❓ Re-installing macOS on an M1 computer? ❓

[sonicthehedgefrog]

Say the next macOS comes out tomorrow (Sacramento or something). If I were to update an M1 computer with macOS Monterey already installed on it to the newest release of Sacramento, would I be able to clean install Monterey back onto the computer if for whatever reason I didn't like Sacramento (or if it broke compatibility with my software)?

Or are M1 computers like iOS devices? (Once you've updated, there's no going back after Apple stops signing the older firmware.)

 

[darngooddesign]

Its not a simple process anymore, but unlike iOS you can downgrade till the version of MacOS your computer came with.

 

[mr_roboto]

Here's the overview of how it works in macOS on Apple Silicon. Short version: out of the box your OS will be in a mode similar to iOS, where you can only move forward, but unlike iOS there is a way to reduce security to permit old OS versions or even completely unsigned operating systems. (The last being how the Asahi Linux project is getting Linux to boot on Apple Silicon.) Another difference from iOS: you can have multiple operating systems installed, and they each get their own security mode setting.

Startup security in macOS

Startup security policies can help restrict who can start up a Mac and what devices can be used to start up the Mac.

support.apple.com

 

[Mike Boreham]

Say the next macOS comes out tomorrow (Sacramento or something). If I were to update an M1 computer with macOS Monterey already installed on it to the newest release of Sacramento, would I be able to clean install Monterey back onto the computer if for whatever reason I didn't like Sacramento (or if it broke compatibility with my software)?

Or are M1 computers like iOS devices? (Once you've updated, there's no going back after Apple stops signing the older firmware.)

Upgrading to the new macOS installs the new macOS Recovery in the firmware of the internal boot drive. Yes you will be able to reinstall and run Monterey but the Internal Revovery and firmware will still be the new macOS.....unless you use Apple Configuator 2 to completely roll back the internal recovery and firmware as well.

 

[haralds]

You have to use DFU mode and the Configurator 2 to keep all the firmware pieces in sync.

 

[Mike Boreham]

Upgrading to the new macOS installs the new macOS Recovery in the firmware of the internal boot drive. Yes you will be able to reinstall and run Monterey but the Internal Revovery and firmware will still be the new macOS.....unless you use Apple Configuator 2 to completely roll back the internal recovery and firmware as well.

Correction. This was true for Big Sur, but changed in Monterey, which allows separate Recovery versions. So you would be able to roll back to Monterey and have Monterey Recovery. Firmware would stay at the updated version.

How Monterey changes Apple Silicon Recovery