Linux System Monitoring Complete Guide 2026

# System resource usage
top              # Interactive process viewer
htop             # Enhanced top (colorful)
atop             # Advanced top
glances          # Cross-platform monitoring

# CPU
mpstat -P ALL 1  # Per-CPU stats
sar -u 1         # CPU utilization

# Memory
free -h          # Memory usage
vmstat 1          # Virtual memory stats

# Disk
df -h            # Disk usage
iostat -x 1      # I/O statistics
du -sh *         # Directory sizes

# Network
iftop            # Network bandwidth
netstat -tuln    # Listening ports
ss -tuln         # Modern netstat

# Install htop
sudo apt install htop

# Custom htop config
# ~/.config/htop/htoprc
config:
    show_cpu_usage: 1
    show_cpu_frequency: 1
    show_cpu_temperature: 1
    show_memory_usage: 1
    detailed_cpu_time: 1
    
columns:
    - PID
    - USER
    - PRIORITY
    - NICE
    - M_SIZE
    - M_RESIDENT
    - STATE
    - CPU
    - MEM
    - TIME
    - Command

# Install
sudo apt install sysstat

# Enable
sudo systemctl enable sysstat
sudo systemctl start sysstat

# CPU report
sar -u 1 5          # 5 reports, 1 second apart
sar -u -s 08:00 -e 12:00  # During specific hours

# Memory
sar -r 1

# Disk I/O
sar -d 1

# Network
sar -n DEV 1

# docker-compose.yml
version: '3'
services:
  prometheus:
    image: prom/prometheus
    ports:
      - "9090:9090"
    volumes:
      - ./prometheus.yml:/etc/prometheus/prometheus.yml
      - prometheus_data:/prometheus
  
  grafana:
    image: grafana/grafana
    ports:
      - "3000:3000"
    volumes:
      - grafana_data:/var/lib/grafana
    environment:
      - GF_SECURITY_ADMIN_PASSWORD=admin

# 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']
  
  - job_name: 'myservice'
    static_configs:
      - targets: ['myservice:8080']

# alerts.yml
groups:
  - name: example
    rules:
      - alert: HighCPUUsage
        expr: 100 - (avg by (instance) (rate(node_cpu_seconds_total{mode="idle"}[5m])) * 100) > 80
        for: 5m
        labels:
          severity: warning
        annotations:
          summary: "High CPU usage on {{ $labels.instance }}"
          
      - alert: HighMemoryUsage
        expr: (node_memory_MemTotal_bytes - node_memory_MemAvailable_bytes) / node_memory_MemTotal_bytes * 100 > 85
        for: 5m
        labels:
          severity: warning