Missing Operating System after installing OS X Yosemite

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sandyblade Author

Level 1

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Missing Operating System after installing OS X Yosemite

Please help to give suggestion on how to recover my bootcamp after installing OS X Yosemite

Mac Pro, OS X Yosemite (10.10.1)

Posted on Nov 28, 2014 8:29 AM

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Answer 1

Loner T

Level 9

59,536 points

Nov 30, 2014 5:47 PM in response to sandyblade

Will you be able to follow Missing Bootcamp Partition (with pastes!)? You will need Testdisk and GPT Fdisk. If you need links, let me know.

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Answer 2

sandyblade Author

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Nov 30, 2014 5:52 PM in response to sandyblade

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Answer 3

sandyblade Author

Level 1

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Nov 30, 2014 5:57 PM in response to sandyblade

Hi Loner T,
I am trying to follow some of discussion, but I dont know much about bytes and offset. Can you help me about what should I do with this operation based on my screen capture:

Sudo gdisk /dev/rdisk0
P (print the full list of parts)
D (delete)
4 (part 4)
N (new part)
4 (part 4)
1447020544 - Start offset in bytes (start point for Bootcamp part)
+506503161 (Size offset as opposed to End offset)
0700 (Windows part type)
P (print list of all parts just to see what changes will be made)
W (Write the new GPT)
Y (Yes! really write the new GPT)

Especially what number that should I use 🙂

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Answer 4

Loner T

Level 9

59,536 points

Nov 30, 2014 5:58 PM in response to sandyblade

Scroll down to the first MS Data entry and use 'P' to list files and look for familiar Windows files including 'System Volume Information'.

Repeat this for all MS Data entries.

Do not use left/right arrow/cursor keys in Testdisk since it alters partitions.

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Answer 5

sandyblade Author

Level 1

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Nov 30, 2014 6:00 PM in response to sandyblade

Here is my hexdump :

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Answer 6

sandyblade Author

Level 1

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Nov 30, 2014 6:04 PM in response to Loner T

The first ms data result:

Second MS data result:

a

I can found all my bootcamp data here and also the system volume information.

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Answer 7

Loner T

Level 9

59,536 points

Nov 30, 2014 6:04 PM in response to sandyblade

You have not found the correct NTFS header, so you cannot change the GPT yet. What does 'P' show within each MS Data partition?

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Answer 8

sandyblade Author

Level 1

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Nov 30, 2014 6:14 PM in response to Loner T

Hi Loner T,

Here is the 1st until the 3rd print screen:

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Answer 9

Loner T

Level 9

59,536 points

Nov 30, 2014 6:36 PM in response to sandyblade

Do not quit yet.

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Answer 10

sandyblade Author

Level 1

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Nov 30, 2014 6:38 PM in response to Loner T

Do you mean I need to wait on that screen?

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Answer 11

sandyblade Author

Level 1

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Nov 30, 2014 6:41 PM in response to Loner T

Do I need to do deeper search on the 1st Ms Data?

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Answer 12

Loner T

Level 9

59,536 points

Nov 30, 2014 6:59 PM in response to sandyblade

No. You have found your lost NTFS partition. Here is a table I use to validate that it is reasonable.

GPT 3 Start	GPT 3 Size	GPT 3 End	NTFS Start	Byte Offset	NTFS Size	NTFS End
205722144	1269536	206991680	207065088	73408	105515001	312580089

So your 'numbers' look as follows...

Sudo gdisk /dev/rdisk0
P (print the full list of parts)
D (delete)
4 (part 4)
N (new part)
4 (part 4)
207065088
- Start offset in bytes (start point for Bootcamp part)
+
105515001
(Size offset as opposed to End offset)
0700 (Windows part type)
P (print list of all parts just to see what changes will be made)
W (Write the new GPT)
Y (Yes! really write the new GPT)

This will delete and re-write the GPT partition info for /dev/disk0s4.

Rebuild MBR to match the new GPT information thus resetting the Hybrid MBR

Sudo gdisk /dev/disk0
P (Print list of parts)
R (Recover)
H (chooses Hybrid)
Partitions numbers to be hybridized: 2 3 4
Y (Good for GRUB question)
N (part 2 flag)
N (part 3 flag)
Y (part 4 flag make bootable partition)
W (Write the new MBR)
Y (Yes! write the new MBR)
Reboot

Test 1 - Does Bootcamp Volume show up in Finder?

Test 2 - Can you 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.

If you see a hanging underline cursor at the top left on a black screen, and it does not proceed further, you may need Windows Startup Repair or a tool called EasyBCD.

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