We have previously seen the manual installation of Monitorix under Ubuntu, you can check the tutorial here. To make the installation easier, I have included Monitorix in a PPA to be able to install it with just few commands.
Open the terminal and run these commands to install Monitorix 2.5.0 under Ubuntu 11.10/12.04:
sudo add-apt-repository ppa:upubuntu-com/ppa
sudo apt-get update
sudo apt-get install monitorix
Start then Monitorix via this link:
If nothing appears, try to restart Apache with this command:
sudo /etc/init.d/apache2 restart