How do I use dd to clone an external USB drive installation to a local hard disk?

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http://askubuntu.com – can I use the dd command to clone my ubuntu installation from my external disk to my local hard drive. will it even boot? I think I can, but not sure. do I need to make the output partition on my local disk the exact size as the input partition on the usb? I'm thinking install and boot off a liveusb on a different small flash drive and run something like "sudo dd if=/media/usbexternaldisk of=/media/localdisk" would that work as is? also if I make an iso image of my external ubuntu installation using dd, can I burn it onto disk or unto another hard drive and have that boot up? (HowTos)