#From bash
#Stop mysql service
$> service mysqld stop
#Start mysql "for free". Seems dangerous :P
$> mysqld_safe --skip-grant-tables --skip-networking &

$> mysql -uroot
mysql> use mysql;
mysql> UPDATE user SET password=PASSWORD('nuevo_pass') WHERE user='root';
mysql> quit;

$> service mysqld restart

How to reset a root password in mysql with OS root user

Reset root password in MySQL

mysql

MySQL