Mount of VSS volumes (//?/GLOBALROOT/...) does not work

[Larry Hall (Cygwin)]

Jason Pyeron wrote:
>  
> 
>> -----Original Message-----
>> From: cygwin-owner at cygwin dot com [mailto:cygwin-owner at 
>> cygwin dot com] On Behalf Of Christian Franke
>> Sent: Friday, November 07, 2008 10:34
>> To: cygwin at cygwin dot com
>> Subject: Re: Mount of VSS volumes (//?/GLOBALROOT/...) does not work
>>
>> Corinna Vinschen wrote:
>>> On Nov  7 15:41, Christian Franke wrote:
>>>> 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.
>>>
>> Now I understand where the problem is. Thanks.
>>
>>
>>> 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 
> 
> Could this be explained please?

The code in Cygwin to handle path conversion and "POSIXification" is very
complex and is already a performance concern.  Adding more code to this
area to handle rare cases is not in the best interest of the entire Cygwin
community, since it adds complexity and reduces performance of Cygwin as a
whole.  So we shy away from making changes in this area unless there's a
definite need and an overall "win".

>>> seems the ability to mount a shadow volume as a dos drive is 
>>> sufficient for this kind of problem, isn't it?
>>>
>> I agree.
> 
> The dosdev.exe is no longer downloadable from Microsoft.

<http://blogs.msdn.com/adioltean/archive/2005/10/04/477164.aspx>

Sounds like if one couldn't find the prebuilt tool somewhere that it's
not that hard to write one.

-- 
Larry Hall                              http://www.rfk.com
RFK Partners, Inc.                      (508) 893-9779 - RFK Office
216 Dalton Rd.                          (508) 893-9889 - FAX
Holliston, MA 01746

_____________________________________________________________________

A: Yes.
 > Q: Are you sure?
 >> A: Because it reverses the logical flow of conversation.
 >>> Q: Why is top posting annoying in email?

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