HYPER-V VMs: Cygwin /bin/getent group 'Virtual Machines' cannot find the group

[Martin Wege]

On Wed, Mar 11, 2026 at 4:17 PM Corinna Vinschen via Cygwin
<cygwin@cygwin.com> wrote:
>
> On Mar  3 09:26, Aurélien Couderc via Cygwin wrote:
> > On Mon, Mar 2, 2026 at 8:19 PM Martin Wege via Cygwin <cygwin@cygwin.com> wrote:
> > >
> > > Hello,
> > >
> > > we use HYPER-V virtual machines on Windows 10 and Windows 11. It seems
> > > they use a "special" kind of group called 'Virtual Machines', which
> > > Cygwin (3.6.5) /bin/getent cannot lookup:
> > >
> > > getent group 'Virtual Machines'
> > > <nothing>
> > >
> > > Does anyone have ideas or clues how to get getent group to work with
> > > this kind of Windows group?
> > >
> > > We want the Cygwin gid for that group, and use Cygwin commands to work
> > > with those files...
> >
> > Déjà vu
> >
> > 1. Please read https://cygwin.com/pipermail/cygwin/2025-July/258505.html
> >
> > 2. Try this:
> > getent group "NT VIRTUAL MACHINE+Virtual Machines"
> > For me, with default (empty, except comments) /etc/nsswitch.conf, it
> > does not work. Which I consider a bug.
>
> It's not a bug, it's a feature.  Truly so.  Keep in mind that there's
> no easy translation from arbitrary SIDs to 32 bit uid/gid values and
> vice versa.  So every time, Microsoft adds YA arbitrary SID not following
> the already implemented and supported schemes, the bijective mapping
> has to be implemented manually.
>
> Done in the main branch.

Thank you!

Martin