Install Nagios 4.1.1 Network Monitoring tool on Ubuntu, Debian & Mint

Nagios is one of the most popular Open-source Computer System Monitoring, Network Monitoring and IT Infrastructure Monitoring Software which prevents the critical issues in IT Infrastructure and run it smoothly without any trouble. It monitors entire IT infrastructure such as servers, switches, applications, network and services which alerts when there is any trouble and as well as the recovery alerts of the system. The latest version of Nagios core 4.1.1 released on Augest 19, 2015. Alternatively you can install other network monitoring tools such as Zabbix, Cacti, Monitorix, Munin & Icinga2.

Nagios Features

  • Monitors the entire IT infrastructure
  • Spot the problems before they occur
  • Know immediately when problems arise
  • Shares availability of data with stakeholders
  • Detects security breaches
  • Plan and budget for IT upgrades
  • Reduces downtime and business losses
  • Automatic fix of the problems when they are detected

What’s New in Nagios core 4.0.8

  • JSON API output has been better aligned in a standard way, and the output size limits has been lifted
  • Check Scheduling has been modified to prevent the bunching checks at the start of their time period
  • Auto-rescheduling of checks has been re-implemented. This can be enabled from settings
  • Nagios 4.0.8 Change log
  • How it works

1) Prerequisites for Nagios

LAMP and below packages should be installed in your system to install Nagios.

$ sudo apt-get install build-essential php5-gd libgd2-xpm libgd2-xpm-dev libapache2-mod-php5 libperl-dev libssl-dev apache2-utils

2) Create User & Group Account for Nagios

Create new user account & group for nagios and assign the user to nagios group and also assign the apache user to nagios group.

# Create new user for nagios #
$ sudo useradd nagios

# Set password for nagios #
$ sudo passwd nagios

# Create new group for nagios #
$ sudo groupadd nagcmd

# Assign nagios user to nagios group #
$ sudo usermod -a -G nagcmd nagios

# Assign apache user to nagios group #
$ sudo usermod -a -G nagcmd www-data

3) Download Nagios and the Plugins

Navigate to /opt directory and download the latest version of nagios and nagios plugin.

$ wget
$ wget

4) Compile and Install Nagios

Use the below commands to compile and install Nagios in your system.

$ tar -xzvf nagios-4.0.8.tar.gz
$ cd nagios-4.0.8
$ sudo configure --with-command-group=nagcmd
$ sudo make all
$ sudo make install

# Install init script for Nagios #
$ sudo make install-init

# Install sample config file for Nagios #
$ sudo make install-config

# set permissions on the external command directory #
$ sudo make install-commandmode

Note: Don’t start Nagios now – there are still more to be done.

5) Customize Configuration

The sample configuration file is installed at /usr/local/nagios/etc and it works fine, but we need to add our email id for Alerts. For that you need to modify the below file /usr/local/nagios/etc/objects/contacts.cfg.

$ nano /usr/local/nagios/etc/objects/contacts.cfg
email  [email protected]

6) Configure the Web Interface

Use the below commands to install Nagios web interface and it will drop the config file to Apache conf.d directory, while installation nagios web interface creates nagios web user called nagiosadmin and you need to set the password to access the interface.

# Install web interface #
$ sudo make install-webconf
/usr/bin/install -c -m 644 sample-config/httpd.conf /etc/httpd/conf.d/nagios.conf
/usr/bin/install: cannot create regular file ‘/etc/httpd/conf.d/nagios.conf’: No such file or directory
make: *** [install-webconf] Error 1

Why do we get an error message ? any guess? Yes, everybody knows Ubuntu based distribution uses apache2 directory instead of httpd that’s why we’re getting that error message. So what to do now ? instead of httpd location we need to drop the nagios.conf file to /etc/apache2/sites-enabled/ directory. Use the below steps.

# Install web interface #
$ sudo /usr/bin/install -c -m 644 sample-config/httpd.conf /etc/apache2/sites-enabled/nagios.conf

# Copy eventhandlers directory #
$ sudo cp -R contrib/eventhandlers/ /usr/local/nagios/libexec/

# Assign Permission #
$ sudo chown -R nagios:nagios /usr/local/nagios/libexec/eventhandlers

# Set password for nagiosadmin user #
$ sudo htpasswd -c /usr/local/nagios/etc/htpasswd.users nagiosadmin

# Restart Apache to make the new settings take effect #
[email protected] [~]# service apache2 restart

7) Compile and Install the Nagios Plugins

After Nagios core installation, you need to install the latest nagios plugin in your system.

# Extract nagios plugin tar archive file #
[email protected] [~]# tar -xzvf nagios-plugins-2.0.3.tar.gz

# Navigate to extracted directory #
[email protected] [~]# cd nagios-plugins-2.0.3

# Run the Nagios plugin configure script, passing the name of the user you created earlier like so #
[email protected] [~]# ./configure --with-nagios-user=nagios --with-nagios-group=nagios

# Compile the Nagios plugin source code #
[email protected] [~]# make

# Install Nagios plugin binaries #
[email protected] [~]# make install

8) Enable the rewrite apache module

Enable the rewrite apache module to access nagios without any issue.

[email protected] [~]# a2enmod rewrite

[email protected] [~]# a2enmod cgi

9) Start Nagios

Before staring nagios, check nagios configuration file whether there is any error occurred and also add the service to system startup.

# Adding nagios to system boot #
[email protected] [~]# ln -s /etc/init.d/nagios /etc/rcS.d/S99nagios

# Checking Nagios Configuration File #
[email protected] [~]# /usr/local/nagios/bin/nagios -v /usr/local/nagios/etc/nagios.cfg

# Start Nagios service #
[email protected] [~]# service nagios start

10) Access Nagios Web Interface

Navigate your browser to http://localhost/nagios or http://IP-Address/nagios or http://Domain-Name/nagios and enter the Username and Password which you created.
Nagios Home Page
Host list By default nagios monitor itself and we can add N number of hosts.
Service status checking

Manage your IT infrastructure with Nagios and minimize the downtime.

Hope this article was useful for you !!

Kindly spare few mins. and post your valuable feedback !! Thank you !!

Magesh Maruthamuthu

Love to play with all Linux distribution

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