Ever since the beta versions of Mac OS Big Sur was introduced, there were a few dozen complaints of the installer not functioning properly at a catastrophic level. The problem happens particularly often with recent Macbook Pro models (Intel & M1), where the installer is stuck in a loop or bricks the computer completely. There is no way to cancel the install once the installer restarts your Mac, and no way to restart from your internal drive because the installer erases the Boot partition and replaces it with an Update partition.
You can check out Mr. McIntosh’s blog for some details on the kinds of installation failures.
If we take the statistic of “how many people report crimes” or “how many people get duped by spam”, we can estimate that the angry posts on the Apple Discussion Forum is only about 1.6% of actual Macs being affected. That means, if 10 people complain, there must be 625 affected machines out there. So far, I’ve seen about two dozen users (developers, mind you) so that’s 1500 Macs affected. Not a HUGE number but significant – especially if they are developers, beta-testers, pro-users, and early adopters.
Anyways, long story short, here are things you MUST DO BEFORE upgrading to or updating Mac OS Big Sur. If the installation fails and your internal drive gets screwed or bricked, this will save you.
- BACKUP – complete cloning of the internal drive is recommended
- Enable at least one Admin user on the local drive
- Enable booting from an External Drive – do this through Recovery Mode
- Install Big Sur on an External Boot Drive as a production drive, if possible
- Migrate Users to the External production drive
- Make sure you have at least 35GB of available space on your internal drive
Yes, yes, that means you have that same data in 3 different places. But you’ll thank me later.