"Missing operating system" after Yosemite upgrade / MBR repair

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"Missing operating system" after Yosemite upgrade / MBR repair

Yesterday I upgraded my Macbook Pro to Yosemite and my Windows 7 Bootcamp vanished i.e. I couldn't see it from the ALT startup options.

In Disk Utility I can see it named as disk0s4.

I followed the steps hereto change the Master Boot Record - now I can see Windows as a startup option, but when I select it I see a "missing operating system" message.

From similar questions on here, here's the output from a few disk commands:

MacBook Pro, OS X Yosemite (10.10.4)

Posted on Jul 6, 2015 3:00 AM

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Answer 1

picturevalve Author

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Jul 6, 2015 3:34 AM in response to picturevalve

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Answer 2

Loner T

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Jul 6, 2015 4:20 AM in response to picturevalve

The gap between GPT3 and GPT4 indicates a lost NTFS header. Can you use Windows 7 Vanished after Yosemite update... help? as a reference and get started with Testdisk?

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Answer 3

picturevalve Author

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Jul 6, 2015 4:49 AM in response to Loner T

Loner T! I was hoping you'd show up 🙂

I've included screenshots from Testdisk below - I've never used it before, so including a few so you can see what I'm doing.

Thanks!

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Answer 4

Loner T

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Jul 6, 2015 5:05 AM in response to picturevalve

Can you scroll down a bit or increase the size of your Testdisk Terminal window? Seeing the System Volume Information is a very good barometer of this being the correct partition. It should look similar to the following.

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Answer 5

picturevalve Author

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Jul 6, 2015 5:10 AM in response to Loner T

Yes, the first MS Data has System Volume Information folder.

If I do P: list files on the second MS Data it says "Can't open filesystem. Filesystem seems damaged"

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Answer 6

Loner T

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Jul 6, 2015 5:25 AM in response to picturevalve

Use the Gdisk steps in the linked thread after you substitute your specific start (231436288) in step 7 and size (258797561) in steps 8, and then rebuild your MBR and test. In most cases, the size is typically the sum of the gap and GPT4, which in your case is 61535384 + 197263360 = 258798744 which leaves a gap of 1183 sectors. Small gap for sector alignment is fine.

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Answer 7

picturevalve Author

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Jul 6, 2015 5:40 AM in response to Loner T

Thanks - I've rebuilt GPT4. Before I rebuild the MBR - should I set the boot flag to Y on another other partition as well as 4? I still want to be able to boot into OSX.

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Answer 8

Loner T

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Jul 6, 2015 5:53 AM in response to picturevalve

MBR Boot flag is valid only for Windows. OSX uses GPT and EFI Boot.

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Answer 9

picturevalve Author

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Jul 6, 2015 6:08 AM in response to Loner T

Getting closer!

I can see Bootcamp in Finder and see all files in the volume.

I can't, however, boot into Windows - it says "the boot selection failed because a required device is inaccessible". A quick look around suggests the Windows Boot Configuration Data Store neesd to be updated with the new partition location, which involves getting the Windows 7 installation disk / USB and choosing "Repair your Computer"

I suppose I should try that?

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