Steps to Configure Nagios 4.1.1 on CentOS, Red Hat & Fedora

Nagios is an open source, effective monitoring system. It empowers associations to recognize and resolve IT foundation issues before they affect critical business processes. Nagios has ability of monitoring application, services, entire IT infrastructure. Nagios will be configured to monitor a few aspects of your local system (CPU load, disk usage, etc.)

This article will help you to install and configure Nagios on CentOS, RHEL and Fedora system.

Nagios and the plugins will be install in /usr/local/nagios

Step 1: Install Dependencies

We have to installed all require packages first. Use the following commands to install all require packages.

# yum install httpd php gcc glibc glibc-common gd gd-devel

Step 2: Create new User & Group

Create a new user account and group for nagios and assign a password. After creating new user and group for nagios now assign both the nagios user and the apache user to the group.

# useradd -m nagios
# passwd nagios
# groupadd nagcmd
# usermod -a -G nagcmd nagios
# usermod -a -G nagcmd apache

Step 2: Download & Extract Nagios Core

Download the source code of Nagios Core latest versions from official site. After download the source file extract that archive. Also you can download it using following commands.

# cd /opt
# wget http://download.techoism.com/nagios-4.1.1.tar.gz
# tar xvf nagios-4.1.1.tar.gz

Step 3: Compile and Install Nagios Core

Now, first we configure Nagios Core and to do as such we have to go to Nagios directory and run configure file.

# cd nagios-4.1.1
# ./configure --with-command-group=nagcmd

After configuring we need to Compile and install all the binaries. Run the Nagios configure script, passing the name of the group you made before like so:

# make all
# make install

Install binaries, init script, sample config files and set permissions on the external command directory.

# make install-init
# make install-config
# make install-commandmode

Step 4: Customize Configuration

Edit the /usr/local/nagios/etc/objects/contacts.cfg config file with your editor and change the email address associated with the nagiosadmin contact definition to receiving alerts.

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

Step 5: Configure the Web Interface

Install the Nagios web config file using following command:

# make install-webconf

Now, we will be create a password for “nagiosadmin” user. Use following command to create password:

# htpasswd -s -c /usr/local/nagios/etc/htpasswd.users nagiosadmin

Restart Apache to make the new settings take effect.

# service httpd restart

Step 6: Compile and Install Nagios Plugin

Download & Extract the Nagios plugins source code and compile it.

# cd /opt
# wget http://www.nagios-plugins.org/download/nagios-plugins-2.0.3.tar.gz
# tar xvf nagios-plugins-2.0.3.tar.gz
# cd nagios-plugins-2.0.3
# ./configure --with-nagios-user=nagios --with-nagios-group=nagios
# make
# make install

Step 7: Start Nagios

Add Nagios to the list of system services and have it automatically start when the system boots.

# chkconfig --add nagios
# chkconfig nagios on

Verify the sample Nagios configuration files.

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

If there are no errors, start Nagios service.

# service nagios start

Step 8: Modify SELinux Settings

See if SELinux is in Enforcing mode. Then disable the selinux even you can change the content of nagios directories using following command:

# chcon -R -t httpd_sys_content_t /usr/local/nagios/sbin/
# chcon -R -t httpd_sys_content_t /usr/local/nagios/share/

Step 9: Login to the Web Interface

You should now be able to access the Nagios web interface at the URL below.

http://server-ip/nagios/

Enjoy it!