An admin user? This box isn't running Plesk by chance, is it? If so, the admin user is the root user. Just log in with
mysql -uadmin -p
and the password for admin. If this is a Plesk box, then I would simply delete the root user you created and use admin. If not, and you still want a root user, then you have to grant the user "root" access from localhost before you can log in from localhost as root.