How many times have you wanted to install rails 3 on a system and you ended up in dependency hell? I know I have. Life was simpler with Rails 1 and 2. You could use ruby 1.8.7 and all was good. Now you should use 1.9.3. On ubuntu systems it is confusing to install ruby 1.9.3 because the package is called ruby1.9.1. If you install the apt package rubygems, Ubuntu will install ruby 1.8.7, just the opposite of what you want to happen. I’ve run into this issue enough times to document a fool proof way to get rails 3 onto your Ubuntu system.
If you read the docs on installing RubyGems you’ll notice they recommend the apt-get packages libyaml-ruby and libzlib-ruby. I installed the first one but the second will already be installed with the above list. With this arrangement you will only have ruby 1.9.3p0 installed and your rails will be 3.2.13
spustay@roar:~$ ruby -v ruby 1.9.3p0 (2011-10-30 revision 33570) [x86_64-linux] spustay@roar:~$ rails -v Rails 3.2.13
I hope you can use this list, I reference it when I need to.