In the early days of the original M1 Macs and versions of Big Sur prior to 11.4, installing and setting up a bootable copy of macOS on an external disk was unreliable and often failed. I’m therefore surprised that users still contact me claiming that they’ve had problems with more recent versions of macOS, including Monterey, and with the new M1 Pro and Max models. As a sequel to my article about the basic principles of using an M1 Mac, this explains how to set up a bootable external disk in Monterey on an M1 Pro. Total time taken should be a few minutes, plus the time required to install macOS on the external disk.
My starting point wasn’t a freshly formatted disk, but a SATA/USB-C SSD which has already been divided up into multiple containers (partitions) containing bootable versions of macOS. One happened to be Monterey 12.0, which I was only too happy to sacrifice for this purpose. One important point here is don’t attempt to do any of this with 12.0, as it could well fail miserably.
I erased the Volume Group in that container using Disk Utility. This gives a detailed commentary, which now makes clear that any Preboot and Recovery volumes are also deleted, and that references to xART sessions are also removed. The latter relate to the recognition of that bootable volume, and confirm that it has thoroughly ceased to exist.
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