[Samba] mapping multiple groups with: net groupmap?

[David Mathog]

Sorry if this is obvious but I'm not up to speed yet
with Samba 3.

Google turned up this command:

    net groupmap modify ntgroups="Domain users" unixgroup=users

which would be all fine and dandy if everybody was in the
same primary group, which they are not, since it completely defeats
the purpose of having groups in the first place.
On my system we currently have 87 groups (one per research group)
and about 1300 registered users.

There's no way I'm putting 1300 names on one line in a "group" file,
even assuming that that sort of secondary group assignment would work
here, which I doubt.

I tried feeding the command above a comma separated list of groups, but
that didn't work:

Unable to lookup UNIX group users,biostaff.  Make sure the group exists.

So what is the magic command to tell Samba to map _ALL_ unix accounts to
"Domain users"?  That's I think what most of us need for the default value.

Samba Version 3.0.6

Thanks.

David Mathog
mathog at caltech.edu