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Chapter 2. Installing Nagios Core

Installing Nagios Core involves downloading the Nagios Core source code; then, configuring, making and installing it on the host that will run Nagios Core instance.

The following sections describe the process for RHEL 7 and later releases.

2.1. Installing Nagios Prerequisites

Install the prerequisites.

[user@nagios]# yum install -y httpd php php-cli gcc glibc glibc-common gd gd-devel net-snmp openssl openssl-devel wget unzip

Open port 80 for httpd.

[user@nagios]# firewall-cmd --zone=public --add-port=80/tcp
[user@nagios]# firewall-cmd --zone=public --add-port=80/tcp --permanent

2.2. Creating a Nagios User and Group

Create a user and group for Nagios Core.

[user@nagios]# useradd nagios
[user@nagios]# passwd nagios
[user@nagios]# groupadd nagcmd
[user@nagios]# usermod -a -G nagcmd nagios

Then, execute the following:

[user@nagios]# usermod -a -G nagcmd apache

2.3. Download Nagios Source Code and Plug-ins

Download the latest version of Nagios Core and Plug-ins.

[user@nagios]# wget --inet4-only
[user@nagios]# wget --inet4-only
[user@nagios]# tar zxf nagios-4.3.1.tar.gz
[user@nagios]# tar zxf nagios-plugins-2.2.1.tar.gz
[user@nagios]# cd nagios-4.3.1

2.4. Make and Install Nagios Core

To make and install Nagios Core, first run ./configure.

[user@nagios]# ./configure --with-command-group=nagcmd

After running ./configure, compile the Nagios Core source code.

[user@nagios]# make all

After making Nagios Core, install it.

[user@nagios]# make install
[user@nagios]# make install-init
[user@nagios]# make install-config
[user@nagios]# make install-commandmode
[user@nagios]# make install-webconf

Copy the event handlers and change their ownership.

[user@nagios]# cp -R contrib/eventhandlers/ /usr/local/nagios/libexec/
[user@nagios]# chown -R nagios:nagios /usr/local/nagios/libexec/eventhandlers

Finally, run the pre-flight check.

[user@nagios]# /usr/local/nagios/bin/nagios -v /usr/local/nagios/etc/nagios.cfg

2.5. Make and Install Nagios Core Plug-ins

Make and install the Nagios Core plug-ins.

[user@nagios]# cd ../nagios-plugins-2.2.1
[user@nagios]# ./configure --with-nagios-user=nagios --with-nagios-group=nagios
[user@nagios]# make
[user@nagios]# make install

2.6. Create a Default Nagios Core User

Create a user for the Nagios Core user interface.

[user@nagios]$ sudo htpasswd -c /usr/local/nagios/etc/htpasswd.users nagiosadmin

If adding a user other than nagiosadmin, ensure the /usr/local/nagios/etc/cgi.cfg file gets updated with the username too.

Also modify the /usr/local/nagios/etc/objects/contacts.cfg file with the user name, full name and email address as needed.

2.7. Start Nagios

Add Nagios Core as a service and enable it. Then start the Nagios Core daemon and Apache.

[user@nagios]# chkconfig --add nagios
[user@nagios]# chkconfig --level 35 nagios on
[user@nagios]# systemctl start nagios
[user@nagios]# systemctl enable httpd
[user@nagios]# systemctl start httpd

2.8. Log in to Nagios Core

With Nagios up and running, log in to the web user interface.


Nagios Core will prompt for a user name and password. Input the login and password of the default Nagios Core user.