Help! My Mac Won't Boot!
Recently my buddy texted me with a plea for help, saying his iMac was extremely slow to boot, taking an hour or more. I ran him through the basic keyboard shortcuts, Shift for Safe Mode, Command+Option+P+R for NVRAM reset, unplug for SMC reset, etc. Unfortunately nothing worked, so I told him I'd check it out in person. I didn't get around to checking it out until a week later.
There are tons of posts on the internet about this and most of them are quite helpful, but generally no two issues are the same so I thought I'd write up what happened here, just in case it's helpful to anyone.
When I got there, I booted the machine. Sure enough, it would chime and the Apple logo would show up, but then it would just hang. So I turned it off and held the option key to select the Recovery Disk as the boot disk. Unfortunately the same thing happened, boot just hung at the Apple logo.
Fortunately for me, I thought to bring an external HD with a fresh install of 10.9.3 (actually it was a backup of my MacBook Pro but who cares). I plugged in the drive and then booted holding down option in order to select my external HD. This time the iMac booted into the OS in a reasonable amount of time. Once in the OS, I ran Disk Utility's Repair and Verify disk commands on the internal hard drive, but they both passed. Still nothing conclusive.
At this point, I selected the internal hard drive as the boot disk in System Preferences and let it reboot. Again, same hang on boot. I did a bit of research on the Mac boot process and the boot was hanging on the Kernel. Nothing insanely conclusive, but something to go on.
From there I decided to run the hardware test that I always see Geniuses running but always forget to do. It's fairly undocumented, but on this iMac running 10.7.2, I had to hold Option+D immediately following the boot chime. A globe icon with the "Internet Recovery" label came on for a few minutes, then it dropped into a very OS 9-looking screen that prompted me to run the Apple Hardware Test.
After running it, we got an error that said:
"Alert! Apple Hardware Test has detected an error: 4HDD/11/40000000 SATA(0,0)"
Finally! Something conclusive! The error message seems to be saying that there's an error with the internal hard drive and that it may be on the verge of failing. This would explain the OS's inability to load along with the recovery disk.
After booting back into my backup, we (slowly) copied over important files from my friend's iMac and got everything we need. I believe the copying was slow since the drive was failing. He has Applecare until August 2014 so he made an Genius Bar appointment tomorrow. Hopefully he'll be on his way with a new HD soon, I imagine I'll have to help him with getting all his apps back on there.