# gem install pg Building native extensions. This could take a while... ERROR: Error installing pg: ERROR: Failed to build gem native extension. /usr/bin/ruby1.8 extconf.rb install pg 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/pg-0.7.9.2008.10.13 for inspection. Results logged to /var/lib/gems/1.8/