Error installing Nokogiri 1.5.0 with rails 3.1.0 and ubuntu

It looks like a gem dependency error.

You need to run the bundle update command. It will resolve dependencies:

bundle update

You need to have all the necessary libraries installed on your machine. When you installed RVM , it should have listed this for you. On the current version of rvm, you can run rvm requirements to see the exact list. Right now, that list is:

sudo apt-get install build-essential openssl libreadline6 libreadline6-dev curl git-core zlib1g zlib1g-dev libssl-dev libyaml-dev libsqlite3-0 libsqlite3-dev sqlite3 libxml2-dev libxslt-dev autoconf libc6-dev ncurses-dev automake libtool bison subversion

You are missing some packages. Try running this (Linux only):

$ sudo apt-get install libxslt-dev libxml2-dev