dd

dd - Copy a file, converting and formatting according to the operands.

Backup entire disk:

dd if=/dev/sda of=/dev/sdb

Create an image of a disk:

dd if=/dev/hda of=/root/hdadisk.img

Restore the image created:

dd if=/root/hdadisk.img of=/dev/hdb

Create an image of a partition:

dd if=/dev/hda1 of=/root/partition1.img

Create a iso file from cdrom:

dd if=/dev/cdrom of=music.iso bs=2048