An Easy Way of Understanding Nagios

NovelVista

Last updated 27/07/2021

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Nagios is an open-source software for continuous monitoring of systems, networks, and infrastructures. It runs plugins stored on a server that is connected with a host or another server on your network or the Internet. In case of any failure, Nagios alerts about the issues so that the technical team can perform the recovery process immediately.

Nagios is used for continuous monitoring of systems, applications, services, and business processes in a DevOps culture.

What is Continuous Monitoring?

Continuous monitoring is a process to detect, report, and respond to all the attacks which occur in its infrastructure. Once the application is deployed into the server, the role of continuous monitoring comes into play. The entire process is all about taking care of the company's infrastructure and respond appropriately.

Services Nagios provides:

• Monitoring of network services (SMTP, POP3, HTTP, NNTP, ICMP, SNMP, FTP, SSH)
• Monitoring of host resources (processor load, disk usage, system logs) on a majority of network operating systems, including Microsoft Windows, using monitoring agents.
• Monitoring of any hardware (like probes for temperature, alarms, etc.) which have the ability to send collected data via a network to specifically written plugins
• Monitoring via remotely run scripts via Nagios Remote Plugin Executor
• Remote monitoring supported through SSH or SSL encrypted tunnels.
• A simple plugin design that allows users to easily develop their own service checks depending on needs, by using their tools of choice (shell scripts, C++, Perl, Ruby, Python, PHP, C#, etc.)
• Available data graphing plugins
• Parallelized service checks
• Flat-text formatted configuration files (integrates with many config editors)
• The ability to define network host using 'parent' hosts, allowing the detection of and distinction between hosts that are down or unreachable
• Contact notifications when service or host problems occur and get resolved (via e-mail, pager, SMS, or any user-defined method through plugin system)
• The ability to define event handlers to be run during service or host events for proactive problem resolution
• Automatic log file rotation
• Support for implementing redundant monitoring hosts
• Support for implementing performance data graphing
• Support for database backend (such as NDOUtils)
• Push notifications
• A web-interface for viewing current network status, notifications, problem history, log files, etc

Nagios agents

NRPE

Nagios Remote Plugin Executor (NRPE) is a Nagios agent that allows remote system monitoring using scripts that are hosted on the remote systems. It allows for monitoring of resources such as disk usage, system load, or the number of users currently logged in. Nagios periodically polls the agent on a remote system using the check_nrpe plugin.

NRPE allows you to remotely execute Nagios plugins on other Linux/Unix machines. This allows you to monitor remote machine metrics (disk usage, CPU load, etc.). NRPE can also communicate with some of the Windows agent add-ons, so you can execute scripts and check metrics on remote Windows machines, as well.

NRDP

Nagios Remote Data Processor (NRDP) is a Nagios agent with a flexible data transport mechanism and processor. It is designed with an architecture that allows it to be easily extended and customized. NRDP uses standard ports and protocols (HTTP and XML) and can be implemented as a replacement for Nagios Service Check Acceptor (NSCA).

NSClient++

This program is mainly used to monitor Windows machines. Being installed on a remote system NSClient++ listens to port TCP 12489. The Nagios plugin that is used to collect information from this addon is called check_nt. As NRPE, NSClient++ allows monitoring the so-called 'private services' (memory usage, CPU load, disk usage, running processes, etc.) Nagios is a host and service monitor which is designed to inform you of network problems.

NCPA

The Nagios Cross-Platform Agent is an open source project maintained by Nagios Enterprises. NCPA installs on Windows, Linux, and Mac OS X. Created as a scale-able API that allows flexibility and simplicity in monitoring hosts. NCPA allows multiple checks such as memory usage, CPU usage, disk usage, processes, services, and network usage. Active checks are queried through the API of the "NCPA Listener" service while passive checks are sent via the "NCPA Passive" service.

Features

Comprehensive Monitoring

• Capabilities to monitor applications, services, operating systems, network protocols, system metrics, and infrastructure components with a single tool
• Powerful script APIs allow easy monitoring of in-house and custom applications, services, and systems

Visibility & Awareness

• Centralized view of entire monitored IT infrastructure
• Detailed status information available through a web interface
• Fast detection of infrastructure outages
• Alerts can be delivered to technical staff via email or SMS
• Escalation capabilities ensure alert notifications reach the right people

Problem Remediation

• Alert acknowledgments provide communication on known issues and problem response
• Event handlers allow the automatic restart of failed applications and services

Proactive Planning

• Trending and capacity planning add-ons ensure you’re aware of aging infrastructure
• Scheduled downtime allows for alert suppression during infrastructure upgrades

Reporting

• Availability reports ensure SLAs are being met
• Historical reports provide a record of alerts, notifications, outages, and alert response
• Third-party add-ons extend reporting capabilities

Multi-Tenant Capabilities

• Multi-user access to web interface allows stakeholders to view infrastructure status
• User-specific views ensure clients see only their infrastructure components

Extendable Architecture

• Integration with in-house and third-party applications is easy with multiple APIs
• Hundreds of community-developed addons extend core Nagios functionality

Stable, Reliable, and Respected Platform

• Over 10 years of active development
• Scales to monitor thousands of nodes
• Failover capabilities ensure non-stop monitoring of critical IT infrastructure components
• Multiple awards, media coverage, and recognition prove Nagios’ value

Vibrant Community

• Over 1 million+ users worldwide
• Active community mailing lists provide free support
• Hundreds of community-developed addons extend Nagios’ core functionality

Customizable Code

• Open Source Software
• Full access to source code
• Released under the GPL license

Disadvantages of Using Nagios

• An important feature like wizards or interactive dashboard is only available on Nagios XI, which is quite an expensive tool
• Nagios Core has a confusing interface
• There're many configuration files that are very hard to configure for users
• Nagios can't monitor network throughput
• The tool not allows you to manage the network but only allows you to monitor the network
• Nagios makes no difference between various devices like servers, routers, or switches as it treats every device as a host

I hope you have enjoyed reading this Nagios tutorial, I will be coming up with more blogs on more DevOps tools soon.

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