Big Sur 11.2.2 still doesn’t fix bugs with M1 external bootable disks

Having now completed the most pointless macOS update ever – that to 11.2.2 – I had hoped that Apple might at least have finally fixed the bug which prevents macOS updates from being installed successfully on most external bootable disks connected to M1 models. TL;DR: it doesn’t.

Currently, I have two different SSDs with bootable copies of macOS 11.2.1 installed on them. They both work fine with either of my two M1 Macs, although swapping them between those Macs gets a bit tedious with all the signing-in required. But accept Software Update’s generous invitation to install the waiting macOS update, and they invariably disappoint.

Just as with installing the 11.2.1 update, another mouse squeezed into an elephant, the process starts with great promise. My local Content Caching Server has proved its worth again, as only the first 1 GB or so of the update for each M1 Mac has had to be downloaded from Apple, with the balance delivered at high speed from my server. Then there’s the obligatory 15 minute wait while the update is prepared, as if it’s only available partly cooked.


Once it’s piping hot and ready to serve, Software Update invites you to authenticate in order to restart, one significant difference from updating on an Intel Mac. That’s when this bug strikes: just as you think you’re about to win at last, here comes the fatal blow, in a small authentication dialog. For no matter what or whose password you enter, the dialog refuses to oblige. On one external disk I got its usual refusal with a shaking of the dialog. On the other it seemingly accepted the (correct) password, then stubbornly refused to go any further.


At least on this occasion, this bug is of little consequence. For all its 3.1 GB size (for an M1), the update to 11.2.2 appears completely vacuous. Apple hasn’t explained why it should be installed on any other than a few recent T2 Intel models. On an M1, it doesn’t even increment the iBoot firmware or kernel versions.

This update isn’t totally ineffective, though. It managed to downgrade my Mac’s copy of MRT to version 1.72, which was released on 12 November last year, so that had to be updated for the second time this week. Immediately after updating my internal storage, each M1 Mac also gained a Fallback Recovery OS too, as expected running macOS 11.2.1, and this time they appear to be persisting. But after this update, I wonder how many Big Sur users still have Automatically keep my Mac up to date ticked in Software Update.

This is the third Big Sur update in less than four weeks. For those updates alone, even with a local Content Caching Server, I’ve downloaded over 20 GB of macOS updates for four Macs, together with two full installers (another 24 GB, because Apple now removes previous installers as soon as the next version is released) and one IPSW image (13 GB, for DFU restore). That’s a grand total of almost 60 GB from Apple’s servers, over 2 GB per day, and those are just release versions of the current release of macOS. I sympathise with developers and sysadmins who are trying to keep pace with 11.3 betas as well.

Yet in all those macOS updates, not one has addressed the failings in M1 Macs working with external bootable disks. It’s almost like Apple doesn’t want to know.