El Capitan, Mac refusing to shut down - Solved

The mysterious case of the undead iMac

Sometime in the last few months, my 5K iMac started misbehaving. Not in any of the ways you’d expect—crashes, lock-ups, weird error messages, that sort of thing. No, one day I came into my office in the morning and the iMac and all the peripherals were still on, the spinning gear animation still right where I had left it upon choosing Shut Down from the Apple menu the night before.

I fancy myself a pretty good Mac troubleshooter, but this was a bit baffling to me. The system has already gone into shutdown mode by the time it gets to this point; I can’t bring up a terminal window or run Activity Monitor to see what might be going on. Even stranger, when I manually powered off the iMac and restarted it, then tried to shut it down, it shut down properly. Okay. Maybe it was nothing. I started up and got about my business.

After a full day’s work, I shut down the iMac again—and once again, the spinning-gear animation appeared. I came back after dinner and it was still there. Okay, this was a problem. I reset my iMac’s power manager, zapped the PRAM, did all of the weird system-level things I could think of, and nothing solved the problem.

(Read on for the fix at: SixColors)

via ehMac.ca http://ift.tt/1Ka11zZ