My machine would not restart.

Recovery is always a safe solution, but not necessarily bringing your machine back to a usable state...

But in the meantime if you can power it on then, you might as well try to reboot with the option key, see if you're on the macOS install drive, select the normal drive if still exists or a valid OS (even an older one is on it) and restart the MM...

If you've managed the above, maybe try to install the update via the combo update? It worked for me! It took me some times to finally install 10.13.2 but eventually made it through the Combo update!

If not then by booting out of the macOS install and restarting your MM can be considered as a usable machine... do the things you have to do and seriously consider a Genius Bar appointment at the nearest Apple Store... as I have mentioned on my previous post these weird Genius guys work magic 99% of the time...

Maybe Kappy or Tesserax could comment on the above, right?

Good luck...

Get it to restart is my guess. Probably you need to make an appointment at the Apple Genius Bar for service. If you need to find an Apple Store - Find a Store - Apple. They will be able to fix it for you.

At what point it the boot up process does it fail:

• Does not power-up at all?
• Powers-up but get a series of beeps?
• The Apple logo appears?
• During the Progress Bar?
• At the logon screen?
• After trying to login?

Hi Crabster,

To restart or to load? I'm a little confused with your comment:

What do I need to do to get back a usable machine?

What do you mean by that? Is your MM powering on but not loading, if you don't mind me asking? Because if it is not powering on then as Kappy rightly said => Apple Genius Bar is the best solution!

Otherwise if it is powering on, then the questions from Tesserax are pertinent and might lead you to a solution...

If like me you're living at 2 ½ hours ferry ride or 30 minutes flight from the nearest Apple Store, then you really would want to find a way around your issue... But hey positive thinking Mac are the most user friendly computers...

So a little more details might help us help you... Let us know, who knows someone on the support communities might very well have a solution for your MM...

Good luck!