Iâ€™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 arenâ€™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 â€” 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 wasnâ€™t the â€œnew userâ€ experience where youâ€™re asked to log into iCloud again.
As a side-note, this is an experimental first post via Ulysses.