Add rubyworks repo in /etc/yum.repos.d/.
vi /etc/yum.repos.d/rubyworks.repo
And insert this text;
# Link file for RubyWorks yum repository
# Place this file in /etc/yum.repos.d[rubyworks]
name=RubyWorks
baseurl=http://rubyworks.rubyforge.org/redhat/$releasever/RPMS/$basearch
enabled=1
gpgcheck=1
gpgkey=http://rubyworks.rubyforge.org/RubyWorks.GPG.key
priority=1
Install Ruby on Rails 2.2.2 on Centos 5.2
yum install ruby ruby-devel ruby-libs ruby-irb ruby-rdoc ruby-mysql
Download and install ruby gems
wget http://rubyforge.org/frs/download.php/45905/rubygems-1.3.1.tgz
tar xvf rubygems-1.3.1.tgz
cd rubygems-1.3.1
ruby setup.rb
Install Rails
gem install rails
Далее по офф. инструкции...