```ruby
# This file is used by Rack-based servers to start the application.

require ::File.expand_path('../config/environment',  __FILE__)
run Rails.application
```

Check for RAILS_RELATIVE_URL_ROOT environment variable on startup
user
```ruby
# This file is used by Rack-based servers to start the application.

require ::File.expand_path('../config/environment',  __FILE__)

if defined?(PhusionPassenger)
  run Rails.application
else
  map ENV['RAILS_RELATIVE_URL_ROOT']||'/' do
    run Rails.application
  end
end
```
assistant