Re: Problems accessing USB Mass Storage

[Matthew Dharm <mdharm-kernel@one-eyed-alien.net>]

[-- Attachment #1: Type: text/plain, Size: 2015 bytes --]

The device may not actually have the beginning few sectors.  Use skip= to
try to read something from the middle of the media.

Yes, I actually have seen this before.  The firmware 'fakes' a partition
table on the first attempt to read one, but sector 0 really isn't there.

Matt

On Tue, Sep 17, 2002 at 02:50:32PM -0500, Thomas Dodd wrote:
> 
> Mark C. Wrote:
>  >>> [root@stimpy dev]# dd if=/dev/sda of=/dev/null bs=1k count=1
>  >>> dd: reading `/dev/sda': Input/output error
>  >>> 0+0 records in
>  >>> 0+0 records out
> 
> 
> Randy.Dunlap wrote:
> > On Tue, 17 Sep 2002, Jonathan Corbet wrote:
> > 
> > |
> > | You might try just using dd to copy your card to disk with an offset of 25
> > | sectors, and see of you can mount the resulting image.
> > 
> > This is a bit like what we (JE, David Brownell, and I) saw at
> > the USB plugfest in 1999.  We had a camera device that we
> > couldn't mount as a filesystem, but we could dd it.
> > When we did that and studied the dd-ed file, we could see a
> > FAT filesystem beginning after the first <N> blocks (but more than
> > 25 sectors IIRC -- more like after 50-100 KB, or maybe even more).
> 
> See the above form Mark's post. He tried to dd a 1K block
> and it failed. Granted, The first few blocks may need to be skipped,
> but right now he cannot even get the raw data out.
> 
> If we can get the data, we can use the loop device to mount it.
> 
> Any ideas to figure out the why the dd fails?
> 
> 	-Thomas
> 
> 
> -
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at  http://www.tux.org/lkml/

-- 
Matthew Dharm                              Home: mdharm-usb@one-eyed-alien.net 
Maintainer, Linux USB Mass Storage Driver

How would you like this tie wrapped around your hairy round head?
					-- Greg
User Friendly, 9/2/1998

[-- Attachment #2: Type: application/pgp-signature, Size: 232 bytes --]