Nagios Installation: A Step-by-Step Guide
Nagios installation is the first crucial step to setting up a comprehensive monitoring system for your IT infrastructure. This guide will walk you through the process of installing and configuring Nagios, so you can monitor your systems, networks, and applications effectively.
Prerequisites for Nagios Installation
Before beginning the Nagios installation, you need to install the required build dependencies. These are essential packages that support Nagios’ functionality:
sudo yum install gcc glibc glibc-common gd gd-devel make net-snmp openssl-devel xinetd unzip
Also, create a “nagios” user and “nagcmd” group to handle installation commands and permissions:
sudo useradd nagios
sudo groupadd nagcmd
sudo usermod -a -G nagcmd nagios
Once the prerequisites are in place, you can move on to the installation process.
Installing Nagios Core
Navigate to the /opt directory and download the Nagios Core package:
cd /opt
curl -L -O https://assets.nagios.com/downloads/nagioscore/releases/nagios-4.4.6.tar.gz
Once the download is complete, extract the package and enter the extracted folder:
tar xvf nagios-*.tar.gz
cd nagios-*
Next, configure Nagios with the following command to ensure the correct group permissions:
./configure --with-command-group=nagcmd
Compile Nagios using the make command:
make all
Now, run these commands to install Nagios, its components, and configure them for proper functioning:
sudo make install
sudo make install-commandmode
sudo make install-init
sudo make install-config
sudo make install-webconf
To allow external command execution via the Nagios web interface, add the Apache user to the nagcmd group:
sudo usermod -G nagcmd apache
Installing Nagios Plugins
Nagios relies on plugins to perform checks on various services and systems. To install the Nagios Plugins, first, download the plugin archive:
cd /opt
curl -L -O http://nagios-plugins.org/download/nagios-plugins-2.1.1.tar.gz
tar xvf nagios-plugins-*.tar.gz
cd nagios-plugins-*
Configure and compile the plugins using the following commands:
./configure --with-nagios-user=nagios --with-nagios-group=nagios --with-openssl
make
sudo make install
Installing NRPE for Remote Monitoring
To monitor remote systems, install the Nagios Remote Plugin Executor (NRPE). Begin by downloading its archive and extracting it:
cd /opt
curl -L -O http://downloads.sourceforge.net/project/nagios/nrpe-2.x/nrpe-2.15/nrpe-2.15.tar.gz
tar xvf nrpe-*.tar.gz
cd nrpe-*
Configure NRPE for remote monitoring:
./configure --enable-command-args --with-nagios-user=nagios --with-nagios-group=nagios --with-ssl=/usr/bin/openssl --with-ssl-lib=/usr/lib/x86_64-linux-gnu
Now, build and install NRPE with the following commands:
make all
sudo make install
sudo make install-xinetd
sudo make install-daemon-config
Once NRPE is installed, restart the xinetd service:
sudo service xinetd restart
Configuring Nagios Installation for Monitoring
Organize Nagios Configuration
For a better-organized Nagios installation, uncomment the configuration directory line in nagios.cfg:
sudo vi /usr/local/nagios/etc/nagios.cfg
Uncomment the following line:
cfg_dir=/usr/local/nagios/etc/servers
Create the servers directory where configuration files for each monitored server will be stored:
sudo mkdir /usr/local/nagios/etc/servers
Configure Nagios Contacts
To receive alerts and notifications, change the contact email address in the configuration:
email nagios@localhost ; <<***** CHANGE THIS TO YOUR EMAIL ADDRESS ******
Add Check_NRPE Command
To monitor remote systems, you need to add the NRPE command to the commands.cfg file:
sudo vi /usr/local/nagios/etc/objects/commands.cfg
Add this configuration:
define command{
command_name check_nrpe
command_line $USER1$/check_nrpe -H $HOSTADDRESS$ -c $ARG1$
}
Configure Apache for Nagios Web Access
Set up a user for the Nagios web interface by creating a password:
sudo htpasswd -c /usr/local/nagios/etc/htpasswd.users nagiosadmin
If you use a different username, make sure to update the cgi.cfg file with your new user.
Start Nagios Service
Finally, reload the system daemon and start Nagios and Apache:
sudo systemctl daemon-reload
sudo systemctl start nagios.service
sudo systemctl restart httpd.service
sudo chkconfig nagios on
Restrict Access by IP (Optional)
If you want to restrict access to the Nagios web interface, modify the nagios.conf file to allow only specific IP addresses:
sudo vi /etc/httpd/conf.d/nagios.conf
Uncomment and modify these lines:
Order deny,allow
Deny from all
Allow from 127.0.0.1
Save the changes and restart both Nagios and Apache:
sudo systemctl restart nagios.service
sudo systemctl restart httpd.service
Accessing the Nagios Installation Web Interface
After completing the installation, access the Nagios web interface by visiting:
http://nagios_server_public_ip/nagios
Log in using the credentials you created during the setup process.
Conclusion for Nagios Installation
Congratulations! You’ve successfully completed the Nagios installation and configuration. Nagios is a powerful monitoring tool, and with the correct setup, it will help you keep track of your infrastructure’s health and performance.
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