从4.0.0降级到3.2.9后，Rails app无法正常工作

Question

我的一个应用程序将我的Rails从4.0.0降级到3.2.9。

的Gemfile

# Bundle edge Rails instead: gem 'rails', github: 'rails/rails'
gem "rails", "~> 3.2.9"

# OTHERS
gem 'will_paginate'

# Use postgresql as the database for Active Record
gem 'pg'

# Use SCSS for stylesheets
gem 'sass-rails',   '~> 3.2.3'

# Use Uglifier as compressor for JavaScript assets
gem 'uglifier', '>= 1.0.3'

# Use CoffeeScript for .js.coffee assets and views
gem 'coffee-rails', '~> 3.2.1'

问题是，每当我运行rails server时，它就像应用程序不存在一样。

my@ubuntu:~/ruby/myapp$ rails s
Usage:
  rails new APP_PATH [options]

Options:
  -r, [--ruby=PATH]              # Path to the Ruby binary of your choice
...

为什么会这样，我该如何解决？