Stop MySQL

sudo service mysql stop

Make MySQL service directory.

sudo mkdir /var/run/mysqld

Give MySQL user permission to write to the service directory.

sudo chown mysql: /var/run/mysqld

Start MySQL manually, without permission checks or networking.

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

Log in without a password.

mysql -uroot mysql
Update the password for the root user.
UPDATE mysql.user SET authentication_string=PASSWORD('YOURNEWPASSWORD'), plugin='mysql_native_password' WHERE User='root' AND Host='%';
EXIT;