Nagios Core Overview

Nagios Core is an open-source monitoring system that enables organizations to identify and resolve IT infrastructure problems before they affect critical business processes.

Key features include:

• Monitoring of network services (SMTP, POP3, HTTP, NNTP, ICMP, etc.)
• Monitoring of host resources (processor load, disk usage, etc.)
• Notification alerts for system administrators

Nagios Core uses a client-server architecture:

1. **Nagios Server**: Central unit that monitors the status of defined hosts and services.
2. **Plugins**: Executable scripts that return status information to the Nagios server.
3. **Notification System**: Sends alerts based on the defined configurations.

To install Nagios Core on a Linux system, follow these steps:

sudo apt update
sudo apt install -y nagios3 nagios-nrpe-plugin

After installation, you can access the Nagios web interface at http://your-server-ip/nagios3.

Nagios configuration is done through text files, primarily located in the /etc/nagios3 directory.

To add a host:

define host {
    use                     linux-server
    host_name               my-server
    alias                   My Server
    address                 192.168.1.1
}

After making changes, restart Nagios:

sudo systemctl restart nagios3

• Regularly update Nagios Core and plugins.
• Backup configuration files before making changes.
• Use templates for hosts and services to simplify configuration.
• Monitor critical services and hosts with appropriate notification settings.