Automatically Start Node.js Server on System Restarts

In this quick tip, we’ll learn about using crontab to automatically start our Node.js app, together with the use of pm2 , a production process manager for Node.js apps.

Normally as a prerequisite, you would run your Node.js server by calling such command syntax:

npm start
# or
node server.js
# or
npm run server
# etc

With pm2 you can do so using the following syntax:

pm2 start server.js

You don’t have pm2 yet? you can simply install it with npm :

sudo npm install -g pm2

Now that you have the command that starts your server handy, let’s keep that for the next step.

Crontab

With crontab you can schedule cron scripts to run frequently following certain user intervals which you set while adding a new cron job. But how can we use crontab to schedule a job that starts only on system startup?

To our luck, there’s the @reboot directive, which any events attached to it will be fired upon system startup from a reboot.

To add a new event (widely referred to as a cron job), make sure you SSH as the user that runs the node.js app normally, just in case, if for example you run the app as appuser:

su appuser

Feel free to skip the above command if your current user is the one that usually schedules the node server.

Next, open crontab jobs:

crontab -e

If you’re running this command for the first time, it’ll prompt you to pick an editor, simply enter a number for the editor you’re most comfortable with and press enter.

Now that you’re editing a file, just get to the bottom of the file and enter a new line:

@reboot sh -c 'cd /path/to/your/app/folder && pm2 start server.js'

Note that you should replace the absolute path to your app folder in the above command. Tip: you can call realpath . or pwd to get the absolute path of the current working directory, in case it happens to be the app root folder.

Now save the file and exit. It should print something as follows:

crontab: installing new crontab

That means you have new or updated cron events added.

Troubleshooting

Make sure to test the scheduling command in case the automated process does not work. You can stop your server, then simply call the cammand:

sh -c 'cd /path/to/your/app/folder && pm2 start server.js'

and see if the paths are correct, pm2 binary is available in the $PATH and whatever errors might show on screen. Once you have the command running, just paste it back to the cron event.

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