Monitoring & observability
Nagios (Core / XI)
Veteran host and service monitor: free Core, commercial XI.
freemiumdesktop
Independent reference — this page is a review. Nagios (Core / XI) is downloaded from the vendor’s official site, not from here.
| Platforms | Linux/Unix server, web UI |
|---|---|
| Licence | Freemium — Core GPLv2 / XI commercial |
| Price | Core free; XI from ~$2,595 (100 nodes) |
| Section | Monitoring & observability |
| Updated | 2026-11-05 |
What it is
Around for a long time, it ships two ways: a free Core engine and a commercial XI edition with a fuller web UI. It watches host, service and resource availability, raises alerts on failure, and leans on an enormous plugin library to stretch what you can observe.
Problems it closes
- You want a proven, scriptable availability monitor with a vast plugin library behind it.
- A plain up/down and threshold model fits the team better than full observability.
How administrators run it
- Declare hosts and services in config and pull community plugins for the checks.
- Wire notifications to email or chat, with escalation in place.
Strengths & trade-offs
Strengths
- Battle-tested and scriptable.
- The plugin ecosystem is huge.
- Core is free.
Trade-offs
- Configuration lives in text files.
- Core’s UI is dated — the polish is in paid XI.
Common questions
What separates Core from XI?
Core is the free, config-driven engine; XI is the commercial edition, adding a richer web UI, configuration tooling and support.
Does it still earn its place?
Yes, for plain availability monitoring backed by a large plugin library — though newer tools come with slicker interfaces.
Alternatives
Zabbix Open-source monitoring across servers, network gear, VMs and applications. open sourcedesktop Linux/Unix server, web UI; agents for Windows/Linux/macOS/Unix Prometheus Time-series monitoring and alerting, the default in cloud-native stacks. open sourcedesktop Linux/Windows/macOS, web UI; CNCF PRTG Network Monitor Sensor-based monitoring from Paessler for networks and infrastructure. freemiumcloud + desktop Windows server + web/mobile; also SaaS (Hosted Monitor)