驱动配置：
Gemfile:gem 'mysql2', '0.2.6' 或者
gem install mysql2 --with-mysql-dir=/usr/local/mysql --with-mysql-config=/usr/local/mysql/bin/mysql_config
windows 两者均可，linux推荐第二种，给驱动指定部分参数（根据你mysql数据库的安装）  

database.yml配置
development:
   adapter: mysql2   
   encoding: utf8   
   reconnect: false  
   database: xxx
   pool: 5   
   username: xxx
   password: xxx
   host: xxx.xxx.x.xxx