$ sudo gem install eventmachine Building native extensions. This could take a while... ERROR: Error installing eventmachine: ERROR: Failed to build gem native extension.
/usr/bin/ruby1.8 extconf.rb extconf.rb:1:in `require': no such file to load -- mkmf (LoadError) from extconf.rb:1
Gem files will remain installed in /var/lib/gems/1.8/gems/eventmachine-0.12.10 for inspection. Results logged to /var/lib/gems/1.8/gems/eventmachine-0.12.10/ext/gem_make.out
