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Date: Fri, 7 Nov 2008 16:08:02 +0100
From: Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
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Subject: Re: Mount of VSS volumes (//?/GLOBALROOT/...) does not work
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On Nov  7 15:41, Christian Franke wrote:
> Corinna Vinschen wrote:
> > On Nov  7 13:06, Christian Franke wrote:
> > > According to
> > > http://sourceware.org/ml/cygwin/2007-05/msg00359.html
> > > http://sourceware.org/ml/cygwin-patches/2006-q4/msg00008.html
> > > Cygwin includes support to mount a //?/GLOBALROOT/... path
> > 
> > No, it doesn't.  It allows to *access* the path, but the mount call
> > follows a somewhat different route.  You can only access the path
> > directly (a concenssion to a necessity which has no POSIX equivalent)
> > or, as you did, map the VSS volume to a drive letter.  The patch is
> > not in 1.5.25, btw., only in 1.7.0.
> > 
> 
> Thanks for clarification.
> 
> The access to the path works, except the access to the root dir of the
> volume. It appears as a regular file which apparently provides raw read
> access to the partition:
> 
> $ ls -l '//?/GLOBALROOT/Device/HarddiskVolumeShadowCopy1'
> -rw-r--r-- 1 ... 0 Dec  1  2006 //?/.../HarddiskVolumeShadowCopy1
> 
> $ xxd '//?/GLOBALROOT/Device/HarddiskVolumeShadowCopy1'
> 0000000: eb52 904e 5446 5320 2020 2000 0208 0000  .R.NTFS    .....

The windows path handling code in Cygwin doesn't recognize the path as
the path to a drive's root dir.  The path normalization code removes all
trailing backslashes.  When accessing a root dir, Windows requires a
trailing backslash.  When accessing the volume without the trailing
backslash, it's opened for raw access.

This is still a highly unusual situation from a POSIXy point of view.
I'm not sure I want to slow down Cygwin for this any further.  It seems
the ability to mount a shadow volume as a dos drive is sufficient for
this kind of problem, isn't it?


Corinna

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

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