What to do when your Mac won’t start
If you’ve ever seen the dreaded ‘cancel’ symbol when starting up your Mac, then you know that sinking feeling. My Mac won’t start. Have I lost data? Can I get it working again?
Let me just say from the outset, that it is super important to have a backup for your Mac. Apple’s Time Machine is great for this, and if you don’t already, start using it immediately. Some of the advice that follows requires that you have a already have a Time Machine backup.
Recovery HD
Since Mac OS X 10.7 was released, every Mac has a hidden tool on it that can be used when your Mac won’t start. A separate section of your disk (called a partition) is set up and hidden away in the event that you need to repair your disk, reinstall your operating system, or perform a handful of other more nerdy tasks (which we may cover in a future article… let us know if that sounds fun). It’s called the Recovery HD.
So, your Mac won’t start. How do you use the Recovery HD to figure out what’s wrong? To start from the Recovery HD, hold the Command and R keys when powering on your computer until you see the Apple logo appear. At the end of the start up process, instead of your familiar desktop, you’ll first see a language selection screen. After you’ve chosen your language, a new window will appear, labeled ‘OS X Utilities.’
Attempt to repair with Disk Utility
The first thing to try is to repair the start up disk. In the OS X Utilities window, you’ll see a number of options. Your first port of call will be Disk Utility. After selecting it and clicking Continue, you’ll see the (perhaps) familiar Disk Utility window. Select your drive, then click First Aid, then click Run when prompted. If a repair is completed successfully, you may be out of the woods. Quit Disk Utility and choose Restart from the Apple menu. If everything starts up normally, you should be good to go.
Restore from Time Machine
If the repair fails, then you will be needing your Time Machine back up. Quit Disk Utility to return to the utilities window you saw earlier. This time, choose Restore From Time Machine. You might notice the fine print here: “Restoring from backup will erase (gulp) the selected destination disk.” This is actually a good thing. The reason that Disk Utility likely failed is that the data on that disk became damaged in some way. Erasing the disk removes the corruption and gives your drive a fresh start.
Now you’ll have to wait, however. After selecting the backup to restore from (this should almost always be the most recent one). The data from your Time Machine will be copied back to your freshly formatted hard drive, but it can take quite some time to complete. Once it has, however, you should find that your Mac is the way you left it.
Hopefully you have a wit or two left to enjoy it with.
The Apple Writer 