Rather than using a full/incremental scheme like Amanda, rsync runs a full backup each time it performs synchronization. That may seem wasteful, but rsync cleverly forwards only the changed bits in files, so it is actually very lightweight. Rsync ordinarily uses SSHas its transfer protocol, so the data is safe in transit -- making it ideal for syncing data to a remote machine outside the firewall -- thereby providing offsite backup.
Since the popular rsync is included in Linux distros, you can avoid the installation process. The most typical configuration of rsync operates in a client/server setup: The client machines contact the rsync server, which makes rsync a very good choice for dynamic environments. For example, rsync is a very good choice for backing up laptops that connect to the network intermittently. Of course, rsync can be configured to work in a polling fashion as well; in fact, it can be configured to work in a two-way fashion, enabling two machines to back up one another.
You'll find more information about rsync and Amanda in my article, Rsync and Amanda: Keeping your data safe with open source backup.
This was first published in August 2005