Nagios 3 Monitoring of a Linux Box

by Mike on December 15, 2008

in Nagios

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 and the nagios server that is doing the monitoring is

# ufw allow proto tcp from to port 5666
Rules updated
# ufw allow proto tcp from to
Rules updated
# ufw enable
Firewall started and enabled on system startup
# ufw status
Status: loaded

To                         Action  From
–                         ——  —-          ALLOW 5666/tcp     ALLOW

This completes the basic configuration of the host that you will monitor.

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