Segundo o site do http://www.debian-administration.org temos aqui um artigo que nos permite criar uma disco de backup "bootável" a partir de uma pen USB ou um disco externo... Resumidante basta seguir a receita...

fonte: http://www.debian-administration.org/articles/575

"Making a backup disk is usually an obvious task, but making the disk ready to boot so that it can immediately be used as a replacement can be tricky. Here I give a recipe for making a bootable disk that can be adapted to whatever block device you may be using as a backup disk. This could be an internal or external hard disk, a USB key, etc. "

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