The purpose of this is to be able to place the nrpe daemon on a remote Linux machine and be able to monitor specific internal aspects of the server that you would not normally be able to get access to.
You will need to become root and create the user nagios with a password.
# useradd nagios
# passwd nagios
On the remote host you must install the plugins for Nagios.
#apt-get install nagios-plugins
#apt-get install nagios-nrpe-plugin
#apt-get install nagios-nrpe-server
Edit the /etc/nagios/nrpe.cfg
Change your allowed_hosts address to reflect the nagios monitoring server.
This IP Address must match the IP Address of your Nagios monitoring server.
The basic plugins that are running for you initially are these listed below.
command[check_users]=/usr/lib/nagios/plugins/check_users -w 5 -c 10
command[check_load]=/usr/lib/nagios/plugins/check_load -w 15,10,5 -c 30,25,20
command[check_hda1]=/usr/lib/nagios/plugins/check_disk -w 20 -c 10 -p /dev/hda1
command[check_zombie_procs]=/usr/lib/nagios/plugins/check_procs -w 5 -c 10 -s Z
command[check_total_procs]=/usr/lib/nagios/plugins/check_procs -w 150 -c 200
Change ownership on the /etc/nagios/nrpe.cfg file so that nagios is able to read the file.
chown nagios /etc/nagios/nrpe*
Set up the Firewall
The ufw firewall, Uncomplicated Firewall, is a little tricky. In the example the remote server being monitored is 192.168.5.178 and the nagios server that is doing the monitoring is 192.168.5.180.
# ufw allow proto tcp from 192.168.5.180 to 192.168.5.178 port 5666
# ufw allow proto tcp from 192.168.5.178 to 192.168.5.180
# ufw enable
Firewall started and enabled on system startup
# ufw status
To Action From
– —— —-
192.168.5.180/tcp ALLOW 192.168.5.178/tcp
192.168.5.178 5666/tcp ALLOW 192.168.5.180
This completes the basic configuration of the host that you will monitor.