嘿，我是 Rails（以及 linux）的新手，我不断收到此错误：
Installing json (1.7.5) with native extensions
Gem::Installer::ExtensionBuildError: ERROR: Failed to build gem native extension.
/usr/bin/ruby1.9.1 extconf.rb
/usr/lib/ruby/1.9.1/rubygems/custom_require.rb:36:in `require': cannot load such file -- mkmf (LoadError)
from /usr/lib/ruby/1.9.1/rubygems/custom_require.rb:36:in `require'
from extconf.rb:1:in `<main>'
Gem files will remain installed in /home/jack/.bundler/tmp/10426/gems/json-1.7.5 for inspection.
Results logged to /home/jack/.bundler/tmp/10426/gems/json-1.7.5/ext/json/ext/generator/gem_make.out
An error occurred while installing json (1.7.5), and Bundler cannot continue.
Make sure that `gem install json -v '1.7.5'` succeeds before bundling.
jack@jack-ThinkCentre:~/rails_projects/sample_app$
我无法单独安装 gem 或使用捆绑安装。我使用 rvm 安装导轨。提前致谢。