Q: Bootcamp Windows 8.1 Missing after Yosemite Upgrade

Here is a cut/paste from a similar thread (Yosemite Upgrade Broke Bootcamp)...

"

Take a look at the following example. You need to use your own start/end rather than what is here...

Post back when you are ready for Step 5.

"Please stop if you see any error messages.

1. Delete the old entry and create a new entry at GPT#4.

sudo gdisk /dev/disk0

p

d

4

n

4

216524807

490233855

0700

p

w

y

2. You will need to reboot after the change, because the disk you are booted from is the one being modified. Reboot will rebuild disk0s4 using the start/end you entered.

3. Run the dd command - sudo dd if=/dev/rdisk0s4 count=1 2>/dev/null | hexdump -C and check that the first line contains "R.NTFS".

4. This is a tedious process and you want to check after the second 'p'rint command that it looks reasonable, before the 'w'rite and 'y'es to confirm.

5. Once you have a working GPT#4, a new hybrid MBR needs to be created which will overwrite what you see in your Fdisk output. This is also done using GPT Fdisk (Gdisk).

6. a. Test 1 - Can you see your Bootcamp volume in Finder.

    b. Test 2 - Can you files in the Bootcamp volume?

    c. Test 3 - Can you see Bootcamp in your System Preferences -> Startup Disk.

    d. Test 4 - If Test 1-3 are successful, select Bootcamp and click on Restart. You may need Windows startup repair, if you see a hanging underline cursor at the top left corner of your screen. In most cases, it is not required.

Here is an example...

Command (? for help): d

Partition number (1-4): 4

Command (? for help): n

Partition number (4-128, default 4): 4

First sector (34-1954210086, default = 1454210080) or {+-}size{KMGTP}: 1454211072

Last sector (1454211072-1954210086, default = 1954210086) or {+-}size{KMGTP}: 1954209791

Current type is 'Apple HFS/HFS+'

Hex code or GUID (L to show codes, Enter = AF00): 0700

Changed type of partition to 'Microsoft basic data'

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  Microsoft basic data

"

Good to see the NTFS Header. Please reboot and re-run the dd command to make sure you can see the NTFS header.

If you need exact steps for Step 5, please post back.

Step 5 example...

You need to create the Hybrid MBR. Here is an example...

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: hybrid

  BSD: not present

  APM: not present

  GPT: present

Found valid GPT with hybrid MBR; using GPT.

Command (? for help): p

Disk /dev/disk0: 490234752 sectors, 233.8 GiB

Logical sector size: 512 bytes

Disk identifier (GUID): 59BDFEEB-1EB4-4529-94FE-3CBC2C3CD513

Partition table holds up to 128 entries

First usable sector is 34, last usable sector is 490234718

Partitions will be aligned on 8-sector boundaries

Total free space is 2604 sectors (1.3 MiB)

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

   1              40          409639   200.0 MiB   EF00  EF

   2          409640       401060383   191.0 GiB   AF05  Macintosh HD

   3       401060384       402329919   619.9 MiB   AB00  Re

   4       402331648       490233848   41.9 GiB    0700  Microsoft basic data

Command (? for help): r

Recovery/transformation command (? for help): h

WARNING! Hybrid MBRs are flaky and dangerous! If you decide not to use one,

just hit the Enter key at the below prompt and your MBR partition table will

be untouched.

Type from one to three GPT partition numbers, separated by spaces, to be

added to the hybrid MBR, in sequence: 2 3 4

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): AF

Set the bootable flag? (Y/N): n

Creating entry for GPT partition #3 (MBR partition #3)

Enter an MBR hex code (default AB): AB

Set the bootable flag? (Y/N): n

Creating entry for GPT partition #4 (MBR partition #4)

Enter an MBR hex code (default 07): 07

Set the bootable flag? (Y/N): y

Recovery/transformation command (? for help): w

Final checks complete. About to write GPT data. THIS WILL OVERWRITE EXISTING

PARTITIONS!!

Do you want to proceed? (Y/N): y

OK; writing new GUID partition table (GPT) to /dev/disk0.

Warning: Devices opened with shared lock will not have their

partition table automatically reloaded!

Warning: The kernel may continue to use old or deleted partitions.

You should reboot or remove the drive.

The operation has completed successfully.

Now Reboot and verify the output of fdisk again.

Is it working after the Hybrid MBR was recreated? If yes, please switch between Windows and OSX and verify it works in both direction. Please take a backup of Windows and OSX.

Mr. @Loner T.  Thank you very much...  I followed your advice here and finally got it going.  My windows partition is finally up and running.

The disconnect for me was that start/end had to come from a partition that could not be opened, rather than the one that could.  I finally noticed it yesterday.

What Testdisk finds, is normally a "lost" partition. It will not show up in the GPT. If you found your files and used the correct start/end, Windows should come up as it did in your case. Very nicely done.

As I was having quite the same problem (5 gpt partitions resulting in the last one being omitted), I tried that solution too, but instead of only loading one partition, I skipped the recovery partition in MBR. Unfortunately, when writing the changes to disk, I got the following information "GPT data structures destroyed! You may now partition the disk using fdisk or other utilities.". Not great. No GPT partition anymore. I have been able to use gdisk again to convert MBR to GPT. Hope it's fine. I'm doing a backup of the volume before restarting. Is there something I can check before restarting?

Please verify your GPT by sudo gpt -vv -r show /dev/disk0.

Thanks for the reply. I checked the partitions using Partition Inspector. Everything seems fine. My backup will be finished in a couple of minutes so I'll be able to check. But by looking at my terminal session, I realized that I made a huge mistake. Instead of using command h to create the hybrid MBR, I used command g. I thought that this command was to create the hybrid MBR from the GPT, with the possibility to modify it before applying. Didn't understand that it was to replace the GPT by a MBR only partitioning. Should have looked at help on Internet before doing this.