Server Monitoring

This guide explains how to monitor your Linux VPS performance with different tools.

Command Line Tools

htop - Interactive Monitor

htop is an improved version of top with a colorful and interactive interface.

# Installation
sudo apt update
sudo apt install htop

# Launch
htop

htop Shortcuts:

Key	Action
F2	Configuration
F3	Search for a process
F5	Tree view
F6	Sort by column
F9	Kill a process
F10	Quit
u	Filter by user

Other Useful Commands

# Memory usage
free -h

# Disk space
df -h

# Usage by folder
du -sh /var/*

# System load
uptime

# Network connections
ss -tuln

# Processes consuming the most RAM
ps aux --sort=-%mem | head

# Processes consuming the most CPU
ps aux --sort=-%cpu | head

Netdata - Real-Time Dashboard

Netdata offers a web dashboard with real-time metrics.

Installation

# Automatic installation
bash <(curl -Ss https://get.netdata.cloud/kickstart.sh)

Access

Open http://YOUR_IP:19999 in your browser.

Secure Access

By default, Netdata is publicly accessible. To secure it:

sudo nano /etc/netdata/netdata.conf

[web]
    bind to = 127.0.0.1

Then use an Nginx reverse proxy with authentication:

server {
    listen 80;
    server_name monitoring.example.com;

    auth_basic "Monitoring";
    auth_basic_user_file /etc/nginx/.htpasswd;

    location / {
        proxy_pass http://127.0.0.1:19999;
        proxy_set_header Host $host;
    }
}

Create the password file:

sudo apt install apache2-utils
sudo htpasswd -c /etc/nginx/.htpasswd admin

Grafana + Prometheus - Advanced Monitoring

For more complete monitoring with history and alerts.

Installation with Docker Compose

version: '3.8'

services:
  prometheus:
    image: prom/prometheus:latest
    volumes:
      - ./prometheus.yml:/etc/prometheus/prometheus.yml
      - prometheus_data:/prometheus
    command:
      - '--config.file=/etc/prometheus/prometheus.yml'
    ports:
      - "9090:9090"
    restart: unless-stopped

  node-exporter:
    image: prom/node-exporter:latest
    volumes:
      - /proc:/host/proc:ro
      - /sys:/host/sys:ro
      - /:/rootfs:ro
    command:
      - '--path.procfs=/host/proc'
      - '--path.sysfs=/host/sys'
      - '--path.rootfs=/rootfs'
    ports:
      - "9100:9100"
    restart: unless-stopped

  grafana:
    image: grafana/grafana:latest
    volumes:
      - grafana_data:/var/lib/grafana
    environment:
      - GF_SECURITY_ADMIN_PASSWORD=your_password
    ports:
      - "3000:3000"
    restart: unless-stopped

volumes:
  prometheus_data:
  grafana_data:

Prometheus Configuration

Create prometheus.yml:

global:
  scrape_interval: 15s

scrape_configs:
  - job_name: 'prometheus'
    static_configs:
      - targets: ['localhost:9090']

  - job_name: 'node'
    static_configs:
      - targets: ['node-exporter:9100']

Launch

docker compose up -d

Grafana Configuration

1. Access http://YOUR_IP:3000
2. Log in (admin / your_password)
3. Add Prometheus as a data source:
   • URL: http://prometheus:9090
4. Import a dashboard:
   • Dashboard ID: 1860 (Node Exporter Full)

Email Alerts

With Grafana

1. Configuration > Alerting > Contact points
2. Add an email contact point
3. Create alert rules on your dashboards

Simple Alert Script

#!/bin/bash
# /root/scripts/alert.sh

# Thresholds
CPU_THRESHOLD=90
MEM_THRESHOLD=90
DISK_THRESHOLD=80

# CPU check
CPU=$(top -bn1 | grep "Cpu(s)" | awk '{print $2}' | cut -d'.' -f1)
if [ $CPU -gt $CPU_THRESHOLD ]; then
    echo "CPU Alert: ${CPU}%" | mail -s "VPS Alert" your@email.com
fi

# Memory check
MEM=$(free | grep Mem | awk '{print int($3/$2 * 100)}')
if [ $MEM -gt $MEM_THRESHOLD ]; then
    echo "Memory Alert: ${MEM}%" | mail -s "VPS Alert" your@email.com
fi

# Disk check
DISK=$(df / | tail -1 | awk '{print $5}' | sed 's/%//')
if [ $DISK -gt $DISK_THRESHOLD ]; then
    echo "Disk Alert: ${DISK}%" | mail -s "VPS Alert" your@email.com
fi

Add to cron:

*/5 * * * * /root/scripts/alert.sh

Tool Comparison

Tool	Complexity	History	Interface	Ideal for
htop	Simple	No	Terminal	Quick debugging
Netdata	Easy	Limited	Web	Basic monitoring
Grafana	Advanced	Yes	Web	Production

Tip

Start with htop and Netdata. Move to Grafana/Prometheus when you have multiple servers to monitor.