In order to confirm that your backup will actually work as a startup disk, you'll need to restart your Mac and verify that it can boot from the backup. The easiest way to do this is to use the Mac's Boot Manager to select the backup as the startup disk. We will use Boot Manager, which runs optionally during the startup process, instead of the Startup Disk option in System Preferences, because the choice you make using Boot Manager only applies to that particular startup. The next time you start or restart your Mac, it will use your default startup disk.
Use Boot Manager
- Close all applications, including Disk Utility.
- Select 'Restart' from the Apple menu.
- Wait for your screen to go black.
- Hold down the command (cloverleaf) key until you see a gray screen with icons of bootable hard drives. This can take a little time, so be patient.
- Click the icon for the backup you just made. Your Mac should now boot from the backup copy of the startup disk.
Once the desktop appears, you know that your backup is usable as a startup disk. You can restart your computer to return to your original startup disk.
If the new backup isn't bootable, your Mac will stall during the startup process, then after a delay, automatically restart using your original startup disk. Your backup may not be bootable because of the type of connection (FireWire or USB) an external drive uses; see the first page of this guide for more information.
