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The other day I tried to install Windows 8.1 on my iMac (Mid-2011, 21.5 inch) running OS X Yosemite 10.10.1. The process froze halfway through, resulting in me losing 100 GB (which was suppose to be allocated for Windows) on my main Hard drive.

After running diskutil list, my output is…

    /dev/disk0
    #:                       TYPE NAME                    SIZE       IDENTIFIER
    0:     FDisk_partition_scheme                        *500.1 GB   disk0
    1:                  Apple_HFS Mac HD                  399.2 GB   disk0s1

As you can see, I have FDisk_partition_scheme which is 500.1 GB and my main Apple_HFS called, Mac HD which has all my files and folders, that is 399.2 GB. I wish to make my Mac HD ~500 GB so I can recover that 100 GB that has disappeared.

I also believe that I'm missing a Recovery HD. When I boot with Command + R, I am shown a spinning globe which downloads some sort of outdated recovery (because it shows the old UI). Every time I boot my iMac, I booted into Windows side (somehow?) with the message of something similar "No disk found" etc.

Any help would be much appreciated, thank you!


Output for sudo fdisk /dev/disk0:

Disk: /dev/disk0        geometry: 60801/255/63 [976773168 sectors]
Signature: 0xAA55
         Starting       Ending
 #: id  cyl  hd sec -  cyl  hd sec [     start -       size]
------------------------------------------------------------------------
 1: AF   25 127  15 - 1023 254  63 [    409640 -  779781456] HFS+        
 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

Output for sudo gdisk /dev/disk0:

GPT fdisk (gdisk) version 0.8.10

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

Found valid MBR and GPT. Which do you want to use?
 1 - MBR
 2 - GPT
 3 - Create blank GPT

Your answer:

Your answer: 2
Using GPT and creating fresh protective MBR.

Command (? for help): 

Output for sudo gpt -r -vv show disk0:

gpt show: disk0: mediasize=500107862016; sectorsize=512; blocks=976773168
gpt show: disk0: MBR at sector 0
gpt show: disk0: Pri GPT at sector 1
gpt show: disk0: Sec GPT at sector 976773167
      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  779781456      2  GPT part - 48465300-0000-11AA-AA11-00306543ECAC
  780191096    1269536      3  GPT part - 426F6F74-0000-11AA-AA11-00306543ECAC
  781460632        872         
  781461504  195311616      4  GPT part - EBD0A0A2-B9E5-4433-87C0-68B6B72699C7
  976773120         15         
  976773135         32         Sec GPT table
  976773167          1         Sec GPT header

Output for sudo gpt show /dev/disk0:

      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  779781456      2  GPT part - 48465300-0000-11AA-AA11-00306543ECAC
  780191096    1269536      3  GPT part - 426F6F74-0000-11AA-AA11-00306543ECAC
  781460632        872         
  781461504  195311616      4  GPT part - EBD0A0A2-B9E5-4433-87C0-68B6B72699C7
  976773120         15         
  976773135         32         Sec GPT table
  976773167          1         Sec GPT header
  • You are definitely missing the EFI Partition (around 200 MB) and the Apple_Boot Partition (around 120 MB). Very strange. – J.C. Dec 28 '14 at 9:47
  • please add the output from the command sudo fdisk /dev/disk0 to the question - depending on the partition layout, there may not be enough space for a GPT – nelson Dec 28 '14 at 10:14
  • start 409640, I think you accident deleted the EFI partition(200M), and the partition scheme change to MBR – nelson Dec 28 '14 at 11:15
  • run sudo gpt show /dev/disk1 and show the result – nelson Dec 28 '14 at 12:31
  • sorry, sudo gpt show /dev/disk0 – nelson Dec 28 '14 at 12:34

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