I am installing Rails 3 but I will do this very clean. I will not use rvm because I will use Ruby 1.9.1 and Rails 3 only.
Get ruby 1.9.1 (latest stable as of now)
sudo apt-get install ruby1.9.1-full
Get latest RubyGems from http://rubyforge.org/frs/download.php/70696/rubygems-1.3.7.tgz
tar -xvf rubygems-1.3.7.tgz
cd rubygems-1.3.7
rails setup.rb
Install Rails 3.0
sudo gem install rails
That’s it…