Re: Chainloading an MS Windows installer DVD

[Philip Couling]

Really I've been as precise as I can and given everything I've seen.  It
was actually the minimalist output that prompted me to come ask. Yes that
was all of the output.

I'll investigate further if that points to an error on my part. I assume
setting root=... is enough to set the device path. But to be clear: no, the
only output from the chainloader command was "/EndEntire".

I didn't realise distributions had customised grub in that way. I'm using
the Ubuntu (22.04) release. If you think that may be a problem I can retry
with upstream version.

If you know of a way to get more debug info out of the chainloader or
command boot command because I was really hoping for more than "Unknown
Error" too!

On Mon, 23 Oct 2023 at 08:25, Andrei Borzenkov <arvidjaar@gmail.com> wrote:

> On Thu, Oct 19, 2023 at 12:36 PM Philip Couling <couling@gmail.com> wrote:
> >
> > Hi
> >
> > Is there any reason why I can't chainload an MS Windows Installer (on
> > USB)?  Currently when I try this I get "UnknownError" when I type "boot"
> at
> > the grub command line.
> >
> > The MS Windows ISOs are a bit weird: found here:
> > https://www.microsoft.com/en-gb/software-download/windows10ISO
> >
> > They are not partitioned and have a UDF filesystem instead of ISO 9660 or
> > FAT32. So my hardware cannot directly boot this.  But I was assuming that
> > all I would need to do would be ask grub to chainload the ISO as it has a
> > UDF driver.
> >
> > I can read the Windows Boot media after I "insmod udf" and then
> > "chainloader /efi/boot/bootx64.efi" which results in the output
> > "/EndEntire".
>
> Is it really *all* that is printed? Because grub should print the
> device path and it sounds like it is empty? Always provide complete
> and accurate information, not some random part of it. At the very
> least there should be "file path: " somewhere before "/EndEntire".
>
> > But when I then type "boot" I get "UnknownError".
> >
>
> grub should really print the EFI error in this case to help in
> troubleshooting such issues.
>
> > Has anyone experienced this? Any ideas about what isn't working? I freely
>
> Assuming you are using the current upstream code (because in the past
> EFI chainloader was heavily patched by distributions) grub reads the
> content of EFI binary in memory, creates an instance of loaded image
> from it and then calls EFI start image function. I would refrain from
> guessing what could have gone wrong until you provide more precise
> information.
>
> > admit it could be a Microsoft weirdness that requires their input, I just
> > wanted to exhaust options here first.
> >
> > Thanks
>