Amanda is one the best open source Linux backup software.

The Advanced Maryland Automatic Network Disk Archiver (AMANDA), is a backup system that allows the administrator to set up a single master backup server to back up multiple hosts over network to tape drives/changers or disks or optical media.

Novell Cool Solutions has published a small how to about Amanda. From the article:
Amanda is simple to use but tricky to configure. It is worth sticking with Amanda until you get a fully working system. Don’t be put off by the lack of a slick GUI interface or the need to configure the software via a console shell, once it is configured Amanda does its job very efficiently.

The configuration files for Amanda are stored in the /etc/amanda directory. Each configuration that you create goes into a separate directory within /etc/amanda. There is a sample configuration in the “example” directory that you can use as a jumping off point for configuring Amanda

Contents

* Background
* Installing Amanda
* Configuring Amanda
* Creating file and directories
* Preparing tapes for use with Amanda
* Checking the configuration
* Performing the backup
* Checking the backup
* Automating the backup
* Conclusions

Read more, Using Amanda to Backup Your Linux Server at Novell.com…