How to reset mysql root password

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

- MySQL version < 5.7
update user set password=PASSWORD("mynewpassword") where User='root';

-- MySQL 5.7, mysql.user table "password" field -> "authentication_string"
update user set authentication_string=password('mynewpassword') where user='root';

update user set plugin="mysql_native_password" where user='root';

sudo /etc/init.d/mysql stop
sudo /etc/init.d/mysql start

When you see a socket error

mkdir -p /var/run/mysqld && chown mysql:mysql /var/run/mysqld