Nagios Server

Install and Configure Nagios Monitoring Server

Nagios is an awesome Open Source monitoring tool, its provides you more comprehensive monitoring environment to always keep an eye on your all machines / networks whether you are in a your data center or just your small labs.

With Nagios, you can monitor your remote hosts and their services remotely on a single window. It shows warnings and indicates if something goes wrong in your servers which eventually helps us to detect some problems before they occur. It helps us to reduce downtime and business losses.

Step 1: Install Required Dependencies

We need to install Apache, PHP and some libraries like gcc, glibc, glibc-common and GD libraries and its development libraries before installing Nagios 4.0.1 with source. And to do so we can use yum default package installer.

# yum install -y httpd php gcc glibc glibc-common gd gd-devel make net-snmp

Step 2: Create Nagios User and Group

Create a new nagios user and nagcmd group account and set a password.

# useradd nagios
# groupadd nagcmd

Next, add both the nagios user and the apache user to the nagcmd group.

# usermod -G nagcmd nagios
# usermod -G nagcmd apache

Step 3: Download Nagios Core 4.0.1 and Nagios Plugin 1.5

Create a directory for your Nagios installation and all its future downloads.

# mkdir /root/nagios
# cd /root/nagios

Now download latest Nagios Core 4.0.1 and Nagios plugins 1.5 packages from the below Links
http://sourceforge.net/projects/nagios/files/nagios-4.x/nagios-4.0.1/nagios-4.0.1.tar.gz/download

https://www.nagios-plugins.org/download/nagios-plugins-1.5.tar.gz

Step 4: Extract Nagios Core and its Plugins

We need to extract downloaded package with tar command as follows.

# tar –xvf nagios-4.0.1.tar.gz
# tar –xvf nagios-plugins-1.5.tar.gz

When you extract these tarballs with tar command, two new folders will appear in that directory.

# ll
drwxrwxr-x 18 root root    4096 Oct 17 03:28 nagios-4.0.1
-rw-r--r--  1 root root 1695367 Oct 15 19:49 nagios-4.0.1.tar.gz
drwxr-xr-x 15  200  300    4096 Oct 14 10:18 nagios-plugins-1.5
-rw-r--r--  1 root root 2428258 Oct  2 11:27 nagios-plugins-1.5.tar.gz

Configure Nagios Core

Now, first we will configure Nagios Core and to do so we need to go to Nagios directory and run configure file and if everything goes fine, it will show the output in the end as sample output. Please see below.

# cd nagios-4.0.1
# ./configure –with-command-group=nagcmd

Now, after configuring we need to Compile and install all the binaries with make command and make install command will install all the needed libraries in your machine and we can proceed further.

# make all
# make install

Following command will install the init scripts for Nagios.

# make install-init

To make nagios work from command line we need to install command-mode.

# make install-commandmode

Next, install sample nagios files, please run following command.

# make install-config

Step 5: Customizing Nagios Configuration

Open the “contacts.cfg” file with your choice of editor and set the email address associated with the nagiosadmin contact definition to receiving email alerts.

# vi /usr/local/nagios/etc/objects/contacts.cfg

Step 6: Install and Configure Web Interface for Nagios

We are done with all configuration in the backend, now we will configure Web Interface For Nagios with following command. The below command will Configure Web interface for Nagios and a web admin user will be created “nagiosadmin”.

# make install-webconf

In this step, we will be creating a password for “nagiosadmin”. After executing this command, please provide a password twice and keep it remember because this password will be used when you login in the Nagios Web interface.

# htpasswd -s -c /usr/local/nagios/etc/htpasswd.users nagiosadmin
New password:
Re-type new password:
Adding password for user nagiosadmin

Restart Apache to make the new settings take effect.

# service httpd start

Step 7: Compile and Install Nagios Plugin

We have downloaded nagios plugins in /root/nagios, Go there and configure and install it as directed below.

# cd /root/nagios
# cd nagios-plugins-1.5
# ./configure --with-nagios-user=nagios --with-nagios-group=nagios
# make
# make install

Step 8: Verify Nagios Configuration Files

Now we are all done with Nagios configuration and its time to verify it and to do so please insert following command. If everything goes smooth it will show up similar to below output.

# /usr/local/nagios/bin/nagios -v /usr/local/nagios/etc/nagios.cfg

Step 9: Add Nagios Services to System Startup

To make Nagios work across reboots, we need to add nagios and httpd with chkconfig command.

# chkconfig --ad
# chkconfig --level 35 nagios on
# chkconfig --add httpd
# chkconfig --level 35 httpd on

Restart Nagios to make the new settings take effect.

# service nagios start 

Step 10: Login to the Nagios Web Interface

Your nagios is ready to work, please open it in your browser with “http://Your-server-IP-address/nagios” or “http://FQDN/nagios” and Provide the username “nagiosadmin” and password.