При попытке изменить root пароль пользователя MySQL и вам не удастся, то делаем:

[-hide-]mysql> UPDATE mysql.user SET Password=PASSWORD('ПАРОЛЬ') WHERE User='root';
Query OK, 0 rows affected (0.00 sec)
Rows matched: 0 Changed: 0 Warnings: 0

mysql> select * from user where User='root';
Empty set (0.00 sec)[-hide-]

Не повезло, но это означает, ,что ваша таблица данных mysql.user была утеряна.
Теперь посмотрим на то, как это восстановить.

Останавливаем mysql

[-hide-]/etc/init.d/mysql stop

Запустите mysqld_safe

mysqld_safe -–skip-grant-tables &

Входим

mysql
mysql> use mysql;

Проверяем

mysql> select * from user where User='root';
Empty set (0.00 sec)

Данных нет … Восстанавливаем.

mysql>INSERT INTO user (Host,User,Password,Select_priv,Insert_priv)

VALUES('localhost','root',PASSWORD('ПАРОЛЬ'),'Y','Y');

UPDATE user set Update_priv = 'Y' WHERE User='root';
UPDATE user set Delete_priv = 'Y' WHERE User='root';
UPDATE user set Create_priv = 'Y' WHERE User='root';
UPDATE user set Drop_priv = 'Y' WHERE User='root';
UPDATE user set Reload_priv = 'Y' WHERE User='root';
UPDATE user set Shutdown_priv = 'Y' WHERE User='root';
UPDATE user set Process_priv = 'Y' WHERE User='root';
UPDATE user set File_priv = 'Y' WHERE User='root';
UPDATE user set Grant_priv = 'Y' WHERE User='root';
UPDATE user set References_priv = 'Y' WHERE User='root';
UPDATE user set Index_priv = 'Y' WHERE User='root';
UPDATE user set Alter_priv = 'Y' WHERE User='root';
UPDATE user set Show_db_priv = 'Y' WHERE User='root';
UPDATE user set Super_priv = 'Y' WHERE User='root';
UPDATE user set Create_tmp_table_priv = 'Y' WHERE User='root';
UPDATE user set Lock_tables_priv = 'Y' WHERE User='root';
UPDATE user set Execute_priv = 'Y' WHERE User='root';
UPDATE user set Repl_slave_priv = 'Y' WHERE User='root';
UPDATE user set Create_view_priv = 'Y' WHERE User='root';
UPDATE user set Show_view_priv = 'Y' WHERE User='root';
UPDATE user set Create_routine_priv = 'Y' WHERE User='root';
UPDATE user set Alter_routine_priv = 'Y' WHERE User='root';
UPDATE user set Create_user_priv = 'Y' WHERE User='root';

mysql> flush privileges;
mysql> exit

Рестартуем MySQL

/etc/init.d/mysql restart

логинимся

mysql -u root -p[-hide-]