看起来该文档已经过时了。

It looks like that documentation is outdated.

尝试使用devise生成器，它将创建相同的迁移，使用正确的参数，如果它现有的模型，则可以：

Try using devise generator, it will create same migration, with correct parameters, it's ok if its an existing model:

rails g devise customer

应该创建 AddDeviseToCustomers 迁移

与此类似：

class AddDeviseToCustomers < ActiveRecord::Migration
def self.up
change_table(:customers) do |t|
  ## Database authenticatable
  t.string :email,              :null => false, :default => ""
  t.string :encrypted_password, :null => false, :default => ""

  ## Recoverable
  t.string   :reset_password_token
  t.datetime :reset_password_sent_at

  ## Rememberable
  t.datetime :remember_created_at

  ## Trackable
  t.integer  :sign_in_count, :default => 0
  t.datetime :current_sign_in_at
  t.datetime :last_sign_in_at
  t.string   :current_sign_in_ip
  t.string   :last_sign_in_ip

  ## Confirmable
  t.string   :confirmation_token
  t.datetime :confirmed_at
  t.datetime :confirmation_sent_at
  t.string   :unconfirmed_email # Only if using reconfirmable

  ## Lockable
  # t.integer  :failed_attempts, :default => 0 # Only if lock strategy is :failed_attempts
  # t.string   :unlock_token # Only if unlock strategy is :email or :both
  # t.datetime :locked_at

  ## Token authenticatable
  # t.string :authentication_token


  # Uncomment below if timestamps were not included in your original model.
  # t.timestamps
end

def self.down
# By default, we don't want to make any assumption about how to roll back a migration when your
# model already existed. Please edit below which fields you would like to remove in this migration.
raise ActiveRecord::IrreversibleMigration
end
end

注意没有更多的 t.confirmable