a utility for creating reverse differential backups
rdiff-backup is a utility that allows a backup of a directory tree with a history of changes that can be retrieved. The user can retrieve the version of a file at certain points in the past. This is achieved by storing the current version and keeping a record of the changes in reverse (i.e. the difference between the current version and the previous version is stored so that the previous version can be re-created) The previous version may have a diff that can be used to go to the next previous version and so on.