Basics of Startup Disks and How to Boot in OS X Mavericks
Although you usually see a stylish Apple logo when you turn on your computer using OS X Mavericks, once in a blue moon, you may not. You may instead see a solid blue screen, a solid gray screen, a solid black screen, or something else entirely.
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 this advice.
How to find or create a startup disk in OS X Mavericks
Booting means using a particular disk or disk partition as your startup disk.
With Mavericks, however, because there is no bootable DVD, the Installer creates a bootable partition named Recovery HD on that disk when you first install Mavericks.
Apple has announced that only App Store purchases will be available for people upgrading to Mavericks. In other words, unless Apple changes its policy between now and the time you read this, you won’t have a Mavericks Install DVD from which to work.
So whatever else you do, make backup copies of the Mavericks Installer file that you receive from the App Store. The lack of a bootable installer disc solution should do wonders for the sale of external hard drives and high-capacity flash drives.
The Recovery HD partition is a good concept, but if your hard disk dies, the Recovery HD partition dies, too. Which is why it is recommend making a bootable clone of your startup disk as soon as possible, just in case.
Apple offers a free program called Recovery Disk Assistant , which can create a bootable Mavericks installer disk for you. Another option is Carbon Copy Cloner , a donationware app that lets you create a clone of your boot disk with a minimum of fuss. Or try this favorite, "SuperDuper!; just add a hard disk as large as or larger than your boot disk, and you’ll be good to go.
They call it a prohibitory sign for a reason
When you turn on your Mac, the first thing it does (after the hardware tests) is check for a startup disk that has OS X on it. If your system doesn’t find such a disk on your internal hard drive, it begins looking elsewhere — on a FireWire, Thunderbolt, Universal Serial Bus (USB) disk or thumb drive, or on DVD.
If you have more than one startup disk attached to your Mac, as many users do, you can choose which one your Mac boots from in the Startup Disk System Preference pane.
At this point, your Mac usually finds your hard drive, which contains your operating system, and the startup process continues on its merry way with the subtle Apple logo and all the rest.
If your Mac can’t find your hard drive (or doesn’t find on it what it needs to boot OS X), you encounter the dreaded prohibitory sign. Think of the prohibitory sign as your Mac’s way of saying, Please provide me a startup disk.
If you encounter any of these warning icons, you can try different options, such as using Disk Tools and First Aid, zapping the parameter RAM (PRAM), and performing a Safe Boot. Try them in the order listed, starting with Step 1. Then, if one doesn’t work, move on to the next.