I think I'm seeing a similar problem (lost access to Windows after Yosemite upgrade), but I have a little different situation.
While my system (MBP 11,1) was still running Mavericks, a while back I used the excellent instructions on how to add a third bootable partition using the hybrid MBR instructions. My partition table looks like this:
Disk /dev/disk0: 977105060 sectors, 465.9 GiB
Logical sector size: 512 bytes
Disk identifier (GUID): 8654C3BA-C230-47F6-A9C4-AC1F5FF234CE
Partition table holds up to 128 entries
First usable sector is 34, last usable sector is 977105026
Partitions will be aligned on 8-sector boundaries
Total free space is 137 sectors (68.5 KiB)
Number Start (sector) End (sector) Size Code Name
1 40 409639 200.0 MiB EF00 EFI System Partition
2 409640 442304239 210.7 GiB AF00 Customer
3 442304240 443573775 619.9 MiB AB00 Recovery HD
4 443573776 741462231 142.0 GiB AF05 Work Boot
5 741462232 742731775 619.9 MiB AB00 Recovery HD
6 742731776 977104895 111.8 GiB 0700 BOOTCAMP
When I first booted after the update with Option held down, I saw only the main boot partition ("Macintosh HD") and the "Work Boot" partition. The first is still Mavericks (10.9.5), the other is Yosemite (10.10.3).
After some messing about I remembered the commands to at least expose the BOOTCAMP partition:
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: 5
Place EFI GPT (0xEE) partition first in MBR (good for GRUB)? (Y/N): n
Creating entry for GPT partition #5 (MBR partition #1)
Enter an MBR hex code (default AB):
Set the bootable flag? (Y/N): y
Unused partition space(s) found. Use one to protect more partitions? (Y/N): n
Recovery/transformation command (? for help): o
Disk size is 977105060 sectors (465.9 GiB)
MBR disk identifier: 0xD2D65B97
MBR partitions:
Number Boot Start Sector End Sector Status Code
1 * 741462232 742731775 primary 0xAB
2 1 741462231 primary 0xEE
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.
and got it so that all three show up when I boot with Option, although I only see one recovery partition (labeled Recovery 10.9). But trying to boot the BOOTCAMP partition (which shows up as "Windows" in the alt boot screen) gets me the "Missing operating system_" error.
Running Repair Disk generates mostly ok output, with the exception of "Invalid Disk Label, cksum error" mismatch errors, e.g.:
disk0s4: Scan for Volume Headers
disk0s4: Scan for Disk Labels
Invalid Disk Label @ 152510496768: cksum mismatch
Running Repair Disk seems to undo the hybrid partition map (but you probably knew that 🙂 )
I'm not sure that that isn't causing additional trouble, as I also got a "Missing operating system_" error on the Work Boot partition at least once after doing those commands and rebooting.
I have some options:
* Nothing on the Windows partition was critical, and I should have a full backup on that external disk I mentioned (Windows 7, using the standard Windows backup routine). So nuke-and-pave is an option, if that's simplest–but I've never done that, so pointers would be good.
* If it's possible to recover what was there, that would be great. As a start, here's the dump from TestDisk 7.0-WIP:
TestDisk 7.0-WIP, Data Recovery Utility, April 2015
Christophe GRENIER <grenier@cgsecurity.org>
http://www.cgsecurity.org
Disk /dev/disk0 - 500 GB / 465 GiB - 977105060 sectors (RO)
Current partition structure:
Partition Start End Size in sectors
1 P EFI System 40 409639 409600 [EFI System Partition]
2 P Mac HFS 409640 442304239 441894600 [Customer]
3 P Mac Boot 442304240 443573775 1269536 [Recovery HD]
4 P Unknown 443573776 741462231 297888456 [Work Boot]
5 P Mac Boot 741462232 742731775 1269544 [Recovery HD]
Warning: number of heads/cylinder mismatches 255 (NTFS) != 1 (HD)
Warning: number of sectors per track mismatches 63 (NTFS) != 1 (HD)
6 P MS Data 742731776 977104895 234373120 [BOOTCAMP]
I don't know if that helps you or not.
* As a last ditch, I have backups of all three partitions (Time Machine for both Mac partitions and a disk image of Work Boot done just before the Yosemite upgrade), so nuke-and-pave for all three is possible. But I'd really, really like to get back to the three partition scheme (personal Mac OS, work Mac OS, personal Windows).
Any advice would be appreciated.
Thanks!
