Managing Systemd Services

What is Systemd?

Systemd is the init system and service manager for modern Linux distributions. It manages services (daemons), mounts, timers, and the entire boot process.

Essential Commands

# Start/stop/restart a service
sudo systemctl start nginx
sudo systemctl stop nginx
sudo systemctl restart nginx
sudo systemctl reload nginx    # Reload config without restart

# Enable/disable at boot
sudo systemctl enable nginx
sudo systemctl disable nginx

# Check status
systemctl status nginx
systemctl is-active nginx
systemctl is-enabled nginx

Listing Services

# All loaded services
systemctl list-units --type=service

# Failed services
systemctl --failed

# All installed service files
systemctl list-unit-files --type=service

Creating a Custom Service

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

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

[Service]
Type=simple
User=www-data
WorkingDirectory=/var/www/myapp
ExecStart=/usr/bin/node /var/www/myapp/server.js
Restart=always
RestartSec=5
Environment=NODE_ENV=production

[Install]
WantedBy=multi-user.target

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

Viewing Logs

# Logs for a specific service
journalctl -u nginx

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

# Logs since last boot
journalctl -u nginx -b

# Last 100 lines
journalctl -u nginx -n 100