Re: [gentoo-user] Corrupt USB pen drive

[Mick]

On Thursday 17 May 2007 23:27, Etaoin Shrdlu wrote:
> On Thursday 17 May 2007 18:04, Mick wrote:
> > > Thanks Dan, as I said above I tried to extract the MBR out of it by
> > > running:
> > >
> > > dd if=/dev/sda of=/tmp/r1 bs=512
> > >
> > > But couldn't access it whatsoever.
> >
> > Oops! I could access it, but of course I had to try it as root!
> > Right, I've got it on my hard drive now, but still cannot mount it:
> > ==================================
> > # mount -t vfat /dev/loop2 /tmp/r1
> > mount: wrong fs type, bad option, bad superblock on /dev/loop2,
> >        missing codepage or other error
> >        In some cases useful info is found in syslog - try
> >        dmesg | tail  or so
> > ==================================
>
> IIRC, that is not the right syntax for mounting a loopback filesystem.
> If /tmp/r1 is the file containing the filesystem, try
>
> mount -o loop /tmp/r1 /mnt/somewhere
>
> and make sure you have support for loopback devices in your kernel.

Thanks for all the suggestions.  I tried the correct mount loopback command 
on /dev/loop2 and I'm getting this error that mentions /dev/loop0 (how does 
this work?):
======================================
# mount -t vfat -o loop /dev/loop2 /tmp/r1
mount: wrong fs type, bad option, bad superblock on /dev/loop0,
       missing codepage or other error
       In some cases useful info is found in syslog - try
       dmesg | tail  or so
======================================

Anyway, regarding a previous comment by Dan I tried accessing /dev/sda1 but it 
complained that the device does not exist, unlike /dev/sda which appears to 
be there.  I have a couple of USB sticks that also have no partition table 
(they are like floppies) and I access these as /dev/sda.  When I look at 
their few first bytes they look like this:
======================================
000000 eb 3c 90 4d 53 44 4f 53 35 2e 30 00 02 20 01 00
000010 02 00 02 00 00 f8 f4 00 3f 00 ff 00 00 00 00 00
000020 00 7a 1e 00 00 00 29 96 9d 62 60 4e 4f 20 4e 41
000030 4d 45 20 20 20 20 46 41 54 31 36 20 20 20 33 c9
======================================

On the other hand the corrupt disk looks like this:
======================================
000000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
*
0001f0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 55 aa
000200 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
*
020000 01 df 02 df 03 df 04 df 05 df 06 df 07 df 08 df
020010 09 df 0a df 0b df 0c df 0d df 0e df 0f df 10 df
020020 11 df 12 df 13 df 14 df 15 df 16 df 17 df 18 df
020030 19 df 1a df 1b df 1c df 1d df 1e df 1f df 20 df
020040 21 df 22 df 23 df 24 df 25 df 26 df 27 df 28 df
020050 29 df 2a df 2b df 2c df ff ff 2e df 2f df 30 df
======================================
which makes me think that it has different partitions on it, but the partition 
table is corrupted.  Otherwise, I guess I would be able to access it 
through /dev/sda1.  So, the question now is how do I recreate/reconstruct it?  
I'll surely need some help with it because all this hex means nothing to me.

-- 
Regards,
Mick