MacOS partition doesnt boot up and shows as MBR part 255

Question

Sadly the post tagged as duplicated does not work for me

———————

Quick specs: Macbook Pro Mid2012 500GB SSD thats been in the Macbook for around 4 years MacOS Mojave BOOTCAMP Windows (100GB)

Yesterday while I was browsing on Safari i refreshed a site and my Macbook Pro just hanged and the spinning cursor appeared when hovering over Safari, everything else seemed to be working, so i tried closing Safari via the dock (the icons still enlarged when i moved over then) but as soon as i right clicked on Safari the dock froze as well. So i gave it a few minutes to see if its going to unfreeze but it didnt. So naturally i restarted the machine only for it to show the circle with line across instead of the apple logo. I restarted it and held ALT. A “Mac” came up but not the “Windows” clickable thingy. I selected the Mac and again the same story with the line across the circle. Restarted the Mac again now holding Command-R for internet recovery. Opened Disk Utility and i could see this Then i verified the "525.11 GB Crucial..." and i got this:

Then i clicked repair volume and it said it was fixed so i restarted the Macbook but i still got the same cross thing and when i got back to Disk Utility and verified the volume again, it again gave me the same error. (forgot to add, tried to reinstall OSX but only the Windows partition showed up)

Fast forward to today I tried to do what i saw in this Stack Exchange. I removed the Windows partition and then removed the Mac one, then i tried to remount the OSX partition but i got no space available error Now instead of showing disk0s2 and BOOTCAMP under the Crucial volume, it only shows the BOOTCAMP one.

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Heres the list before i tried to unmount:

And after:

Heres a few more pictures i took:

Heres me retrying to repair disk volume after the Macbook was turned off for a day (but before i unmounted it!!!). I tried to repair it a few times but getting th same error and then after like 3-5 times it just said it repaired. Verify still says theres an error but when i click repair it says its repaired

Heres a repair volume in terminal, it gives me an error of unrecognized file system (also before i unmounted stuff)

-bash-3.2# diskutil repairVolume /dev/disk0s2
Error starting file system repair for disk0s2: Unrecognized file system (-69846)

Heres the CoreStorage and a command i saw someone request it in some other Stack Exchange

-bash-3.2# diskutil cs list
No Corestorage logical volume groups found
-bash-3.2# gpt -r show /dev/disk0s2
     start          size      index      contents
         0     829890520

Answer 1

The easiest solution is to use DiskWarrior. It is a litte expensive though, its a "no brainer" i.e. no thinking is involved.

You run it/ boot it from the flash drive (which they post to you), and in fact in Mojave thats definitely preferred (arguably the only way).

Answer 2

The drive you are trying to modify is hybrid partitioned. This is why you are having problems entering some of your commands. You have to first remove the corresponding entry in the Master Boot Record (MBR) partition table before adding an entry back into the GUID Partition Table (GPT).

Note: The commands in this answer need to be entered while booted to Internet Recovery.

1. Enter the commands shown below to remove the 2nd entry from the MBR partition table.

   Note: fdisk is an interactive command.

   fdisk -e /dev/disk0
   setpid 2
   0
   q
   y
   

   Before entering the above commands, the output from fdisk /dev/disk0 should appear as shown below. These are the values stored in the MBR partition table.

   Disk: /dev/disk0        geometry: 63841/255/63 [1025610768 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: FF 1023 254  63 - 1023 254  63 [    409640 -  829890520] Xenix BBT   
   *3: 0C 1023 254  63 - 1023 254  63 [ 830300160 -  195309568] Win95 FAT32L
    4: 00    0   0   0 -    0   0   0 [         0 -          0] unused      
   

   After entering the above commands, the output from fdisk /dev/disk0 should appear as shown below. The 2nd entry has been removed from the MBR partition table.

   Disk: /dev/disk0        geometry: 63841/255/63 [1025610768 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: 00    0   0   0 -    0   0   0 [         0 -          0] unused      
   *3: 0C 1023 254  63 - 1023 254  63 [ 830300160 -  195309568] Win95 FAT32L
    4: 00    0   0   0 -    0   0   0 [         0 -          0] unused      
   

2. Enter the commands shown below to add the 2nd entry to GPT.

   diskutil unmountdisk /dev/disk0
   gpt add -i 2 -b 409640 -s 829890520 -t 7C3457EF-0000-11AA-AA11-00306543ECAC /dev/disk0
   

3. Enter the following commands to undo step 1.

   fdisk -e /dev/disk0
   edit 2
   ff
   n
   409640
   829890520
   q
   y
   

Below is an approximate example of what you should encounter.

$ fdisk -e /dev/disk0
fdisk: could not open MBR file /usr/standalone/i386/boot0: No such file or directory
Enter 'help' for information
fdisk: 1> setpid 2
         Starting       Ending
 #: id  cyl  hd sec -  cyl  hd sec [     start -       size]
------------------------------------------------------------------------
 2: FF 1023 254  63 - 1023 254  63 [    409640 -  829890520] Xenix BBT   
Partition id ('0' to disable)  [0 - FF]: [FF] (? for help) 0
fdisk:*1> q
Writing current MBR to disk.
Device could not be accessed exclusively.
A reboot will be needed for changes to take effect. OK? [n] y
$ diskutil unmountdisk /dev/disk0
Unmount of all volumes on disk0 was successful
$ gpt add -i 2 -b 409640 -s 829890520 -t 7C3457EF-0000-11AA-AA11-00306543ECAC /dev/disk0
gpt add: /dev/disk0: Suspicious MBR at sector 0
/dev/disk0s2 added
$ fdisk -e /dev/disk0
fdisk: could not open MBR file /usr/standalone/i386/boot0: No such file or directory
Enter 'help' for information
fdisk: 1> edit 2
         Starting       Ending
 #: id  cyl  hd sec -  cyl  hd sec [     start -       size]
------------------------------------------------------------------------
 2: 00    0   0   0 -    0   0   0 [         0 -          0] unused      
Partition id ('0' to disable)  [0 - FF]: [0] (? for help) ff
Do you wish to edit in CHS mode? [n] n
Partition offset [0 - 1027343790]: [409640] 409640
Partition size [1 - 1026934150]: [1026934150] 829890520
fdisk:*1> q
Writing current MBR to disk.
Device could not be accessed exclusively.
A reboot will be needed for changes to take effect. OK? [n] y
$ 

You also seem to be getting error messages regarding the EFI partition (disk0s1). You can reformat this partition by entering the command given below.

newfs_msdos -F 32 -v EFI /dev/rdisk0s1

Below is example output.

$ newfs_msdos -F 32 -v EFI /dev/rdisk0s1
512 bytes per physical sector
/dev/rdisk0s1: 403266 sectors in 403266 FAT32 clusters (512 bytes/cluster)
bps=512 spc=1 res=32 nft=2 mid=0xf8 spt=32 hds=32 hid=40 drv=0x80 bsec=409600 bspf=3151 rdcl=2 infs=1 bkbs=6
$