Network monitoring with Cacti
GNU/Linux is without doubt a brilliant server OS, but monitoring your Linux server can be a challenge. Cacti is an extremely useful and easy to use tool for network administrators, and best of all, you do not need to be a network guru to use it.
Cacti's Web site describes the software as
a complete network graphing solution designed to harness the power of RRDTool's data storage and graphing functionality. Cacti provides a fast poller, advanced graph templating, multiple data acquisition methods, and user management features out of the box. All of this is wrapped in an intuitive, easy-to-use interface that makes sense for LAN-sized installations up to complex networks with hundreds of devices.