Re: Create legacy bios/uefi dual boot usb stick

[Andrei Borzenkov]

On Wed, Dec 23, 2015 at 3:09 PM, John Frankish
<address@hidden> wrote:
>
>> > ..there is no error message, uefi boot works fine, but legacy bios
>> > boot fails with an "invalid partition table" error
>> >
>> Where this error comes from? I do not see this string in GRUB sources
>> and it really does not care; it would stop in rescue mode then
>>
> I guess the error message comes from the machine's bios - the legacy boot 
> doesn't get as far as starting grub.
>
>> Recently someone reported problem with booting rescue image on legacy BIOS
>>  - it would refuse to consider medium bootable unless medium has
>> *msdos* partition table with active partition. This sounds like it could be 
>> the reason.
>>
> I'm not sure I understand - I thought the "EF02 BIOS boot partition" achieved 
> this aim?
>

BIOS boot is still GPT partition.

> If not, what would the gpt partition table above look like including an 
> *msdos* partition table with active partition?
>

You can start with creating standard MSDOS partition table. EFI should
be able to boot from it as well; and there is MSDOS partition type
reserved for ESP (0xef). Install grub in MBR. If booting still fails,
try to mark second partition bootable.