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 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
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.
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.
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