Chapter 2. Installing Nagios Core

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

[user@nagios]# apt-get install wget build-essential apache2 php apache2-mod-php7.0 openssl libssl-dev gcc make php-gd libgd-dev 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

Open port 80 for apache2:

[user@nagios]# iptables -A INPUT -p tcp --dport 80 -j ACCEPT
[user@nagios]# apt-get install iptables-persistent

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

[user@nagios]# usermod -a -G nagios,nagcmd www-data

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

[user@nagios]# wget --inet4-only https://assets.nagios.com/downloads/nagioscore/releases/nagios-4.3.1.tar.gz
[user@nagios]# wget --inet4-only http://www.nagios-plugins.org/download/nagios-plugins-2.2.1.tar.gz
[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

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

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

[user@nagios]# ./configure --with-command-group=nagcmd --with-httpd-conf=/etc/apache2/

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

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

Create a user for the Nagios Core user interface.

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

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

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

[user@nagios]# a2ensite nagios
[user@nagios]# a2enmod rewrite cgi
[user@nagios]# sudo cp /etc/init.d/skeleton /etc/init.d/nagios

Then, edit the initialization file:

[user@nagios]# vi /etc/init.d/nagios

Add the following lines:

DESC="Nagios"
NAME=nagios
DAEMON=/usr/local/nagios/bin/$NAME
DAEMON_ARGS="-d /usr/local/nagios/etc/nagios.cfg"
PIDFILE=/usr/local/nagios/var/$NAME.lock

Finally, start Nagios:

[user@nagios]# systemctl restart apache2
[user@nagios]# systemctl start nagios

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

http://<ip-address>/nagios

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