Zenoss is an award-winning open source IT monitoring product that effectively manages the configuration, health and performance of networks, servers and applications through a single, integrated software package.
Start by adding a zenoss entry to your apt sources (pico /etc/apt/sources.list):
deb http://dev.zenoss.org/deb main stable
Update apt repository
Install Zenoss and depending packages
apt-get install zenoss-stack
You can now login by navigating to http://yourhost:8080/ using the username: admin and password: zenoss