find mysqld configure file position

检查mysqld读取配置文件的位置，可以用下面这个命令：

 mysqld --verbose --help|grep -A 1 'Default options'

Default options are read from the following files in the given order:
/etc/my.cnf /etc/mysql/my.cnf /usr/local/etc/my.cnf ~/.my.cnf

摘自《高性能MySQL》