$ sudo apt-get install ruby1.9.1
$ sudo ln -s /usr/bin/ruby1.9.1 /usr/bin/ruby

$ sudo apt-get install libopenssl-ruby1.9.1
	

$ sudo apt-get install rubygems1.9.1
$ sudo ln -s /usr/bin/gem1.9.1 /usr/bin/gem
	

Installing Rails

$ sudo apt-get install rails
	

or

$ sudo gem install rails

Successfully installed rake-0.8.7
Successfully installed activesupport-2.3.5
Successfully installed activerecord-2.3.5
Successfully installed rack-1.0.1
Successfully installed actionpack-2.3.5
Successfully installed actionmailer-2.3.5
Successfully installed activeresource-2.3.5
Successfully installed rails-2.3.5
8 gems installed
Installing ri documentation for rake-0.8.7...
Installing ri documentation for activesupport-2.3.5...
Installing ri documentation for activerecord-2.3.5...
Installing ri documentation for rack-1.0.1...
Installing ri documentation for actionpack-2.3.5...
Installing ri documentation for actionmailer-2.3.5...
Installing ri documentation for activeresource-2.3.5...
Installing ri documentation for rails-2.3.5...
Updating class cache with 0 classes...
Installing RDoc documentation for rake-0.8.7...
Installing RDoc documentation for activesupport-2.3.5...
Installing RDoc documentation for activerecord-2.3.5...
Installing RDoc documentation for rack-1.0.1...
Installing RDoc documentation for actionpack-2.3.5...
Installing RDoc documentation for actionmailer-2.3.5...
Installing RDoc documentation for activeresource-2.3.5...
Installing RDoc documentation for rails-2.3.5...