shouldiuse.io

VERDICT

Should I use Nagios Open Source?

Free, open source IT monitoring with Nagios Core. Monitor servers, networks, applications, and infrastructure. 25+ years, self-hosted, GPL licensed. - nagios.org

Depends. Buy if you have sysadmin time and want free, self-hosted monitoring that scales to huge environments. Skip if you want turnkey dashboards, vendor support, or minimal configuration.

Confidence

Medium. Based on 20+ public sources; verbatim user quotes scarce in extracted snippets, so only two clean Reddit quotes recovered.

Ratings

  • Value for money
  • Ease of use
  • Feature depth
  • Support qualityNo Core support evidence found
  • Security posture

Pricing

$0

Nagios Core

ModelNot disclosed
Monthly feesNot disclosed
HardwareNot disclosed
Free tierYes
Nagios XIPer-node, perpetual (vendor quote)

Best for

  • Hands-on sysadmin teams
  • Self-hosters on a $0 budget
  • Very large infrastructures (100k+ hosts)
  • Linux-centric shops

Not for

  • Teams without time to edit config files
  • Anyone wanting modern dashboards out of the box
  • Buyers needing vendor SLA support
  • Non-technical ops staff wanting one-click setup

Gotchas - check before you buy

medium

Core is free, but many features live in paid XI; Reddit users complain the open version lags

medium

Self-hosted means you own patching; releases ship security fixes you must apply manually

medium

Outgrowing Core pushes you to XI's per-node perpetual licensing — budget for it

low

Migration away happens: Edeka originally chose Nagios, then moved to Checkmk

Pros and cons

Pros

  • Completely free: no licensing costs, hidden fees, or limitations
  • Proven scale: 100,000 hosts and 1,000,000 services
  • Used by hundreds of thousands of organizations; 25+ years mature
  • Dozens of official plugins extend monitoring coverage
  • Public security disclosure process

Cons

  • File-based alarm configuration is laborious versus rivals
  • Requires manual server install and setup
  • Web UI has had unauthorized-access vulnerabilities
  • Users question whether focus shifted to paid XI

Sources & method

Analyzed 9/20/2026 - 14 sources - Publicly disclosed and patched vulnerabilities exist; no unpatched crisis in evidence — patch promptly.

official x2review x8security x3news x1
  • CVE-2016-9565 and earlier CVEs, Listed as fixed in the official Nagios Core 4.x changelog.
  • Web interface unauthorized access, An attacker could access more service-monitor pages than specified.
  • XSS and IDOR flaws, Disclosed on Nagios's official security disclosures page, including cross-user favoriting.

Key stats

  • Value for money: 5/5

    Rating

  • $0

    Starting price

  • 14

    Sources

  • Analyzed

  • Value for money: 5/5. 100% free, no hidden fees
  • Ease of use: 2/5. File-based config; manual install required
  • Feature depth: 4/5. Scales to 100k hosts; plugin ecosystem
  • Support quality. No Core support evidence found
  • Security posture: 3/5. CVEs patched; web UI flaws disclosed
  • 7.7/10 TrustRadius rating 172 reviews
  • $0 Starting price Nagios Core, GPL
  • Yes Free tier No licensing costs or limitations
  • 25+ years Age Founded-era open source monitoring

Pricing

Nagios Core

$0

  • Full infrastructure monitoring
  • GPL, self-hosted
  • No limitations

Nagios XI

Per-node, perpetual (vendor quote)

  • Enterprise features
  • Vendor support
  • Priced by node

Security

Publicly disclosed and patched vulnerabilities exist; no unpatched crisis in evidence — patch promptly.

  • CVE-2016-9565 and earlier CVEsListed as fixed in the official Nagios Core 4.x changelog.⁹
  • Web interface unauthorized accessAn attacker could access more service-monitor pages than specified.10
  • XSS and IDOR flawsDisclosed on Nagios's official security disclosures page, including cross-user favoriting.⁸

What users say

Admins rate Core 7.7/10 on TrustRadius across 172 reviews, but Reddit chatter questions how much attention the free version still gets.

“Is Nagios now mostly commerical and lot less open?”
Reddit, r/nagios
“There's also Nagios (open source), but I haven't used it.”
Reddit, r/sysadmin

Companies that could

  • Edeka12 Uses Checkmk instead
Full analysis

Based on 20+ public sources; verbatim user quotes scarce in extracted snippets, so only two clean Reddit quotes recovered.

Free and battle-tested, but config-heavy: great for hands-on sysadmins, painful for anyone wanting turnkey dashboards or support.

Methodology

Based on 20+ public sources; verbatim user quotes scarce in extracted snippets, so only two clean Reddit quotes recovered.

Sources

  1. Nagios Core | The #1 Open Source Monitoring Solutionnagios.org
    official
  2. Nagios Core Reviews — TrustRadiustrustradius.com
    review
  3. Nagios Open Source — SourceForge reviewssourceforge.net
    review
  4. Comparative Analysis of Nagios and OpenNMSacademia.edu
    review
  5. Using Nagios as a Groundwork for Better Network Monitoringacademia.edu
    review
  6. Is Nagios now mostly commercial and a lot less open? — Redditreddit.com
    review
  7. Install Nagios on Ubuntu 20.04cloudinfrastructureservices.co.uk
    review
  8. Nagios Security Disclosuresnagios.com
    security
  9. Nagios Core 4.x Changelognagios.org
    security
  10. Nagios web interface unauthorized access — Vigilance.frvigilance.fr
    security
  11. Nagios XI pricing — Nagios.comnagios.com
    official
  12. Edeka case study (Checkmk, formerly Nagios)checkmk.com
    review
  13. Nagios: Open-source monitoring solution — Help Net Securityhelpnetsecurity.com
    news
  14. Nagios — ithub.directory profileithub.directory
    review

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