The rsync utility is a file-transfer and synchronization program widely available for Linux® and UNIX® and even ported to Windows®. Its key feature is a very fast algorithm that just sends file differences over the data link, thus minimizing the total data flow between machines. (If you use the File Transfer Protocol [FTP] or utilities such as rcp or scp, complete files will be sent, even if just one byte has changed.) Of course, rsync isn’t limited to existing files: It can also deal with files and directories that might be present only at one end of the link. Finally, communications are optimized by compressing data, so you can use the tool even without a broadband connection.
Article by Federico Kereki