Having trouble installing the nokogiri gem under rvm ruby 1.9.1. gem install nokogiri I'm getting ... /usr/include/libxml2... no libxml2 is missing. try 'port install libxml2' or 'yum install libxml2-devel' *** extconf.rb failed *** but i checked: sudo apt-get install libxml2 and i got: Reading state information... Done libxml2 is already the newest version. is this a root thing perhaps? RVM runs everything in userspace.