How to fix partition scheme? (Retina 2012, became MBR)

Question

Level 1

90 points

How to fix partition scheme? (Retina 2012, became MBR)

I recently used bootcamp to install Windows 7 on my MacBook retina (2012).

Later, I realized I needed more space in the hard drive. I booted back into OS X and shrunk my OS X volume using disk utility and added a third partition since disk utility doesn't give you the option to leave it as free space anymore. I then lost the ability to boot into Windows, so I booted using my USB Windows install drive and was able to delete the new partition and allow Windows to boot up properly again.

The problem I had, was that the unallocated space from creating a third partition was to the 'left' of my BOOTCAMP drive on the partition table, or starting at a later address.

I tried using a third party tool to 'move' my Windows partition to the left to be able to use the unallocated memory, leaving some space inbetween for good measure. I thought the other volumes would be left untouched.

Now however, I see a "prohibition symbol" both when I attempt to boot from the OSX or recovery partition. Windows 7 still boots fine, and in the default Windows partition tool, both OS X volumes appear to be untouched.

I was able to boot into internet recovery however and get info on the disk. "Disk0s1" is my OS X partition, greyed out, unmountable and I can't see its name. The entire disk seems to now have a Master Boot Record partition scheme now. Within terminal, I type 'diskuril list' to find the TYPE: Apple_Boot for the NAME: 'Recovery HD' and TYPE: 0xAC for my OS X disk and it is un-named.

Also, via terminal, I can mount the recovery disk but not the OSX disk. (But recovery disk still not shown in disk utility)

Is there a possibility to restore the scheme to GPT without erasing the volume? What is preventing me from accessing my OS X volume?

Please let me know if there are any solutions. Again, I can still boot into Windows 7 if there is a tool that works with mac partitions. My mac is a mid 2012 retina with a SSD drive, with OSX sierra on the main volume and currently running mavericks 10.9.3 via the internet recovery tool.

Cheers,

Max

Message was edited by: Mad Maxx

Posted on Jan 8, 2017 4:50 PM

Reply

Answer 1

Loner T

Level 9

59,536 points

Jan 10, 2017 3:58 AM in response to Mad Maxx

Step A - Creates a blank GPT. Choose 2 for GPT, if prompted. (Do not enter such text, it is for informational purpose).

sudo gdisk /dev/rdisk0

o (Create new GPT and Protective MBR)

p (Print)

w (Write)

y (Confirm write)

q (Quit Gdisk)

Step B. Create individual entries. For entry 4 (Windows), we use offset notation, because the MBR uses size, while Gdisk reports end sector. This is entered as size with '+' notation, not end of the partition.

sudo gdisk /dev/rdisk0

x (Experts Menu)

l (This is is lower case L )

1 (This is digit 1 - sets the sector alignment to 1 sector)

m (Go to main menu)

n (New GPT)

1 (Part 1)

40 (Start)

409639 (End)

EF00 (EFI)

n

2

409640 (Start)

684728431 (End)

AF05 (CoreStorage containing JHFS+)

n

3

684728432 (Start)

685997967 (End)

AB00 (Apple Boot - Recovery HD)

n

4

686514176 (Start)

+290177024 (+Size)

0700 (Microsoft Basic Data)

p (Print)

w (Write)

y (Confirm Write)

Reboot. At this point you can/should see Windows files in Finder, but Windows will not boot. If this is successful, then we can create the MBR to make Windows boot.

Reply

Answer 2

Loner T

Level 9

59,536 points

Jan 8, 2017 11:25 PM in response to Mad Maxx

Boot into Internet Recovery - About macOS Recovery - Apple Support - and click on Utilities -> Terminal and run

diskutil list

diskutil cs list

Copy the output using Command+C, quit Terminal, start Safari, Paste the output using Command+V as a reply to this discussion.

If your disk was converted to a MBR disk from a GPT disk using Windows tools, you may also want to install OS X on an external disk using How to set up and use an external Mac startup disk - Apple Support and upgrade it to match the version on the internal disk. You will also need GPT Fdisk (https://sourceforge.net/projects/gptfdisk/).

Do not use Mavericks to manipulate Sierra partitions.

Reply

Answer 3

Mad Maxx Author

Level 1

90 points

Jan 8, 2017 11:24 PM in response to Loner T

Thank you for the reply; I can try working on a bootable OS tomorrow if necessary. For now, I threw my laptop into Target Disk Mode and attached it to another mac via thunderbolt.

Here is the output of "diskutil list", disk 2 being the troubling computer:

mmbp:~ a$ diskutil list

/dev/disk0 (internal, physical):

#: TYPE NAME SIZE IDENTIFIER

0: GUID_partition_scheme *1.0 TB disk0

1: EFI EFI 209.7 MB disk0s1

2: Apple_CoreStorage Macintosh HD 949.9 GB disk0s2

3: Apple_Boot Recovery HD 650.0 MB disk0s3

4: Microsoft Basic Data WINDOWS HD 49.4 GB disk0s4

/dev/disk1 (internal, virtual):

#: TYPE NAME SIZE IDENTIFIER

0: Apple_HFS Macintosh HD +949.5 GB disk1

Logical Volume on disk0s2

EF209FAC-3358-4271-9DD6-7E5F9840C3D8

Unencrypted

/dev/disk2 (external):

#: TYPE NAME SIZE IDENTIFIER

0: FDisk_partition_scheme 500.3 GB disk2

1: 0xAC 350.4 GB disk2s1

2: Apple_Boot Recovery HD 650.0 MB disk2s2

3: Windows_NTFS BOOTCAMP 148.6 GB disk2s3

I hope the second command still works using target disk... The output of "diskutil cs list" is as follows:

mmbp:BOOTCAMP a$ diskutil cs list

CoreStorage logical volume groups (1 found)

|

+-- Logical Volume Group 1CD4B3CA-D070-42B4-909C-0E9AD7BD4518

=========================================================

Name: Macintosh HD

Status: Online

Size: 949860909056 B (949.9 GB)

Free Space: 18931712 B (18.9 MB)

|

+-< Physical Volume 3DC3E59F-CB17-4081-9AAC-D7E894211778

| ----------------------------------------------------

| Index: 0

| Disk: disk0s2

| Status: Online

| Size: 949860909056 B (949.9 GB)

|

+-> Logical Volume Family AF329912-4E63-4000-B872-EC6FE4C659BF

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

Encryption Type: None

|

+-> Logical Volume EF209FAC-3358-4271-9DD6-7E5F9840C3D8

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

Disk: disk1

Status: Online

Size (Total): 949489655808 B (949.5 GB)

Revertible: Yes (no decryption required)

LV Name: Macintosh HD

Volume Name: Macintosh HD

Content Hint: Apple_HFS

mmbp:BOOTCAMP a$

~~~

Earlier I read a reply of yours on an earlier thread regarding the gdisk tool. I was able to successfully download it on the windows 7 volume and now I also have it on the external mac.

Max

Reply

Answer 4

Mad Maxx Author

Level 1

90 points

Jan 8, 2017 11:50 PM in response to Mad Maxx

Also, I tried verifying both the RecoveryHD volume and the OS X volume.

I got two different results..:

mmbp:Volumes a$ diskutil verifyvolume /dev/disk2s2

Started file system verification on disk2s2 Recovery HD

Verifying file system

Checking Journaled HFS Plus volume

Checking extents overflow file

Checking catalog file

Checking multi-linked files

Checking catalog hierarchy

Checking extended attributes file

Checking volume bitmap

Checking volume information

The volume Recovery HD appears to be OK

File system check exit code is 0

Finished file system verification on disk2s2 Recovery HD

mmbp:Volumes a$ diskutil verifyvolume /dev/disk2s1

Error starting file system verification for disk2s1: Unrecognized file system (-69846)

mmbp:Volumes a$

Where Disk2s1 is the OS X volume and disk2s2 is the RecoveryHD

Reply

Answer 5

Loner T

Level 9

59,536 points

Jan 9, 2017 6:11 AM in response to Mad Maxx

Please post the output of

sudo gpt -vv -r show /dev/disk2

Since you can use Target Disk Mode, I suggest installing Gdisk on OS X side of the working Mac, which can be used to correct the non-working Mac's GPT and MBR.

Reply

Answer 6

Mad Maxx Author

Level 1

90 points

Jan 9, 2017 7:55 AM in response to Loner T

mmbp:~ a$ sudo gpt -vv -r show /dev/disk2

Password:

gpt show: /dev/disk2: mediasize=500277790720; sectorsize=512; blocks=977105060

gpt show: /dev/disk2: MBR at sector 0

gpt show: /dev/disk2: Pri GPT at sector 1

gpt show: error: bogus map

gpt show: unable to open device '/dev/disk2': Undefined error: 0

mmbp:~ a$

Gdisk is also now installed.

Reply

Answer 7

Mad Maxx Author

Level 1

90 points

Jan 9, 2017 4:43 PM in response to Loner T

mmbp:~ a$ sudo gdisk -l /dev/disk2

Password:

GPT fdisk (gdisk) version 1.0.1

Warning: Devices opened with shared lock will not have their

partition table automatically reloaded!

Partition table scan:

MBR: MBR only

BSD: not present

APM: not present

GPT: present

Found valid MBR and GPT. Which do you want to use?

1 - MBR

2 - GPT

3 - Create blank GPT

Your answer:

Reply

Answer 8

Mad Maxx Author

Level 1

90 points

Jan 9, 2017 5:04 PM in response to Loner T

Using GPT and creating fresh protective MBR.

Disk /dev/disk2: 977105060 sectors, 465.9 GiB

Logical sector size: 512 bytes

Disk identifier (GUID): C9FE6C58-9225-486C-8FFB-7ED3CFB232CB

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 262281 sectors (128.1 MiB)

Number Start (sector) End (sector) Size Code Name

1 40 409639 200.0 MiB EF00 EFI System Partition

2 409640 684728431 326.3 GiB AF05 Naamloos

3 684728432 685997967 619.9 MiB AB00

4 685997968 781531135 45.6 GiB 0700

5 781793280 977104895 93.1 GiB 0700

mmbp:~ a$

...

Done.. Also, not sure why naamloos is the name of my volume.

Reply

Answer 9

Loner T

Level 9

59,536 points

Jan 9, 2017 6:35 PM in response to Mad Maxx

Namloos is Nameless or Untitled. Can you also post the output of

sudo fdisk /dev/disk0

before we rebuild the GPT and MBR? It will also help in re-building it correctly.

Does Windows boot properly right now?

Reply

Answer 10

Mad Maxx Author

Level 1

90 points

Jan 9, 2017 9:29 PM in response to Mad Maxx

Yes, I can boot into windows just fine. If I hold down the option key on power-on, I see bootcamp AND the OSX volume. The OS X volume boots for some time but I later see the prohibitory symbol. Here is my fdisk terminal output...I wasn't sure if you meant to say disk2, so I copied over both.

-max

mmbp:~ a$ sudo fdisk /dev/disk0

Password:

Disk: /dev/disk0 geometry: 121601/255/63 [1953525168 sectors]

Signature: 0xAA55

Starting Ending

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

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

1: EE 1023 254 63 - 1023 254 63 [ 1 - 409639] <Unknown ID>

2: AC 1023 254 63 - 1023 254 63 [ 409640 - 1855197088] <Unknown ID>

3: AB 1023 254 63 - 1023 254 63 [1855606728 - 1269536] Darwin Boot

4: 0B 1023 254 63 - 1023 254 63 [1856876264 - 96386720] Win95 FAT-32

mmbp:~ a$ sudo fdisk /dev/disk2

Disk: /dev/disk2 geometry: 60821/255/63 [977105060 sectors]

Signature: 0xAA55

Starting Ending

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

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

1: AC 25 127 15 - 1023 254 63 [ 409640 - 684318792] <Unknown ID>

2: AB 1023 254 63 - 1023 254 63 [ 684728432 - 1269536] Darwin Boot

*3: 07 1023 254 63 - 1023 254 63 [ 686514176 - 290177024] HPFS/QNX/AUX

4: 00 0 0 0 - 0 0 0 [ 0 - 0] unused

mmbp:~ a$

Reply

Answer 11

Loner T

Level 9

59,536 points

Jan 10, 2017 3:34 AM in response to Mad Maxx

I need to consolidate relevant information in a single post. Assuming we need to address/correct the 500GB disk2, your MBR (manipulated by the third-party tool) is

Mad Maxx wrote:

mmbp:~ a$ sudo fdisk /dev/disk2

Disk: /dev/disk2 geometry: 60821/255/63 [977105060 sectors]

Signature: 0xAA55

Starting Ending

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

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

1: AC 25 127 15 - 1023 254 63 [ 409640 - 684318792] <Unknown ID>

2: AB 1023 254 63 - 1023 254 63 [ 684728432 - 1269536] Darwin Boot

*3: 07 1023 254 63 - 1023 254 63 [ 686514176 - 290177024] HPFS/QNX/AUX

4: 00 0 0 0 - 0 0 0 [ 0 - 0] unused

mmbp:~ a$

Your GPT is

Using GPT and creating fresh protective MBR.

Disk /dev/disk2: 977105060 sectors, 465.9 GiB

Logical sector size: 512 bytes

Disk identifier (GUID): C9FE6C58-9225-486C-8FFB-7ED3CFB232CB

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 262281 sectors (128.1 MiB)

Number Start (sector) End (sector) Size Code Name

1 40 409639 200.0 MiB EF00 EFI System Partition

2 409640 684728431 326.3 GiB AF05 Naamloos

3 684728432 685997967 619.9 MiB AB00

4 685997968 781531135 45.6 GiB 0700

5 781793280 977104895 93.1 GiB 0700

The MBR entry works

*3: 07 1023 254 63 - 1023 254 63 [ 686514176 - 290177024] HPFS/QNX/AUX

but is not valid on the GPT side, as it does not match either of the following entries.

4 685997968 781531135 45.6 GiB 0700

5 781793280 977104895 93.1 GiB 0700

We need to rebuild the GPT (4 and 5), but ensure that your working Windows stays working (MBR3). The next step is to re-build the GPT.

Reply

Answer 12

Mad Maxx Author

Level 1

90 points

Jan 10, 2017 10:31 AM in response to Loner T

Ok, I'm about to give that a try.

Before I do, if my disk is still connected via thunderbolt, so I should use /dev/rdisk2 rather than rdisk0 right?

Also, typing 'o' gave me:

"This option deletes all partitions and creates a new protective MBR."

That won't touch erase the drives right?

Just want to be on the safe side.

-Max

Reply

Answer 13

Loner T

Level 9

59,536 points

Jan 10, 2017 10:38 AM in response to Mad Maxx

Yes, it should be disk2 in your specific case. I took the values from your GPT and MBR. Please verify.

The GPT is a mapping of the physical disk addresses to a partition map. It will not touch any of your data, unless you decide to manipulate it after the reboot. I suggest not modifying any content till we can get a good backup. OSX Finder just reads the NTFS file system, so we are safe.

We first want to ensure OSX is visible and bootable. We can then re-create the MBR and get Windows to boot.

Reply

Answer 14

Mad Maxx Author

Level 1

90 points

Jan 10, 2017 11:33 AM in response to Mad Maxx

I can't edit my previous post, but I went ahead and followed the steps using rdisk2.

The computer boots into mac fine now. Everything appears to work. I can view the windows disk read only on the mac and it shows up in 'startup disk'. I haven't tried booting into windows.

So now all thats left is recreating the MBR?

Reply

Answer 15

Loner T

Level 9

59,536 points

Jan 10, 2017 11:38 AM in response to Mad Maxx

Before we go further, can you post the output of

diskutil list

diskutil cs list

sudo gpt -vv -r show /dev/disk2

This is to prevent any future issues, if we make a mistake in next set of steps. Your GPT and partitions are now fixed and should not require any further modifications. I suggest a backup of the Mac, once we recreate the MBR.

Reply