I’m simply recording this for the benefit of others who may have similar weird experiences updating to 10.13.6.
I recently updated macOS via the App Store from 10.13.5 to 10.13.6 and it was unusual in that it got about two-thirds of the way through the install fast (while saying it had 16 minutes to go) and then got stuck.
When I noticed the problem a couple of hours later, I
- forced power off and restarted. It then quickly went up to about the same point it previously hung, rebooted, got to about 90% of the way done, rebooted again, then got to about the same spot and the screen went black and stayed black.
- forced power off and restarted (I might have had to do this more than once at this point) and then it got to the faux sign-in screen you now get when Macs aren’t fully booted (e.g. after the battery runs flat during stand-by).
- I logged in and got to the proper login screen, and was was relieved to find that everything from there proceeded normally — the OS asked me if I wanted to send feedback to Apple, etc., which seems to happen after some OS updates but not others, but also wasn’t the “new user” experience where you’re asked to log into iCloud again.
As a side-note, this is an experimental first post via Ulysses.