How to boot from External Drive?

Discussion in 'macOS' started by Yamcha, Mar 24, 2010.

  1. Yamcha macrumors 68000

    Mar 6, 2008
    Hi Guys,

    I have a 21.5" iMac, I installed Snow Leopard on a external drive, but I am unable to boot from it.. I've tried pressing the option(alt) key, and the only drive that shows up is the Macintosh HD..

    How do I boot from the external USB drive?

    Hope someone can help :]

  2. macintoshmanic macrumors newbie

    Mar 24, 2010
    Land of 10000 Lakes
    Booting from an external drive on a Mac

    In order for you to boot from an external drive, you will need a Mac formatted firewire drive. That's about it.
  3. iShater macrumors 604


    Aug 13, 2002
    That is not 100% correct.

    New Intel macs should be able to boot from USB IIRCC.

    Op, how do you know the other drive is a bootable drive? did you format it/clone it that way?
  4. Yamcha thread starter macrumors 68000

    Mar 6, 2008
    I installed Snow Leopard on it using the OSInstall.mpkg file and chose GUID Partition.. (/Volumes/Mac OS X Install DVD/System/Installation/Packages) Just because I can install it while I'm on Snow Leopard..

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