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Date:	Tue, 3 Nov 2009 16:44:30 +0100
From:	Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
To:	cygwin AT cygwin DOT com
Subject:	Re: Accessing GLOBALROOT paths - a potential compromise???
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On Nov  3 01:49, Jeffrey J. Kosowsky wrote:
> I know that there have been multiple threads about the pros/cons of
> being able to access XP/Vista style \\?\GLOBALROOT paths.
> 
> However, not being able to access them limits one's abilities to use
> things like shadow copies since they create shadow devices that are only
> accessible by such a path. For example
> 		   \\?\GLOBALROOT\Device\HarddiskVolumeShadowCopy1

In Cygwin 1.7 you can do this for any subdir in your volume shadow copy:

  $ ls -l //?/GLOBALROOT/Device/HarddiskVolumeShadowCopy1/subdir

It just doesn't work for the root directory of a drive due to internal
path handling restrictions.  But there's a simple workaround.  Use your
own tool as below.
  
> The only hack that I have found to get around this is to use an *old*,
> *unsupported* Microsoft routine called 'dosdev' which allows you to
> assign drive letters to devices, including using the GLOBALROOT
> format.

Try this:

  $ cat > DefDosDevice.c << EOF
  #include <stdio.h>
  #include <windows.h>

  int
  main (int argc, char **argv)
  {
    DWORD flags = 0;

    if (argc < 2)
      {
	fprintf (stderr, "usage: %s DosDevice [NTDevice]\n", argv[0]);
	return 1;
      }
    if (argc == 2)
      flags = DDD_REMOVE_DEFINITION;
    else
      flags = DDD_RAW_TARGET_PATH;
    if (!DefineDosDevice (flags, argv[1], argc == 2 ? NULL : argv[2]))
      {
	fprintf (stderr, "Error %d\n", GetLastError ());
	return 1;
      }
    return 0;
  }
  EOF
  $ gcc DefDosDevice.c -o DefDosDevice
  $ ./DefDosDevice X: '\??\GLOBALROOT\Device\HarddiskVolumeShadowCopy1
  $ cd /mnt/x
  $ ls
  [...]
  $ cd /mnt/c
  $ ./DefDosDevice X:   # this deletes drive X: again

Drive X: is not visible in Explorer, but you can access it from CMD and
any Cygwin process just fine.  To make it visible in Explorer, assign
another drive letter using subst:

  $ cmd /c subst W: X:\\

Afterwards you can access drive X: as drive W: from Explorer which,
for some reason, thinks it's accessing a "RAM Disk" on Windows 7.


Corinna

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

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