Below is the correct way:
To create the compressed image:
dd if=/dev/hda | gzip -c | split -b 2000m - system_drive_backup.img.gz.
It will create the 2GB files:
system_drive_backup.img.gz.aa
system_drive_backup.img.gz.ab
To restore:
cat system_drive_backup.img.gz.* | gzip -dc | dd of=/dev/hda
Mount an external USB drive or a remote NFS drive for the dumps. I would recommend first to empty out the unused blocks of your hard disk with zeros, using command:
dd if=/dev/zero of=filefullofzeros && rm filefullofzeros
Otherwize the dd command will dump the bits of even the files that where previously deleted.
Refer to document:
http://wiki.linuxquestions.org/wiki/...ns_using_split