Reinstalling MacOS on External Harddrive but met with 'Missing Fimrware Partition' - Help!

[patneligan]

Hey there,

My Macbook internal SSD failed recently (shown question marks and no entry signs, cannot boot up) and we are in lockdown so cant get it looked at.

In the meantime I have forked out for an external SSD to boot up the Mac but when trying to install via recovery mode / internet recovery mode I am met with 'you may not install to this volume because the computer is missing a firmware partition'. This happens for both Mojave normal recovery mode and Catalina via internet recovery mode.

Where is this firmware? I have correctly partitioned the external harddrive as GUID via the disk utilities in Recovery Mode. Its a 500gb Sandisk Extreme SSD plugged in via USB-C.

Its a 2016 macbook and I am at the end of my tether, please help. I have looked online but can't decode anything.

Thanks in advance

G

 

[chscag]

How did you format the external SSD? You will need to format it as GUID, APFS. Do not use HFS+ as that will not work to install either Mojave or Catalina. You also will need to use a flash drive installer and not Recovery. If you're trying to install to the Sandisk via Recovery, that's not going to work.

Also, if there is an AASP near where you live, you can take your MacBook Pro there to get it looked at. They mostly remain open. (AASP = authorized Apple service provider)

 

[patneligan]

How did you format the external SSD? You will need to format it as GUID, APFS. Do not use HFS+ as that will not work to install either Mojave or Catalina. You also will need to use a flash drive installer and not Recovery. If you're trying to install to the Sandisk via Recovery, that's not going to work.

Also, if there is an AASP near where you live, you can take your MacBook Pro there to get it looked at. They mostly remain open. (AASP = authorized Apple service provider)

Just quickly super grateful for your response, thank you.

How do you mean a flash drive installer? Why won’t recovery work with this external hard drive. I don’t understand? What do I need to do to get a flash drive installer?

My Mac’s recovery mode is now crashing after language selection, without fail. It restarts and says encountered a problem - how is this issue going from bad to worse? Haha.

I will try internet recovery and check how I’ve partitioned it. Could you explain the flash drive installer section?

 

[chscag]

How to make a bootable Flash Drive Installer:

How to create a bootable installer for macOS - Apple Support

 

[ferrarr]

Have a read of this Apple Support Document, which describes the different keyboard startup options to boot from Internet Recovery.


How to reinstall macOS from macOS Recovery - Apple Support

You cant create a bootable USB installer at this time, but they are great to have already made in these situations. If you had one, you could just use that to install the OS, and you would be on your way.


Sent from my iPad using Mac-Forums