Maintaining group ownership of new files

[Upayavira <uv@upaya.co.uk>]

Hi,

I've used a freeBSD server where, when a file is created, that file 
becomes owned by the group who owns the containing folder.

However, I cannot seem to make this happen on a Debian box. Anyone know how?

Basically, I want to 'partition' a server using Unix groups. If a member 
of a group creates, uses modifies a file, that file is usable, 
modifiable, by other members of their group.

I of course will be a member of all of these groups.

Any ideas how to make this happen?

Regards, Upayavira