I got a similiar task to do for a couple of days, you just need to extend the FOSUserBundle User Entity with your UserEntity where you're going to add all the Columns you need that the BaseUser doesn't provide.
use FOS\UserBundle\Model\User as BaseUser;
/**
* user
*
* @ORM\Table(name="user")
*
*/
class User extends BaseUser
{
//Here you can extend the BaseUser provided from the FOSUserBundle
//with the Columns you need
}
After that you just need to write a SQL Script with migrates the Data from the one Table to the new Table
INSERT INTO fos_user(`id`, `username`, `username_canonical`, `email`, `email_canonical`, `enabled`, `password`)
SELECT `id`, `name`, `name`, `email`, `email`, `active`, `password`
FROM old_user_table;
This is the script i was using to do this datamigration. Just run it in phpmyadmin.
It is not necessary to add the *_canonical fields manually AFAIK, i'm just doing it to be safe.
Hope it helped.