The Nagios current release is v4 however you’ll need to build this. Nagios3 is available from a repository with minimal interaction and as far as I’m aware offers the same functionalities required by most admins. That is… to see if something is live and not under heavy utilisation,
Nagios 3 can be installed easily using the following command:
sudo apt-get install nagios3
You will be prompted for an administrative password for the “nagiosadmin” account. Once installed the se http://localhost/nagios3/