nagios3-core software package provides host/service/network monitoring and management system core files, you can install in your Ubuntu 14.04 LTS (Trusty Tahr) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install nagios3-core
nagios3-core is installed in your system.
Make ensure the nagios3-core package were installed using the commands given below,
$ sudo dpkg-query -l | grep nagios3-core *
You will get with nagios3-core package name, version, architecture and description in a table
| Distro | Ubuntu 14 04 lts trusty tahr |
| Section | Network |
| Package | nagios3-core |
| Version | 3.5.1-1ubuntu1 |
| Description | host/service/network monitoring and management system core files |
| Sub Section | Net |