wget http://rubyforge.org/frs/download.php/13890/rsruby-0.4.0.tar.gz
sudo apt-get install ruby1.8-dev
tar -zxf rsruby-0.4.0.tar.gz
export R_HOME=/usr/lib/R
cd rsruby-0.4.0
ruby setup.rb config -- --with-R-dir=/usr/lib/R
ruby setup.rb setup
sudo ruby setup.rb install

sudo ln -s /usr/lib/R/lib/libR.so /usr/lib/libR.so
sudo ldconfig

# add to .xsession
#export R_HOME=/usr/lib/R