Nagios Core

Nagios Core is an open-source monitoring system that can also serve as an incident alerting solution. It watches hosts, services, or network resources, sending notifications when issues arise. A web interface shows status and event logs, and community plugins expand coverage. While primarily a monitoring tool, Nagios can be adapted for incident response, with alerts triggering scripts or escalation. It suits sysadmins wanting a free, extensible platform for infrastructure monitoring and basic incident alerting.