If you are getting the following message in Ubuntu when trying to run gem install mysql:
Building native extensions. This could take a while... ERROR: Error installing mysql: ERROR: Failed to build gem native extension.
You can resolve this issue by installing libmysqlclient-dev package. Type the following in your terminal:
sudo apt-get install libmysqlclient-dev
After this is done, do a gem install of mysql again:
gem install mysql