Step 1: Stop MySQL Service.

sudo stop mysql

Step 2: Kill all running mysqld.

sudo killall -9 mysqld

Step 3: Starting mysqld in Safe mode.

sudo mysqld_safe --skip-grant-tables --skip-networking &

Step 4: Start mysql client

mysql -u root

Step 5: After successful login, please execute this command to change any password.

FLUSH PRIVILEGES;

Step 6: You can update mysql root password .

UPDATE mysql.user SET Password=PASSWORD('newpwd') WHERE User='root';

Step 7: Please execute this command.

FLUSH PRIVILEGES;