My mac hung up while installing an update. It took hours and still did not complete the update. I restarted my mac. Upon turning it back on, a wheel has been spinning on a grey screen. I tried to reinstall OS X from utilities, but encounter an error. Why?

Question

My mac hung up while installing an update. It took hours and still did not complete the update. I restarted my mac. Upon turning it back on, a wheel has been spinning on a grey screen. I tried to reinstall OS X from utilities, but encounter an error. What do I do?

Answer 1

Hey Manaskala,
First point of call on all grey screen issues is the following:
http://support.apple.com/kb/TS2570
Given this issue has appeared after a software update, I'd advise you do the following instead though:
1. Get an external hard drive, with enough space to put the entire hard drive of your Mac onto. Make sure you've safely copied any data you have off of it, as the next step will erase it.
2. In the recovery HD of your machine, use Disk Utility to format you EXTERNAL hard drive with the partition table as GUID, and the format as Mac OS Extended (Journaled).
3. Get out of Disk Utility, and click Reinstall Mac OS X.
4. When asked where, choose to install onto your external hard drive.
5. When the download and installation is complete, your Mac will reboot into a clean fresh setup screen. Make your user account an administrator, and make up a name and password; I use 'Test' and 'test'.
6. Your machine is now running from the external hard drive, not the internal hard drive, so don't be alarmed when you don't see your files.
7. Open the finder, you should see 'Macintosh HD' in the sidebar. This is the internal hard drive of your computer.
8. Open Macintosh HD, and copy out the following folders into a new folder on your desktop:
-Users.
-Applications.
-Library. (This only needs to be done if you use 3rd party software that saves things in the /Library, do a quick google and see if it does e.g. Photoshop, Protools).
9. When these have copied (it'll take quiet a while), you can now use Disk Utility to erase your hard drive. Don't erase Macintosh HD but the ENTIRE hard drive on the inside of your Mac, and as Thomas A Reed mentioned, there was likely an existing issue on your HDD so please go to Security Options and choose 'Zero Out' before clicking erase. This will rebuild the partition table which was a possible cause of the failed update.
10. Reboot the machine holding 'Option', go to recovery HD.
11. Choose 'Reinstall Mac OS X', this time onto your INTERNAL hard drive.
12. When this is complete, make another admin user called test and password test, like you did last time.
13. Run Software Update from the  menu of your Mac.
14. In the Finder, you should see your external Hard Drive. open it up, inside that you should see your desktop etc, and on the desktop will be your folder containing Library, Applications and Users.
15. Go to Finder up next to the  and choose File -> New Finder Window.
16. In your second finder window, open up Macintosh HD (through the Go -> Computer menu), and go to your Users folder.
17. Open the Users folder in your first finder window, and copy your user folder (has your name on it) into the second user folder (the one inside Macintosh HD).
18. This might take a while.
19. When complete, go to System Preferences -> Users and Groups and unlock the padlock.
20. Click the '+' sign, and make a new administrator user.
21. Now, the fun bit. Note the name of your user folder you copied, e.g. 'Nathan', containing all of your stuff. Note the difference between your user folder (has your name on it) and the Users folder (contains YOUR user folder, guest folder and shared folder).
22. Make the ACCOUNT NAME of your new adminstrator user the EXACT name of your user folder (normally lower case and without spaces), this is case sensitive folks. Your full name can be whatever you want, usually your full name.
23. Then click create. You should be informed that a home folder with that name in it already exists in the Users folder, would you like to make your new account from that folder? say YES!
24. When this is complete, log out of the Test user, log into your new account we've just made, all your stuff should be there.
25. ???????
26. Profit.
There's a few little bits that may need to be cleaned up afterwards, applications folder from your external hard drive should replace the applications folder on your internal hard drive, if the previously mentioned /Library folder contained important goodies then that should replace the /Library folder on your new Mac.
Hopefully that will help you out, straight after that is done make sure your stuff is there, erase your external hard drive and turn on time machine!