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Level 1

0 points

Boot Camp won't start after OSX Yosemite upgrade

Like so many others, I installed OSX Yosemite this morning and now Boot Camp no longer works.

After I updated to Yosemite I restarted my computer, held down alt, and was presented nothing but a Macintosh HD. I followed “Loner T’s” instructions…

ndiskutil list

diskutil cs list

sudo gpt -vv -r show /dev/disk0

sudo fdisk /dev/disk0

Enter you password when prompted.

…and now a windows option is available during startup. However, when selected, all I get is a black screen with "A disk read error occurred" notice.

I’m in serious trouble if I cannot repair this issue. PLEASE HELP.

iMac, OS X Yosemite (10.10), Windows 7

Posted on Oct 18, 2014 12:00 PM

59 replies

Loner T

Level 9

59,471 points

Oct 18, 2014 4:11 PM in response to Baja Tym

Please scroll down the first MS Data partition and use "P: List Files". Look for familiar files. Repeat this process till you have exhausted all MS Data partitions. You may end up executing a "Deeper Scan" (a per sector scan) to find deleted partition headers. For each such, you will look for familiar files within. You may end up with one, two or more such candidates. For each such candidate, first test is to see if they represent a NTFS header. If they do test if Bootcamp will allow repair and bring up Windows.

For machines which have bootcamp, no software installer should ever move partitions around. Apple broke what they designed and they continue to do so for every software update. The Late 2013+ machines finally have UEFI, but all Macs that can run Mavericks/Yosemite should get a retrospective EFI update to make them UEFI compliant.Instead, it has been used as a tool for selling newer hardware.

Loner T

Level 9

59,471 points

Oct 18, 2014 4:14 PM in response to olypdd

olypdd wrote:

Interesting. Some folks say that if you upgrade from the OSX partition it will be fine. But sounds like that's not always the case so I'll hold off.

The problem with such a thought process is that Windows successfully booting does not imply it worked. I have collected several threads which show disk space discrepancies ranging from 20GB to 125GB. I suggest you preserve a before and after state and compare to be 100% certain.

I had much rather see a failure which indicates potential data loss than losing data silently and finding out several months later.

olypdd

Level 1

15 points

Oct 18, 2014 4:25 PM in response to Loner T

My 15" MBP is late 2013. I don't understand what is meant by UEFI compliant and how that bears on this issue. I have a sense of what is meant but maybe you could help me understand it. Thanks.

Baja Tym Author

Level 1

0 points

Oct 18, 2014 4:32 PM in response to Loner T

Okay... here are screen caps of what I'm seeing.

I don't know how to do what you are asking... "first test is to see if they represent a NTFS header. If they do test if Bootcamp will allow repair and bring up Windows."

1. I don't know how to determine if they "represent a NTFS header"

2. I don't know how to test if Boot Camp will allow a repair.

olypdd

Level 1

15 points

Oct 18, 2014 4:32 PM in response to olypdd

OK, I've been reading about UEFI vs bios...wow. In short, looks like UEFI respects or works with partitions better?

Loner T

Level 9

59,471 points

Oct 18, 2014 4:35 PM in response to Baja Tym

1. Please press enter on Deeper Search. This will be a very slow process may take several hours.

2. Once it completes, it provide a list of partitions. You should focus on the MS Data partitions, because OS X works fine.

3. Scroll through each MS Data from the results of Deeper Search and use "P: List Files" to look for Windows files.

Baja Tym Author

Level 1

0 points

Oct 18, 2014 4:59 PM in response to Loner T

I'm running the deeper scan now. I also again read some of your other recommendations and ran this.... not sure if it will help.

I'm finding that I'm a real idiot...this stuff makes my mind turn to jelly. I can't thank you enough! You're an awesome person for helping everyone like you're doing!!

Baja Tym Author

Level 1

0 points

Oct 18, 2014 5:05 PM in response to Loner T

Okay, I found one with loads of Windows files.

Loner T

Level 9

59,471 points

Oct 18, 2014 5:23 PM in response to Baja Tym

1. If the 'dd' command shows the "R.NTFS" string, it indicates that the NTFS header is intact. A repair is possible. Since you are using rdisk0s4, it may save you some time.

2. Please post a screen shot of the Testdisk window which shows the files. Is there a file called 'System Volume Information' in that list? Does the start/size shown in the Testdisk window match the following entry?

1752625152 200898560 4 GPT part - EBD0A0A2-B9E5-4433-87C0-68B6B72699C7

Loner T

Level 9

59,471 points

Oct 18, 2014 5:54 PM in response to olypdd

olypdd wrote:

OK, I've been reading about UEFI vs bios...wow. In short, looks like UEFI respects or works with partitions better?

Yes. I have two rMBPs Late 2013, both run UEFI based Windows. Please see Problem installing Windows (7, 8.0, 8.1) on BOOTCAMP - Mavericks for a UEFI installation.

Baja Tym Author

Level 1

0 points

Oct 18, 2014 6:07 PM in response to Loner T

I closed it without taking a snap. I'm rerunning it now... as you know it may take a few. Thanks again for all your help.

Loner T

Level 9

59,471 points

Oct 18, 2014 6:19 PM in response to Baja Tym

If the start/size you saw matches your GPT#4 start/size, and you are getting a disk read error when selecting Windows, since your DD indicated a valid NTFS header, you can try a Windows Repair to check if that works first, rather than a full deeper search again, which can take a while.