Repairing Boot Camp after creating new partition

So the problem is that only GPT partition #5 has been place in the MBR, therefore Windows is only aware of that one partition. You need to use gdisk to add partitions 4 and 5 to the MBR, and flag (presumably) the 5th partition as bootable.

Then should I do same solution again with new hybrid MBR has partition 4 and 5 both like below?

...

...

r <enter> go to the recovery & transformation menu

h <enter> create a new hybrid MBR

4 5 <enter> add partion 5 to the MBR

...

...

p.s. I'm so sorry for my poor English. 😟

Hi Christopher,

Just wanted to thank you for your solution to the same issue I encountered.

Works beautifully!

Yes. Add 4 and 5, make sure 4 is not bootable and 5 is bootable.

Thank you very much. 🙂🙂🙂🙂🙂

I have solved all problems thanks to your answers.

By the way, What is the hybrid MBR?

It seems like a kind of virtual partition... but I want to know more detail what I did.

Has privious hybrid MBR I made been overwriten since I did your solution again?

Your knowledge is so amazing. Thank you. XD

BIOS is to MBR, and (U)EFI is to GPT. And (U)EFI computers can sometimes have a CSM (compatiblity support module) to emulate BIOS, which is how Macs boot Windows for the moment, instead of natively EFI booting it. So at first glance it's GPT vs MBR. Because GPT is newer, there had to be a way to inform old MBR tools that the disk was reserved for GPT usage, so that they wouldn't inadvertenly think the disk wasn't used for anything else. So part of a normal GPT disk is to include an MBR also, but with a single "protective" entry that basically says "this whole disk, all of its sectors, are defined in the GPT, go look there". A hybrid MBR is a totally non-standard thing that has additional entries. And it gets really complicated...and mind numbing.

The creator of GPT fdisk (gdisk) has more info on hybrid MBRs.

And yes, the former one was replaced. There is only room for one hybrid MBR. It takes up exactly one sector on the disk, which happens to be the first sector (LBA 0).

I want to first thank Christopher and the other users in this thread for the discussion and advice. I think I was able to correctly figure out what I needed to do to bootcamp OSX 10.8 and Windows 7 on my new retina pro, with an additional shared partition. My intention was to have three equal sized partitions formatted as follows:

1) HFS for OSX

2) NTFS for Windows

3) exFAT for shared data

My goal was to be able to essentially use the exFAT data drive as an external hard drive that could be swapped between a Mac and a PC. Everything was working great for the first few days, but I think some Windows updates seem to have unmounted this data drive.

When I boot into Windows, the Mac OS drive is still visible in explorer. The data drive shows up in the disk manager as empty unformatted space. In OSX the disk utility shows the data drive as being unmounted, and titles it `disk0s4'.

I am hoping all of my data is still there, and that somehow the Windows update messed it up, although I am not even sure this is possible. In any case, I was hoping someone could offer some advice with the hope that I only need to enter a few commands to repair whatever happened, and my data will still be there.

Thanks in advance!

I don't have any idea without seeing the GPT. The normal case of OS X 10.8 + Windows means already four partitions. An exFAT partition would be partition 5. So your case is already not usual.

Also, exFAT is more for flash media than hard drives. It's actually less robust than FAT32 which has two FATs, whereas exFAT/FAT64 has one FAT. If it gets corrupt, it's much more difficult to repair. You really need to use NTFS to share data between Mac OS and Windows if FAT32 isn't going to work.

Thank you for the reply, Christopher. I hope the following command provides the information you wanted to see.

sudo gpt -r -vv show disk0

It returns:

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 488886712 2 GPT part - 48465300-0000-11AA-AA11-00306543ECAC

489296352 263712

489560064 488884224 3 GPT part - EBD0A0A2-B9E5-4433-87C0-68B6B72699C7

978444288 488894464 4 GPT part - EBD0A0A2-B9E5-4433-87C0-68B6B72699C7

1467338752 1027

1467339779 32 Sec GPT table

1467339811 1 Sec GPT header

The additional exFAT partition was added as a fifth, but I created a dedicated USB drive on which to store the recovery utility, and deleted the recovery partition. I hope this is OK, and won't cause issues down the line when OSX updates are released, or something.

I do not know too much about the different file systems, but it seemed exFAT would be the best choice for read/write access between Windows 7 and OSX without having to use any third-party software. The disk in my MacBook is SSD, if that matters at all. In any case, I am completely open to reformatting the data partition with any other file system of your recommendation. I have all of the data that was on there backed up so I won't lose anything. As long as I can have a shared partition reliably between OSX and Windows 7, I will be very happy.

At this point, is there any other information I can look at to determine what the trouble is? Or should I go ahead and reformat the data partition in FAT32 using GPTdisk in OSX and continue from there.

Thank you again for the help and advice.

I am also experiancing this issue, I tried creating an extra FAT parition and when I rebooted I got this error. Disk Util looks like this now:

also, here are the results from sudo gpt

Disk: /dev/disk0

geometry: 30515/255/63 [490234752 sectors]

Signature: 0xAA55

Starting Ending

#: id cyl hd sec - cyl hd sec [ start - size]

------------------------------------------------------------------------

1: EE 1023 254 63 - 1023 254 63 [ 1 - 409639] <Unknown ID>

2: AF 1023 254 63 - 1023 254 63 [ 409640 - 87932512] HFS+

3: AB 1023 254 63 - 1023 254 63 [ 88342152 - 1269536] Darwin Boot

4: 0B 1023 254 63 - 1023 254 63 [ 89612288 - 146442240] Win95 FAT-32

Administrators-MacBook-Air:~ administrator$

----------------------------------------------------------------------------

gpt show: disk0: mediasize=251000193024; sectorsize=512; blocks=490234752

gpt show: disk0: Suspicious MBR at sector 0

gpt show: disk0: Pri GPT at sector 1

gpt show: disk0: Sec GPT at sector 490234751

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 87932512 2 GPT part - 48465300-0000-11AA-AA11-00306543ECAC

88342152 1269536 3 GPT part - 426F6F74-0000-11AA-AA11-00306543ECAC

89611688 600

89612288 146442240 4 GPT part - EBD0A0A2-B9E5-4433-87C0-68B6B72699C7

236054528 254179328 5 GPT part - EBD0A0A2-B9E5-4433-87C0-68B6B72699C7

490233856 863

490234719 32 Sec GPT table

490234751 1 Sec GPT header

Also, when i try to run "sudo gdisk /dev/disk0", I type my password in and get a message stating that the command can not be found? Is it worth deleting the parition that I made? I just really need the data from the bootcamp parition and I need it to work. I can't seem to mount it and it won't even let me make a back-up.

Thanks,

Mo

I need to see the results from this command also:

sudo fdisk /dev/disk0

There is no advantage to deleting the Recovery HD, because it's in between two partitions. So you now have unusable free space in between. The GPT itself appears to be properly formed. That the disk is not visible/usable in Mac OS X is not a good sign.

Also, when i try to run "sudo gdisk /dev/disk0", I type my password in and get a message stating that the command can not be found?

gdisk, a.k.a. GPT fdisk, is found here.

Is it worth deleting the parition that I made?

Doesn't matter.

I just really need the data from the bootcamp parition and I need it to work. I can't seem to mount it and it won't even let me make a back-up.

Obviously you need to reconsider your backup strategy, that you're in this situation without a viable/current backup. Just saying.

I take it Mac Evans 2 is the Boot Camp volume? It should mount as read-only in Mac OS X for you to get your data off of it, without booting into Windows. You should do that first. Then you can use gdisk to create a new hybrid MBR, adding partitions 4 and 5, and making 5 bootable.

Thanks again for the reply. The results of the command

sudo fdisk /dev/disk0

returns

Disk: /dev/disk0

geometry: 91337/255/63 [1467339812 sectors]

Signature: 0xAA55

Starting Ending

#: id cyl hd sec - cyl hd sec [ start - size]

------------------------------------------------------------------------

1: EE 1023 254 63 - 1023 254 63 [ 1 - 409639] <Unknown ID>

2: AF 1023 254 63 - 1023 254 63 [ 409640 - 488886712] HFS+

*3: 07 1023 254 63 - 1023 254 63 [ 489560064 - 488884224] HPFS/QNX/AUX

4: 07 1023 254 63 - 1023 254 63 [ 978444288 - 488894464] HPFS/QNX/AUX

And here is a screenshot of the disk utility with the unmodifiable disk0s4 data partition.

Thanks again!

The MBR and GPT match up. The problem is not with the partition maps. I'd boot in Windows and see if it can repair the exFAT volume. I don't know if Apple's Disk Utility can repair exFAT. The thing is, exFAT is inherently fragile as it lacks duplicate FATs like other file systems, and it lacks a journal to recovery more quickly/easily from abrupt crashes or power loss, so I'm not sure what the likelihood is for successful repair or recovery.