dd is a common Unix program whose primary purpose is the low-level copying and conversion of raw data. dd is an application that will "convert and copy a file" dd can also be used to copy regions of raw device files, e.g. backing up the boot sector of a hard disk, or to read fixed amounts of data from special files like /dev/zero or /dev/random.
The dd utility copies the specified input file to the specified output with possible conversions. The standard input and output are used by default. The input and output block sizes may be specified to take advantage of raw physical I/O. Sizes are specified in bytes; a number may end with k, b, or w to specify multiplication by 1024, 512, or 2, respectively
There is a command line involved in using dd command and if you are afraid of using command line or you are just a normal desktop user you can use the GUI version of the dd command know as - Gdiskdump
Continue Reading... The dd utility copies the specified input file to the specified output with possible conversions. The standard input and output are used by default. The input and output block sizes may be specified to take advantage of raw physical I/O. Sizes are specified in bytes; a number may end with k, b, or w to specify multiplication by 1024, 512, or 2, respectively
There is a command line involved in using dd command and if you are afraid of using command line or you are just a normal desktop user you can use the GUI version of the dd command know as - Gdiskdump
source:http://linuxpoison.blogspot.com/2011/07/13578167753955.html