2002-09-17 22:13:41

by Thomas Dodd

[permalink] [raw]
Subject: Re: [Linux-usb-users] Re: Problems accessing USB Mass Storage



Rogier Wolff wrote:
> On Tue, Sep 17, 2002 at 10:13:13PM +0100, Mark C wrote:

> 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.

Fair enough. I, and the others though it did a seek.


> Try the following program:
<snip>
> 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.....

Where did the sector 200 come from?
Something in the dmesg output from before?
(I don't really grok SCSI or USB at that level :( )

> Cheap basterds.

Agree:)

-Thomas


2002-09-17 22:21:42

by Randy.Dunlap

[permalink] [raw]
Subject: Re: [Linux-usb-users] Re: Problems accessing USB Mass Storage

On Tue, 17 Sep 2002, Thomas Dodd wrote:

| Rogier Wolff wrote:
| > On Tue, Sep 17, 2002 at 10:13:13PM +0100, Mark C wrote:
|
| > 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.
|
| Fair enough. I, and the others though it did a seek.
|
| > Try the following program:
| <snip>
| > 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.....
|
| Where did the sector 200 come from?
| Something in the dmesg output from before?
| (I don't really grok SCSI or USB at that level :( )

I think that's part of the hypothesis, but if we can read the
first sector, it should be trivial to decode the partition table,
if it's a typical DOS/Windows/PC-type partition table.

If someone can read the first sector, I'll be glad to decode it;
just send it.

--
~Randy
"Linux is not a research project. Never was, never will be."
-- Linus, 2002-09-02