Phusion's Passenger (mod_rails) is an exciting development in serving your Ruby on Rails application with the Apache web server.

Incredibly simple to install and use, you can have a rails application up and running in no time. You don't have to worry about ports or setting up a proxy to another server.

Prerequisites

To get the most out of this article you need to have a couple of things preinstalled:

Firstly, you need Apache installed (see Ubuntu Hardy - installing Apache and PHP5).

Secondly, you need ruby and rubygems installed (if not please see Ubuntu Hardy - Ruby on Rails).

mod_rails installation

Passenger (mod_rails) is a rubygem.

We need to update the rubygems install:

sudo gem update

and then install passenger:

sudo gem install passenger

Once completed, we need to install the Apache2 module:

sudo passenger-install-apache2-module

A dialogue opens in the terminal and starts with:

As suggested, press 'Enter/Return':

I deliberately left the Apache headers off the installation until this point as I want to demonstrate how easy the installation is.

The passenger (mod_rails) install has found a missing dependency - let's press 'Enter/Return':

How cool is that? It tells us what to do.

Well, let's go ahead and install the headers (we'll use aptitude though):

sudo aptitude install apache2-prefork-dev

Once done, we can try the install again:

sudo passenger-install-apache2-module

All being well, the install will complete with instructions at the end letting us know we need to add some lines to the main Apache2 config file.

No problem:

sudo nano /etc/apache2/apache2.conf

Note: Passenger is an active gem and is being updated all the time. Rather than copy and paste the output I show below, please ensure you copy and paste the output from the install itself.

At the time of writing the article (well, updating it actually) I installed passenger v1.0.4 - you may have installed a later version.

So, for my v1.0.4 install, I added the following lines to my apache2.conf:

LoadModule passenger_module /usr/lib/ruby/gems/1.8/gems/passenger-1.0.4/ext/apache2/mod_passenger.so
RailsSpawnServer /usr/lib/ruby/gems/1.8/gems/passenger-1.0.4/bin/passenger-spawn-server
RailsRuby /usr/bin/ruby1.8

Apache restart

Now all we need to do is restart Apache:

sudo /etc/init.d/apache2 restart

Done

That's all we need to do to install mod_rails onto our Cloud Server.

The next article Ubuntu Hardy - using mod_rails to serve your application, will show how to create a Ruby on Rails application and serve it using passenger - an incredibly easy process.