Creating image with dd

*This does not work on the fly, so you need to boot from CD. 

Quick way with non-compressed image.

Create image from hda and save it on remote server:
# dd if=/dev/sda | ssh username@backupserver "dd of=/directory_of_backups_on_ssh_server/backupfile.iso"

Extract image to disk: 
# ssh user@hostname dd if=backupfile.iso | dd of=/dev/sda


Way with compressed image.

Create compressed image from sda on remote server:
# dd if=/dev/sda | gzip | ssh username@backupserver dd of=/directory_of_backups_on_ssh_server/backupfile.img.gz

Restore:
# ssh user@hostname dd if=backupfile.iso | gzip -d | dd of=/dev/sda


Clearing MBR with dd:
# dd if=/dev/zero of=/dev/hda bs=512 count=1