sudo /etc/init.d/mysql stop
sudo mysqld_safe --skip-grant-tables --skip-networking &

mysql -u root

USE mysql;
UPDATE user SET password=PASSWORD("new_password") WHERE User='root';
UPDATE user SET plugin="mysql_native_password";
exit

sudo /etc/init.d/mysql stop
sudo kill -9 $(pgrep mysql)

sudo /etc/init.d/mysql start

You will be asked to autheticate using your system admin password.
Done!