Getting Started with Nagios Core

Getting Started with Nagios Core

If you’re looking to implement Nagios, this quick start guide is for you. Below I’ll touch on how to get Nagios up and running quickly, the differences between Core and XI, and how you can get the most out of Nagios in your environment.

Nagios Capabilities and Features

Nagios offers a powerful monitoring system that can alert IT staff about network issues before they become major problems. Nagios is known for its flexibility, scalability, and powerful native graphing, allowing users to develop their own service checks based on the needs of their network.

  • Comprehensive Monitoring Nagios ensures nothing slips through the cracks by keeping an eye on your entire IT infrastructure. This tool checks the health of your servers, networks, and applications, alerting you to problems before they impact your operations. It can monitor thousands of metrics, from server load to website downtime, ensuring you have the data you need to make informed decisions. This real-time visibility allows IT teams to address issues promptly, maintaining smooth operations.
  • Flexible and Customizable One of Nagios’s strongest suits is its adaptability to nearly any monitoring scenario. Users aren’t limited to predefined checks; you can create custom scripts to monitor specific services or applications vital to your business.
  • This flexibility extends to notifications as well, allowing you to set up alerts through email, SMS, or custom scripts that integrate with your existing tools. The customization doesn’t stop there; Nagios offers a comprehensive dashboard that can be tailored to display the metrics most relevant to you or your NOC team.
  • Detailed Reporting and Graphs With Nagios, you gain access to a wealth of historical data and reporting capabilities. It automatically generates detailed reports and graphs on network health, performance trends, and problem resolution times. These insights are crucial for planning future IT infrastructure investments and for troubleshooting recurring problems. By analyzing this data, organizations can optimize their systems for peak performance and reliability.
  • Scalability Nagios grows with your organization, capable of monitoring a few devices to thousands across multiple sites. Its distributed monitoring capabilities ensure that as your network expands, Nagios can handle the increased load without sacrificing performance. This scalability makes it a long-term solution for businesses of any size, from small startups to large enterprises. Implementing Nagios as a core part of your IT infrastructure ensures that your monitoring capabilities can evolve as your business does.

Nagios Use Cases and Scope

Nagios is a versatile tool that fits into a variety of scenarios, from small businesses to large enterprises. Let’s break down how different sectors can leverage Nagios:

  • IT Infrastructure Monitoring For IT teams burdened with overseeing complex networks, Nagios offers a lifeline. It monitors servers, switches, and routers to ensure everything runs smoothly. This is especially crucial for businesses that rely heavily on their IT infrastructure for daily operations. With Nagios, teams can detect and fix problems before they escalate, reducing downtime and maintaining productivity.
  • Application and Service Monitoring Developers and service providers can use Nagios to keep tabs on the performance of their applications. Whether you’re running web services, databases, or custom applications, Nagios helps ensure they’re performing optimally. It alerts you to slowdowns or failures, so you can quickly address the root cause. This is key to delivering a seamless user experience and maintaining high customer satisfaction.
  • Network Health and Performance Network administrators find Nagios invaluable for monitoring network health and traffic. It helps identify bottlenecks, failed devices, or unauthorized access attempts. By providing a comprehensive view of network performance, Nagios assists in optimizing traffic flow and ensuring secure, efficient operations. This capability is essential for maintaining robust network security and performance.
  • Compliance and Reporting For organizations subject to regulatory compliance, Nagios aids in monitoring and reporting on system health and vulnerabilities. It can help track compliance with standards such as HIPAA, SOX, or PCI DSS by ensuring that critical systems are properly monitored and documented. This aspect of Nagios is crucial for avoiding penalties and maintaining trust with customers and stakeholders.

Nagios Quick Start Guide

For system administrators aiming to deploy Nagios on an Ubuntu-based infrastructure, this guide assumes SELinux is either disabled or set to permissive mode, aligning with common configurations in Ubuntu systems.

1. Preparing the Environment

First, start by updating your system’s package database and installing the necessary development and web server packages. Execute the following commands to install dependencies such as autoconf, gcc, libc6, make, wget, unzip, apache2, PHP, and the necessary PHP and Apache modules.

Prerequisite Commands:

sudo apt-get update

sudo apt-get install -y autoconf gcc libc6 make wget unzip apache2 php libapache2-mod-php7.4 libgd-dev

sudo apt-get install openssl libssl-dev

2. Acquiring Nagios Core

Navigate to the /tmp directory and retrieve the Nagios Core source code using wget. The command provided downloads the latest version of Nagios Core as a tar.gz file, which you will then need to extract using tar.

Download Commands:

cd /tmp

wget -O nagioscore.tar.gz

tar xzf nagioscore.tar.gz

3. Compiling and Installing Nagios Core

Change into the directory containing the extracted Nagios Core source code. Initiate the compilation process by configuring the build environment with the appropriate options, specifically pointing towards the Apache configuration directory.

Following this, the make all command compiles the source code into executable binaries and sets up the web interface files. This compilation process is critical, transforming the raw source code into a functioning monitoring tool.

Compile Command:

cd /tmp/nagioscore-nagios-4.4.14/

sudo ./configure –with-httpd-conf=/etc/apache2/sites-enabled

sudo make all

4. System Integration and Configuration

Post-compilation, system administrators must integrate Nagios Core into the system by creating necessary user groups and permissions. The make install-groups-users command establishes the Nagios user and group, ensuring proper security and operational permissions. Additionally, incorporating the www-data user into the Nagios group facilitates web server interaction with Nagios.

The installation steps continue with the deployment of binaries, initialization scripts, command mode setup, and sample configuration files. These steps lay the groundwork for Nagios’s operational framework, allowing for subsequent fine-tuning and customization based on specific monitoring needs.

User Group Commands:

sudo make install-groups-users

sudo usermod -a -G nagios www-data


sudo make install


sudo make install-daemoninit

Install and Configuration Files:

sudo make install-commandmode

sudo make install-config

5. Web Interface and Access Configuration

Finalizing the installation involves setting up Nagios’s web interface through Apache. This includes installing the Apache configuration files for Nagios and enabling necessary Apache modules to support the web interface. Adjusting firewall settings to permit web traffic is essential for remote access, ensuring administrators can reach the Nagios dashboard from other networked devices.

Apache Configuration:

sudo make install-webconf

sudo a2enmod rewrite

sudo a2enmod cgi

Firewall Config:

Note: You will need to allow port 80 inbound traffic on your firewall for access to Nagios Core Web UI.

sudo ufw allow Apache

sudo ufw reload

Creating the nagiosadmin account:

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

6. Testing Your Nagios Installation

With Nagios Core successfully installed, the next step is to verify its operation by accessing the Nagios Web Interface.

To do this, navigate to your web browser and enter the IP address or FQDN (Fully Qualified Domain Name) of your server hosting Nagios Core. Examples include:

  • http://core-013.domain.local/nagios

Upon attempting to access this URL, you will encounter a login prompt. Here, use “nagiosadmin” as the username — this was established during the setup process. The password will be the one you specified at that time.

Successfully logging in will bring you to the main dashboard of the Nagios interface.

7. Installing Nagios Plugins

To fully operationalize Nagios Core, I found that it’s essential to integrate plugins. This segment guides you through the plugin installation process, which extends Nagios Core’s monitoring capabilities.

Update on Plugin Versions

We will be installing Nagios Plugins version 2.4.6, though it’s worth noting that newer versions might be available. For the latest releases, check the GitHub releases page. While this guide covers the installation of most standard plugins, some may require additional libraries not covered here.

Installing Dependencies

sudo apt-get install -y autoconf gcc libc6 libmcrypt-dev make libssl-dev wget bc gawk dc build-essential snmp libnet-snmp-perl gettext

Downloading and Installing the Plugins

Navigate to a temporary directory and download the Nagios Plugins source code using wget. Extract the downloaded tar.gz file and proceed with the compilation and installation:

cd /tmp

wget –no-check-certificate -O nagios-plugins.tar.gz

tar zxf nagios-plugins.tar.gz

cd /tmp/nagios-plugins-release-2.4.6/

sudo ./tools/setup

sudo ./configure

sudo make

sudo make install

Verifying Plugin Installation

After installation, verify the functionality of the plugins by accessing your Nagios Core server’s web interface and rescheduling a check for a host or service object. Any prior errors should be resolved, displaying the expected output.

The commands to manage the Nagios service vary by Linux distribution. For Ubuntu systems, use the following commands to start, stop, restart, and check the status of Nagios:

sudo systemctl start nagios.service

sudo systemctl stop nagios.service

sudo systemctl restart nagios.service

sudo systemctl status nagios.service

Nagios Tips & Best Practices

For system administrators and IT professionals, effectively deploying and managing Nagios Core can significantly enhance network and system monitoring efforts. Here are some tips and best practices to optimize your Nagios Core installation:

Regularly Update Nagios Core and Plugins

I found that staying current with the latest versions of Nagios Core and its plugins ensures you benefit from improved features, bug fixes, and security patches. Regular updates minimize vulnerabilities and enhance monitoring efficiency. Check the official Nagios and plugins repositories for updates and follow the recommended procedures for upgrading.

For Ubuntu, commands like sudo apt-get update && sudo apt-get upgrade nagios* will check for and apply updates. For plugins, navigate to the official plugins page, download the latest version, and follow the compilation and installation instructions provided earlier.

Utilize Configuration Management

To streamline the management of Nagios configurations, especially in complex environments, adopt configuration management tools like Ansible, Puppet, or Chef. These tools can automate the deployment and configuration of Nagios across multiple servers, ensuring consistency and saving time.

Create a playbook (Ansible), manifest (Puppet), or recipe (Chef) that defines how Nagios and its plugins should be installed and configured. Include tasks for copying configuration files, setting up user accounts, and ensuring services are running.

For example, with Ansible, you’d run ansible-playbook -i inventory_file nagios_setup.yml to apply your configurations.

Implement Comprehensive Monitoring

Beyond basic system metrics, configure Nagios to monitor application-specific metrics and log files. This approach provides deeper insights into the performance and health of your applications, allowing for more proactive issue resolution. Customize plugin scripts when necessary to cover unique monitoring requirements of your IT environment.

Write custom scripts for monitoring specific application metrics or logs not covered by default plugins. Place these scripts in the libexec directory where Nagios stores its plugins. Edit your Nagios configuration files to include these custom scripts as command definitions. Then, apply these commands to host or service objects as needed

Always test new configurations and custom scripts for accuracy and effectiveness before deploying them into production.

Optimize Alerting Mechanisms

Fine-tune Nagios’s alerting mechanisms to avoid alert fatigue. Establish clear thresholds for alerts and ensure they are directed to the appropriate team members. Utilize Nagios’s capabilities to escalate issues automatically if not acknowledged within a certain timeframe, ensuring critical issues receive the necessary attention.

Organize your team members into contact groups within Nagios for targeted alerting. Edit the contacts.cfg file to define groups based on roles or responsibilities. In your service and host definitions, set appropriate thresholds for warnings and critical alerts to manage alert volumes effectively.

You can set up escalation policies by editing the escalations.cfg file, ensuring critical alerts escalate if not acknowledged in a timely manner.

Secure Your Nagios Installation

Security is paramount when deploying Nagios Core. Regularly review and apply security best practices, such as securing the web interface with SSL, implementing firewall rules to restrict access, and using secure passwords. Additionally, consider running Nagios in a chroot environment to isolate it from the rest of the system, reducing potential attack surfaces.

Configure Apache to use SSL/TLS for the Nagios web interface, ensuring data transmitted is encrypted. Obtain a certificate and edit the Apache site configuration for Nagios to use HTTPS.

Limit access to the Nagios server using firewall rules. Only allow necessary traffic to and from the server, and restrict access to known IP addresses if possible.

To isolate Nagios, use chroot to run it in a sandboxed environment. This involves setting up a minimal environment with only the necessary libraries and binaries for Nagios to run, minimizing potential security risks.

Nagios Pricing

Nagios Core, the open-source engine at the heart of many Nagios monitoring solutions, is freely available. However, for those seeking advanced features, comprehensive reporting, and a more user-friendly interface, Nagios XI offers a robust alternative.

Here’s a short breakdown between the two platforms:

FeatureNagios CoreNagios XI
Available as Source Install Script
Complete Infrastructure Monitoring
Hundreds of Free Addons
Open Source Monitoring Engine
Forum Support
Pre-Configured Virtual Machine
Quickstart Guides
Web Configuration UI (CCM)
Performance Graphing (PNP)
SNMP Trap Support
Mobile App (Nagios Mobile)
Business Process Monitoring
Custom Maps (Nagvis)
Database Backend
Integrated UI
User-Specific Customization
Configuration Wizards
Scheduled Reporting
Capacity Planning
Executive Reports
Bulk Management
Configuration Rollback
Audit Logging
Email and Phone Support

Nagios XI offers several plans depending on the number of nodes you need and the features you require:

Nagios Core: Complimentary Edition

  • Offers monitoring for up to 7 nodes or 100 services, whichever cap is met first.
  • Provides many features found in the Standard package, excluding support services.
  • Ideal for small-scale or initial-setup environments.
  • Cost: Free

Nagios XI: Standard Licensing Options

  • Comprehensive infrastructure monitoring and graphing tools.
  • Advanced alerting and reporting functionalities.
  • User-friendly configuration GUI and over 65 configuration wizards.
  • Automation capabilities and open API for integration with your tech stack.
  • 12 months of email support and maintenance included.

Pricing Tiers for Standard License:

  • 100 Nodes: $2,495
  • 300 Nodes: $5,995
  • 500 Nodes: $8,495
  • 1000 Nodes: $14,495
  • Unlimited Nodes: $23,995

Nagios XI: Enterprise Add-On

  • Advanced capacity planning reports and scheduled reporting features.
  • Tools for bulk modifications and detailed SLA reports.
  • Business Process Intelligence (BPI) and comprehensive audit logs.
  • All features of the Standard License are included.

Pricing Tiers for Enterprise Add-On:

  • 100 Nodes: $4,490
  • 300 Nodes: $7,990
  • 500 Nodes: $10,490
  • 1000 Nodes: $16,490
  • Unlimited Nodes: $25,990

Nagios XI: Sitewide Licensing

  • Designed for extensive Nagios XI deployments.
  • Free Nagios Fusion license and Enterprise features included.
  • Facilitates distributed and centralized monitoring setups.
  • Offers a significant cost reduction for large-scale operations.

Package Options:

  • Multiple Unlimited Nodes: Custom pricing, please reach out to our sales team for a detailed quote.

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