1 sudo apt-get install sun-java6-jdk

2 sudo gedit /etc/environment

3 add two line and save:
CLASSPATH=/usr/lib/jvm/java-6-sun/lib
JAVA_HOME=/usr/lib/jvm/java-6-sun

4 download netbeans-6.0-ruby-linux.sh

5 double click netbeans-6.0-ruby-linux.sh and select "Run in Terminal"(make sure System->Preference->Appearence->Visual Effect turn to 'None' or you can't see the install botton)

6 if you want use subversion in Netbeans do this: sudo apt-get install subversion

7 if you want use MySQL do this: sudo apt-get install mysql-server-5.0

8 Applications->Add/Remove to install the "MySQL Query Browser"

9 $ sudo apt-get install ruby rubygems irb ri rdoc ruby1.8-dev build-essential
$ sudo gem install rails --include-dependencies
$ export PATH=$PATH:/var/lib/gems/1.8/bin

10 $ sudo gem install -v=1.2.5 rails

11 open netbeans and Tools->Options->Ruby, set the Ruby Interpreter "/usr/bin/ruby1.8"

12 add the socket: /var/run/mysqld/mysqld.sock to the database.yml:
development:
adapter: mysql
database: financing_rails2_development
username: root
password:
host: localhost
socket: /var/run/mysqld/mysqld.sock

ref:
[url]http://blog.donews.com/maverick/archive/200[/url]7/05/22/1167648.aspx
[url]http://www.qyjohn.net/?p=266[/url]
http://ubuntuguide.org/wiki/Ubuntu:Gutsy#MySQL
[url]http://wiki.[/url]rubyonrails.org/rails/pages/RailsOnUbuntu
[url]https://help.[/url]ubuntu.com/community/RubyOnRails