Testing for fake SD Cards
Install f3
sudo apt install f3
On my system, it’s run like this
sudo f3probe --destructive --time-ops /dev/mmcblk0
F3 probe 7.2
Copyright (C) 2010 Digirati Internet LTDA.
This is free software; see the source for copying conditions.
WARNING: Probing normally takes from a few seconds to 15 minutes, but
it can take longer. Please be patient.
Good news: The device `/dev/mmcblk0' is the real thing
Device geometry:
*Usable* size: 59.69 GB (125173760 blocks)
Announced size: 59.69 GB (125173760 blocks)
Module: 64.00 GB (2^36 Bytes)
Approximate cache size: 0.00 Byte (0 blocks), need-reset=no
Physical block size: 512.00 Byte (2^9 Bytes)
Probe time: 1'16"
Operation: total time / count = avg time
Read: 246.3ms / 4816 = 51us
Write: 1'15" / 4192321 = 17us
Reset: 0us / 1 = 0us
https://superuser.com/questions/631633/how-to-tell-if-you-have-a-fake-sd-card