[root@s15745022 /]# /etc/init.d/mysqld stop
Stopping MySQL:                                            [  OK  ]


//here i change the my.cnf, adding skip-grant-tables=1 under [mysqld]

[root@s15745022 /]# /etc/init.d/mysqld start
Starting MySQL:                                            [  OK  ]
[root@s15745022 /]# mysql -u root
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 2
Server version: 5.0.77 Source distribution

Type 'help;' or '\h' for help. Type '\c' to clear the buffer.

mysql> use mysql;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Database changed
mysql> UPDATE user SET Password = PASSWORD('newpass') WHERE User = 'root';
Query OK, 0 rows affected (0.01 sec)
Rows matched: 0  Changed: 0  Warnings: 0

mysql> Aborted
[root@s15745022 /]# /etc/init.d/mysqld stop
Stopping MySQL:                                            [  OK  ]

//here i change the my.cnf, removing skip-grant-tables=1 under [mysqld]

[root@s15745022 /]# /etc/init.d/mysqld start
Starting MySQL:                                            [  OK  ]
[root@s15745022 /]# mysql -u root -p
Enter password:
ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: YES)
[root@s15745022 /]# mysql -u root -p
Enter password:
ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: YES)
[root@s15745022 /]#