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SubjectRe: [Linux-usb-users] Re: Problems accessing USB Mass Storage
On Tue, Sep 17, 2002 at 10:13:13PM +0100, Mark C wrote:
> On Tue, 2002-09-17 at 21:13, Thomas Dodd wrote:
>
> >
> > Give that a go Mark.
> >
> > Try a few values like 25, 50, 75, and 100. with bs=1k and
> > unset (default 512 byte).
>
> If I'm reading this correctly, I have been trying:
>
> [root@stimpy mark]# dd if=/dev/sda of=tmp/tmp.img skip=50 \
> bs=1k dd: reading `/dev/sda': Input/output error
> 0+0 records in
> 0+0 records out

Guys,

When dd is told to skip a certain number of input blocks it doesn't
seek past them, but reads them and then discards them. Thus if you're
not supposed to read sectors 1-100 then this will not work.

Try the following program:


/* seek.c (C) R.E.Wolff@harddisk-recovery.nl */
/*
gcc -Wall -O2 seek.c -o seek
*/
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <sys/types.h>

#ifndef O_LARGEFILE
#define O_LARGEFILE 0100000
#endif
long long lseek64 (int fd, long long offset, int whence);

int main (int argc,char **argv)
{
long long off;
long long tt;
if(argc < 2)
exit(0); /* don't seek at all */
if (strncmp (argv[1],"0x",2) )
sscanf (argv[1],"%Ld",&off);
else
sscanf (argv[1],"%Lx",&off);
if (argc > 3) {
if (strncmp (argv[3],"0x",2) )
sscanf (argv[3],"%Ld",&tt);
else
sscanf (argv[3],"%Lx",&tt);
if (argv[2][0] == '+')
off += tt;
else
off -= tt;
}
errno = 0;
if ((lseek64 (0,off,SEEK_CUR) < 0) &&
(errno != 0))
perror ("seek");
exit (0);
}

with the command:

dd if=/dev/sda of=firstpart

(Get the partition table)

(seek 0x100000;dd of=secondpart) < /dev/sda
Get everything beyond 1Mb. If this works, then we have to figure out
how low we can make the "0x100000" number to get all of the data.
Hypothesis: The partition table specifies that the data starts
on sector 200, and they didn't implement sectors 1-199.....
Cheap basterds.
(My memory stick is just over 128 * 10^6 bytes, and not even
close to 128 * 2^20 bytes....)
Roger.

--
** R.E.Wolff@BitWizard.nl ** http://www.BitWizard.nl/ ** +31-15-2600998 **
*-- BitWizard writes Linux device drivers for any device you may have! --*
* The Worlds Ecosystem is a stable system. Stable systems may experience *
* excursions from the stable situation. We are currenly in such an *
* excursion: The stable situation does not include humans. ***************
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