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Boot your Mac using the “Mac OS X Install Disc”, then select “Utilities > Terminal…” to get a command prompt. With an external drive attached, run the following command substituting the name of the disk you want to clone (source) and the name of the partition onto which you want to place the clone (target):

asr —source /Volumes/Macintosh\\ HD —target /Volumes/Clone —erase

This will do a fast, block-level bootable clone of your Mac. I use this all the time before doing any major upgrades or changes to the partition table.