Re: Offset into block file for mounting?

From: Martin Nybo Andersen
Date: Mon Jan 03 2011 - 09:35:25 EST

Hi Tom,

On Mon, 3 Jan 2011, Tom Watson wrote:


I recently got a "floppy drive emulator" that uses an USB thumb drive to
emulate floppy images to be used as a floppy drive. In trying out the
software (it is a bit cryptic), I found that this model stores the
floppy images consecutively on said thumb drive (with some padding to
make the drives on 1.5 Mbyte borders on the thumb drive. When plugging
in the thumb drive, the 'vfat' module just mounts the first image (as I
expect). What I would like to do is mount some of the other images that
exist (I dumped out the raw thumb drive). I believe that a simple way
to do this is to add an offset to the vfat mount, so that the accesses
begin at (as in my example) 0x180000 (and multiples thereof) from the
start of the physical drive.

Is there any way to add such an offset?
Would it be useful in any other file systems?

mount diskimage /dir -t vfat -o loop,offset=xxx,sizelimit=yyy

mount will then forward the offset and sizelimit options to losetup which sets up a loop device before mounting.

Have a look at the man-pages for mount and losetup. :-)

Hope that helps.

Tom Watson <tsw@xxxxxxxxxx>
I'm at home now

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