Converts and copies a file
The dd (device-to-device copy) utility converts and copies a file. The primary use of dd is to copy files to and from such devices as tape and floppy drives. Often dd can handle the transfer of information to and from other operating systems when other methods fail. This utility is often used to create a GNU/Linux boot disk from a file containing an image of the boot disk. A rich set of arguments gives you precise control over the characteristics of the transfer.
By default dd copies standard input to standard output.
input file Reads from filename instead of from standard input. You can use a device name for filename to read directly from that device.
output file ...