Deploy Nodejs on digital Ocean

generate ssh key

ssh-keygen

change the name of the key if you want like id_ad908409328_digitalocean

copy the public key and paste in the digital ocean (the key can be found where you created the private key with a .pub extension)
Create new user Creating new user

adduser username

Give the user sudo privileges:

usermod -aG sudo username

Switch to that user:

# Switch to another user (with their environment) 
su - username

Install nvm from https://github.com/nvm-sh/nvm
nvm install 16
install git

sudo apt install git-all

clone your github repo (for private repos on AWS EC2, see Clone a Private Repo ( for EC2 or digitalOcean or any other VM))
install the dependencies by npm i and copy your env variables.
install a process manager to run the app.

npm i pm2@latest -g

start your app using pm2

pm2 start entry_file
#example pm2 start index.js
 
# pm2 start "npm run dev" --name myAppName

Tip
to start your app on reboot
pm2 startup ubuntu 

Now your api is live on droplet_id:port.

Additional steps

setup ufw firewall

ufw enable 
ufw allow ssh && ufw allow http && ufw allow https

#check the status of firewall 
ufw status

Install nginx reverse proxy to listen on default port

sudo apt install nginx

edit the /etc/nginx/sites-available/default file. Find the server_name and location lines and replace with these

server_name yourdomain.com www.yourdomain.com;
 
location / {
        # First attempt to serve request as file, then
        # as directory, then fall back to displaying a 404.
        proxy_pass http://localhost:8000; #or your app port
        proxy_http_version 1.1;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection 'upgrade';
        proxy_set_header Host $host;
        proxy_cache_bypass $http_upgrade;
}

# To run two sepearte backend on two different domain
server {
    listen 80;
    server_name abc.com;
 
    location / {
        proxy_pass http://localhost:3000;  # First backend on port 3000
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
    }
}
 
server {
    listen 80;
    server_name xyz.com;
 
    location / {
        proxy_pass http://localhost:4000;  # Second backend on port 4000
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
    }
}

restart the nginx server

$ sudo /etc/init.d/apache2 stop
Stopping apache2 (via systemctl): apache2.service.
$ sudo systemctl restart nginx
$ sudo service nginx restart

install a free ssl certificate form Let’s Encrypt

# Install Certbot
sudo snap install --classic certbot
 
# Prepare the Certbot command
sudo ln -s /snap/bin/certbot /usr/bin/certbot
 
# Run this command to get a certificate
sudo certbot --nginx
 
# Test automatic renewal
sudo certbot renew --dry-run