MySQL -u root
　　mysql> SET PASSWORD FOR 'root'@'localhost' = PASSWORD('newpass');

mysqladmin -u root password "newpass"

mysqladmin -u root password oldpass "newpass"

mysql -u root
　　mysql> use mysql;
　　mysql> UPDATE user SET Password = PASSWORD('newpass') WHERE user = 'root';
　　mysql> FLUSH PRIVILEGES;

mysqld_safe --skip-grant-tables
　　mysql -u root mysql
　　mysql> UPDATE user SET password=PASSWORD("new password") WHERE user='root';
　　mysql> FLUSH PRIVILEGES;