Make full hard disk copy
sudo dd if=/dev/hdx of=/dev/hdy
sudo dd if=/dev/hdx of=/path/to/image.img
sudo dd if=/dev/hdx | gzip > /path/to/image.gz
Restore Backup of hard disk copy
sud dd if=/path/to/image of=/dev/hdx
To see the progress of dd without killing
sudo kill -USR1 $(pgrep ^dd)
MBR backup
sudo dd if=/dev/hdx of=/path/to/image count=1 bs=512
MBR restore
sudo dd if=/path/to/image of=/dev/hdx