Rdiff-backup

rdiff-backup is a GPL-licensed incremental backup utility based on the rsync command. It is able to store changes to files instead of file duplicates therefore reducing storage requirements. Incremental data can be viewed and restored as if it were whole a file backup via FUSE-based rdiff-backup-fs.

External resources

 * rdiff-backup tutorial at howtoforge.com
 * Unattended rdiff-backup HOWTO
 * A Debian based tutorial at linode.com