Nagios is an industry standard for open source monitoring and reporting. It is incredibly flexible and extendable, for better or worse. Getting it set up and running is not too difficult, but additional thought and understanding both Nagios and the systems which you would like to monitor will be necessary in order to create a configuration which is easy to understand and maintain.
Install
nagios
:sudo apt-get install nagios3
Select a password when prompted.
Visit the web UI at
http://YOURSERVER/nagios3/
. You can log in usingnagiosadmin
as a username, and the password, which you selected in the previous step. Since this system requires you to log in, you'll want to follow the instructions in the Apache chapter to configure and require SSL/TLS for the system.