Macintosh HD partition missing from startup options I tried to shrink my Windows Bootcamp partition using third-party software which led to my Macintosh HD partition missing from startup options. Unfortunately I don't have a recent backup for the whole drive to restore from. If I try to reinstall macOS from scratch it doesn't see the partition either.



Disk utility sees it but it's greyed out and is being shown as Unmounted without the option to mount it back.



Is there a way to fix this without wiping out the whole drive and reinstalling everything from scratch?
The second image you posted shows a partition type of DE94BBA4-06D1-4D40-A16A-BFD50179D6AC. This is for a Windows Recovery Environment type partition.

From Windows, you can open a Command Prompt window as an Administrator. Next, you could enter the commands given below to change disk0s2 to an Hierarchical File System Plus (HFS+) type partition.

diskpart
select disk 0
select partition 2
set id=48465300-0000-11AA-AA11-00306543ECAC override
gpt attributes=0x0000000000000000
exit



  Note: This answer assumes you are not using Core Storage. 


A more comprehensive solution is given as the accepted answer to the question: OS volume shows as type 'FFFFFFFF-FFFF-FFFF-FFFF-FFFFFFFFFFFF'. Despite the fact that your partition type is DE94BBA4-06D1-4D40-A16A-BFD50179D6AC and the linked question partition type is FFFFFFFF-FFFF-FFFF-FFFF-FFFFFFFFFFFF, the accepted answer provides a solution that would work in your case.