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Date: Tue, 13 Dec 2011 16:11:16 +0100
From: Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
To: cygwin AT cygwin DOT com
Subject: Re: Cygwin dll: UID and GID information not shown from remote drive
Message-ID: <20111213151116.GF23590@calimero.vinschen.de>
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On Dec 13 16:24, Jari Aalto wrote:
> 
> ** To CC Emacs BTS, use 10257(at)debbugs.gnu.org
> 
> My full original bug report was sent initially to Emacs, because the editor
> started considering remotes file as read-only and requiring confirmation
> after every save. See:
> 
>     http://debbugs.gnu.org/cgi/bugreport.cgi?bug=10257
> 
> It appears that Cygwin doesn't show UID and GID on Network drives (Win 7
> x64), that are connected with windows "Map Network Drive" to a
> Debian/Samba(2.3.5.11):
> 
>     $ ls -la /cygdrive/z/tmp/test-epackage.el
>     -rwxr--r-- 1 ???????? ???????? 437 Dec  9 20:02 /cygdrive/z/tmp/test-epackage.el

It's not a bug.

If you use winbind and the user accounts are correctly mapped to
Windows accounts, then you would see the Cygwin UIDs/GIDs correspoding
to the SID of the AD user account.

If you don't do that, there's only an invisible mapping from the Windows
SID to the Unix uid/gid.  The actual UNIX account has not the same mapping
back to the Windows SID.  Instead, the SID returned from Samba to
Windows is a fake SID S-1-22-1-UnixUID or S-1-22-2-UnixGID.

The easiest way to workaround this issue is to mount the share with
the noacl mount option:

  //sambaserver/share /myserver somefs binary,noacl 0 0

Alternatively you must coax Cygwin into thinking that both SIDs are the
same account.  What you can do is to map these SIDs to the desired
Cygwin UID/GID using matching entries in /etc/passwd and /etc/group,
like this:

  /etc/passwd:

    corinna:unused:11001:11125:corinna,U-VINSCHEN\corinna,S-1-5-21-2913048732-1697188782-3448811101-1001:/home/corinna:/bin/tcsh
    corinna:unused:11001:99999:,S-1-22-1-500::

  /etc/group

    vinschen:S-1-5-21-2913048732-1697188782-3448811101-1125:11125:
    vinschen:S-1-22-2-11125:11125:
  
To generate the Unix SID entries for /etc/passwd and /etc/group, see
the mkpasswd/mkgroup -U options:

  $ mkpasswd -l sambaserver -U corinna
  corinna:unused:10500:99999:,S-1-22-1-500::
  $ mkgroup -l sambaserver -U vinschen
  vinschen:S-1-22-2-11125:21125:

Just tweak the UID/GID fields and make sure that the Samba fake entries
are later in the file than the entries with the correct Windows SID mapping.


Corinna

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

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