rsync-based backup utility

 Backups are stored as complete filesystem trees on a (perhaps
 external) hard disk. Multiple backups use hard links between
 identical files to save space.
 .
 Backups may be taken from multiple machines (over SSH) and stored to
 multiple disks.
 .
 Backups may be made automatically, i.e. without relying on the
 operator to remember to make a backup.