Section 140. Select the Boot Volume at Boot Time

140. Select the Boot Volume at Boot Time

SEE ALSO

141 Boot from Different Disks Using Keystrokes

142 Change the Startup Disk

22 Partition a Hard Disk

If you have multiple copies of Mac OS X (or other operating systems) installed on different volumes on your disk, or on different disks attached to your computer, you can boot from any one of them without having to configure anything in software. This is done through the use of the Option key while booting.

1.	Restart the Computer Select Restart from the Apple menu to restart your computer. If the computer is powered off, start it up.
2.	Hold Down the Option Key Immediately after the "bong" sound, press and hold the Option key. Hold the key down until the boot volume selection screen appears.
3.	Select the Volume to Boot From The Mac scans all available disks for bootable volumes. Each such volume that it finds appears as a button-style icon on the screen, along with two buttons for rescanning and booting. The default boot volumeusually the primary partition on the built-in hard diskis selected by default. If you click the Boot button (with a right arrow symbol), the Mac boots from that partition as it normally does. TIP If you want to boot from an external disk that isn't currently plugged in, and you didn't plug it in in time for the Mac to recognize it during the scan, plug it in now and click the Rescan button. The Mac should recognize the disk this time. If not, restart the computer holding down Option again. (You may have to turn off the computerhold down the Power button for several secondsand turn it back on.) To boot instead from a different available volume, wait several moments for the computer to finish scanning for boot volumes (the mouse pointer changes from a stopwatch to a pointer), and then select the volume you want to boot from. This volume can be a hard disk partition, a CD-ROM or DVD, an external FireWire drive, or any of several other devicesand it doesn't have to be Mac OS X, either. You can have Linux or BeOS installed on some of your volumes, and you can select these volumes as well from this screen.
4.	Boot the Computer After you have selected the boot volume you want, click the Boot button. The Mac will boot using that volume.

140. Select the Boot Volume at Boot Time

NOTE

Using the boot volume selection screen and the Option key is a one-time override operation. The next time you boot the computer, it will use the default boot volume it normally uses.