disk0s2 can't mount - Partition shows as "MBR part 255"

Something happened with my BootCamp configuration and now my MBP will only boot into windows. When I booted into recovery and checked the Disk Utility, the "disk0s2" was unmounted and couldn't be mounted. I tried to follow guides where people had similar issues, however, I believe I've dug my hole deeper.

I'm getting an error that there's a "suspicious" and "malformed" MBR at sector 0. I'm also getting an error the there is "no space available on device" when trying to add the partition back.

The image below shows my current gpt output. Can anyone help get my OSX partition back to bootable?

Thank you in advance!!!

MacBook Pro

Posted on Jul 31, 2018 1:44 PM

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Loner T

Level 9

59,536 points

Posted on Aug 1, 2018 4:41 PM

Run

gpt remove -i 2 /dev/disk0

gpt add -i 2 -b 409640 -s 158339032 -t apfs /dev/disk0

If 'apfs' gives you an error, then

gpt add -i 2 -b 409640 -s 158339032 -t 7C3457EF-0000-11AA-AA11-00306543ECAC /dev/disk0

Now run

diskutil repairDisk disk0

and reboot and test if macOS will boot properly.

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81 replies

Loner T

Level 9

59,536 points

Aug 11, 2018 5:46 AM in response to langridgedean

You will need to run 'p'rint and then 'w'rite and then 'y' (to confirm write). Once written, try to run

diskutil repairDisk disk0

and post the output.

Loner T

Level 9

59,536 points

Aug 14, 2018 8:15 AM in response to langridgedean

Yes, you can eraseVolume disk0s2 and re-install macOS.

Loner T

Level 9

59,536 points

Aug 6, 2018 6:34 AM in response to langridgedean

Reboot and hold Alt/Option and select the internal macOS installation. Do you get any errors when trying to boot macOS? If there are no errors, download and install GPT Fdisk (https://sourceforge.net/projects/gptfdisk/) to address the Windows side.

Aug 9, 2018 1:09 PM in response to Loner T

Repairing the partition map might erase disk0s1, proceed? (y/N) y

Started partition map repair on disk0

Checking prerequisites

Checking the partition list

Adjusting partition map to fit whole disk as required

Checking for an EFI system partition

Checking the EFI system partition's size

Checking the EFI system partition's file system

Checking the EFI system partition's folder content

Checking all HFS data partition loader spaces

Checking booter partitions

Reviewing boot support loaders

Checking Core Storage Physical Volume partitions

The partition map appears to be OK

Finished partition map repair on disk0

Aug 11, 2018 4:47 AM in response to Loner T

sudo gdisk /dev/disk0

Password:

GPT fdisk (gdisk) version 1.0.4

Warning: Devices opened with shared lock will not have their

partition table automatically reloaded!

Partition table scan:

MBR: protective

BSD: not present

APM: not present

GPT: present

Found valid GPT with protective MBR; using GPT.

Command (? for help): t

Partition number (1-3): 2

Current type is 'Apple APFS'

Hex code or GUID (L to show codes, Enter = AF00): AF05

Changed type of partition to 'Apple Core Storage'

Command (? for help):

Loner T

Level 9

59,536 points

Aug 2, 2018 11:20 AM in response to langridgedean

Do not rerun the commands. Do you have output when you removed/added the gpt entry?

Loner T

Level 9

59,536 points

Aug 8, 2018 1:44 PM in response to langridgedean

Can you post the output of

diskutil info disk0

Loner T

Level 9

59,536 points

Aug 11, 2018 12:18 PM in response to langridgedean

We have tried the three native file systems that Macs support. The next option is to re-install macOS in the current GPT2. You may not get your files back.

Loner T

Level 9

59,536 points

Aug 12, 2018 2:05 PM in response to langridgedean

At this point, if you try to re-install macOS, can you select and use this partition without any errors?

Loner T

Level 9

59,536 points

Aug 6, 2018 9:33 AM in response to langridgedean

If you can get a USB3 Flash drive, it will work much better than a USB2 one. You can also use an external HDD. You do not need another Mac.

See About macOS Recovery - Apple Support for reference. You can re-install macOS from the Recover Console -> Re-install macOS.

Aug 8, 2018 4:17 PM in response to Loner T

Device Identifier: disk0

Device Node: /dev/disk0

Whole: Yes

Part of Whole: disk0

Device / Media Name: APPLE SSD SD128E

Volume Name: Not applicable (no file system)

Mounted: Not applicable (no file system)

File System: None

Content (IOContent): GUID_partition_scheme

OS Can Be Installed: No

Media Type: Generic

Protocol: SATA

SMART Status: Verified

Disk Size: 121.3 GB (121332826112 Bytes) (exactly 236978176 512-Byte-Units)

Device Block Size: 512 Bytes

Read-Only Media: No

Read-Only Volume: Not applicable (no file system)

Device Location: Internal

Removable Media: Fixed

Solid State: Yes

Virtual: No

Hardware AES Support: No

Aug 11, 2018 5:01 PM in response to langridgedean

Ran a couple of other commands to see the results. Still an error in verifying the volume:

diskutil verifyDisk /dev/disk0

Started partition map verification on disk0

Checking prerequisites

Checking the partition list

Checking the partition map size

Checking for an EFI system partition

Checking the EFI system partition's size

Checking the EFI system partition's file system

Checking the EFI system partition's folder content

Checking all HFS data partition loader spaces

Checking booter partitions

Checking Core Storage Physical Volume partitions

The partition map appears to be OK

Finished partition map verification on disk0

diskutil verifyVolume /dev/disk0s2

Started file system verification on disk0s2

Error: -69564: Unable to find an APFS Container Reference

Loner T

Level 9

59,536 points

Aug 13, 2018 7:40 PM in response to langridgedean

langridgedean wrote:

https://apple.stackexchange.com/questions/221114/how-to-fix-broken-gpt-guid-and- unmountable-no-type-volumes

This assumes that you have a CS LV/LVG, but with APFS on High Sierra, this causes issues.

langridgedean wrote:

https://apple.stackexchange.com/questions/220018/macbook-does-not-mount-does-not -boot-does-not-read-drive

This is a really messy GPT, with a triple-boot configuration, and at least two Recovery HDs.

langridgedean wrote:

manually repair GUID table

"Missing Operating System"

I really need help! Bootcamp Partition GONE! Loner T please Help!

Using Disk Utility to resize partitions, on a legacy BIOS system, causes GPT vs MBR issues. Hybrid MBRs can be very nasty. See http://www.rodsbooks.com/gdisk/hybrid.html as a reference.

langridgedean wrote:

https://www.cnet.com/news/tackle-stubborn-disk-partitioning-in-os-x/

Topher Kessler used to post on ASC. Sad that he no longer posts here. I do not recommend using Fdisk on GPT-only disks. It is very nasty.

langridgedean wrote:

Main partition, disk0s2 won't mount after resizing Bootcamp partition | MacRumors Forums

Very similar to the previous ASC posts about Bootcamp resizing.

Loner T

Level 9

59,536 points

Aug 9, 2018 4:03 AM in response to langridgedean

We cannot determine the file system on the internal disk. The next step can be destructive with the potential of data loss.

Do you have a backup of the files on the macOS and Windows side for safety?

Loner T

Level 9

59,536 points

Aug 11, 2018 9:00 AM in response to langridgedean

Can you test with AF00?

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disk0s2 can't mount - Partition shows as "MBR part 255"