Redirect naked domain to www with Kamal

You're using Rails and Kamal, and you want to redirect users from touterrain.com, for instance, to www.touterrain.com.

Here's a quick recipe explaining how to redirect your naked domain to the www subdomain.

Step 1: Update your deploy.yml

First, you'll need to modify your Kamal deployment file, within config/deploy.yml. Head over to the proxy section and make sure it includes both versions of your domain:

proxy:
  ssl: true
  hosts:
    - touterrain.com
    - www.touterrain.com

This tells Kamal to accept traffic for both the naked domain and the www subdomain.

You probably already have this setup, but just to make sure. Under the servers part you should have your server IP:

servers:
  web:
    - 116.203.103.239

Step 2: Set A records in your DNS provider

Now go to your domain provider (I use name.com, but it works similarly everywhere) and add two A records:

• One for the root: usually @ or an empty entry
• One for www

Both should point to your server's IP. For example:

• @ → A record pointing to 116.203.103.239
• www → A record pointing to 116.203.103.239

Step 3: Add a redirect inside your Rails app

To make sure that anyone landing on the naked domain is redirected to www, add the following code to your ApplicationController:

class ApplicationController < ActionController::Base
  before_action :redirect_to_www, if: -> { Rails.env.production? && request.subdomain != "www" }

  private

  def redirect_to_www
    redirect_to "https://www.touterrain.com" + request.fullpath, status: :moved_permanently, allow_other_host: true
  end
end

This ensures a 301 redirect from touterrain.com to www.touterrain.com, which is also relevant for SEO.

That's it. If you click on touterrain.com, you should always land on www.touterrain.com, and Google will be happy with the canonical URL.