Our NRPE daemon is now built and ready to be deployed on the remote machines. We need to configure it and set up the system so that it accepts connections from other computers.

The NRPE daemon should use a separate user and password.

First, let's create a user and a group named nagios:

groupadd -g 5000 nagios
useradd -u 5000 -g nagios -d /opt/nagios nagios

We also need to create a home directory for the user, and it is a good idea to lock out access for that user if no checks are to be performed over SSH. To do this, run the following commands:

mkdir /opt/nagios
chown nagios.nagios /opt/nagios
passwd -l nagios

There are many ways of setting this up — NRPE can work either as a standalone process that handles incoming connections, or as part of the inetd (http://en.wikipedia.org/wiki/inetd) or the xinetd (http://www.xinetd.org/) setup. In all cases, a configuration file is needed. This file specifies the commands to be used and the additional options for running the...