1. mysql bench 中修改用户密码后, >If you started mysql using mysql -u root -p

Try ALTER USER 'root'@'localhost' IDENTIFIED BY 'MyNewPass';

Source: http://dev.mysql.com/doc/refman/5.7/en/resetting-permissions.html

http://stackoverflow.com/questions/33467337/reset-mysql-root-password-using-alter-user-statement-after-install-on-mac