Q: GPT help

Can you post the output of gpt/gdisk and fdisk? It may no longer be /dev/rdisk0, so a diskutil list would also be helpful.

1. Computer 1 with Bootcamp (in Target Disk Mode).

2. Computer 2 with Mac OS X.

3. Connect Computer 1 to Computer 2 via Firewire/Thunderbolt cable.

4. Computer 1's hard drive should now be visible on Computer 2.

Iyassou wrote:

 

I can't boot into anything. My computer is shut down and I'm replying from my phone.

Do you have access to a second MAC computer?

Do you have an external CD/DVD?

Can you also post the GPT for this disk? Just need to ensure they are both in sync.

sudo gpt -vv -r show /dev/disk1

The MBR looks correct. MAC OS X not booting is strange!

This is strange, because they both match.

One possibility is that bless information was lost when Partition 2 was changed from '07' to 'AF'. Can you run the following command.

The "Macintosh\ HD" string in the following command needs to be replaced with the volume name that you can see when you run diskutil list command for /dev/disk1. Sample output from my machine is shown below.

diskutil list

/dev/disk0

  #:                      TYPE NAME                    SIZE      IDENTIFIER

  0:      GUID_partition_scheme                        *1.0 TB    disk0

  1:                        EFI EFI                    209.7 MB  disk0s1

  2:                  Apple_HFS Macintosh HD            743.7 GB  disk0s2

  3:                Apple_Boot Recovery HD            650.0 MB  disk0s3

  4:      Microsoft Basic Data BOOTCAMP                256.0 GB  disk0s4

sudo bless --info /Volumes/Macintosh\ HD/System/Library/CoreServices/

finderinfo[0]:    45 => Blessed System Folder is /System/Library/CoreServices

finderinfo[1]: 1478210 => Blessed System File is /System/Library/CoreServices/boot.efi

finderinfo[2]:      0 => Open-folder linked list empty

finderinfo[3]:      0 => No alternate OS blessed file/folder

finderinfo[4]:      0 => Unused field unset

finderinfo[5]:    45 => OS X blessed folder is /System/Library/CoreServices

64-bit VSDB volume id:  0x3EE7659409EF64D1

Bless is OSX specific. Do not use it on Bootcamp volume. The last string in this line (called the PartitionType GUID)

     409640  469338128      2  GPT part - EBD0A0A2-B9E5-4433-87C0-68B6B72699C7

is incorrect. It should

      409640  1452530904      2  GPT part - 48465300-0000-11AA-AA11-00306543ECAC

OS X will not recognize this and boot from it. Fdisk and GPT are two separate entities. the '07' to 'AF' was corrected in MBR (via fdisk), but the GPT needs to be corrected via gdisk.

This is what it should look like...

Partition number (1-4): 2

Partition GUID code: 48465300-0000-11AA-AA11-00306543ECAC (Apple HFS/HFS+)

Partition unique GUID: 98D8DC3F-F7F8-41A2-B5AA-6FBFC53694BB

First sector: 409640 (at 200.0 MiB)

Last sector: 1452940543 (at 692.8 GiB)

Partition size: 1452530904 sectors (692.6 GiB)

Attribute flags: 0000000000000000

Partition name: 'Customer'

I suggest you read this first - http://www.rodsbooks.com/gdisk/repairing.html before an attempt is made to fix the GPT.

Need to ensure the commands I give you do not cause further damage.

Can you run the following commands? These do not change the GPT in any way.

sudo gdisk /dev/disk1

p

i

2

q

Here is what I did on my system.

sudo gdisk /dev/disk0

Password:

GPT fdisk (gdisk) version 0.8.9

Warning: Devices opened with shared lock will not have their

partition table automatically reloaded!

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 /dev/disk0: 1954210120 sectors, 931.8 GiB

Logical sector size: 512 bytes

Disk identifier (GUID): 6ED0C429-00D1-4759-B50E-04B6FB80D0E3

Partition table holds up to 128 entries

First usable sector is 34, last usable sector is 1954210086

Partitions will be aligned on 8-sector boundaries

Total free space is 1293 sectors (646.5 KiB)

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

   1              40          409639   200.0 MiB   EF00  EFI System Partition

   2          409640      1452940543   692.6 GiB   AF00  Customer

   3      1452940544      1454210079   619.9 MiB   AB00  Recovery HD

   4      1454211072      1954209791   238.4 GiB   0700  BOOTCAMP

Command (? for help): i

Partition number (1-4): 2

Partition GUID code: 48465300-0000-11AA-AA11-00306543ECAC (Apple HFS/HFS+)

Partition unique GUID: 98D8DC3F-F7F8-41A2-B5AA-6FBFC53694BB

First sector: 409640 (at 200.0 MiB)

Last sector: 1452940543 (at 692.8 GiB)

Partition size: 1452530904 sectors (692.6 GiB)

Attribute flags: 0000000000000000

Partition name: 'Customer'

Command (? for help): q

The partition type needs to be changed via GPT fdisk(disk). The GPT is backed-up via the first command (it will prompt for a filename which will be written to the current local directory). After the backup, the partition type for partition 2 is changed from 0700 (Microsoft...) to HFS/HFS+ (AF00).

sudo gdisk /dev/disk1

b

<FileName>

t

2

AF00

i

2

w

This should allow the currently "broken" Mac to boot.

Here is test I ran (without the write part).

sudo gdisk /dev/disk0

GPT fdisk (gdisk) version 0.8.9

Warning: Devices opened with shared lock will not have their

partition table automatically reloaded!

Partition table scan:

  MBR: hybrid

  BSD: not present

  APM: not present

  GPT: present

Found valid GPT with hybrid MBR; using GPT.

Command (? for help): t

Partition number (1-4): 2

Current type is 'Apple HFS/HFS+'

Hex code or GUID (L to show codes, Enter = AF00):

Changed type of partition to 'Apple HFS/HFS+'

Command (? for help): i

Partition number (1-4): 2

Partition GUID code: 48465300-0000-11AA-AA11-00306543ECAC (Apple HFS/HFS+)

Partition unique GUID: 98D8DC3F-F7F8-41A2-B5AA-6FBFC53694BB

First sector: 409640 (at 200.0 MiB)

Last sector: 1452940543 (at 692.8 GiB)

Partition size: 1452530904 sectors (692.6 GiB)

Attribute flags: 0000000000000000

Partition name: 'Customer'

Command (? for help): q