Centreon is a free Open Source monitoring software which allows an administrator to easily configure alerts based on thresholds, generate email alerts, add systems to be monitored quickly without the need of configuring complicated configuration files.
Install and configure telegraf on pfsense to provides system information to prometheus.
Use Influxdb to as storage for Prometheus.
I prefer to use Naemon (a fork of nagos) with Influxdb as a storage for graphical data.
The Alertmanager handles alerts sent by client applications such as the Prometheus server.
Install node-exporter to provides detailed information about the system, including CPU, disk, and memory usage.
Prometheus is an open-source monitoring system with a built-in noSQL time-series database. It offers a multi-dimensional data model, a flexible query language, and diverse visualization possibilities. Prometheus collects metrics from http nedpoint. Most service dind’t have this endpoint so you need optional programs that generate additional metrics cald exporters.