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niall_mc Author

Level 1

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Bootcamp partition will not boot

hi there,

I am having an issue with my bootcamp partition on my MacBook.

The windows partition is showing up when I hold down the Option key on startup but it just brings a cursor saying:

A disk Read error occurred.

Press Ctrl+Alt+Del

When I boot into Mac OS X the partition and check Disk Utility the windows partition is greyed out and showing up as disk0s4

From reading other solutions on this site I thought it may be the GPT and the MBr but I am unsure how to fix it.

The results of my fdisk and gpt checks are:

sudo fdisk /dev/disk0

Disk: /dev/disk0 geometry: 60801/255/63 [976773168 sectors]

Signature: 0xAA55

Starting Ending

#: id cyl hd sec - cyl hd sec [ start - size]

------------------------------------------------------------------------

1: EE 0 0 2 - 25 127 14 [ 1 - 409639] <Unknown ID>

2: AF 25 127 15 - 1023 254 63 [ 409640 - 388671872] HFS+

3: AB 1023 254 63 - 1023 254 63 [ 389081512 - 1269536] Darwin Boot

*4: 07 1023 254 63 - 1023 254 63 [ 390352896 - 586420224] HPFS/QNX/AUX

sudo gpt -r -vv show disk0

Password:

gpt show: disk0: mediasize=500107862016; sectorsize=512; blocks=976773168

gpt show: disk0: Suspicious MBR at sector 0

gpt show: disk0: Pri GPT at sector 1

gpt show: disk0: Sec GPT at sector 976773167

start size index contents

0 1 MBR

1 1 Pri GPT header

2 32 Pri GPT table

34 6

40 409600 1 GPT part - C12A7328-F81F-11D2-BA4B-00A0C93EC93B

409640 388671872 2 GPT part - 48465300-0000-11AA-AA11-00306543ECAC

389081512 1269536 3 GPT part - 426F6F74-0000-11AA-AA11-00306543ECAC

390351048 1848

390352896 586420224 4 GPT part - EBD0A0A2-B9E5-4433-87C0-68B6B72699C7

976773120 15

976773135 32 Sec GPT table

976773167 1 Sec GPT header

Any help would be appreciated.

MacBook Pro, Mac OS X (10.7.4)

Posted on Oct 7, 2015 11:11 PM

Best reply

Loner T

Level 9

59,477 points

Posted on Oct 8, 2015 3:26 PM

Please post the output of

sudo dd if=/dev/rdisk0s4 count=1 2>/dev/null | hexdump -C

View in context

61 replies

Loner T

Level 9

59,477 points

Oct 26, 2015 3:00 AM in response to niall_mc

In roughly five days, it has moved from 393914695 to 396623872. that is ~1.3GB. Has Testdisk reported any more errors?

niall_mc Author

Level 1

0 points

Oct 27, 2015 5:58 PM in response to Loner T

Hi Loner T,

It still only had the one error as far as I could see. It now seems to be finished and it is at the following screen:

What should I be selecting here?

Loner T

Level 9

59,477 points

Oct 27, 2015 6:04 PM in response to niall_mc

You need to look for partitions around these start addresses (first column).

389081512 1269536 3 GPT part - 426F6F74-0000-11AA-AA11-00306543ECAC

390351048 1848

390352896 586420224 4 GPT part - EBD0A0A2-B9E5-4433-87C0-68B6B72699C7

Your Testdisk looks to be at the beginning of the disk. Please scroll down (quite a bit) till you get closer. Please be very careful with key strokes, since this has take a long time to get here.

niall_mc Author

Level 1

0 points

Oct 27, 2015 6:08 PM in response to Loner T

There is a partition starting at 389081508 with an End at 777753379 as per the attached photo.

Loner T

Level 9

59,477 points

Oct 27, 2015 6:25 PM in response to niall_mc

Scroll down a bit and see if you get any MS Data entries. Testdisk does not support HFS+ file system, so some options that are available for NTFS are missing at the bottom of your screen.

niall_mc Author

Level 1

0 points

Oct 27, 2015 6:28 PM in response to Loner T

There is an MS Data partition starting at 390352896 and finishing at 976771071.

Loner T

Level 9

59,477 points

Oct 27, 2015 6:40 PM in response to niall_mc

This is the same start as this

390352896 586420224 4 GPT part - EBD0A0A2-B9E5-4433-87C0-68B6B72699C7

but slightly smaller. It might be a good sign. Scroll down to this MS Data entry and you should see an option 'p' to print the list of files in this entry. Please post the listing. It should look similar to

This is bizarre. 20,224 - 18,176 = 2,048, which exactly 1,024 MB or 1GiB.

niall_mc Author

Level 1

0 points

Oct 27, 2015 7:22 PM in response to Loner T

Hi Loner T,

It is coming back with an error again saying the FileSystem seems damaged:

Loner T

Level 9

59,477 points

Oct 27, 2015 7:27 PM in response to niall_mc

Given this entry and the one from your original GPT output, the two possible partition tables have the following two layouts.

GPT 3 Start	GPT 3 Size	GPT 3 End	NTFS Start	Sector Offset	NTFS Size	NTFS End	Sector Offset (MB)	NTFS(Gb)	Disk End	Disk Difference
389081512	1269536	390351048	390352896	1848	586420224	976773119	1	279.63	976773168	49
GPT 3 Start	GPT 3 Size	GPT 3 End	NTFS Start	Sector Offset	NTFS Size	NTFS End	Sector Offset (MB)	NTFS(Gb)	Disk End	Disk Difference
389081512	1269536	390351048	390352896	1848	586418176	976771071	1	279.63	976773168	2097

niall_mc Author

Level 1

0 points

Oct 27, 2015 7:31 PM in response to Loner T

Sorry Loner T. I am not sure what that signifies.

Does this mean I might have to change my partition table?

Loner T

Level 9

59,477 points

Oct 27, 2015 7:34 PM in response to niall_mc

In this Terminal window, hit Escape only once. It will take you back a single screen. Once you get to the previous screen, click on the top left yellow icon (in the middle) and put this terminal in your task bar. We cannot afford to lose this.

Start a new Terminal window and start Testdisk using /dev/rdisk0, but we will use the Advanced option. The goal of this window is to look at the boot sectors and MFT to see if we can locate any discrepancies.

Let me know once you get to this point and I will provide example screen shots to proceed further.