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I created a clone partition of my main drive with SuperDuper on an external (USB) drive. How can I boot from it?

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up vote 4 down vote accepted

Press and hold the 'Option' key when you first start your Mac, which should then show you a list of bootable drives. You should then be able to select your external drive and go.

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It worked fine, thanks! – Fernando Oct 6 '10 at 18:19

In addition to Brad's answer, before you shut down you can connect the external disk, open the "Startup Disk" system preference item, and pick the startup image that you want.

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