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it seems I had a bad idea yesterday. I got a new SD card for my Fairphone 3+ (running Fairphone OS/Android 10). There was already an SD card inserted I assumed not to be in use. So I turned off the phone, exchanged the cards, booted the device and when asked to extend the phones memory I confirmed that.

Now I have two problems:

  • I'm missing a couple of pictures.

    I wondered if these were on the old (luckily only 8GB) SD card and recognized that there are two partitions on it: android_meta and android_expand. As far as I learned, this means the SD card also was used as phone memory extension and thus encrypted. And the posts on Android Enthusiasts read like the phone has only one encryption key and won't recognize the old SD card anymore.

  • The Camera can't save pictures anymore.

    Whenever I take a photo I'm able to immediately open it by tapping its preview. Then I see a black picture, I'm told its size is 0 bytes and it's located in /storage/emulated/0/DCIM/Camera. Using the cx File Explorer I'm able to open that directory, but it's empty. And I'm not able to create files there.

    Using the ADB shell I was able to ls -la /storage the directory and got this:

    total 7
drwxr-xr-x  4 root root        80 2020-12-21 06:52 .
drwxr-xr-x 21 root root      4096 2009-01-01 01:00 ..
drwx--x--x  4 root sdcard_rw 3488 2021-01-12 21:38 emulated
drwxr-xr-x  2 root root        60 1970-01-01 01:00 self

    So only root is able to write in /storage/emulated. BTW: "total 7"?

Currently I'm trying to find out the following:

  • is it possible to decrypt the pictures on the old SD card? Would be fine for me if it meant some work :)
  • is the encryption key for the old SD card still on the phone or could I reset the phone without making things worse regarding the old encrypted SD card?
  • is the phone in a bad state?
    • The Camera doesn't save pictures.
    • All other apps seem to work as expected.
    • The SD card overview in the Memory settings tell me there are apps on the new SD card (about 5GB). But when I tap the App category to get all apps listed, the list is empty.
    • When I eject the SD card, a couple of apps start, but only show a blank canvas.
  • if the phone is in a bad state: could this easily be fixed? If yes, how?

Would be great to get some hints. Thank you very much in advance.

Newlukai
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  • Sorry, forgot to link accounts before asking. My bad. But I got the Camera working again by "formatting the card as mobile" (translated from German, I hope it matches somehow). There was no new data on the SD card, so it seemed reasonable to me. And it worked (this time I saved the remaining pictures :) ). – Newlukai Jan 13 '21 at 13:41
  • Would it be possible now to create an image from the old SD card (using dd on Linux), let the phone use it as memory extension again, remove the card and restore the image (android_meta and android_expand) and then trick the phone to use this card again with old data? Seems feasible to me if the encryption mechanism is not based on some random data but only on some static card and device information. – Newlukai Jan 13 '21 at 13:41
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    Why not simply give it a try – what can you lose? Either the adoptable storage is still recognized (in which case you can recover all data from it) or not (then you will have no chance anyway). As long as you did not trigger "forget this card", there's still a chance. – Izzy Jan 13 '21 at 17:27
  • as Izzy said, swap the cards back! do not factory reset – alecxs Jan 13 '21 at 19:24
  • Thanks. Unfortunately, it did not work. After I restored the old image on a newly created adoptable storage (same card), the phone tells me the storage was broken :( So I assume there is some dynamic information in the encryption key. – Newlukai Jan 14 '21 at 06:44
  • you must not re-create adoptable-storage that will of course force new encryption key. instead clone 1:1 disk image of the entire old (broken?) MicroSD Card (including all partitions) with gddrescue and write it back to another (working) MicroSD Card with dd. encryption key for old SD card is still on phone, just insert, boot and check from df or mount – alecxs Jan 14 '21 at 13:49
  • Thanks for that hint and the link. You said the encryption key for the old SD card is still on the phone. I'm wondering if this holds true: as I told in the initial post, the old card (adoptable storage) got inaccessible after I inserted the new card and turned that new card into an adoptable storage. If the phone kept the encryption key of the old card I would give the instruction in the referenced post a try. – Newlukai Jan 14 '21 at 14:46

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