step by step install ruby + apache + ubuntu server

1.sudo apt-get update
2.sudo apt-get dist-upgrade
3.sudo apt-get install build-essential
4.sudo apt-get install ruby ri rdoc mysql-server libmysql-ruby ruby1.8-dev irb1.8 libdbd-mysql-perl libdbi-perl libmysql-ruby1.8 libmysqlclient15off libnet-daemon-perl libplrpc-perl libreadline-ruby1.8 libruby1.8 mysql-client-5.0 mysql-common mysql-server-5.0 rdoc1.8 ri1.8 ruby1.8
5.sudo wget http://rubyforge.org/frs/download.php/20989/rubygems-0.9.4.tgz
6.tar xvzf rubygems-0.9.4.tgz
7.cd rubygems-0.9.4
8.sudo ruby setup.rb
9.sudo ln -s /usr/bin/gem1.8 /usr/bin/gem

just in case it went wrong somewhere like u received an error saying

- /usr/bin/gem:10:Warning: Gem::manage_gems is deprecated and will be removed on or after March
2009. OR/AND
- /usr/bin/gem:23: uninitialized constant Gem::GemRunner (NameError)

simply sudo aptitude remove rubygems or ruby and start all over.

10. sudo gem install rails --include-dependencies
11. if later version of rails required simply type
sudo gem install rails -v=1.2.6
12. for installing phusion passeger go to http://www.modrails.com/install.html. its really quick n easy too