jimisat
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Q: after installing bootcamp Yosemite won't boot just gives me a no sign

I installed bootcamp  for Win 8.1 on a 1 year old mac with Yosemite. Windows boots fine but when I press option an try to boot into OSX, it just gives me a black circle with a No Sign.

MacBook Pro, OS X Yosemite (10.10.2)

Posted on Feb 4, 2015 9:25 AM

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jimisat

Q: after installing bootcamp Yosemite won't boot just gives me a no sign

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  • Helpful answers

  • by Loner T,

    Loner T Loner T Feb 4, 2015 10:31 AM in response to jimisat
    Level 7 (24,825 points)
    Safari
    Feb 4, 2015 10:31 AM in response to jimisat

    Your GPT has been corrupted or the incorrect partition was used to install Windows, causing the disk to be a non-GPT disk or OSX was overwritten.

     

    Can you post the output of

     

    sudo gpt -vv -r show /dev/disk0

  • by jimisat,

    jimisat jimisat Feb 4, 2015 10:45 AM in response to Loner T
    Level 1 (0 points)
    Feb 4, 2015 10:45 AM in response to Loner T

    Thanks for helping.

    I can't log in at all. Can you tell me how to run the sudo since I just get the no sign sometime call the Prohibitory Sign. I have tried to reset pram, hold shift, hold command-s all with no resolution. I can log into windows 8.1 though.

    Jim

  • by Loner T,

    Loner T Loner T Feb 4, 2015 10:59 AM in response to jimisat
    Level 7 (24,825 points)
    Safari
    Feb 4, 2015 10:59 AM in response to jimisat

    You can

     

    1. use Windows CMD and diskpart commands, or,

    2. use OS X: Installing OS X on an external volume - Apple Support boot from this external volume, install GPT Fdisk on this external disk, and post the output, or,

    3. use Internet Recovery (Command+Opt+R) or Local Recovery (Command+R) - OS X: About OS X Recovery - Apple Support - and run the GPT command.

  • by jimisat,

    jimisat jimisat Feb 4, 2015 11:24 AM in response to jimisat
    Level 1 (0 points)
    Feb 4, 2015 11:24 AM in response to jimisat

    How would I use the Windows CMD and diskpart commands

  • by jimisat,

    jimisat jimisat Feb 4, 2015 11:51 AM in response to Loner T
    Level 1 (0 points)
    Feb 4, 2015 11:51 AM in response to Loner T

    How would I use the Windows CMD and diskpart commands

  • by Loner T,

    Loner T Loner T Feb 4, 2015 12:08 PM in response to jimisat
    Level 7 (24,825 points)
    Safari
    Feb 4, 2015 12:08 PM in response to jimisat

    Please see the attached screen shot.

     

    diskpart-list.PNG

  • by jimisat,

    jimisat jimisat Feb 4, 2015 12:30 PM in response to Loner T
    Level 1 (0 points)
    Feb 4, 2015 12:30 PM in response to Loner T

    Thank you again,

    I actually got that far but don't know how to rebuild the GPT for the OSX partition.

    I have

    partition 1 system    200MB 20K offset

    partition 2 unknown  185GB 200mb offset

    partition 3 unknown  619MB 185GB offset

    partition 4 Primary    47GB 186GB offset

     

    Volume 0  C Bootcamp NTFS  partition      47gb  healthy boot

    Volume 1     EFI           FAT32  partition     200mb  healthy system

    Volume 3  E                            removable  0mb    on media

  • by Loner T,

    Loner T Loner T Feb 4, 2015 1:02 PM in response to jimisat
    Level 7 (24,825 points)
    Safari
    Feb 4, 2015 1:02 PM in response to jimisat

    Download GPT Fdisk (http://sourceforge.net/projects/gptfdisk/). Please also see http://www.rodsbooks.com/gdisk/walkthrough.html

     

    Once you have it extracted and installed, you can use it as follows

     

    C:\Users\MyName\Downloads\gdisk-windows-0.8.10>gdisk64 \\.\physicaldrive0

    GPT fdisk (gdisk) version 0.8.10

     

     

    Partition table scan:

      MBR: hybrid

      BSD: not present

      APM: not present

      GPT: present

     

     

    Found valid GPT with hybrid MBR; using GPT.

     

     

    Command (? for help): p

    Disk \\.\physicaldrive0: 500118192 sectors, 238.5 GiB

    Logical sector size: 512 bytes

    Disk identifier (GUID): 22749ACF-207D-458E-B255-5DF02C39DC2D

    Partition table holds up to 128 entries

    First usable sector is 34, last usable sector is 500118158

    Partitions will be aligned on 8-sector boundaries

    Total free space is 1325 sectors (662.5 KiB)

     

     

    Number  Start (sector)    End (sector)  Size       Code  Name

       1              40          409639   200.0 MiB   EF00  EFI System Partition

       2          409640       250801735   119.4 GiB   AF05  OSY-MBP13

       3       250801736       252071271   619.9 MiB   AB00  Recovery HD

       4       252071936       500117503   118.3 GiB   0700  BOOTCAMP

     

     

    Command (? for help):