You haven't provided much information; but, if you're looking for network backup of multiple Linux machines to a central Linux server,
I would choose Amanda. You can find various bookmarks for Amanda and other options here:
http://www.linuxquestions.org/bookmarks/tags/backup. You can find out more about Amanda here:
http://amanda.zmanda.com/. And you can get details and documentation on Amanda here:
http://wiki.zmanda.com/index.php/Main_Page.
Some of the Linux distributions are pretty far behind on their Amanda packages. That might not be a big deal if you want an easy install and the package is at least 2.5.1p3. But, if you want the latest and greatest, download a package from Zmanda or build from source. There has been a huge amount of good development work in the last couple of years.