I will give a simplified example of the only product I've used for this: Zabbix. Disclaimer: I'm not a sysadmin but a developer, who happened to work somewhere

I will give a simplified example of the only product I've used for this: Zabbix. Disclaimer: I'm not a sysadmin but a developer, who happened to work somewhere they used Zabbix for monitoring all kinds of network devices, databases, services, etc. Perhaps there are better solutions available, I welcome any discussion on that. Deploying Zabbix roughly consists of setting up one (or more) Zabbix Master servers, and installing a 'zabbix-agent' process on each device you want to monitor. The agent process extracts a variety of statistics about the system and makes them available to the Monitoring server, either in push ("active") or pull ("passive") fashion. The Master logs all of these statistics over time. You can then define 'Triggers' that apply logical tests to statistics, such as "in the last 5 minutes, was the free diskspace < 10GB". When this happens, it triggers an event. Then elsewhere you have defined your Notification rules that act upon generated events, to send out an email or text message. https://www.zabbix.com/features#notification https://www.zabbix.com/features#notification This was obviously really simplified, and there is so much more you can do, but I hope this at least gave you a basic picture.