OS X Mountain Lion For Dummies

About Startup Disks and Booting

Although you usually see a stylish Apple logo when you turn on your computer, once in a blue moon, you might not. You might instead see a solid blue screen, a solid gray screen, a solid black screen, or something else entirely, as described in the next section.

The point is that your Mac isn’t starting up as it should. When this happens, it usually indicates that something bad has happened to your Mac. Sometimes, it’s a hardware component that has bitten the dust; at other times, OS X itself has somehow been damaged.

Rest assured that these occurrences are rather uncommon — many Macs and Mac users go an entire lifetime without seeing one. If you ever have a Mac that won’t boot, don’t despair. Before you declare your Mac terminally ill, try out the advice in this chapter.

Finding or creating a startup disk

When I talk about booting, I mean using a particular disk or disk partition as your startup disk. I bet you have a copy of the ultimate startup disk right there on your computer table — the installation DVD (or the first disc if you received more than one) that came with your computer.

For the entire history of OS X, I’ve advised my readers to keep their OS X installation disc close at hand . . . the one that came in the boxed retail copy they bought. ...