I had a little difficulty installing the MySQL gem for Ruby 1.9.1. I constantly received an error that said “/usr/local/lib/ruby/1.9.1/mkmf.rb:362:in `try_do’: The complier failed to generate an executable file. (RuntimeError) You have to install development tools first.”.

Well, after a couple of days of tinkering around on my server and several Google searches, the solution was found at the following site:

http://smangal.wordpress.com/2007/05/17/mysql-gem-on-centos/

If the above site is not available, the mysql-devel RPM had to get installed/updated. I did this through YUM. After getting that updated, the MySQL Ruby gem installed just fine.