My son went out of town and, upon returning, turned on his iMac. It rebooted and went into the progress bar typically showing during updates. It goes to the 50% mark, fairly quickly but then stayed there for 10 minutes. He rebooted and tried again but, this time let it sit overnight, at least six hours, but still stuck at 50%.

He tells me he installed Yosemite but not any time in the last few days before he left. From Googling around we tried resetting PRAM and also verifying the hard disk form disk utilities. The hard disk gave a green check mark(?) and said the volume was OK. I asked him to verify permissions but that was now grayed out.

Unfortunately, I am not a Mac user and I'm trying to help him over the phone. I'm very technically inclined but don't know what to do about this issue.

EDIT: So now things are getting worse as he tries rebooting and, after the start up sound, the computer powers down.

EDIT2: I just learned that the computer was not turned off while he was away which leads me to believe the system tried to update itself and something went wrong causing some system files to not be found or, perhaps, the few things we tried to do to the system helped that along.

So we found out Apple will check out his system even though it's not under warranty and, if it can be fixed in the software, they'll also fix it for free. What a great company!

EDIT3: Apple decided the hard drive had gone bad and replaced it. My son has a friend in the data recovery business who will attempt to extract the data.

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    – bmike
    Commented Jan 9, 2015 at 17:20

3 Answers 3


From your describe("progress bar typically showing during updates"). sound like the system is updating and doing something. Click "⌘L" will show you installation log, you can check what's going on

  • I asked him twice to do that and he never did. Unfortunately, now the computer shuts down right after the start up sound.
    – Rob
    Commented Dec 30, 2014 at 2:22
  • you can try verbose mode support.apple.com/en-us/HT201573
    – nelson
    Commented Dec 30, 2014 at 2:46
  • We get nothing but a white screen trying that. I had him try single user mode with Cmd+S but he only got a folder with a throbbing question mark in the center. I don't know what that means.
    – Rob
    Commented Dec 30, 2014 at 3:37
  • seems like can't find the boot volume support.apple.com/en-us/TS1440
    – nelson
    Commented Dec 30, 2014 at 4:03
  • I found that last link just before you posted it. I also found out he left the computer turned on while he was away. My guess is the system tried to update itself and something went wrong causing it either to use system boot files or what we did tonight helped it along. He says he's taking the easy way out and take it to the Apple store because we also found out that they will check it for free and, if it's only software, fix it for free. What a great company!
    – Rob
    Commented Dec 30, 2014 at 5:14

My son took the computer to the Apple store which found, through their testing, that the hard drive had gone bad and he replaced the drive. Everything is working now though he lost all his data.


for more information, see this thread: https://jamfnation.jamfsoftware.com/discussion.html?id=12589

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    – grg
    Commented Jan 9, 2015 at 16:53

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