Server Monitoring Bash Scripts

Your monitoring setup should answer three questions in under 30 seconds: is the service running, is the disk about to fill, and is the network reachable? Most teams buy a SaaS platform to answer these. Most of the time, six bash scripts do the same job at zero cost.

The scripts on this page use nothing beyond coreutils, systemctl, curl, and openssl — tools present on every Linux distribution and every cloud provider's base image. No agents to install. No API keys to rotate. No dashboard to log into at 2am. Just shell scripts on a cron that pipe clean output to a log and send an alert when something breaks.

The monitoring gap is always the same: things fail silently. A disk fills incrementally — 70%, 80%, 90% — until writes start failing and services begin crashing in confusing ways. A website goes down on a holiday weekend. A service segfaults and doesn't restart because there's no watchdog. An SSL certificate expires at 2am and HTTPS silently breaks. By the time a human notices, the window for a graceful fix is usually closed.

The scripts here are the watchdogs. Each one checks one thing, emits a clean status line, and fails loudly when the threshold is crossed. They are designed to be composed: run all of them from a single monitoring wrapper script, or schedule each independently depending on what you care about most.

Start with disk-space-warning — it is the most likely script to save you from a production outage in the next 90 days. Then add check-if-website-is-up if you run any public-facing service. If you manage a server with auto-renewing Let's Encrypt certificates, check-ssl-certificate-expiry closes the monitoring gap that renewal hooks miss: the hook runs, certbot silently fails, and the certificate expires anyway without anyone knowing until the browser warning appears.

All of these scripts assume the problem has already happened to you or someone you know. They are not tutorials. They are the scripts you add to /opt/scripts, chmod +x, and add to crontab the day you set up a new server.