How to setup a generic shared hosting environment with Passenger

Mar 7, 2019

Passenger is a nice little web server that has the capability to start, stop and scale web server applications with ease.

Here we will use it in conjunction with Nginx to setup a shared hosting environment with multiple users, each running their own web server with their environment of choice (we’ll use Node.js, but you can use whatever you want as long as you install the dependencies). We will also start from a fresh Ubuntu server 18.04.

Note that you will need one subdomain per user (or a wildcard pointing to your server).

Installation of Nginx and Passenger

First things first, let’s install Passenger:

# Install our PGP key and add HTTPS support for APT
sudo apt-get install -y dirmngr gnupg
sudo apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 561F9B9CAC40B2F7
sudo apt-get install -y apt-transport-https ca-certificates

# Add our APT repository
sudo sh -c 'echo deb https://oss-binaries.phusionpassenger.com/apt/passenger bionic main > /etc/apt/sources.list.d/passenger.list'
sudo apt-get update

# Install Passenger
sudo apt-get install -y passenger

A little command to validate it’s working correctly:

passenger-config validate-install

Now we can install Nginx:

sudo apt-get install -y nginx

And the relevant Nginx plugin for passenger:

sudo apt-get install -y libnginx-mod-http-passenger

We also must activate the passenger plugin:

if [ ! -f /etc/nginx/modules-enabled/50-mod-http-passenger.conf ]; then sudo ln -s /usr/share/nginx/modules-available/mod-http-passenger.load /etc/nginx/modules-enabled/50-mod-http-passenger.conf ; fi

Time to restart Nginx:

sudo service nginx restart

That should be OK for the base configuration.

Setup of a user

Here we’ll install Node.js for our example:

sudo apt install nodejs npm
# Update npm
sudo npm install npm -g

Now we can create a user:

sudo adduser test

Let’s make a little setup for that user by switching to him:

sudo su - test

OK, we’re “him”. Let’s make a basic web application with Node.js:

mkdir app
cd app
npm init # enter what you want
npm install --save connect commander
cat > app.js << EOL
var connect = require('connect');
var http = require('http');
var program = require('commander');

program.option("-p, --port <port>", "The port", parseFloat)
    .parse(process.argv);

const port = program.port || 3000;

var app = connect();

app.use(function(req, res){
  res.end('Hello world!\n');
})

http.createServer(app).listen(port);
console.log("Example app listening on http://127.0.0.1:" + port);
EOL

We can test our simple website:

node app.js --port 4000 # Ctrl-C to stop

Now it’s time we create some wrapper script for Passenger:

cat > app << EOL
#! /bin/bash
node app.js --port \$PORT
EOL
chmod a+x app
mkdir public # This is important for Passenger

Time to go back to our normal user with sudo capabilities:

exit

Let’s go create some nginx configuration for our test user.

cd /etc/nginx/sites-enabled/
sudo nano test

Use this example configuration by adding the proper subdomain:

server {
    listen 80;
    server_name MY_SUBDOMAIN;

    # Tell Nginx and Passenger where your app's 'public' directory is
    root /home/test/app/public;

    # Turn on Passenger
    passenger_enabled on;
    passenger_app_start_command "./app $PORT";
}

Time to ask Nginx to reload its configuration:

sudo systemctl reload nginx

Now your application should be available on the configured subdomain.

Going further

As you’ve seen it’s just a matter of installing dependencies then writing a small wrapper script (and also providing a public folder for Passenger to serve public files). You could have multiple applications in completely different languages like Go, Python, Ruby, PHP, etc…

The downsides to using Passenger is that it’s not really a tool monitoring the CPU, RAM or disk usage of the processes it launches. So it would necessitates additionnal setup to be absolutely sure none of your users are doing anything wrong. But that’s another story…