How to Set Up Linux Server Monitoring in 10 Minutes (Free)

#linux #devops #sysadmin #monitoring

How to Set Up Linux Server Monitoring in 10 Minutes (Free)

If you're running a production app on a VPS and you're relying on "it seems fine" as your monitoring strategy — this post is for you.

Here's a minimal, free monitoring setup that covers the basics in under 10 minutes.

What We're Monitoring

CPU usage
RAM usage
Disk usage
Service health (is your app actually running?)
Basic alerting when things go wrong

Step 1: Install netdata (2 minutes)

Netdata is free, open source, and installs with one command:

bash <(curl -Ss https://my-netdata.io/kickstart.sh)

It auto-discovers services, requires no config, and gives you a real-time dashboard on port 19999.

# Access it (from your server)
http://your-server-ip:19999

# Or tunnel it securely
ssh -L 19999:localhost:19999 user@your-server
# Then visit http://localhost:19999 in your browser

Step 2: Basic Cron-Based Alerting (3 minutes)

For dead-simple email alerts without a third-party service:

# Install mailutils
sudo apt install mailutils -y

# Create a monitoring script
sudo nano /usr/local/bin/server-check.sh

#!/bin/bash
ALERT_EMAIL="you@yourdomain.com"
THRESHOLD_DISK=85
THRESHOLD_RAM=90

# Disk check
DISK_USAGE=$(df -h / | awk 'NR==2{print $5}' | tr -d '%')
if [ "$DISK_USAGE" -gt "$THRESHOLD_DISK" ]; then
    echo "ALERT: Disk usage is ${DISK_USAGE}% on $(hostname)" | mail -s "Disk Alert - $(hostname)" $ALERT_EMAIL
fi

# RAM check
RAM_AVAILABLE=$(free | awk '/^Mem/{print int($7/$2*100)}')
if [ "$RAM_AVAILABLE" -lt $((100 - THRESHOLD_RAM)) ]; then
    echo "ALERT: RAM available is ${RAM_AVAILABLE}% on $(hostname)" | mail -s "RAM Alert - $(hostname)" $ALERT_EMAIL
fi

# Service check (change 'node' to your process name)
if ! pgrep -x "node" > /dev/null; then
    echo "ALERT: node process is DOWN on $(hostname)" | mail -s "Service DOWN - $(hostname)" $ALERT_EMAIL
fi

chmod +x /usr/local/bin/server-check.sh

# Add to cron (run every 5 minutes)
crontab -e
# Add:
*/5 * * * * /usr/local/bin/server-check.sh

Step 3: PM2 Monitoring (if using Node.js)

# Install PM2 globally
npm install -g pm2

# Start your app with PM2
pm2 start server.js --name your-app

# Set up startup script (survive reboots)
pm2 startup
pm2 save

# Monitor in terminal
pm2 monit

Step 4: Quick Health Endpoint

Add this to your Node.js app:

app.get('/health', (req, res) => {
  const healthCheck = {
    uptime: process.uptime(),
    message: 'OK',
    timestamp: Date.now(),
    memoryUsage: process.memoryUsage(),
  };
  res.status(200).json(healthCheck);
});

Then add to your cron monitor:

# Health endpoint check
HTTP_STATUS=$(curl -s -o /dev/null -w "%{http_code}" http://localhost:3000/health)
if [ "$HTTP_STATUS" != "200" ]; then
    echo "ALERT: Health check failed with status $HTTP_STATUS" | mail -s "App Health Fail" $ALERT_EMAIL
fi

The 10-Minute Summary

# 1. Install netdata for visual monitoring
bash <(curl -Ss https://my-netdata.io/kickstart.sh)

# 2. Add cron monitoring script
# (copy from above)

# 3. Set up PM2 if Node.js
pm2 startup && pm2 save

# 4. Add /health endpoint to your app

# 5. Test your alerts
# ./server-check.sh (run manually, check email)