Access denied for user 'root'@'localhost' (using password: no)

Access denied for user 'root'@'localhost' (using password: no)

sudo /etc/init.d/mysqld stop      //关闭mysql
mysqld_safe --user=mysql --skip-grant-tables --skip-networking &
mysql -u root mysql
mysql> UPDATE user SET Password=PASSWORD('你想要的密码') where USER='root';
mysql> FLUSH PRIVILEGES;
mysql> quit
sudo /etc/init.d/mysqld start
mysql -uroot -p 你的密码