Nagios

Nagios is an application that monitors systems, networks and infrastructure with alerting capabilities. There is different Nagios agents for collection data are available.

Some features of Nagios Core include:

• Monitoring of network services (SMTP, POP3, HTTP, NNTP, PING, etc.)
• Monitoring of host resources (processor load, disk usage, etc.)
• Simple plugin design that allows users to easily develop their own service checks
• Parallelized service checks
• Ability to define network host hierarchy using "parent" hosts, allowing detection of and distinction between hosts that are down and those that are unreachable
• Alerts or contact notifications when service or host problems occur and get resolved (via email, pager, or user-defined method)
• 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
• Optional web interface for viewing current network status, notification and problem history, log file, etc.

Configuration file

• /etc/nagios3/nagios.cfg

Activities

• Review check_http options
• Review more than 60 plugins installed by Nagios: /usr/lib/nagios/plugins/check_*
• Read StackExchange questions about Nagios: https://serverfault.com/questions/tagged/nagios?tab=Votes
• Read Nagios core changelog: https://github.com/NagiosEnterprises/nagioscore/blob/master/Changelog
• Install Nagios Core using docker: docker pull jasonrivers/nagios && docker run --name nagios4 -p 0.0.0.0:8080:80 jasonrivers/nagios:latest and connect to http://localhost:8080 using nagiosadmin / nagios or apt install nagios3
• Run a manual test: /usr/lib/nagios/plugins/check_tcp -H 127.0.0.1 -p 80

TCP OK - 0.000 second response time on 127.0.0.1 port 80|time=0.000274s;;;0.000000;10.000000

See also

• Monitoring: Prometheus, Cacti, monit, munin, RRDtool, Zabbix, Netdata, Nagios, Check MK, Icinga, Pingdom, OpsGenie and Datadog, Opsgenie, PRTG, Checkmk
• Nagios Remote Plugin Executor
• Nagios Cross-Platform Agent (NCPA)

https://en.wikipedia.org/wiki/Nagios#Nagios_agents

https://assets.nagios.com/downloads/nagioscore/docs/nagioscore/3/en/about.html#whatis