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User profile for user: Scotch_Brawth
Scotch_Brawth Author
User level: Level 3
827 points

Repairing Boot Camp after creating new partition

I'm running OS X 10.8 and Windows 7 x64 Pro.


After properly setting up Boot Camp to dual-boot Windows on my Mac mini, I decided to test whether or not it was true that creating another partition (a data partition for OS X) would interfere with Boot Camp. Wikipedia claims it does interfere but without citing a source, whilst the Boot Camp documentation itself only specifies that the disk must be a single partition _prior_ to setup - there's no mention of whether the disk must be _kept_ that way afterwards.


I opened Disk Utility, reduced the size of my OS X parition from 420GB to 80GB, and created a new partition in the unallocated space. Here's how it looks now:

User uploaded file

When I attempted to proceed with the process, I did receive a warning that doing this (and I quote), "may" cause problems with Boot Camp. Seeing as it was inconclusive, I thought I'd give it a shot - nothing ventured…


Of course, it borked Boot Camp, otherwise I wouldn't be posting here. Whilst OS X boots just fine, the Boot Camp partition now no longer shows up in the Startup Manager, though it does in the Startup Disk prefPane. If I do attempt to boot into Boot Camp, I receive the following message on a black screen:

No bootable device --- insert boot disk and press any key

The advice given to someone who had this same problem was, "fix your damaged Boot Camp volume." But I'm at a loss as to how to do that.


So, anyone know how to proceed now so that I can keep my partitions as is, whilst fully restoring normal Boot Camp functionality?

Mac mini (Mid 2011), Mac OS X (10.7.4)

Posted on Jul 26, 2012 11:28 PM

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1,534 replies
User profile for user: Xeshnon
Xeshnon
User level: Level 1
4 points

Feb 19, 2017 9:42 AM in response to Scotch_Brawth

Hi all, i have this issue too.


Will Chris be able to assist me?


I have recently partitioned my MacOS to allow more space to be partitioned away from Macintosh HD.
(this is so i can have more space to be given to partition to bootcamp)

My bootcamp was running fine in Windows 8.User uploaded file


given what i have read, i would need help for the MBR to detect the new partition created (5th) due to the resizing?

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User profile for user: Community User
Community User

Jan 4, 2017 9:03 AM in response to Christopher Murphy

This is probably the single greatest answer I've ever read. This problem has haunted me for years and I've used a variety of hacks to get around it. Your's is by far the best solution. I wish I had found it sooner. Thanks.

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User profile for user: leke49
leke49
User level: Level 1
4 points

Mar 12, 2017 10:38 AM in response to Christopher Murphy

Hi Christoper,


I am having the same issue. I tried to extend by bootcamp partition and it wouldn't boot again. I have tried to follow the this thread to fix mine, but it looks so steps are missing.


Here is a print of protective MBR data

Disk size is 490234752 sectors (233.8 GiB)

MBR disk identifier: 0x00004774

MBR partitions:



Number Boot Start Sector End Sector Status Code

1 1 409639 primary 0xEE

2 409640 274257479 primary 0xAF

3 274257480 275527015 primary 0xAB

4 353243136 490233855 primary 0x0C



what do you do before you get to this section below

------

Found valid GPT with protective MBR; using GPT.


Command: r <enter>


Recovery/transformation command: h <enter>


Place EFI GPT (0xEE) partition first in MBR (good for GRUB)? (Y/N):

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User profile for user: Christopher Murphy
Christopher Murphy
User level: Level 3
560 points

Jul 28, 2012 8:38 AM in response to Scotch_Brawth

Yes I know how to fix this without starting over from scratch, but it requires committment to the command line and most people turn into wimps and bail out. So unless you commit to the process I'm not going to put in the investment. In the meantime you can provide the output from the following to comfirm/deny what I think is the likely problem and solution:


sudo gpt -r -vv show disk0

sudo fdisk /dev/disk0


These are read only commands, no modification to the disk is made.

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User profile for user: Christopher Murphy
Christopher Murphy
User level: Level 3
560 points

Jul 28, 2012 9:49 AM in response to dalstott

Winclone can't help in this case. Even if it backs up, and can restore both the MBR and GPT, he's already altered the GPT by resizing/splitting a Mac OS partition. What's happened is Disk Utility shouldn't merely warn, it should have disallowed this because while it looks like he has only three partitions, he actually has five:


EFI System, Mac HD, Recovery HD, Internal Storage, Bootcamp. Two of those are hidden. Five partitions. MBR can only hold four. So with GUI tools, he's actually hosed. He'll have to use something like gdisk to create a new hybrid MBR, stuffing GPT partitions 1-4 into MBR partition 1. And then he can put Bootcamp, GPT partition 5, into MBR partition 2 and mark it bootable. Then his computer will boot both systems again.


But that's my speculation until I see both partition maps.

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User profile for user: Scotch_Brawth
Scotch_Brawth Author
User level: Level 3
827 points

Jul 28, 2012 10:45 AM in response to Christopher Murphy

Hi,


@Christopher Murphy:


Okay, you seem confident. Let's give this a shot. I use the command-line myself for the odd thing, so I'll try not to bail.


Results of the "sudo gpt -r -vv show disk0" command:

gpt show: disk0: mediasize=500107862016; sectorsize=512; blocks=976773168

gpt show: disk0: PMBR 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 PMBR

1 1 Pri GPT header

2 32 Pri GPT table

34 6

40 409600 1 GPT part - REDACTED UUID

409640 156303528 2 GPT part - REDACTED UUID

156713168 1269536 3 GPT part - REDACTED UUID

157982704 659841040 4 GPT part - REDACTED UUID

817823744 262144

818085888 158687232 5 GPT part - REDACTED UUID

976773120 15

976773135 32 Sec GPT table

976773167 1 Sec GPT header

Results of the "sudo fdisk /dev/disk0" command:

Disk: /dev/disk0 geometry: 60801/255/63 [976773168 sectors]

Starting EndingSignature: 0xAA55

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

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

1: EE 1023 254 63 - 1023 254 63 [ 1 - 976773167] <Unknown ID>

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

Does this indicate a fix is possible?

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User profile for user: Christopher Murphy
Christopher Murphy
User level: Level 3
560 points

Jul 28, 2012 11:09 AM in response to Scotch_Brawth

The GUIDs you redacted are not private data, they are partition type GUIDs,However based on the partition start, sizes, and sequence, I'm reasonably certain the GPT is intact. The MBR has been totally obliterated, however. In my opinion this constitutes severe data loss, and I think I'll report this in the Apple dev bug reporter. It should be disallowed, or at least not be so vague as to what will happen and give you the option of effectively losing access to your Windows partition.


Yes a repair is possible. Yes it's easy. If you can format those results with a monospaced font, you can do this.


1. Download the Mac OS X binary of gdisk, a.k.a. GPT fdiskand install it.

2. Tell me how you formatted your partition results with monospaced font so I can more clearly write out the command line sequence for you to follow to create a new hybrid MBR to fix this problem.

3. Tell me the build number of Mac OS X from the About this Mac Window.

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User profile for user: Scotch_Brawth
Scotch_Brawth Author
User level: Level 3
827 points

Jul 28, 2012 11:57 AM in response to Christopher Murphy

The GUIDs you redacted are not private data, they are partition type GUIDs,

Ah, I mistook them for UUIDs. Thanks for pointing that out. Interesting link 🙂

However based on the partition start, sizes, and sequence, I'm reasonably certain the GPT is intact. The MBR has been totally obliterated, however. In my opinion this constitutes severe data loss, and I think I'll report this in the Apple dev bug reporter. It should be disallowed, or at least not be so vague as to what will happen and give you the option of effectively losing access to your Windows partition.

At the very least, I can use this thread to back up the citation-less assertion on Wikipedia.

Yes a repair is possible. Yes it's easy.

Praise Jebus.

If you can format those results with a monospaced font, you can do this.

😀

1. Download the Mac OS X binary of gdisk, a.k.a. GPT fdisk and install it.

Shall be done.

2. Tell me how you formatted your partition results with monospaced font so I can more clearly write out the command line sequence for you to follow to create a new hybrid MBR to fix this problem.

LOL. It's simple, you just have to be in the Advanced Editor instead of the basic editor given at the foot of the thread - there's a link to it to the top right of the Reply text box. Then just choose Andale Mono from the Font family drop-down.

3. Tell me the build number of Mac OS X from the About this Mac Window.

12A269


By the way, I was a little nervous about the use of a Hybrid MBR to fix this, because the gdisk documentation specifically cautions against it. But then it points out that this is what Boot Camp uses anyway! So, what's next?

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Repairing Boot Camp after creating new partition

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