# File lib/docker/util.rb, line 242
  def build_config_header(credentials)
    if credentials.is_a?(String)
      credentials = MultiJson.load(credentials, symbolize_keys: true)
    end

    header = MultiJson.dump(
      credentials[:serveraddress].to_s => {
        'username' => credentials[:username].to_s,
        'password' => credentials[:password].to_s,
        'email' => credentials[:email].to_s
      }
    )

    encoded_header = Base64.urlsafe_encode64(header)

    {
      'X-Registry-Config' => encoded_header
    }
  end