アプリケーションにdeviseをインストール

$ rails generate devise:install
      create  config/initializers/devise.rb
      create  config/locales/devise.en.yml
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Some setup you must do manually if you haven't yet:

  1. Ensure you have defined default url options in your environments files. Here
     is an example of default_url_options appropriate for a development environment
     in config/environments/development.rb:

       config.action_mailer.default_url_options = { :host => 'localhost:3000' }

     In production, :host should be set to the actual host of your application.

  2. Ensure you have defined root_url to *something* in your config/routes.rb.
     For example:

       root :to => "home#index"

  3. Ensure you have flash messages in app/views/layouts/application.html.erb.
     For example:

       <p class="notice"><%= notice %></p>
       <p class="alert"><%= alert %></p>

  4. If you are deploying on Heroku with Rails 3.2 only, you may want to set:

       config.assets.initialize_on_precompile = false

     On config/application.rb forcing your application to not access the DB
     or load models when precompiling your assets.

  5. You can copy Devise views (for customization) to your app by running:

       rails g devise:views

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ジェネレーターでUesrモデルを生成

$ rails generate devise User
      invoke  active_record
      create    db/migrate/20130920003112_devise_create_users.rb
      create    app/models/user.rb
      insert    app/models/user.rb
       route  devise_for :users