Netdata is an open-source (GPLv3) real-time server monitoring tool, collecting system metrics at second-level resolution with hundreds of preconfigured alert rules and 200+ application monitoring.
Cockpit is the Red Hat-led open-source Linux server web management console, letting you handle system monitoring, Podman container management, LVM storage management, and user configuration from a browser, free and open source, ideal for Linux server administrators and cloud server ops.
Munin is an open-source server resource monitoring tool from Norway with a Perl-based Master/Node architecture and RRDTool graphing engine. Its plug-and-play plugin mechanism keeps deployment simple for small server clusters.
Founded in 1999 and headquartered in Saint Paul, Minnesota, USA, Nagios is the pioneer of IT infrastructure monitoring. Nagios Core is free and open source, while Nagios XI offers web management and reporting.
Cockpit is a Red Hat-sponsored open-source web server management console (LGPL v2.1+) supporting Fedora, RHEL, Debian and Ubuntu, offering free management of system services, storage, networking, VMs and containers.