If the server was auto provisioned with MySQL then the root password is the same as the server root password.
If you have Plesk auto provisioned on your server, then use "admin" and the admin password for Plesk.
If you installed MySQL through source, RPM, or up2date, then the initial root account passwords are empty, so anyone can connect to the MySQL server as root - without a password - and be granted all privileges. Unless you set the root password during or after the MySQL installation
