Re: [gentoo-user] SD memory card not erasing, even with dd.

[Mark Knecht]

On Wed, Dec 29, 2021 at 10:14 AM Dale <rdalek1967@×××××.com> wrote:
>
> Mark Knecht wrote:
> > <SNIP>
> >>
> >> So while rare, it's not just me.  ;-)  I've had cards fail by just plain
> >> refusing not to mount at all, mounting read only and such.  I've never
> >> had one to fail like this tho.  I guess if this was some sort of
> >> sensitive files, I'd have to put it in a shredder or take a pair of
> >> scissors to it.  LOL
> >>
> >> I ordered 6 new cards as replacements.  They came in yesterday.  Like I
> >> said, I wouldn't trust that card even if it started working again.  So,
> >> off to the trash the weird card goes.  Now I just have to wonder why dd
> >> and such didn't report problems.  :/
> >>
> >> Thanks to all for the info.  Interesting.
> >>
> >> Dale
> >>
> >> :-)  :-)
> >>
> > Actually, it's possible that it failed this way by design. What if the
> > card recognized that it's in some sort of a wear out condition and
> > just shut off new writes? One might see it as a failure but a
> > different view is as a potential opportunity to retrieve data before
> > it's gone.
> >
> > You might want to check out this tool:
> >
> > https://github.com/BertoldVdb/sdtool
> >
> > which advertises that it can view, set and reset the write protection
> > status of an SD card. Can't hurt if you're committed to throwing the
> > device in the trash can anyway. (Well, it could possibly hose your
> > system if you use it incorrectly or if it has bugs, but that's true
> > about all software, right?) ;-)
> >
> > But at least you could view the status of the card.
> >
> > Cheers,
> > Mark
> >
> >
>
>
> I downloaded sdtool but I don't have the required devices in /dev to use
> it.  In the readme it says not to use /dev/sd* but to use /dev/mmcblk*.
> It seems my card reader doesn't connect in a way for those to be
> created.  Would have been nice just to see what it does tho.  I still
> wouldn't trust it of course but being curious . . . .
>
> By the way, the card is a Sandisk which has a fairly good reputation.
> It is possible that it failed in the best way it could.  On the positive
> side, it did fail in a way that the files could be recovered.  That's
> always a good thing.  It's certainly better than failing with no way to
> get the files.
>
> Dale

OK, sorry it's not easy. I suppose now that you are using some sort of
USB bridge for reading your SD cards? That probably makes it show up
as a standard /dev/sd device like other USB drives.

I may be wrong, and it might not help you, but I think /dev/mmc is
enabled through the MMC_BLOCK option in the kernel, but even if you
enable that it may not change things if you have a USB bridge in the
way.

On Windows there are some partition editors that show the state of
these bits. I haven't looked for a standard Linux partition editor
that does that but it's probably out there somewhere if you go
hunting.

If you own a DSLR that supports whatever size SD card you are using
then it probably has a way to write protect cards while in the camera.
However if it's just a web cam that you're using it probably doesn't
but check the documentation.

Good luck,
Mark