Munin

Munin monitors servers, networks, and applications by collecting data through a plugin architecture and storing it in RRDtool databases. It uses a master/node model where each monitored machine runs a node daemon that reports metrics to a central master server. The master generates HTML pages with graphs showing historical trends for CPU, memory, disk, network traffic, and hundreds of other metrics. Alerts can be configured to trigger when values exceed thresholds. Munin supports plugins written in any language, making it easy to extend. Its web interface presents a top-level overview with drill-down capability. The project has been maintained since the early 2000s and runs on most Unix-like systems, particularly Linux and BSD. It is lightweight compared to enterprise alternatives and works well for small to medium deployments. Configuration is done through simple text files. Munin is developed by a community of volunteers and released under the GNU General Public License v2. It is a solid choice for sysadmins who want a straightforward, self-hosted monitoring solution without a heavy agent or cloud dependency.