Re: Re: Windows 8 group won't respect /etc/passwd or /etc/group

[John Smith <john at whitelancer dot com>]

Hi there,

First, thanks for the detailed reply!!

> > I've been struggling with an issue trying to figure out why Windows
> > 8.1 won't seem to respect the trick of setting your /etc/password to
> > use a default group such as users instead of 'none'.  There are a
> > few other discussions on this board around changing the group to
> > "Users" and modifying the /etc/passwd to have a default group.
>
> Not sure if the User's Guide is explaining it badly or not, but "None"
> *is* a group.  It's the primary (what you call "default") group for all
> users on a local machine not connected to a Windows domain, and it has
> the SID S-1-5-21-<xxx>-<yyy>-<zzz>-513.  If you call mkgroup -l it shows
> up like this:
>
>   None:S-1-5-21-3229976424-329291882-2774727752-513:513:
>
> assuming you have an english system, otherwise you see a localized
> group name.

Yes, I understand this part.  And I would be happy to see this group 
show up, but it does not seem to be able to identify "None" as the group.>

> Yes, of course.  Changing the primary group via /etc/passwd only
> works for Cygwin processes and their child processes.  It does not
> change the default user token of all processes.  How should that
> work, especially since the OS itself doesn't allow to change the
> primary group of local user accounts.

Interesting -- so we can change permissions via cygwin, (unless we're 
mounted as noacl) but not groups?  I'm not trying to change the default 
group necessarily - that would be convenient, of course, but the most 
frustrating part is that it's changing it *back*.

In *nix, once you change a group, just editing a file won't change the 
group back to something else.  Is there a way to get to this within 
cygwin?

Optimally I would find a way to change the default created group, but I 
can survive if cygwin (the OS?) will at least remember the group when I 
change it to something else.

> > Well, technically
> > it's coming back as 4294967295.  (64 bit cygwin)
>
> This can only happen if you dropped the "None" group from your
> /etc/group file.  mkgroup -l > /etc/group will rectify it.

See, this is why I'm so baffled: I *do* have this group.  It's the last 
entry in my /etc/groups:

None:S-1-5-21-339652832-68357117-3096367938-513:513:

> Except for the 4294967295, which is just a missing entry for "None" in
> /et/cgroup, this is normal.  See above.  It's not a problem of the OS or
> Cygwin, you're just misunderstanding how this works.  User tokens
> are propagated from process to child process.  The parent processes
> of any first Cygwin process is a native Windows process with an
> unchanged user token, so it has "None" as primary group.  At startup
> of the first Cygwin process, it reads /etc/passwd and /etc/group
> and changes the primary group in its user token if requested by your
> settings.  This changed user token will be inherited by child processes

Ah, I see.  So do you know if there is anyway to tell applications to 
change groups, to avoid this issue of the None/blank/missing group?

> started from this process and subsequent processes, but it does not
> affect the user tokens of unrelated processes, especially not of
> non-CYgwin processes started from Explorer.  If you want Notepad to
> use your group setting, start it from a Cygwin process.

Just tested this, and yes, that definitely works.  OK, thank you for 
this.  It's not the solution yet but it's on the right track.

Do you have any suggestions or thoughts as to why I'm still seeing that 
group of ??????????? even though "none" exists in my /etc/group?  I was 
assuming that the default group must be something else, not "None", 
maybe some virtual group that cygwin can't detect with mkgroup.  I just 
can't figure out what group cygwin is detecting it as.  Once I do an 
'ls', cygwin has already tried to map the group and just returns 
'??????' (well, -1 or whatever).  Is there a way to see what group 
cygwin is trying to look up?  If I can detect that it's not defaulting 
to the 'None' group, but some other random group, maybe it's a 
configuration option on the OS level to start using "none" again or 
something?

Thank you so much for your thoughts and help on this.

-J





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