Configuring Nagios to monitor remote load, disk, swap etc using NRPE

Remote server — the server to be monitored

First we’ll install the needed plugins and daemon on the remote server.

sudo apt-get install nagios-plugins nagios-nrpe-server

Once installed, open up /etc/nagios/nrpe_local.cfg

And place the following in it

allowed_hosts=NAGIOS.SERVER.IP,127.0.0.1

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_all_disks]=/usr/lib/nagios/plugins/check_disk -w 20 -c 10
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
command[check_swap]=/usr/lib/nagios/plugins/check_swap -w 20 -c 10

Save and exit.

Commands need to explicitly be enabled on the remote server to actually be runnable remotely, so you can add more plugins to this command list any time you want.

Start the nagios-nrpe-server daemon.

sudo /etc/init.d/nagios-nrpe-server start

Monitoring server — the server with Nagios installed

Install the nagios nrpe plugin

sudo apt-get install nagios-nrpe-plugin

Now test the connection to the remote server we set up just now.

/usr/lib/nagios/plugins/check_nrpe -H REMOTE.SERVER.IP
NRPE v2.8.1

If you get a version response it means it all works.

Now we simply add a service check for the host but use the check_nrpe plugin to do so.

define service {
    host_name HOSTNAME
    service_description Load
    check_command check_nrpe_1arg!check_load
    use generic-service
    notification_interval 0
}

We have already defined the tolerances on the remote server in nrpe_local.cfg so we only need to use the check_nrpe_1arg command, you can actually pass arguments using check_nrpe as below.

define service {
    host_name HOSTNAME
    service_description Load
    check_command check_nrpe!check_load!5!10
    use generic-service
    notification_interval 0
}

Save, exit and reload nagios.

sudo /etc/init.d/nagios2 restart