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Nagios

The classic open-source server and network monitoring engine with a vast plugin ecosystem.

Open sourceSelf-hostableMonitoring and error tracking tools
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About Nagios

Nagios Core is one of the oldest open-source monitoring tools and still runs in many data centres. It schedules checks against hosts and services using small plugins, records whether each is OK, warning or critical, and sends notifications and escalations when things change. Its real strength is the plugin ecosystem: thousands of community checks exist for almost any device, service or application, and the plugin format has been adopted by many other tools, including Icinga and Checkmk. The weaknesses are age and effort. Configuration lives in text files, the bundled web interface is dated, and there is no built-in time series database or modern dashboarding, so most installations add other tools for graphs. Nagios Core is free under the GPL; Nagios Enterprises sells Nagios XI, a commercial edition with a web-based configuration UI and reporting. It runs on Linux and Unix servers.

Best for: Admins who want a proven, plugin-based check engine for servers and networks.

Pros and cons

What works

  • Enormous library of community check plugins
  • Stable and well understood after decades of use
  • Free open-source core

Why people leave

  • Text-file configuration is laborious
  • Dated web interface
  • No built-in metrics storage or modern dashboards

Top Nagios alternatives

See all 5
  1. 1Icinga logo
    Icinga

    Started as a Nagios fork and keeps plugin compatibility with a modern UI and API.

    66.5
  2. 2Checkmk logo
    Checkmk

    Uses Nagios-style checks but adds auto-discovery and a web configuration UI.

    62.6
  3. 3Zabbix logo
    Zabbix

    All-in-one web UI, templates and metrics storage without text-file config.

    59.6
  4. 4Prometheus logo
    Prometheus

    Metrics-first approach better suited to cloud-native systems.

    57.2
  5. 5Netdata logo
    Netdata

    Instant dashboards and alerts with almost no configuration.

    55.3

Why people left Nagios

In reviewers' own words, from reviews of the apps they moved to. These are their opinions, not ours.

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Nagios: common questions

Is Nagios free?

Yes. Nagios is free, open-source software that you can host yourself.

Is Nagios open source?

Yes. The source code is on GitHub at NagiosEnterprises/nagioscore. You can also run it on your own server.

What platforms does Nagios run on?

Nagios is available for Self-hosted and Linux.

What are the best alternatives to Nagios?

The highest-ranked Nagios alternatives right now are Icinga, Checkmk and Zabbix. See the full ranked list for pricing, platforms and verified facts.

See all 5 Nagios alternatives