Re: Cannot boot from dual bios/uefi boot CD

[Andrei Borzenkov]

On Thu, Dec 24, 2015 at 3:47 PM, John Frankish
<address@hidden> wrote:
>>>>>> Yes, I have reproduced it now. The reason is, grub-mkrescue adds
>>>>>> commands to load all partition drivers to embedded config and if
>>>>>> some of them (or may be the last one) is missing it sets error 
>>>>>> indication.
>>>>>> Later grub misinterprets this error indication when loading normal
>>>>>> module; loading it manually succeeds (insmod normal; normal).
>>>>> If I add code to reset error indication before trying to load normal it 
>>>>> works.
>>>>>>
>>>>>> So it still works for your purposes, albeit with manual workaround
>>>>>> :)
>>>>>
>>>>> Indeed - but I could hardly make it available to others like this :)
>>>>>
>>>>>
>>>> For the record - it should be fixed in current GIT.
>>>> If you have chance to retest it would be good.
>>>>
>>> Thanks for the update.
>>>
>>> The dual boot cd/iso I was working on used isolinux for legacy boot and 
>>> grub2 for uefi boot.
>>>
>>> What I would like to do is to use grub2 for both legacy and uefi boot by 
>>> embedding the various
>>> grub modules as before (which would also test your fix).
>>>
>>> Is this (grub2 dual boot cd/iso) possible?
>>
>> Of course. This is what grub-mkrescue does.
>>
>>> Is there an explanation somewhere?
>>>
>>
>> I though we have been there already last time, not?
>
> OK, I understand that what is now fixed in git is that if I use grub-mkrescue 
> to make an iso and then remove the unneeded modules from i386-pc/ and 
> x86_64_efi/, the iso will still boot - is that correct?
>

Loosely speaking - yes.

> I can see that grub-mkrescue makes an efi.img that contains 347kb of 
> bootx64.efi, but is there a way to know which modules this contains?
>

part_gpt, part_msdos, part_apple, iso9660 and whatever dependencies
they pull in.

> Similarly, there must be an equivalent legacy-bios img file 
> (cdboot.img/core.img?) , but where is it in the iso, is it accessible and 
> which modules does it contain?
>

/boot/grub/i386-pc/eltorito.img on ISO image. Same modules + biosdisk
- part_apple.

> ..the reason I ask this is so I know which modules I can remove from i386-pc/ 
> and x86_64_efi/ - I could always make a new efi.img, but I don't know if it 
> is possible to make a new cdboot.img/core.img?

Not sure I follow again. grub-mkrescue will of course re-create it as needed.

You can get detailed list of what it does using --verbose option to
grub-mkrescue.

>
> Happy Christmas :)
>

Same to you! Although strictly speaking we have two weeks until
Christmas here ... :p