Ruby on rails 更新gems后出现Rails错误

运行

gem update

后，当我尝试启动rails时，出现以下错误：

$ rails s
/usr/lib/ruby/1.9.1/rubygems.rb:238:in `activate': can't activate rack (~> 1.4.5, runtime)
for ["actionpack-3.2.12", "railties-3.2.12"], already activated rack-1.5.2 for ["rack-
ssl-1.3.3", "railties-3.2.12"] (Gem::LoadError)
    from /usr/lib/ruby/1.9.1/rubygems.rb:254:in `block in activate'
    from /usr/lib/ruby/1.9.1/rubygems.rb:253:in `each'
    from /usr/lib/ruby/1.9.1/rubygems.rb:253:in `activate'
    from /usr/lib/ruby/1.9.1/rubygems.rb:254:in `block in activate'
    from /usr/lib/ruby/1.9.1/rubygems.rb:253:in `each'
    from /usr/lib/ruby/1.9.1/rubygems.rb:253:in `activate'
    from /usr/lib/ruby/1.9.1/rubygems.rb:1065:in `gem'
    from /usr/local/bin/rails:18:in `<main>'

$rails
/usr/lib/ruby/1.9.1/rubygems.rb:238:in'activate'：无法激活机架（~>1.4.5，运行时）
对于[“actionpack-3.2.12”，“railties-3.2.12”]，已经为[“rack”激活了rack-1.5.2-
ssl-1.3.3、“railties-3.2.12”]（Gem:：LoadError）
from/usr/lib/ruby/1.9.1/rubygems.rb:254:in'block in activate'
from/usr/lib/ruby/1.9.1/rubygems.rb:253:in'each'
from/usr/lib/ruby/1.9.1/rubygems.rb:253:in'activate'
from/usr/lib/ruby/1.9.1/rubygems.rb:254:in'block in activate'
from/usr/lib/ruby/1.9.1/rubygems.rb:253:in'each'
from/usr/lib/ruby/1.9.1/rubygems.rb:253:in'activate'
from/usr/lib/ruby/1.9.1/rubygems.rb:1065:in'gem'
from/usr/local/bin/rails:18:in`'

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任何人都可以帮助我，这意味着什么以及如何解决问题吗？

您必须使用bundler运行它

$ bundle exec rails s

否则，您需要卸载机架版本1.5.2。

删除Gemfile.lock

然后跑

$> bundle install

---

对我来说，这可能是一个更优雅的解决方案。事实上，这一切都是关于那些被锁定在那里的版本。