Backup and block data copy with dump device (dd)

# save partition / disk to image
dd if=/dev/hda bs=16065b | gzip -9 > hda_backup.dd.gz
 
# restore partition / disk from image
gunzip -dc hda_backup.dd.gz | dd of=/dev/hda bs=16065b
 
# copy over network
netcat -l -p 1234 | dd of=/dev/hdc bs=16065b
dd if=/dev/hda bs=16065b | netcat TARGET_IP 1234
 
# backup mbr
dd if=/dev/hda of=mbr.img bs=512 count=1 
 
# restore mbr (better will by bs=446)
dd if=bs.img of=/dev/hda bs=512 count=1