2015 27” iMac stuck on install screen after reboot

[arksun]

My iMac was trying to install a small macOS Mojave update last night received a message saying it was not able to install at this time (I can’t recall exactly what it said). After rebooting, my iMac was stuck on the black screen with the Apple logo and the status bar all night. I reset the NVRAM and that didn’t seem to help. I tried booting in safe mode, but the system seems to just shut off.

Has any one experienced this?

 

[CoastalOR]

Do you have a backup?
Have you tried booting from Recovery (command+r)? If that works then you can Reinstall the macOS.

 

[mikehalloran]

Do you have a backup?
Have you tried booting from Recovery (command+r)? If that works then you can Reinstall the macOS.

Exactly.

What this does is download the latest complete OS installer and runs it after you log into your Apple account — not the updater. It takes awhile but should fix you up.

Unless...

If you partitioned your drive and have more than one OS available or if another drive is connected that has a Mac OS available, you will not be able to select the Repair partition in High Sierra or Mojave.

Likewise, it may not exist if you created your boot drive by cloning and did not run the OS installer afterwards as was recommended.

In those cases, you will need to use an external installer drive or make one.