A Not Join

I have three table:
Users - Contains username, ID etc...
Permissions - A permission name and ID
Link up table - The user.id and permission.id

If a user.id and a permission.id row exists in the linkuptable the user
have that permission granted.

With the statement below I can see the permissions a user have.

SELECT users.username, permissions.name
FROM users INNER JOIN linkuptable
  ON (users.id = linkuptable.userid)
INNER JOIN permissions
  ON (permissions.id = linkuptable.permissionid)
WHERE users.username = 'DummyUser'

How do I see the permissions that user DON'T have with a fast SQL statement.

Thus, a NOT the statement for the above SQL statement

Regards

Lani