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Date: Tue, 11 Jan 2011 15:51:07 +0100
From: Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
To: cygwin AT cygwin DOT com
Subject: Re: 1.7.7 on Windows 7: can't write to removable disk
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On Jan 10 10:40, tomas AT datasupporten DOT se wrote:
> Hello.
> I'm trying to write a disk image to a compact flash card with dd, but I
> get the error:
> "dd: writing to /dev/sdj: Permission denied"
> 
> Apart from the CF-card, I also tried a USB-stick with the same results.
> I'm logged in as administrator.

Please have a look into http://support.microsoft.com/kb/942448 first.

[...listening "De-Loused In The Comatorium" while waiting...]

Finished reading?  Ok.

That's quite a serious restriction starting with Vista.  If I destroy the
filesystem on one of my sd cards under Linux, I can then overwrite it
with dd under Cygwin.  However, if that dd call created a valid
filesystem on the sd card, the next write fails again.  For some reason
it does not help to unmount the filesystem on the drive via the "Disk
Management" MMC snap-in, despite the claim in the aforementioned
article.

The solution I just checked in to Cygwin is rather complicated, but
I really tested this a couple of hours now, and I didn't find any
other solution.

If you just want to write to a partition with a filesystem on it, say,
/dev/sdj1, then Cygwin just has to call DeviceIoControl(FSCTL_LOCK_VOLUME)
after opening the partition.

However, if you want to write to the entire device (/dev/sdj), then
Cygwin has to call DeviceIoControl(FSCTL_LOCK_VOLUME) for every single
volume on the disk!  This in turn only works if you don't have an
open handle on any file on anyu of the partitions.  Usually that should
be ok, and I didn't find any other solution for the problem.






Corinna

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

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