#to copy or backup the MBR

MBR information is stored on the first 446 bytes of a disk, to backup this information you can save it with dd to another disk, or to a file.

dd if=/dev/sda of=/dev/sdg bs=446 count=1

dd if=/dev/sda of=/path/to/a/file.mbr bs=446 count=1

To restore the data to its original place using our backup file:

dd if=/path/to/a/file.mbr of=/dev/sda  count=1