Я пытаюсь загрузить изображение на AWS.

class Asset < ActiveRecord::Base
  belongs_to :post
  attr_accessible :image
  has_attached_file :image, :styles => { :medium => "640x480>", 
                                     :thumb => "100x100#"},
  :storage => :s3,
   :s3_credentials => "#{Rails.root}/config/s3.yml",
  :path => ":attachment/:id/:style.:extension",
  :bucket => 'yourbucket'
end

s3.yml

development:
  access_key_id: xxxxxxxx

   secret_code: xxxxx

Я получаю сообщение

 AWS::Errors::MissingCredentialsError in PostsController#create

Missing Credentials.

 Unable to find AWS credentials.  You can configure your AWS credentials
 a few different ways:

 * Call AWS.config with :access_key_id and :secret_access_key

 * Export AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY to ENV

* On EC2 you can run instances with an IAM instance profile and credentials 
 will be auto loaded from the instance metadata service on those
  instances.

* Call AWS.config with :credential_provider.  A credential provider should
either include AWS::Core::CredentialProviders::Provider or respond to
the same public methods.

= Ruby on Rails

В приложении Ruby on Rails вы также можете указать свои учетные данные в    следующие способы:

Via a config initializer script using any of the methods mentioned above (e.g. RAILS_ROOT/config/initializers/aws-sdk.rb).

Via a yaml configuration file located at RAILS_ROOT/config/aws.yml. This file should be formated like the default RAILS_ROOT/config/database.yml file.

Я считаю, что я делаю последний шаг.

Gemfile

gem 'rails', '3.1.3'
gem 'mysql'
gem 'koala'
gem 'paperclip'
gem 'aws-s3'
gem 'aws-sdk'