You may also try copying over a valid groups file from a different machine.

On Mon, Dec 13, 2010 at 2:15 AM, Jan Stary <hans@stare.cz> wrote:

quoted text
> On Dec 13 12:01:58, OpenBSD Geek wrote:
> > I have 100 users in groups : clients, and ftp_group
> > How can i remove these 100 users from ftp_group ?
> > I have already try usermod, but it only add users to group, not remove.
> > Is there a way to achieve my task ?
>
> Sadly, no. These users will be members of these groups forever.
> There's nothing you can do about it. You can only reinstall.