ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: NO)

sudo mysql -u root

and if you get error - like below

ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: NO)

then use mysql -u root -p

mysql -u root -p 

mysql> use mysql;

mysql> ALTER USER 'root'@'localhost' IDENTIFIED BY 'NewPassword';

mysql> flush privileges;

mysql> exit;