Obscure error: dd: failed to open: No medium found

I got this error message when I wanted to use dd  to copy a raw image to a MicroSD card. You will see this message if you have unmounted the card with a file manager like Nautilus. I guess it unmounts not fully, or in a special way.

The fix is easy:

Unmount the card via the terminal:

The dd  command will work now.

Another variant of this error can be seen when using bmaptool :