mysql -u root
update user set password=(“YOUR_ROOT_PW”) where User=’root’; or /usr/bin/mysqladmin -u root password 'yourmysqlpassword'
Above command can be used to reset plesk admin password as well.
/etc/init.d/mysqld stop /etc/init.d/mysqld start mysql -u root -p
If you want to reset MySQL user password you can check How to reset MySQL user Password in Linux through command prompt.