Date: Sun, 24 Feb 2019 08:10:42 +0100 From: Polytropon <freebsd@edvax.de> To: Andrea Venturoli <ml@netfence.it> Cc: "freebsd-questions@freebsd.org" <freebsd-questions@freebsd.org> Subject: Re: Recover failed SD card Message-ID: <20190224081042.d2211ba6.freebsd@edvax.de> In-Reply-To: <9cb7d703-bef2-8245-615c-4a471e858f32@netfence.it> References: <2341a9ac-42aa-737e-441f-b69cccc826c6@netfence.it> <20190224055321.14e7e462.freebsd@edvax.de> <9cb7d703-bef2-8245-615c-4a471e858f32@netfence.it>
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On Sun, 24 Feb 2019 07:53:28 +0100, Andrea Venturoli wrote: > On 2/24/19 5:53 AM, Polytropon wrote: > > > Did you ask your customer to recover from his backups? > > Yes, of course you did. :-) > > "Back-what"? :) "We don't need backups - we have RAID!" ;-) > > This will probably apply to _any_ copying tool. For things > > where dd fails, I often try dd_rescue and ddrescue > > As I said I tried "recoverdisk" (which is like ddrescue, but it's in base). It suffers from the same problem as probably all tools will: System reports "end of medium", and that's it. :-( > >> The card should hold pictures, so I could go ahead with photorec once I > >> got an even partial image. > > > > That is the recommended approach. Maybe you can already recover > > a fraction of the images stored on the card. > > Tried that before posting; it finds nothing. > To me it looks like I'm not even seeing the *first* 120 MB of the card. That's quite possible. I assume the card is supposed to carry a FAT file system. For technical purposes, that file system doesn't have to begin at the _start_ of the memory unit. The controller might use several MB for internal use, such as "re-mapping" and "accounting", and the actual "payload" begins later - in an area that the controller does no longer present to the media interface. It sometimes helps to use a file viewer to check what's in the obtained image, or a hex dump. If you get only 0x00 bytes, it's even "worse than garbage", because garbage could mean something (like "mutilated former file content"). > > There is another possibility, but it's actually _very_ hard > > to do, and it's not guaranteed to work: > > > > Obtain an identical SD card. It has to be "as identical as > > possible": same control unit, same memory unit, same firmware > > revision (yes, there's "a whole computer with hard- and software" > > on that thing!). Transplant the old memory chip to the new > > card, removing its new memory chip (empty) beforehand. Then > > try another identification. > > > > If it's a micro-SD card, don't inhale the chip. ;-) > > It's a micro-SD card and I'm not able to do this. As I auggested, this approach takes a _lot_ of work (and very specific tools & skills), and you might end up with the same result you're seeing now... -- Polytropon Magdeburg, Germany Happy FreeBSD user since 4.0 Andra moi ennepe, Mousa, ...
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