3 ways to bakcup linux filesystem or disk with dd command
	
	
		Using below dd command to backup an entire copy of a hard disk to another one, open ternimal or shell prompt and type the following command:
	Code:
	
#dd if=/dev/hdc of=/dev/hdd
 where,
    if=/dev/hdc : input file
    if=/dev/hdd : output file
2.backup hard disk as a image file
If you don’t want to bakcup disk to a disk, you can backup it as image file and save it in removeable storage device or Flash disk. then you can easy to use it in anywhere and can be quickly restored.
	Code:
	
# dd if=/dev/hdc of=/hdc.image
 Restore disk image
using the following dd command to restore a disk with the image file have backup before
	Code:
	
#dd if=hdc.img of=/dev/hdc
 3. Backup file from CDROM
dd command can generate an iso file from a source file read from CDROM.(insert the CD disk to CDROM)
	Code:
	
#dd if=/dev/cdrom of=cdromfile.iso