How to change some GID

[Olivier Vogel]

Of course, I have tried to reboot the computer!

It is Ubuntu that requires that the users belong to cdrom group (gid 24)
and so on. So it serves nothing to create a second group cdrom2 on
Ubuntu. What I need is that the users belong to cdrom group.

I repeat: the problem comes from the fact that the OSX admininistrator
cannot put users in a group with a gid < 500.

Olivier