collectd

A daemon that collects system performance statistics periodically, and provides tons of plugins to store and analyze these values

     

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Nagios Core

Nagios Core network monitoring software is a powerful, enterprise-class host, server, application, monitoring and alerting tool

     

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Pallet

A tool to provision and maintain servers across various cloud platforms as well as virtual machine platforms, without any dependencies. Provides cloud and operating system independence.

     

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Rex

A agent-less server orchestration tool built on Perl

     

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Zabbix

An open source, enterprise-class monitoring framework

     

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