处理rails server 错误问题

　　在我安装好 Ruby on Rails 后,使用 rails new 命令新建一个项目,然后切换到项目下执行 rails server,出现如下错误:
 
　　sam@linux-qo4p:~/front/ror|master⚡⇒  rails server
　　Ignoring RedCloth-4.2.9 because its extensions are not built.  Try: gem pristine RedCloth-4.2.9
　　Ignoring posix-spawn-0.3.9 because its extensions are not built.  Try: gem pristine posix-spawn-0.3.9
　　Ignoring rdiscount-2.1.7.1 because its extensions are not built.  Try: gem pristine rdiscount-2.1.7.1
　　/usr/lib/ruby/site_ruby/2.0.0/rubygems/core_ext/kernel_require.rb:54:in `require': cannot load such file -- bundler/setup (LoadError)
　　        from /usr/lib/ruby/site_ruby/2.0.0/rubygems/core_ext/kernel_require.rb:54:in `require'  --phpfensi.com
　　        from /home/sam/front/ror/config/boot.rb:4:in `<top (required)>'
　　        from bin/rails:3:in `require_relative'
　　        from bin/rails:3:in `<main>'
　　这似乎是我把 openSUSE 系统从 13.1 升级到 13.2 后才出现的错误,我的情况里,尝试错误信息中的提示方法 gem pristine RedCloth 并不能消除以上错误.
 
　　最后的解决办法是:gem pristine --all,切换到项目根目录,bundle install,再次跑 rails server,可以正常启动不报错,此后,rails new 新建的项目也不再报错.