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Re: GRUB doesn't recognize partitions on El-Torito image during EFI boot

From: Andrey Borzenkov
Subject: Re: GRUB doesn't recognize partitions on El-Torito image during EFI boot from CD
Date: Tue, 12 Nov 2013 12:40:44 +0400

On Tue, Nov 12, 2013 at 11:50 AM, Jacek Konieczny <address@hidden> wrote:
>> Could you give example how your image is seen in EFI shell?
> What EFI shell command should I use for that?

Using "map" would be a good start. You may use "map -b" to paginate.
Could you dump it to a file (use e.g. USB stick for it) and attach?

Assuming that fs2: refers to writable partition

map -v > map.out

>> It is not forbidden in any way; it is just that such CD will not be
>> directly bootable by EFI.
> The strange thing is – my previous 'prototype', with EFI shell and
> ELILO, was bootable. And GRUB loads too, it just cannot see the other
> files on the image.

Could you please describe step by step how you build your CD? Exact
command line(s) would be helpful.

> Would [grub] see the files on ESP when it was a proper EFI El-Torito image,
> as defined by the specs (unpartitioned, no emul)? If not, would it still
> be possible to chainload any other EFI application from this image?

Not without special arrangements. grub-mkrescue is using xorriso which
builds hybrid ISO image containing extra partition table(s) which
results in GRUB being able to access El-Torito boot image as normal
HDD partition.

> I wanted to be able to chain-load other EFI applications (like the EFI
> shell) from the GRUB, so I wanted files to be available via the EFI
> services – putting the files on the 'ESP' FAT file system made them
> available to any EFI application. I could not use the 'standard CD' this
> way, as EFI cannot read ISO9660 file system directly.

Makes sense. Hmm ... it sounds like extending grub-mkrescue to allow
adding arbitrary content to ESP will be the most easy solution in your

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