How to Install Nagios Server on CentOS/RHEL 8/7/6

Nagios is the most popular, open source, powerful monitoring system. It enables organizations to identify and resolve IT infrastructure problems before they affect critical business processes. Nagios has the capability of monitoring application, services, entire IT infrastructure.

This is Part-1 of complete article How to Setup Nagios Monitoring Server with NagiosQL on CentOS/RHEL 7/6, In this part, you will find the steps to setup Nagios Monitoring Server on CentOS, Redhat, and Fedora systems.

Step 1 – Install Required Packages

We assume that you have fresh installed CentOS, Red Hat or Fedora systems, So our first requirement is to install Apache and PHP first. Use the following commands to complete it. You can find detailed LAMP setup instruction here.

Install Packages:

yum install httpd php php-cli gcc unzip wget glibc glibc-common gd gd-devel net-snmp
yum groupinstall "development tools"

Start Apache:

service httpd start

Step 2 – Setup User Accounts

Now create a new nagios user account and setup a password to this account

useradd nagios
passwd nagios

Now create a groud for nagios setup “nagcmd” and add nagios user to this group. Also add nagios user in apache group.

groupadd nagcmd
usermod -a -G nagcmd nagios
usermod -a -G nagcmd apache

Step 3 – Install Nagios Core Service

After installing the required dependencies and adding user accounts. Let’s start with the Nagios core installation. Download the latest Nagios core service from the official site.

cd /opt/
wget https://assets.nagios.com/downloads/nagioscore/releases/nagios-4.4.5.tar.gz
tar xzf nagios-4.4.5.tar.gz
cd nagios-4.4.5
./configure --with-command-group=nagcmd
make all
make install
make install-init
make install-daemoninit
make install-config
make install-commandmode
 make install-exfoliation

Now use below command to setup Apache configuration for Nagios installation.

make install-webconf

Step 4 – Configure Apache Authentication

We need to setup apache authentication for user nagiosadmin. Do not change this username. else you would required more changes in configuration.

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

Now restart Apache service to make the new settings take effect.

service httpd restart

Step 5 – Install Nagios Plugins

After installing and configuring Nagios core service, Download latest nagios-plugins source and install using the following commands.

cd /opt
wget http://nagios-plugins.org/download/nagios-plugins-2.2.1.tar.gz
tar xzf nagios-plugins-2.2.1.tar.gz
cd nagios-plugins-2.2.1

Now compile and install nagios plugins

./configure --with-nagios-user=nagios --with-nagios-group=nagios
make
make install

Step 6 – Verify and Start Nagios

First, verify the Nagios configuration file using the following command.

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

If there is no error, let’s start the Nagios serivce

service nagios start

Step 7 – Access Nagios in Web Browser

Nagios creates its own apache configuration file /etc/httpd/conf.d/nagios.conf. There are no need to make any changes to it. Simply open below url in browser.
[change domain name with your domain or ip]

 http://tecadmin.example.net/nagios/

Prompting for Apache Authentication Password –

Nagios After login screen –

Finally, you have successfully installed and configured Nagios core service in your system. Now go to article install NagiosQL3 web interface for managing Nagios.