Install Ruby Platform
Metasploit is Ruby based. Need install the Ruby first:

yum install ruby
yum install ruby-rdoc


Install RubyGems

wget http://rubyforge.org/frs/download.php/45905/rubygems-1.3.1.tgz
tar xvzf rubygems-1.3.1.tgz


Install Metasploit

wget http://spool.metasploit.com/releases/framework-3.2.tar.gz
tar xvzf framework-3.2.tar.gz
cd framework-3.2
./msfweb