无法加载此类文件 - 捆绑程序/安装程序（LoadError）

我正在使用 Ruby 2.0 设置 Rails 4 应用程序，但收到“Web 应用程序无法启动”并获取以下跟踪信息：

cannot load such file -- bundler/setup (LoadError)
  /usr/local/lib/ruby/site_ruby/2.0.0/rubygems/core_ext/kernel_require.rb:53:in `require'
  /usr/local/lib/ruby/site_ruby/2.0.0/rubygems/core_ext/kernel_require.rb:53:in `require'
  /usr/lib/ruby/gems/1.8/gems/passenger-4.0.19/lib/phusion_passenger/loader_shared_helpers.rb:212:in `run_load_path_setup_code'
  /usr/lib/ruby/gems/1.8/gems/passenger-4.0.19/helper-scripts/rack-preloader.rb:96:in `preload_app'
  /usr/lib/ruby/gems/1.8/gems/passenger-4.0.19/helper-scripts/rack-preloader.rb:150:in `<module:App>'
  /usr/lib/ruby/gems/1.8/gems/passenger-4.0.19/helper-scripts/rack-preloader.rb:29:in `<module:PhusionPassenger>'
  /usr/lib/ruby/gems/1.8/gems/passenger-4.0.19/helper-scripts/rack-preloader.rb:28:in `<main>'

我的 apache2.conf 是：

LoadModule passenger_module /usr/lib/ruby/gems/1.8/gems/passenger-4.0.19/buildout/apache2/mod_passenger.so
   PassengerRoot /usr/lib/ruby/gems/1.8/gems/passenger-4.0.19
   PassengerDefaultRuby /usr/local/bin/ruby

bundle -v is:

Bundler version 1.3.5

ruby -v is:

ruby 2.0.0p247 (2013-06-27 revision 41674) [x86_64-linux]

gem env is:

RubyGems Environment:
  - RUBYGEMS VERSION: 2.1.5
  - RUBY VERSION: 2.0.0 (2013-06-27 patchlevel 247) [x86_64-linux]
  - INSTALLATION DIRECTORY: /usr/lib/ruby/gems/1.8
  - RUBY EXECUTABLE: /usr/local/bin/ruby
  - EXECUTABLE DIRECTORY: /usr/lib/ruby/gems/1.8/bin
  - SPEC CACHE DIRECTORY: /root/.gem/specs
  - RUBYGEMS PLATFORMS:
    - ruby
    - x86_64-linux
  - GEM PATHS:
     - /usr/lib/ruby/gems/1.8
  - GEM CONFIGURATION:
     - :update_sources => true
     - :verbose => true
     - :backtrace => false
     - :bulk_threshold => 1000
  - REMOTE SOURCES:
     - https://rubygems.org/
  - SHELL PATH:
     - /root/.gems/bin
     - /usr/lib/ruby/gems/1.8/bin/
     - /usr/local/bin
     - /usr/bin
     - /bin
     - /usr/bin/X11
     - /usr/games
     - /usr/sbin
     - /sbin

echo $GEM_PATH is:

/usr/lib/ruby/gems/1.8:/usr/lib/ruby/gems/1.8

不应该GEM_PATH be /usr/lib/ruby/gems/2.0?

在 apache2.conf 的虚拟主机内我添加了：

SetEnv GEM_HOME /usr/lib/ruby/gems/1.8

现在它正在发挥作用。

这是解决这个问题的正确方法吗？

我遇到了几乎完全相同的错误，并且只需运行以下命令即可完全修复它：

gem install bundler

您的捆绑程序安装可能已损坏或丢失 - 这就是我的情况。请注意，如果上述方法失败，您可以尝试：

sudo gem install bundler

...但一般来说你可以不用 sudo 来完成。