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

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.

Run

diskutil unmountDisk disk0

gpt remove -i 2 /dev/disk0

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

gpt add -i 3 -b 158748672 -s 78225408 -t windows /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

gpt add -i 3 -b 158748672 -s 78225408 -t windows /dev/disk0

Now run

diskutil repairDisk disk0

Please post the output of the Terminal session.

langridgedean wrote:

I did not get an error with "apfs."

Here's the latest output:

-bash-3.2# diskutil unmountDisk disk0

Unmount of all volumes on disk0 was successful

-bash-3.2# gpt remove -i 2 /dev/disk0

gpt remove: /dev/disk0: Suspicious MBR at sector 0

/dev/disk0s2 removed

-bash-3.2# gpt add -i 2 -b 409640 -s 158339032 -t apfs /dev/disk0

usage: gpt add [-b lba] [-i index] [-s lba] [-t uuid] device ...

-bash-3.2# gpt add -i 3 -b 158748672 -s 78225408 -t windows /dev/disk0

gpt add: /dev/disk0: Suspicious MBR at sector 0

gpt add: /dev/disk0: error: no space available on device

-bash-3.2# diskutil repairDisk disk0

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

Started partition map repair on disk0

Checking prerequisites

Checking the partition list

Problems were encountered during repair of the partition map

Error: -69770: Partition map check failed because no slices were found

The highlighted commands did not work.

Reboot can renumber disks. Is disk0 still your internal disk? Change disk0 to appropriate disk, if it is not.

Run, using the appropriate disk,

diskutil unmountDisk disk0

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

gpt add -i 3 -b 158748672 -s 78225408 -t windows /dev/disk0

gpt -vv -r show /dev/disk0

and post the output.

Since you already have HS on the external disk, it would be faster to reboot and hold Alt/Option, select the Recovery HD from the external disk, and then click on re-install macOS and choose the internal disk's current APFS partition. If the internal partition was not converted during the original HS upgrade/install, you may not get any of your files back.

Update: Do you want to try and make this a CS LV/LVG and try to recover first?

If you run

sudo gdisk /dev/disk0

There is a 't' command. It allows you to change the type of the partition. We will only modify GPT2. You can use the 'l' command to get a list of hex codes for various file types. First try AF05.

Can you post a text version of

gpt -vv -r show /dev/disk0

so we can update the macOS partition to be APFS?

You can run the command in Terminal, Select and Copy (Command+C) the output, quit Terminal, start Safari (Get Help Online), and Paste (Command+V) the output as a reply to this discussion.

Can you run

sudo dd if=/dev/rdisk0s2 count=10 2>/dev/null | hexdump -C

This will show us the first 10 blocks of the file system header.

Do you recall if the internal disk was converted to APFS or not?

Try to run

sudo fsck_apfs -n -l /dev/disk0s2

The repairDisk is complaining about an APFS container, which should not be the case with AF00. Can you post the output of

diskutil list

sudo gpt -vv -r show /dev/disk0

Can you post the output of

fdisk dev/disk0

Post the output of

fdisk /dev/disk0

Can you post the output of

diskutil list

before we get started?

Try and run

diskutil repairDisk disk0

We can also try HFS or CS, if this does not work.

You have an option to re-install macOS HS on this disk, without erasing it. You may or may not get your old files back on the macOS side.