Clonezilla

Clonezilla is a free and open-source disk cloning, disk imaging, data recovery, and deployment computer program. Clonezilla is designed by Steven Shiau and developed by the NCHC Free Software Labs in Taiwan. Clonezilla SE provides multicast support similar to Norton Ghost Corporate Edition.
Clonezilla Live.
Clonezilla Live enables a user to clone a single computer's storage media, or a single partition on the media, to a separate medium device. The cloned data can be saved as an image-file or as a duplicated copy of the data. The data can be saved to locally attached storage device, an SSH server, a Samba server, or an NFS file-share. The clone file can then be used to restore the original when needed.
Clonezilla does not support online imaging, so the partition being cloned has to be unmounted. To circumvent this restriction, Clonezilla can be run from a USB flash drive, CD/DVD-ROM or Android mobile phone, requiring no modification to the computer, with the software running in its own booted environment.
Clonezilla Server.
Clonezilla Server is used to clone many computers simultaneously across a network. This is done using a Diskless Remote Boot in Linux (DRBL) server and computer workstations that can boot from a network.