[root@gw ~]# gem install mysql --include-dependencies
Select which gem to install for your platform (i386-linux)
 1. mysql 2.7.3 (mswin32)
 2. mysql 2.7.1 (mswin32)
 3. mysql 2.7 (ruby)
 4. mysql 2.6 (ruby)
 5. Skip this gem
 6. Cancel installation
> 4
Building native extensions.  This could take a while...
ERROR:  While executing gem ... (Gem::Installer::ExtensionBuildError)
    ERROR: Failed to build gem native extension.

ruby extconf.rb install mysql --include-dependencies
can't find header files for ruby.


Gem files will remain installed in /usr/lib/ruby/gems/1.8/gems/mysql-2.6 for inspection.
Results logged to /usr/lib/ruby/gems/1.8/gems/mysql-2.6/gem_make.out