MacOS – How to clean install of MacOS on 2018 MBP

macbook promacosrecoveryt2

I have a 13" 2018 MacBook Pro. My System Integrity Protection is off, and T2 security is set to None. After an update to MacOS Catalina 10.15.3, my mac would stay at the bootup screen with an apple logo. I salvaged all my data in recovery mode and tried to reinstall MacOS from there. I ended up getting A software update is required to use this startup disk error in recovery. I then completely wiped the internal SSD, and using another mac and disk drill made a bootable USB with MacOS 10.15.3. I booted that and got the same A software update is required to use this startup disk error in recovery. I tried to reset the mac to its original OS after that with Shift+Option+Command+R, but after loading with a rotating earth for a few minutes I get an exclamation mark sign over that earth with the following below it:

apple.com/support  
-1008F

Regarding the inability to boot the MacOS USB stick, I've read that the newer macs can only boot from APFS drives. However, I do not know how to do that. After using disk drill to flash MacOS to a USB, I tried using a disk utility option Convert to APFS..., but that threw an error.

I have no idea what to do anymore, and would rather not go to an apple store to fix this. Is it even possible for a genius bar person to fix the software? How could I fix this myself?
I do have access to a few decently sized USB drives and a tri boot Windows/Linux/MacOS computer, but no professional tools.

I would like to add I have not been able to install linux either onto my Mac, and not even rEFInd.

Best Answer

According to everymac.com, your 2018 Mac should be able to run macOS 10.13.6. You could try using the 2014 Mac to download High Sierra from this website. This download should be the latest High Sierra macOS 10.13.6. You can the use the instructions from this website to transfer High Sierra to a flash drive. After booting from the flash drive, use the Disk Utility to erase and APFS format the internal drive. Finally, try installing High Sierra. If successful, then you can try upgrading to Catalina.

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MacOS partition startup Volume type FFFFFFFF-FFFF-FFFF-FFFF-FFFFFFFFFFFF

The proper GUID of APFS partitions is 7C3457EF-0000-11AA-AA11-00306543ECAC.

The default pMBR was replaced with an old-style MBR, probably by the Linux installation!

Your boot system (in Internet Recovery Mode) seems pretty old. Any disk or partition verification executed with diskutil may yield some bogus result. In no case try to repair anything with diskutil!

To get your APFS partition back remove partition disk0s2 and restore it with the proper type:

Open in the menubar > Utilities > Terminal

get some details:

diskutil list #below I assume the disk identifier of the internal disk is disk0
gpt -r show disk0

Unmount disk0:
```
diskutil umountDisk disk0
```

remove and restore the 2nd partition:

gpt remove -i 2 disk0
diskutil umountDisk disk0
gpt add -i 2 -b 409640 -s 372637568 -t 7C3457EF-0000-11AA-AA11-00306543ECAC disk0

verify disk and partition:

diskutil list
diskutil verifyDisk disk0       
diskutil verifyVolume disk0s2

Your Mac should be able to boot despite the MBR.

If you want (or have) to restore the pMBR because the MBR is stubborn/blocks the modification of the partition table do the following:

get all disk details:

diskutil list #below I assume the disk identifier of the internal disk is disk0
gpt -r show disk0

replace the GUID partition table:

diskutil umountDisk disk0
gpt destroy disk0
gpt create -f disk0

re-add all previous partitions visible in the last gpt -r show disk0 output:

gpt add -i 1 -b 40 -s 409600 -t C12A7328-F81F-11D2-BA4B-00A0C93EC93B disk0
gpt add -i 2 -b 409640 -s 372637568 -t 7C3457EF-0000-11AA-AA11-00306543ECAC disk0
gpt add -i 3 -b 373047208 -s 262144 -t 426F6F74-0000-11AA-AA11-00306543ECAC disk0
gpt add -i 4 ...
gpt add -i 5 ...

If you get a resource busy error after one of the steps, just unmount disk0 again with

diskutil umountDisk /dev/disk0

Finally verify disk and partitions:

diskutil list
diskutil verifyDisk disk0       
diskutil verifyVolume disk0s1
diskutil verifyVolume disk0s2
diskutil verifyVolume disk0s3
#disk0s4 & disk0s5 can't be verified with the default macOS tools because the latter is a Linux swap and the former a Linux partition, probably with ext4

Best Answer

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MacOS partition startup Volume type FFFFFFFF-FFFF-FFFF-FFFF-FFFFFFFFFFFF

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