Error
$ mysql -u root
Error 1045 (28000): Access denied for user 'root'@'localhost' (using password: NO)
Stop mysqld deamons
$ sudo service mysql stop
Start a mysql deamon with the –skip-grant-table option
$ sudo mysqld_safe --skip-grant-tables
Open a separate terminal and and run the following commands
$ mysql
mysql> use mysql;
mysql> UPDATE user SET password=PASSWORD('YOUR_NEW_PASSWORD_HERE') WHERE user = 'root';
mysql> exit;
Kill the mysqld_safe process and restart mysqld
$ sudo service mysql restart