How do I run a Node.js app as a systemd service that starts on boot and restarts on crash?

Create a unit file. Systemd handles start on boot, restart on failure, logging and resource limits.

/etc/systemd/system/myapp.service:

[Unit]
Description=My Node app
After=network.target

[Service]
Type=simple
User=deploy
WorkingDirectory=/var/www/myapp
EnvironmentFile=/var/www/myapp/.env
Environment=NODE_ENV=production
ExecStart=/usr/bin/node server.js
Restart=on-failure
RestartSec=5
# Hardening (optional)
NoNewPrivileges=true
ProtectSystem=full

[Install]
WantedBy=multi-user.target

Enable and start:

sudo systemctl daemon-reload
sudo systemctl enable --now myapp
sudo systemctl status myapp
journalctl -u myapp -f

Details

• Use the absolute path to node (which node). If you use nvm, the path lives in the user's home, and systemd will not load shell profiles. Install Node system-wide or point to the nvm binary path explicitly.
• EnvironmentFile takes KEY=value lines without export and without shell quoting tricks.
• Do not run as root; create a dedicated user.
• Restart=on-failure restarts on crashes; always also restarts after clean exits.
• After editing the unit, run daemon-reload before restarting.
• Logs go to the journal; view with journalctl -u myapp --since "1 hour ago".

Put Nginx in front as a reverse proxy to http://127.0.0.1:3000 and keep the app bound to localhost so only Nginx is public.