On Mon, Oct 18, 2021 at 9:46 PM Carl Karsten <carl@xxxxxxxxxxxxxxxx> wrote: > > I'm trying to overlay an empty upper dir onto a fat/loop/img fs and getting: > > juser@negk:~/boot$ sudo mount -o ro /dev/mapper/loop0p1 img > juser@negk:~/boot$ sudo mount -t overlay overlay > -olowerdir=img,upperdir=upper,workdir=work merged > mount: /home/juser/boot/merged: wrong fs type, bad option, bad superblock > on overlay, missing codepage or helper program, or other error. > > [ 2449.670177] overlayfs: filesystem on 'lower' not supported > fat was never supported as lower or upper layer AFAIK, see: https://lore.kernel.org/linux-unionfs/2527352.xHhNOModH5@nerdopolis/ This is due to the case insensitive and special name encoding of fat. It is not unfixable, but it was never a priority for anyone to fix it. I suppose it would be easier for you to copy the image to another filesystem before constructing the overlay. Thanks, Amir.
