Migrating MySQL dumps in default Debian installations
Debian uses a separate user for the maintanance of MySQL. That user is called debian-sys-maint and will be created automatically when you install MySQL. If you accidentally delete that user or import an old dump with the “mysql” user database, the MySQL init-script will complain with such an error-message:
Access denied for user ‘debian-sys-maint’@'localhost’ (using password: YES)
In that case you should recreate that user with the following steps:
1. Get the password of the user from /etc/mysql/debian.cnf