Specify Rails versions

I have installed Rails 2.2.3 in Ubuntu 10.04 through the repository. After found that it i开发者_高级运维s not the newest version, I decided to install it through RubyGems. So how do I specify which Rails version to use when I start a project?

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After you have created your project, modify the following statement in config/environment.rb

RAILS_GEM_VERSION = '2.1.1' unless defined? RAILS_GEM_VERSION