Mailinglist Archive: opensuse-factory (914 mails)

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Re: [opensuse-factory] Can't mount fat32 USB sticks anymore
  • From: Pierre de Villemereuil <flyos@xxxxxxxxxx>
  • Date: Sun, 25 Jun 2017 14:07:32 +1200
  • Message-id: <2023987.oALC2YJuaF@flyosflip>
Hi Carlos,

You were right, I did a big purge of a non-working USB stick using:
dd if=/dev/zero of=/dev/sdb bs=1M
dd if=/dev/zero of=/dev/sdb bs=446 count=1

(I'm sure one of these two is not needed, but I just wanted to make sure I
erased all partition data and the MBR)

Then creating a partition table and FAT32 partition restores the ability to
mount the USB stick!

I'm still puzzled as to:
- why this suddenly became a problem?
- why the key was working on the Linux Mint laptop?

I'm leaning toward a kernel update as the culprit, but this far above my skill
set to investigate...

Thanks for your help!

Cheers,
Pierre.

Le dimanche 25 juin 2017, 13:10:27 NZST Carlos E. R. a écrit :
On 2017-06-25 02:55, Pierre de Villemereuil wrote:
Oh, yeah, forgot to say, I tested different USB keys (all FAT32), they all
behave the same. All where used to host a live USB though... Another thing
is that they all work on another laptop with Linux Mint installed.

I managed to find a key that worked. The main difference of that key is
that it's a USB3-compatible one. It might that it was erased "better" than
the others after hosting a live USB, though I don't remember doing anything
different with it.

If it helps, Gparted recognise the partition of the USB sticks not working
as "iso9660" (I'm positive they're in fat32 and they are recognised as
fat32 on the other laptop), while the USB stick that is working is actually
recognised as a fat32.

Ah, then, that hitches it.


I'm clueless about what's happening... Thanks for your help!

The issue is that the areas that the system uses to recognize an ISO
image as an ISO image were not deleted or overwritten because they
occupy different sectors than those overwritten when the media was
formatted again as FAT. Remember that nowdays "format" means "fast
format", ie, only the structures needed for FAT (in this case) are
initialized, the rest are left intact. This usually means the data
sectors are intact, but in this case the metadata for the iso and the
fat do not use the same sectors so were not erased.

Very probably the information is in the partition table or following few
sectors.

I would backup each stick, erase a bunch of raw sectors at the start of
each stick - say 200 MB - and then partition-format as FAT again, and
finally reload files from backup.

Maybe someone remembers the thread where this thing happened some years
ago and what steps were taken to investigate; might be mail list or forum.

--
Cheers / Saludos,

Carlos E. R.
(from 42.2 x86_64 "Malachite" at Telcontar)


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