Guides‎ > ‎NRPE‎ > ‎Installing NRPE Client / Agent‎ > ‎Unix & Linux‎ > ‎

CentOS 6.5 - NSClient++ From RPM

This is all new to me but hey it's worth having a play with so I've recorded what I've needed to do to get it working.

These steps were performed on a CentOS 6.5 server (minimal install).

NSClient++ RPMs were only available from 0.4.3 onwards.


Install EPEL Repository

NSClient++ requires some packages that are in the EPEL Repository.
  • Type yum -y install epel-release and press Enter
  • Wait while the component is downloaded and installed


Install NSClient++

  • Type cd /tmp and press Enter
  • Type wget https://github.com/mickem/nscp/releases/download/0.4.3.143/NSCP-0.4.3.143-1.el6.x86_64.rpm and press Enter
  • Wait for the file to download 
  • Type yum -y install NSCP-0.4.3.143-1.el6.x86_64.rpm and press Enter
  • Wait for NSClient++ to install
  • Type iptables -I INPUT -p tcp --destination-port 5666 -j ACCEPT and press Enter
  • Type service iptables save and press Enter


At this point NSClient++ is:

  • Installed but currently not running
  • Installed in /usr/sbin
  • The configuration file is /etc/nsclient/nsclient.ini but if you look you'll find it is relatively empty

Configure NSClient++

I'm going to allow the entire 10.25.0.0/16 subnet to connect to NSClient++, you could change the steps below to a specific IP Address

  • Type nscp settings --activate-module NRPEServer --add-defaults and press Enter
  • Type nscp settings --activate-module CheckSystemUnix --add-defaults and press Enter
  • Type nscp settings --path /settings/default --key "allowed hosts" --set 127.0.0.1,10.25.0.0/16 and press Enter
  • Type nscp settings --path /settings/NRPE/server --key "allow arguments" --set true and press Enter
  • Type nscp settings --path /settings/NRPE/server --key "allow nasty characters" --set true and press Enter
  • Type nscp settings --path /settings/NRPE/server --key insecure --set true and press Enter

Start NSClient++

  • Type service nsclient start and press Enter
  • We'll also configure it to boot at startup
  • Type ln -s /etc/init.d/nsclient /etc/rc.d/rc2.d/S35nsclient and press Enter
  • Type ln -s /etc/init.d/nsclient /etc/rc.d/rc3.d/S35nsclient and press Enter
  • Type ln -s /etc/init.d/nsclient /etc/rc.d/rc4.d/S35nsclient and press Enter
  • Type ln -s /etc/init.d/nsclient /etc/rc.d/rc5.d/S35nsclient and press Enter

Test NRPE Client / Agent

This will test that NSClient++ is properly installed and listening on port 5666.

The following command is executed on a Nagios Core server and the computer running NSClient++ has the ip address 192.168.142.132.
  • Type /usr/local/nagios/libexec/check_nrpe -H 192.168.142.132 and press Enter
  • You should receive a response like:
    • I (0.4.3.143 2015-04-29) seem to be doing fine...
  • This confirms that NSClient++ is working

  • Some other checks you could perform:
  • Type check_nrpe -H 192.168.142.132 -c check_uptime show-all and press Enter
  • Type check_nrpe -H 192.168.142.132 -c check_memory show-all and press Enter
  • Type check_nrpe -H 192.168.142.132 -c check_os_version show-all and press Enter


The following command is executed on the computer running NSClient++ and is using the nscp command.

  • Type nscp nrpe host=127.0.0.1 insecure and press Enter
  • You should receive a response like:
    • I (0.4.3.143 2015-04-29) seem to be doing fine...
  • This confirms that NSClient++ is working