unicorn-rails is a simple gem that sets the default server for rack (and rails) to unicorn.

unicorn-rails overrides the Rack::Handler.default method to return Rack::Handler::Unicorn which will cause rack (and rails) to use unicorn by default.

Add this line to your application's Gemfile:

gem "unicorn-rails"

And then execute:

$ bundle install

Just add the gem to your Gemfile and then rails server will default to using unicorn.

Fork, branch & pull request.