Downgrade macOS

[bill99]

Hello

I intend to buy an iMac Pro (with the newest macOS). But the Autodesk-application does require and older
release of macOS Catalina.

- Does downgrade the macOS require to reinstall the OS from scratch with Internet recovery (command-option-r boot)
and is it even possible not to install the newest release of macOS with Internet recovery?

- Does it make sense to make a fullbackup (=image) with a bootable rescue media like Acrons TrueImage
before starting to experiment with OS downgrades?


Thank's a lot for any feedback!

Bill

 

[casperes1996]

It does require a full reinstall, but not with internet recovery; Internet recovery will not let you pick the version that is installed - instead you will make your own installer of whatever macOS version you want.

And I mean sure you can make a bootable backup image, but if you're doing this straight out of box anyway, you don't really have any data to lose

 

[Fishrrman]

Important question:
WHAT VERSION of the OS do you require?

The iMac Pro originally shipped with 10.13.2 (High Sierra).
Anything "earlier than" that won't boot.

You might be able to reinstall (back to High Sierra) by using a special version of internet recovery:
Shift-Option-Command-R
(although I'm not sure if this works with the iMac Pro, but worth a try)

If the above DOESN'T WORK, you could create (or buy) a USB flashdrive with a copy of the High Sierra installer on it, and wipe and install that way.

 

[bill99]

Thanks for the feedback!

->If the above DOESN'T WORK, you could create (or buy) a USB flashdrive with a copy of the High Sierra installer on it
With the help of one of the following scripts?

-GitHub - grahampugh_macadmin-scripts_ Scripts of possible interest to macOS admins
-GitHub - munki_macadmin-scripts_ Scripts of possible interest to macOS admins


Regards,

Bill