Not OP, but we use Nagios XI for such alerting, it provides SMS and email monitoring for infrastructure (disk space as an example) and service monitoring. [1]

Their open source NCPA (Nagios Cross Platform agent) plugin for Windows and Linux hosts is pretty great, though we were stung when we found out it didn't natively support SPARC as of yet unless you compiled your own client from the source (I did). [2]

Plenty of other monitoring services equivalent to Nagios offer equivalent services. Nagios was just the flavour I suggested to my current employer because of my familiarity with the product over my last few employments.

If you don't want to fork out the licensing for the supported version (XI), their open source version is free and relatively easy to deploy using Ansible if you don't mind writing in PHP. [3]

Edit: words, grammar.

[1] https://www.nagios.com/products/nagios-xi/

[2] https://github.com/NagiosEnterprises/ncpa

[3] https://hobo.house/2016/06/24/automate-nagios-deployment-wit...

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

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.

Have a look at netdata: https://github.com/firehol/netdata

It's very straight forward to setup. I have used Prometheus for the same and so far the experience has been much better compared to Zabbix.

# node_exporter on the client to get metrics # prometheus on server to pull the metrics from node_exporter # alertmanager for raising alerts # grafana on top of it for pretty graphs(optional)

Have a look at nagios. It's a popular open source server/application monitoring tool. You can define custom alerts and monitor basicly everything.

Outside of nagios, you can also use pricier but arguably more fully featured setups like New Relic + PagerDuty.