How can I automatically start a node.js application in Amazon Linux AMI on aws?

Question

Is there a brief guide to explain how to start up a application when the instance starts up and running? If it were one of the services installed through yum th

Answer 1

My Amazon Linux instance runs on Ubuntu, and I used systemd to set it up.

First you need to create a .service file. (in my case cloudyleela.service)

sudo nano /lib/systemd/system/cloudyleela.service

Type the following in this file:

[Unit]
Description=cloudy leela
Documentation=http://documentation.domain.com
After=network.target

[Service]
Type=simple
TimeoutSec=0
User=ubuntu
ExecStart=/usr/bin/node /home/ubuntu/server.js
Restart=on-failure

[Install]
WantedBy=multi-user.target

In this application the node application is started. You will need a full path here. I configured that the application should simply restart if something goes wrong. The instances that Amazon uses have no passwords for their users by default.

Reload the file from disk, and then you can start your service. You need to enable it to make it active as a service, which automatically launches at startup.

ubuntu@ip-172-31-21-195:~$ sudo systemctl daemon-reload
ubuntu@ip-172-31-21-195:~$ sudo systemctl start cloudyleela
ubuntu@ip-172-31-21-195:~$ sudo systemctl enable cloudyleela
Created symlink /etc/systemd/system/multi-user.target.wants/cloudyleela.service → /lib/systemd/system/cloudyleela.service.
ubuntu@ip-172-31-21-195:~$

A great systemd for node.js tutorial is available here.

If you run a webserver:

You probably will have some issues running your webserver on port 80. And the easiest solution, is actually to run your webserver on a different port (e.g. 4200) and then to redirect that port to port 80. You can accomplish this with the following command:

sudo iptables -t nat -A PREROUTING -i -p tcp --dport 80 -j REDIRECT --to-port 4200

Unfortunately, this is not persistent, so you have to repeat it whenever your server restarts. A better approach is to also include this command in our service script:

1. ExecStartPre to add the port forwarding
2. ExecStopPost to remove the port forwarding
3. PermissionStartOnly to do this with sudo power

So, something like this:

[Service]
...
PermissionsStartOnly=true
ExecStartPre=/sbin/iptables -t nat -A PREROUTING -p tcp --dport 80 -j REDIRECT --to-port 4200
ExecStopPost=/sbin/iptables -t nat -D PREROUTING -p tcp --dport 80 -j REDIRECT --to-port 4200

Don't forget to reload and restart your service:

[ec2-user@ip-172-31-39-212 system]$ sudo systemctl daemon-reload
[ec2-user@ip-172-31-39-212 system]$ sudo systemctl stop cloudyleela
[ec2-user@ip-172-31-39-212 system]$ sudo systemctl start cloudyleela
[ec2-user@ip-172-31-39-212 system]$