Minimalist home network monitoring with shell scripts and ntfy.sh

Running a home server does not have to mean setting up a full-blown monitoring stack. For my needs, a few shell scripts and push notifications are all it takes to keep things simple, reliable, and easy to maintain.

I use ntfy.sh for notifications. It is a simple, open-source tool that lets you send push notifications to your devices via a single HTTP request. It is lightweight, easy to set up, and fits perfectly with my minimalist approach.

Why minimal monitoring?

My home server is an old ThinkPad T440s. It is quiet, efficient, and runs everything I need for my home infrastructure. I keep it minimal by only installing Tailscale directly and running everything else in Docker. This includes services like AdGuardHome for network-wide ad blocking, automated backups, and more. I have documented the full setup and all services in detail in my thinkserver GitHub repository.

I do not want to deal with complex dashboards or heavyweight monitoring tools. I just want to know, right away, if something goes wrong, like low disk space or a network issue.

Here is how I keep tabs on my setup with just cron, shell scripts, and ntfy.sh.

Low disk space monitoring

Let us start with the basics: disk space. Here is a simple shell script that checks if my root disk has less than 15 GB available. If it does, I get a push notification via ntfy.sh.

#!/bin/bash

mingigs=15
avail=$(df | awk '$6 == "/" && $4 < '$mingigs' * 1024*1024 { print $4/1024/1024 }')
topicurl=https://ntfy.sh/my_topic

if [ -n "$avail" ]; then
  curl -k \
    -d "Only $avail GB available on the root disk. Better clean that up." \
    -H "Title: Low disk space on $(hostname)" \
    -H "Priority: high" \
    -H "Tags: warning,cd" \
    $topicurl
fi

I run this every hour with cron. If something fills up the disk, like runaway logs, Docker images, I get an instant push notification and can act before things break.

Detecting WAN speed downgrade

Recently, my internet speed dropped from 1 Gbps to 100 Mbps. My EdgeRouterX showed the WAN cable (running two floors down) was the culprit: old, flaky, and sensitive to movement.

The fix? Sometimes just wiggling the cable helps, but I am planning to crimp a new RJ45 connector soon. Meanwhile, I want to know if the link speed drops again.

Here is a script for the EdgeRouterX that checks the WAN port speed and notifies me if it drops to 100 Mbps:

#!/bin/bash

topicurl=https://ntfy.sh/my_topic
SPEED=$(show interfaces ethernet eth0 physical | grep "Speed: 100Mb/s")

if [ -n "$SPEED" ]; then
  curl -k \
    -d "WAN link speed dropped to 100 Mbps. Check the cable." \
    -H "Title: WAN speed issue on EdgeRouterX" \
    -H "Priority: default" \
    -H "Tags: wan,speed" \
    $topicurl
fi

To automate this check, I added it to cron to run every 5 minutes. This ensures I get notified promptly if the link speed drops.

Simple, no-dependency monitoring

This setup is as simple as it gets: no Prometheus, no Grafana, no InfluxDB. Just cron, a few lines of shell, and ntfy.sh. It is minimal, understandable, and easy to maintain.

With this approach, I can detect real-world issues before they cause downtime. Whether it is low disk space or a flaky Ethernet cable, I get notified instantly and can act quickly. It is a practical, no-fuss solution that works perfectly for my needs.