1.Install rvm(Ruby version manager)
sudo gem install rvm
2.Go to install path of rvm and do
rvm-install
3.Check if the install was successful by running
rvm
4.Check for current version of ruby
ruby -v
5.Install ruby 1.9.2 using rvm
rvm install 1.9.2
6.User ruby 1.9.2 with the help of rvm do
rvm 1.9.2
(you can switch back to system's default ruby version by running command >rvm system)
7.Install gems using rvm do
rvm gem install tzinfo builder memcache-client rack rack-test rack-mount erubis mail text-format thor bundler i18n
This will install gems locally for ruby1.9.2 without touchin the sytem ruby
8.Install RAILS3 beta release
rvm gem install rails --pre
9.Install railties which are required for RAILS3
rvm gem install railties --pre
10.For generating a new app with RAILS3 skeleton now do
rails myapp
Note all ruby script/ commands have changed to rails *
e.g: RAILS<3
ruby script/server -p 3004
RAILS3
rails server -p 3004
Hope it helps...