How to configure Systemd service unit to start Node app with "npm start" instead of "app.js"

Question

Environment: CentOS 8, Node.js, Digital Ocean Droplet

My Systemd setup starts a node app with the following command. It works as expected.

$ sudo systemctl start myapp

File 1: /etc/systemd/system/myapp.service

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

[Service]
ExecStart = /root/start-myapp.sh
Restart=on-failure

[Install]
WantedBy = multi-user.target

File 2: /root/start-myapp.sh

#!/bin/sh
/usr/bin/node /srv/myapp/app.js

However when I'm not using Systemd I normally start my app with Node Package Manager using the command, npm start. I'd rather have the Systemd unit also start the app with npm start.

Unfortunately it threw an error when I changed app.js to npm start in /root/start-myapp.sh,

/usr/bin/node /srv/myapp/npm start

I made another attempt by switching the path from node to npm but it produced the same error.

/usr/bin/npm /srv/myapp/npm start

Question: How do I get my Systemd unit file to start my app with the command npm start?

Solution

I'm running a similar setup on Debian, and my service looks like this:

...

[Service]
Environment=NODE_PORT=3000
Type=simple
User=www-data
Restart=on-failure
WorkingDirectory=/var/www/<your-code-directory>
ExecStart=npm start

...

Hope this helps!