[Samba] setting permissions for unix users on samba shares

[Robert Watson]

I'm trying to grant permissions for linux system users (apache,mysql...) to
have permissions on samba shares. I've established domain users permissions
while logged in as the domain admin and thought the SYSTEM account would
cover these types of users....but apparently not.
Is there a built in linux group that maps to a windows domain group or do I
have to establish this manually.