Install Ruby using apt-get
sudo apt-get install ruby rdoc irb libyaml-ruby libzlib-ruby ri libopenssl-ruby
Install RubyGems manually from source
wget http://rubyforge.org/frs/download.php/29548/rubygems-1.0.1.tgz
tar xzvf rubygems-1.0.1.tgz
cd rubygems-1.0.1
sudo ruby setup.rb
# This creates /usr/bin/gem1.8, but every guide you find will just use “gem”
# so create a symbolic link
sudo ln -s /usr/bin/gem1.8 /usr/bin/gem
# update rubygems
sudo gem update –system
Install Rails using RubyGems
sudo gem install rails