Managing System Services with systemctl

What Is systemd?

systemd is the init system and service manager used by most modern Linux distributions. It manages service startup, dependencies, and lifecycle.

Basic Service Commands

# Start a service
sudo systemctl start nginx

# Stop a service
sudo systemctl stop nginx

# Restart a service
sudo systemctl restart nginx

# Reload configuration without restart
sudo systemctl reload nginx

# Check status
systemctl status nginx

Enable and Disable Services

# Start automatically on boot
sudo systemctl enable nginx

# Enable and start immediately
sudo systemctl enable --now nginx

# Disable auto-start
sudo systemctl disable nginx

# Check if enabled
systemctl is-enabled nginx

Viewing Service Information

# List all running services
systemctl list-units --type=service --state=running

# List all services (including inactive)
systemctl list-units --type=service --all

# List failed services
systemctl --failed

# Show service dependencies
systemctl list-dependencies nginx

Service Logs

# View logs for a service
journalctl -u nginx

# Follow logs in real-time
journalctl -u nginx -f

# Show last 50 lines
journalctl -u nginx -n 50

Creating a Custom Service

Create /etc/systemd/system/myapp.service:

[Unit]
Description=My Application
After=network.target

[Service]
Type=simple
User=www-data
WorkingDirectory=/opt/myapp
ExecStart=/opt/myapp/start.sh
Restart=on-failure
RestartSec=5
Environment=NODE_ENV=production

[Install]
WantedBy=multi-user.target

sudo systemctl daemon-reload
sudo systemctl enable --now myapp

Useful Tips

• systemctl daemon-reload — run after editing any .service file
• systemctl mask — completely prevent a service from starting
• systemctl cat nginx — view the service file contents
• systemctl edit nginx — create an override file