User profile for user: im_chc
im_chc Author
User level: Level 1
8 points

Cannot boot to boot camp Windows after shrinking the Mac os partition

I have a Macbook pro (Retina, 15-inch, Mid 2014, "El Capitan"), also contained a BootCamp partition - installed Windows 7 after the partition was created, and then upgraded to Win 10 later.


After I used Disk Utility (GUI) to shrink the mac partition, I can't boot into Windows anymore (Mac OS still work, posting the post using it now).


However, in Mac's Finder I can still read the files in the BootCamp partition, seems that the partition is still intact.


Tried building a "USB recovery disk" created from another Windows 10, boot from it, and used its "auto fix" feature, but it didn't work. I can still fire up the command prompt though, so I should be able to do things like bootrec, fdisk etc.


Is my Boot Camp sort of a "Hybrid MBR" thing? I tried to get more info about how my machine's partitioned, but I dare not do anything drastic as I fear that I might broke something again.


  1. What should I do to make Windows work again?
  2. Is there a way to let me back up the partition layout (instead of the partitions themselves) so that if I screwed up fixing the partitions, I can safely return to the point before things were screwed up? I'm sure that the partition info should not take a lot of spaces.


Not sure if it helps, but here is what diskutil and fdisk (in Mac OS terminal) shows (the disk0s4 partition is got as a result of shrinking the Mac partition):


xxxx$ diskutil list

/dev/disk0 (internal, physical):

   #:                       TYPE NAME                    SIZE       IDENTIFIER

   0:      GUID_partition_scheme                        *500.3 GB   disk0

   1:                        EFI EFI                     209.7 MB   disk0s1

   2:                  Apple_HFS Macintosh HD            120.1 GB   disk0s2

   3:                 Apple_Boot Recovery HD             650.0 MB   disk0s3

   4:                  Apple_HFS Untitled                29.2 GB    disk0s4

   5:       Microsoft Basic Data BOOTCAMP                350.0 GB   disk0s5

xxxx$ fdisk /dev/disk0

Disk: /dev/disk0	geometry: 60821/255/63 [977105060 sectors]

Signature: 0xAA55

         Starting       Ending

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

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

 1: EE 1023 254  63 - 1023 254  63 [         1 -  977105059] <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  

MacBook Pro 15", OS X 10.11

Posted on May 1, 2019 2:50 AM

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User profile for user: im_chc
im_chc Author
User level: Level 1
8 points

May 11, 2019 2:34 AM in response to Loner T

I've used TestDisk to probe the disk a bit without applying any changes, and from my limited knowledge of TD I've spotted a few lines from the TestDisk.log file that seems alarming:



Warning: number of heads/cylinder mismatches 255 (NTFS) != 1 (HD)
Warning: number of sectors per track mismatches 63 (NTFS) != 1 (HD)



The harddisk (500 GB / 465 GiB) seems too small! (< 918 GB / 855 GiB)
The following partition can't be recovered:



I will post the whole log in the next post.

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User profile for user: im_chc
im_chc Author
User level: Level 1
8 points

May 1, 2019 7:29 AM in response to Loner T

Thanks for your prompt reply, you don't know how grateful I am to see help coming.

I have gone through the forum post a bit, what I got so far is


  1. to use diskutil and GParted to reallocate the freed up space to the boot camp partition
  2. Use the Windows installation disc to make Windows boot up again


But a few questions come to mind:


  1. So GParted will be aware of the stuffs that bootcamp did (Hybrid/Protective MBR?) and will do the resize right? (just asking, know that will work, but want to kind of know what I am doing before messing with critical stuffs like this)
  2. I don't have a Windows 10 installation disc on hand (free upgrade downloaded from MS), just the recovery drive created using Win 10, will that work? (did that once and no good)


Loner T wrote:

If you are able to see Windows files, it is a good sign. Assuming you want to add the space in disk0s4 to disk0s5, take a look at Bootcamp Partition Missing after Resize - Apple Community.
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User profile for user: Loner T
Loner T
User level: Level 9
59,606 points

May 1, 2019 10:38 AM in response to im_chc

im_chc wrote:

So GParted will be aware of the stuffs that bootcamp did (Hybrid/Protective MBR?) and will do the resize right? (just asking, know that will work, but want to kind of know what I am doing before messing with critical stuffs like this)

GParted has no concept of Hybrid MBRs. It needs to be recreated using GPT Fdisk after the partitions are coalesced.


. I don't have a Windows 10 installation disc on hand (free upgrade downloaded from MS), just the recovery drive created using Win 10, will that work? (did that once and no good)

You can build a USB Installer or burn the ISO to a DVD-R SL for Startup Repair. For a 2014 Mac, you will need to use a USB2 Flash drive Installer.

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User profile for user: Loner T
Loner T
User level: Level 9
59,606 points

May 2, 2019 4:55 AM in response to im_chc

im_chc wrote:

If I am to back up the bootcamp partition, can I use WinClone?

Yes.

2. To GParted, expanding the bootcamp partition to take up the free space of disk0s4 is like expanding an ordinary GPT partition, right? From the perspective of Windows, nothing has changed, since the MBR info before and after the expansion stays the same (by using GPT fdisk I saw that it contains a protective MBR instead of a Hybrid so I think all of the MBR info is toast) .... What I'm trying to say is, I might consider to leave the free space alone and just make Windows bootable again, if the GParted expansion thing is risky or something... so if I leave the space alone, I just need to use the USB Installer, right?

The GParted expansion is fairly straightforward. All manipulation of partitions is 'risky', hence backup are highly recommended.

3. Is a (pure) GPT-based Windows 10 more performant than a Hybrid-MBR? I'm not sure if it is Hybrid or not before I screwed the disk up. I think now it is already a GPT partition. Would the USB installer hybridize the partition again?

Your 2014 Mac support both EFI and BIOS.

  • BIOS requires a MBR disk or a Hybrid MBR overlay
  • EFI will use a GPT-only disk


If the de-hybridize thing makes things complicated to you, then forget it (I think it might need reinstalling Windows anyway... even if it doesn't, if it makes the config more prone to errors/config mistakes or incompatible with Apple stuffs, then I will just give it up) ...

'De'hybridizing doe into change the underlying installation of Windows. It just makes the bootability construct disappear, as you already know from your experience. Typically, GPT and Hybrid MBRs are a 1:1 mapping.

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User profile for user: im_chc
im_chc Author
User level: Level 1
8 points

May 3, 2019 3:08 AM in response to Loner T

1. I'm stucked on the backup part.

I have a 2TB USB disk in MBR + NTFS format, WinClone Basic said it's "read only". I used Windows to shrink the partition to obtain 360GB of unallocated space, and then

1) use gdisk to convert the disk to GPT (just gdisk /dev/disk1 and then "w") and

2) use gdisk to create a "Apple HFS+" (? not the exact name) partition - it was the default type determined by the tool.

But the new partition is still not showing up in Finder, and in WinClone.


2. I created the Win 10 USB installer like https://www.windowscentral.com/how-create-windows-10-usb-bootable-media-uefi-support. I only have the ISO of Windows 10 Enterprise LTSB - not the same version of the original Win 10 (Pro? Home?). It can boot, and in the command prompt I can see the files in C:\.


On the other hand during the disk creation in Rufus I choose GPT and UEFI.


So if I click "startup repair", will it perform the repair like the disk is GPT and UEFI? Like it would create an MSR and no Hybrid MBR etc? And will Windows boot in UEFI mode?

(Note that nothing is done on the hard disk yet.)

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User profile for user: Loner T
Loner T
User level: Level 9
59,606 points

May 3, 2019 7:44 AM in response to im_chc

im_chc wrote:

What I did was telling winclone to back up the windows partition to my 2tb external USB disk

As a backup destination, it should work. It does not need to have NTFS or a MBR. The Restore destination should be FAT32 on your internal disk, that Winclone will convert to NTFS during restore. Winclone typically uses Apple HFS.


See http://twocanoes.com/getting-started-winclone/backup-restore-boot-camp/ for reference.



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User profile for user: Loner T
Loner T
User level: Level 9
59,606 points

May 6, 2019 4:21 PM in response to im_chc

Rebuild MBR to match the new GPT information thus resetting the Hybrid MBR. Use defaults for other questions (like partition codes). The only values that need modifications are the Boot flags and step 10. Accept all other defaults that Gdisk offers. Please see thesample Q&A as an example. These steps can be repeated if you make a mistake before you get to Step 12, otherwise start from Step 1 for these steps. Step 6 has numbers which are typed with a space between the numbers. Please see the sample Q&A before you execute these steps.

  1. Sudo gdisk /dev/rdisk0
  2. P (Print list of parts)
  3. R (Recover)
  4. O (print current Hybrid MBR)
  5. H (chooses Hybrid)
  6. Partitions numbers to be hybridized: 2 3 4
  7. Y (Good for GRUB question)
  8. N (part 2 boot flag)
  9. N (part 3 boot flag)
  10. Y (part 4 boot flag make NTFS bootable partition)
  11. O (print current Hybrid MBR)
  12. W (Write the new MBR)
  13. Y (Yes! write the new MBR)
  14. Reboot


Here is sample Q&A for this section. Please notice the Press Enter/Return.


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

Creating entry for GPT partition #2 (MBR partition #2)
Enter an MBR hex code (default AF): Press Enter/Return
Set the bootable flag? (Y/N): N

Creating entry for GPT partition #3 (MBR partition #3)
Enter an MBR hex code (default AB): Press Enter/Return
Set the bootable flag? (Y/N): N

Creating entry for GPT partition #4 (MBR partition #4)
Enter an MBR hex code (default 07): Press Enter/Return
Set the bootable flag? (Y/N): Y


Test 1 - Does Bootcamp Volume show up in Finder?

Test 2 - Can you see files in Bootcamp Volume?

Test 3 - Can you select Bootcamp in System Preferences -> Startup Disk?

Test 4 - If Test 3 is successful, select Bootcamp and Click Restart.

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Cannot boot to boot camp Windows after shrinking the Mac os partition

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