dan@dan-VirtualBox:~/octopress$ sudo bundle install
Fetching gem metadata from http://rubygems.org/.......
Fetching gem metadata from http://rubygems.org/..
Using rake (0.9.2.2)
Installing RedCloth (4.2.9)
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 /var/lib/gems/1.9.1/gems/RedCloth-4.2.9 for inspection.
Results logged to /var/lib/gems/1.9.1/gems/RedCloth-4.2.9/ext/redcloth_scan/gem_make.out

An error occurred while installing RedCloth (4.2.9), and Bundler cannot
continue.
Make sure that `gem install RedCloth -v '4.2.9'` succeeds before bundling.