我是一个完整的 Ruby on Rails 新手，遵循railstutorial.org
我刚刚安装了 rails 3.2.13，使用rails new.
但是我无法使用以下命令启动服务器：
rails server
它返回rails下面的命令帮助消息（而不是 WEBrick 信息），其中根本没有提到该server命令。那么如何启动服务器呢？谢谢
Usage:
rails new APP_PATH [options]
Options:
-r, [--ruby=PATH] # Path to the Ruby binary of your choice
# Default: /Users/nathanzylbersztejn/.rvm/rubies/ruby-2.0.0-p0/bin/ruby
-b, [--builder=BUILDER] # Path to a application builder (can be a filesystem path or URL)
-m, [--template=TEMPLATE] # Path to an application template (can be a filesystem path or URL)
[--skip-gemfile] # Don't create a Gemfile
[--skip-bundle] # Don't run bundle install
-G, [--skip-git] # Skip Git ignores and keeps
-O, [--skip-active-record] # Skip Active Record files
-S, [--skip-sprockets] # Skip Sprockets files
-d, [--database=DATABASE] # Preconfigure for selected database (options: mysql/oracle/postgresql/sqlite3/frontbase/ibm_db/sqlserver/jdbcmysql/jdbcsqlite3/jdbcpostgresql/jdbc)
# Default: sqlite3
-j, [--javascript=JAVASCRIPT] # Preconfigure for selected JavaScript library
# Default: jquery
-J, [--skip-javascript] # Skip JavaScript files
[--dev] # Setup the application with Gemfile pointing to your Rails checkout
[--edge] # Setup the application with Gemfile pointing to Rails repository
-T, [--skip-test-unit] # Skip Test::Unit files
[--old-style-hash] # Force using old style hash (:foo => 'bar') on Ruby >= 1.9
Runtime options:
-f, [--force] # Overwrite files that already exist
-p, [--pretend] # Run but do not make any changes
-q, [--quiet] # Suppress status output
-s, [--skip] # Skip files that already exist
Rails options:
-h, [--help] # Show this help message and quit
-v, [--version] # Show Rails version number and quit
Description:
The 'rails new' command creates a new Rails application with a default
directory structure and configuration at the path you specify.
You can specify extra command-line arguments to be used every time
'rails new' runs in the .railsrc configuration file in your home directory.
Note that the arguments specified in the .railsrc file don't affect the
defaults values shown above in this help message.