F-11D2-BA4B-00A0C93EC93B
    409640 291015616 2 GPT part - 48465300-0000-11AA-AA11-00306543ECAC
    291425256 1269536 3 GPT part - 426F6F74-0000-11AA-AA11-00306543ECAC
    292694792 1272
    292696064 1174642688 4 GPT part - EBD0A0A2-B9E5-4433-87C0-68B6B72699C7
    1467338752 1027
    1467339779 32 Sec GPT table
    1467339811 1 Sec GPT header


    Short of completely wiping the disks and starting from scratch (but how without ML disks?!?) I have no idea how I am going to fix Apple's monumental **** up.

    Don't they test their damn patches? This one was specifically for the rMBP so it's not as if they have a lot of variations test?
  2. AppleFanatic10 macrumors 68030


    Nov 2, 2010
    Encino, CA
    My BootCamp partition boots up fine.
  3. flipnap macrumors 6502

    May 1, 2012
  4. \-V-/ Suspended


    May 3, 2012
    You can make a bootable Mountain Lion installer using a USB flash drive: http://www.macrumors.com/2012/07/25/create-a-bootable-mountain-lion-usb-key-installer/

    You just need to download the Mountain Lion installer.

    You can also use the recovery partition by holding the alt/option key at boot up.
  5. PhoenixMac macrumors 65816

    Mar 7, 2010
    Mine works fine, and plus one for having backups and a ML USB.
  6. murphychris macrumors 6502a

    Mar 19, 2012
    Well, having lurked around the Apple forums and hearing about this, I haven't seen a before and after upgrade output of the GPT and MBR, from those having problems. So I don't know what happened to their systems. I've seen hybrid MBRs that have been replaced with PMBRs, but there's no good reason for Apple's installer to do this at all, and obviously most people aren't having the problem. So I don't know what's happening, let alone the trigger for it.

    Yeah and, what's the problem? I see four partitions in the usual order: EFI System, Mac OS, Recovery HD, Windows.

    Yeah I'm not exactly happy with the lack of a Live CD/DVD image (which could be written to a USB stick as well as burned). This has been standard on linux for many years and it's beyond redonkulous that Apple doesn't do it.

    Anyway so long as you can boot Mac OS X, this is repairable there, most likely without starting from scratch. But I can't tell what you think is wrong with the GPT, what your symptoms are, and you also haven't included the hybrid MBR. Please use the following command:

    sudo fdisk /dev/disk0
    Umm?? Yes. Except yours. They intentionally did this just to you. Is that better?
  7. CountBrass, Aug 9, 2012
    Last edited: Aug 9, 2012

    CountBrass thread starter macrumors regular

    Mar 17, 2009

    I left my machine on over night on the grey boot screen (clutching at straws) and this morning everything works again.

    Something strange was going on, no idea what, but simply leaving on the grey boot screen seems to have resolved whatever the issue was.

  8. PhoenixMac macrumors 65816

    Mar 7, 2010
    Did you have Bootcamp partition made prior to upgrading to Mountain Lion or after?
  9. murphychris macrumors 6502a

    Mar 19, 2012
    Sounds like possible NVRAM corruption or confusion. I'd zap the PRAM, and reselect the Mac OS and Windows disks in System Preferences > Startup Disk.

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