Update all packages
yum update
Install RVN.
note: Don't do this as a root user!
curl -L get.rvm.io | bash -s stable
Source the RVM executable
source ~/.rvm/bin/rvm
Install the requirements for RVM
rvm requirements
List the available version
rvm list known
Install Ruby 2.0.0
rvm install 2.0.0
Use it
rvm use 2.0.0 --default
Create a gemset
rvm gemset create rails4
Use it
rvm gemset use rails4
Install rails 4.0.1, this will take while
gem install rails --version 4.0.1
Based on: https://www.digitalocean.com/community/articles/how-to-install-ruby-on-rails-on-centos-6-with-rvm