Booting different versions of MacOS from USB on Apple Silicon

[elliots11]

The short and sweet of it is: I would like to boot my Macbook Pro M1 Max from an external USB that I'd set up to use a different version of MacOS than what's running internally. I've done that with Intel Macs before and it went ok, is there anything different with Apple Silicon Macs that I should know before I dive in? Like are there security features that would prevent this on Apple Silicon Macs?

The longer version goes - I have an M1 Max MBP running 12.7 Monterey. I would like to update it to 15.x Sequoia, but probably it'll end up going to 14.x Sonoma because I've read my main software I run for work is going to play nicer with Sonoma right now. Would it be possible to install 15.x Sequoia on a USB and boot from that as needed while keeping the internal SSD loaded with 12 Monterey or 14 Sonoma? 15 Sequoia has some features I'd like to use for personal stuff but not work stuff.

I might also like to have and keep an external USB boot drive to act as my personal or secure stuff while keeping work only stuff on the internal, sort of turning 1 computer into 2 or more. I suppose virtualization could be used to enable some of this, but I'm exploring this idea.

 

[bogdanw]

It’s a nightmare on Apple silicon. It requires permanent Internet connection, even if you use a bootable installer. It has to not be connected to the DFU port. And even if you respect Apple’s requirements, the installation might still fail. After that, it’s OK

“If you're using a Mac with Apple silicon, plug your storage device into any compatible port except the DFU port. Learn how to identify the DFU port. After macOS installation is complete, you can connect your storage device to any compatible port, including the DFU port.”

Install macOS on an external storage device and use it as a startup disk
https://support.apple.com/en-us/111336

How to identify the DFU port on Mac
https://support.apple.com/en-us/120694

Create a bootable installer for macOS
https://support.apple.com/en-us/101578

 

[Fishrrman]

It can be done.
It's more complicated, as bog says above. Pay attention to the part about "DFU ports".

If you're going to try, use a USB3.1 gen2 enclosure with an nvme blade SSD inside.

DO NOT attempt this with:
- a USB flashdrive (even a fast one)
- an SD card
- a platter-based hard drive

I don't believe any of the above will work, either due to a lack of proper controlling circuitry (flashdrive and SD cards) or speed (HDD).
You want an SSD...

It's probably best done by booting from a flash drive installer.
I recommend the free, small utility named "Mist", which can download the OS installer AND create the flashdrive in one operation.

Personal experience:
I have a bootable 2.5" SATA SSD (in a USB3.1 gen2 enclosure) with Sequoia installed that will boot and run my MacBook Pro (m1pro) 14" which normally runs Sonoma.

 

[elliots11]

It can be done.
It's more complicated, as bog says above. Pay attention to the part about "DFU ports".

If you're going to try, use a USB3.1 gen2 enclosure with an nvme blade SSD inside.

DO NOT attempt this with:
- a USB flashdrive (even a fast one)
- an SD card
- a platter-based hard drive

I don't believe any of the above will work, either due to a lack of proper controlling circuitry (flashdrive and SD cards) or speed (HDD).
You want an SSD...

It's probably best done by booting from a flash drive installer.
I recommend the free, small utility named "Mist", which can download the OS installer AND create the flashdrive in one operation.

Personal experience:
I have a bootable 2.5" SATA SSD (in a USB3.1 gen2 enclosure) with Sequoia installed that will boot and run my MacBook Pro (m1pro) 14" which normally runs Sonoma.

Thanks for both your replies, I’m glad I asked. I figured there’d be something.

When you’re recommending the USB 3.1 gen2 enclosure are you specifically recommending like a USB-A connection with a USB-C adapter, or just to make sure that the USB-C enclosure supports the USB3.1 gen2 protocol?

I’d imagine the protocol but who knows? Better to ask and be sure