#### a>
Purpose
The NRPE addon is designed to allow you to execute Nagios plugins on remote Linux/ Unix machines. The
main reason for doing this is to allow Nagios to monitor" local" resources( like CPU load, memory usage,
etc.>
on remote machines. Since these public resources aren't generally exposed to external machines, an
agent like NRPE must be installed on the remote Linux/ Unix machines.
Note It's possible to execute Nagios plugins on remote Linux/ Unix machines through SSH. There's a
plugin that allows you to do this. Using SSH is more secure than the NRPE addon, but it also
imposes a larger( CPU>
overhead on both the monitoring and remote machines. This can become an issue
when you start monitoring hundreds or thousands of machines. numerous Nagios admins conclude for using the
NRPE addon because of the lower load it imposes.
#### b>
Design Overview
The NRPE addon consists of two pieces
• Thecheck\_nrpe plugin, which resides on the local monitoring machine
• The NRPE daemon, which runs on the remote Linux/ Unix machine
When Nagios needs to monitor a resource of service from a remote Linux/ Unix machine
• Nagios will execute thecheck\_nrpe plugin and tell it what service needs to be checked
• Thecheck\_nrpe plugin connections the NRPE daemon on the remote host over an( optionally>
SSL
protected connection
• The NRPE daemon runs the applicable Nagios plugin to check the service or resource
• The results from the service check are passed from the NRPE daemon back to thecheck\_nrpe plugin,
which also returns the check results to the Nagios process.
Note The NRPE daemon requires that Nagios plugins be installed on the remote Linux/ Unix host. Without
these, the daemon wouldn't be suitable to monitor anything.
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