像这样的东西：
gem install rails Fetching: activesupport-3.0.10.gem (100%) Fetching: builder-2.1.2.gem (100%) WARNING: builder-2.1.2 has an invalid nil value for @cert_chain Fetching: i18n-0.5.0.gem (100%) Fetching: activemodel-3.0.10.gem (100%) Fetching: rack-1.2.3.gem (100%) Fetching: rack-test-0.5.7.gem (100%) Fetching: rack-mount-0.6.14.gem (100%) Fetching: tzinfo-0.3.29.gem (100%) Fetching: abstract-1.0.0.gem (100%) WARNING: abstract-1.0.0 has an invalid nil value for @cert_chain Fetching: erubis-2.6.6.gem (100%) Fetching: actionpack-3.0.10.gem (100%) Fetching: arel-2.0.10.gem (100%) Fetching: activerecord-3.0.10.gem (100%) Fetching: activeresource-3.0.10.gem (100%) Fetching: mime-types-1.16.gem (100%) Fetching: polyglot-0.3.2.gem (100%) Fetching: treetop-1.4.10.gem (100%) Fetching: mail-2.2.19.gem (100%) Fetching: actionmailer-3.0.10.gem (100%) Fetching: thor-0.14.6.gem (100%) Fetching: railties-3.0.10.gem (100%) Fetching: bundler-1.0.18.gem (100%) Fetching: rails-3.0.10.gem (100%) Successfully installed activesupport-3.0.10 Successfully installed builder-2.1.2 Successfully installed i18n-0.5.0 Successfully installed activemodel-3.0.10 Successfully installed rack-1.2.3 Successfully installed rack-test-0.5.7 Successfully installed rack-mount-0.6.14 Successfully installed tzinfo-0.3.29 Successfully installed abstract-1.0.0 Successfully installed erubis-2.6.6 Successfully installed actionpack-3.0.10 Successfully installed arel-2.0.10 Successfully installed activerecord-3.0.10 Successfully installed activeresource-3.0.10 Successfully installed mime-types-1.16 Successfully installed polyglot-0.3.2 Successfully installed treetop-1.4.10 Successfully installed mail-2.2.19 Successfully installed actionmailer-3.0.10 Successfully installed thor-0.14.6 Successfully installed railties-3.0.10 Successfully installed bundler-1.0.18 Successfully installed rails-3.0.10 23 gems installed Installing ri documentation for activesupport-3.0.10... Installing ri documentation for builder-2.1.2... unable to convert "\xF1" from ASCII-8BIT to UTF-8 for README,skipping Installing ri documentation for i18n-0.5.0... Installing ri documentation for activemodel-3.0.10... Installing ri documentation for rack-1.2.3... Installing ri documentation for rack-test-0.5.7... Installing ri documentation for rack-mount-0.6.14... Installing ri documentation for tzinfo-0.3.29... Installing ri documentation for abstract-1.0.0... Installing ri documentation for erubis-2.6.6... Installing ri documentation for actionpack-3.0.10... Installing ri documentation for arel-2.0.10... Installing ri documentation for activerecord-3.0.10... Installing ri documentation for activeresource-3.0.10... Installing ri documentation for mime-types-1.16... Installing ri documentation for polyglot-0.3.2... Installing ri documentation for treetop-1.4.10... Installing ri documentation for mail-2.2.19... Installing ri documentation for actionmailer-3.0.10... Installing ri documentation for thor-0.14.6... Installing ri documentation for railties-3.0.10... Installing ri documentation for bundler-1.0.18... Installing ri documentation for rails-3.0.10... file 'lib' not found Installing RDoc documentation for activesupport-3.0.10... Installing RDoc documentation for builder-2.1.2... unable to convert "\xF1" from ASCII-8BIT to UTF-8 for README,skipping Installing RDoc documentation for i18n-0.5.0... Installing RDoc documentation for activemodel-3.0.10... Installing RDoc documentation for rack-1.2.3... Installing RDoc documentation for rack-test-0.5.7... Installing RDoc documentation for rack-mount-0.6.14... Installing RDoc documentation for tzinfo-0.3.29... Installing RDoc documentation for abstract-1.0.0... Installing RDoc documentation for erubis-2.6.6... Installing RDoc documentation for actionpack-3.0.10... Installing RDoc documentation for arel-2.0.10... Installing RDoc documentation for activerecord-3.0.10... Installing RDoc documentation for activeresource-3.0.10... Installing RDoc documentation for mime-types-1.16... Installing RDoc documentation for polyglot-0.3.2... Installing RDoc documentation for treetop-1.4.10... Installing RDoc documentation for mail-2.2.19... Installing RDoc documentation for actionmailer-3.0.10... Installing RDoc documentation for thor-0.14.6... Installing RDoc documentation for railties-3.0.10... Installing RDoc documentation for bundler-1.0.18... Installing RDoc documentation for rails-3.0.10... file 'lib' not found
如果我运行rake db：migrate
它说：
............
rake aborted!
stack level too deep
解决方法
试试这个 ：
sudo gem install rails --no-ri --no-rdoc
如果你想安装RDoc使用：
sudo gem install rdoc-data sudo rdoc-data --install sudo gem rdoc --all --overwrite
如果那不起作用试试这个：
sudo apt-get install ruby-dev build-essential
