I'm just making a note to myself on what I had to do to get the rails server to work on my Ubuntu 10.04. Both Ruby and Rails installed without any difficulty but upon issuing the final command , "rails server", I got the frequently reported "../.rvm/gems/ruby-1.9.3-p448/gems/execjs-1.4.0/lib/execjs/runtimes.rb:51:in
https://github.com/sstephenson/execjs for a list of available runtimes.
There are all kinds of solutions and suggestions out there for dealing with this. My own solution was to install nodejs. The problem here was that the repository for this was not in my list. I did find it at:
sudo add-apt-repository ppa:chris-lea/node.js
allowing me to:
sudo apt-get install nodejs
RoR is off and running.