I installed 11.6 on to an external drive and can boot from it. On install I was asked about setting up another user/admin account on the external drive so I presume it is linked in some way to the account on the internal drive (I understand there is some boot security check involved here).
My plan, after Monterey public release, will be to boot into the external drive and update to Monterey only on that drive so I can test it a bit before updating the internal (I’m not part of the Monterey beta programme – I’ll wait for final release).
What I did notice, however, is that a Data Volume from the external drive seems to persist even when I boot from the internal which needed unmounted separately. I also thought that having booted into the external that I’d be able to perform disk maintenance on the internal drive, but when I try I get a message about ‘cannot unmount internal drive’ [I know of the option to boot into recovery mode]
So, is this a problem with how I set up the external boot, and if I update the external to Monterey will that have any knock on effects on the internal drive? If I later erase the external drive do I need to do anything first to ‘unlink’ it from my iMac to prevent any kind of phantom account persisting?