Image to disk and vice versa on unix

Backup all your usb drivers or your disk drivers, or clone them using dd, the ultimate tool.
We will first list all our available disks, watching out not making any mistake.

fdisk -l

Then after the output, notice the /dev/sdA or /dev/hdA or /dev/sdB etc, take a note on what device you want to take backup from, then think about the location of it going, like a folder or in another device.
if stands for input file.
of stands for output file.
By issueing the following command, we will backup our second drive into ~/.

dd if=/dev/sdb of=~/test.img

To restore it, simply swap /dev/sdb with ~/test.img, so simple!
You can also change the block size by using the bs command, eg:

dd if=/dev/sdb of=~/test.img bs=512