[Samba] Idmap backend for winbind

[Wong, G. MR EECS]

I'm trying to set up an Idmap Backend LDAP server for winbind.  I don't
need a full blown SAMBA PDC; just a server to provide the SID to UID/GID
mappings.  We're using a Windows Active Directory server to authenticate
against but we want the above mappings to be the same across multiple
samba machines.  Can we just stand up a simple ldap server and just add
the mappings
and that's it or do we have to have a full blown Samba PDC for this
purpose?  If just the mappings are built, what are the specifics?  What
entries do we have to add?  All the documentation I've read talks about
an idmap backend in the context of building a PDC.