Restoring from BTRFS SD card

[nickfx]

So it seems my SD card had some failures, not entirely sure why. The result is that while XBIAN boots, neither internet nor USBs work, so I can't access it at all. I'd really like to save the /etc folder, as it has quite a lot of settings.

I've mounted the SD in my Ubuntu 18.10, and can copy most files. However, with quite a few important ones, I get an input-output error.

I tried

Code:

btrfs restore -s -i -o /dev/mmcblk0p2 /home/nick/restored

.

This restored several snapshots and with all files except those damaged (those files are length 0). Moreover, I get a repeated errors such as this on:

Code:

Error copying data for /home/nick/restored/root/@/var/lib/dpkg/alternatives/display-im6
ERROR: zstd decompress failed Unknown frame descriptor

, that I can't seem to find any help for.

Any idea whether this is related to the LZ4 compression, and whether I can restore these files somehow?

Nick