Re: sd .img partition loop support

Re: sd .img partition loop support

[Carl Karsten]

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

code to replicate:

mkdir boot
cd boot
mkdir img  lower  upper work merged

wget http://downloads.raspberrypi.org/raspios_lite_armhf/images/raspios_lite_armhf-2020-05-28/2020-05-27-raspios-buster-lite-armhf.zip
unzip 2020-05-27-raspios-buster-lite-armhf.zip

sudo kpartx -av 2020-05-27-raspios-buster-lite-armhf.img
sudo mount /dev/mapper/loop0p1 img

# this errors:
sudo mount -t overlay overlay -olowerdir=img,upperdir=upper,workdir=work
merged

# this does not
cp img/* lower/
sudo mount -t overlay overlay -olowerdir=lower,upperdir=upper,workdir=work
merged

https://github.com/CarlFK/pici/blob/main/test1.sh

The goal is to netboot a pi using the files from the .img with a few
changes, the root kernel parameter needs to be changed from local storage
to nfs:
# tftp/cmdline.txt
root=/dev/nfs nfsroot=10.21.0.1:/srv/nfs/rpi/root,vers=4.1,proto=tcp rw
ip=dhcp rootwait elevator=deadline consoleblank=0

I can copy all the files from the .img into a dir,  but I am thinking I
should be able to overlay a dir on top to manage the changes.

If you want to see my netboot pi server setup
https://github.com/CarlFK/pici/blob/main/setup.md

--
Carl K

Re: sd .img partition loop support

[Amir Goldstein]

On Mon, Oct 18, 2021 at 9:46 PM Carl Karsten <carl@nextdayvideo.com> 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.

Re: sd .img partition loop support

[Carl Karsten]

case insensitive, I can see how that would be a problem.

Now that I understand that I'll stop trying to make it work
thank you.

On Tue, Oct 19, 2021 at 1:53 AM Amir Goldstein <amir73il@gmail.com> wrote:
>
> On Mon, Oct 18, 2021 at 9:46 PM Carl Karsten <carl@nextdayvideo.com> 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.



-- 
Carl K