Setting up NRPE daemon

Install daemon:

apk add nrpe

Set up config file to bind to local IP, only allow needed hosts to connect. Add a definition for a check command to /etc/nrpe.cfg, for example:

command[check_routes]=/usr/bin/check_routes.sh

Create the above script, and populate:

##!/bin/bash
##
NUMROUTES=`ip route | grep -n  | awk -F ':' '{print $1}' | tail -n 1`
if [[ $NUMROUTES > 80 ]];
then echo "OK: $NUMROUTES routes in routing table" && exit 0;
elif [[ $NUMROUTES < 80 ]] && [[ $NUMROUTES > 15 ]];
then echo "WARNING: $NUMROUTES routes in routing table" && exit 1;
elif $NUMROUTES = "" ;
then echo "WARNING: No routing information received" && exit 1;
else echo "CRITICAL: $NUMROUTES routes in routing table" && exit 2;
fi

Restart NRPE. Allow port 5666 through Shorewall (in /etc/shorewall/rules) through to monitoring hosts. On the monitoring host, run the following command to test:

/usr/local/nagios/libexec/check_nrpe -H 10.14.8.3 -p 5666 -c check_routes

You should get output like:

OK: 173 routes in routing table

If you are having trouble, enable debugging in /etc/nrpe.cfg, and check /var/log/messages for errors. Most likely error(s) has to do with permissions of what you are trying to execute.