This post describes  to install and configure Nagios-Client on Ubuntu system, 

You need to updates  necessary packages, install libtool, openssl, libssl-dev.
 

# sudo apt-get update -y

# sudo apt-get gcc perl libtool -y

# sudo apt-get install openssl libssl-dev -y

Download Nagio-Plugin and NRPE package using wget command,
 
# wget http://www.nagios-plugins.org/download/nagios-plugins-2.1.1.tar.gz

# wget http://liquidtelecom.dl.sourceforge.net/project/nagios/nrpe-2.x/nrpe-2.15/nrpe-2.15.tar.gz

Extract and configure the package,
 
# tar -zxvf nagios-plugins-2.1.1.tar.gz

# cd /root/nagios-plugins-2.1.1

# ./configure

# make

# make install

Give the Nagios user permission to Nagios installed path, 
 
# chown  -R nagios.nagios /usr/local/nagios

# chown -R nagios.nagios /usr/local/nagios/libexec

Install and configure  xinetd and nrpe,
 
# apt-get install xinetd -y

# tar -zxvf nrpe-2.15.tar.gz

# cd /root/nrpe-2.15

# ./configure --with-ssl=/usr/bin/openssl --with-ssl-lib=/usr/lib/x86_64-linux-gnu

# make all

# make install-plugin

# make install-daemon

# make install-daemon-config

# make install-xinetd

 Assume that the Nagios IP address is 192.168.2.141

open NRPE file and add Nagios IP Address
 
# vi /etc/xinetd.d/nrpe
       
 only_from  = 127.0.0.1  192.168.2.141


Add below line in services file
 
# vi  /etc/services
  
 5666    /tcp      # NRPE 


Finally, you need to configure in Nagios Server,