systemd services: manage, start, stop, enable

systemd is the init system on most modern Linux distributions. Services are managed with systemctl — the main tool for starting, stopping, enabling, and diagnosing services.

Basic systemctl commands

systemctl start nginx       # Start service now
systemctl stop nginx        # Stop service now
systemctl restart nginx     # Stop then start
systemctl reload nginx      # Reload config without restart
systemctl enable nginx      # Auto-start on boot
systemctl disable nginx     # Remove auto-start

Check service status

systemctl status nginx
# Shows: active (running), PID, memory, recent log lines

systemctl is-active nginx   # Returns "active" or "inactive"
systemctl is-enabled nginx  # Returns "enabled" or "disabled"

systemctl list-units --type=service --state=running  # All running services

View service logs

journalctl -u nginx          # All logs for nginx
journalctl -u nginx -f       # Follow (live tail)
journalctl -u nginx --since "1 hour ago"  # Recent logs
journalctl -p err -u nginx   # Errors only

Create 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 server.js
Restart=on-failure

[Install]
WantedBy=multi-user.target

systemctl daemon-reload     # Load the new service file
systemctl enable myapp      # Enable auto-start
systemctl start myapp       # Start it now

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