The rdiff-backup command – the target directory ends up a copy of the source directory but extra reverse diffs are stored in a special subdirectory of that target directory so you can still recover files lost some time ago. The idea is to combine the best features of a mirror and an incremental backup and you can use ssh to securely back a hard drive up to a remote location and only the differences will be transmitted
rdiff-backup {{ -l | –list-increments } | –remove-older-than time_interval | –list-at-time time | –list-changed-since time | –list-increment-sizes | –verify | –verify-at-time time} [[[user@]host2.foo]::destination_directory]