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Date: Wed, 6 Oct 2010 22:42:50 +0200
From: Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
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Subject: Re: In what way is /cygdrive special WRT to permissions?
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On Oct  6 13:19, Andy Hall wrote:
> Notice that the test -w /cygdrive/f/builds reports that /cygdrive/f/builds
> is not writeable, yet you can create and write files in /cygdrive/f/builds!
> THIS IS INCONSTENT BEHAVIOR.  Cygwin 1.5 did not have this behavior.

I somehow doubt that.  I'm just not sure if I can explain that
correctly, given how tired I am.  The difference is that under 1.5 all
smb drives were by default mounted with "noacl", aka
"CYGWIN=nosmbntsec".  So all permissions were just faked and Cygwin's
access call was more or less a wild guess.  With a drive mounted with
"acl" the OS (yes, Windows itself) is asked if the current user has
write permissions, based on the current user token and the ACL of the
file.  Apparently "non writable" is what you get here, because the ACL
returned by the Samba drive only contains the ACEs for the Linux user and
group, not for your current Windows user and group.  You can add these
Linux user's and groups to your local passwd and group file (see
http://cygwin.com/cygwin-ug-net/using-utils.html#mkpasswd and
http://cygwin.com/cygwin-ug-net/using-utils.html#mkgroup), but it won't
change what the OS returns in the access check.  I'm sorry, this bugs
me for years, but there nothing Cygwin can do about this.  Nor can Samba
do anything.  Yes, I asked on the samba developer mailing list at one
point...

The fact that the admin can write is normal, too, since admins (those
not restricted by UAC) always have write permissions under Cygwin 1.7.7,
just like a root user under Linux.  That's probably even documented
somewhere, I just don't recall where.


Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Project Co-Leader          cygwin AT cygwin DOT com
Red Hat

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