RE: Create legacy bios/uefi dual boot usb stick

[John Frankish]

>>>>>> ..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.
>>>
>> Thanks, this works:
>> 
>>$ sudo fdisk /dev/sdc
>> ...
>>    Device Boot      Start         End      Blocks  Id System
>> /dev/sdc1   *           2         128     1020127+ ef EFI (FAT-12/16/32)
>>
>Could you do me a favor and test if it also still works without any active 
>partition?
>
Yes, it works without an active partition

>> /dev/sdc2             129        3797    29471242+ 83 Linux
>> ...
>> $ sudo x86_64-grub-install --target=x86_64-efi 
>> --boot-directory=/mnt/sdc1/EFI/BOOT --efi-directory=/mnt/sdc1 --removable 
>> Installation finished. No error reported.
>> 
>> $ sudo x86_64-grub-install --target=i386-pc 
>> --boot-directory=/mnt/sdc1/EFI/BOOT /dev/sdc Installation finished. No error 
>> reported.
>> 
>>
> Hmm ... are sizes above in cylinders?
>
Yes, 129 and 3797 are sizes in cylinders.

>> ..and both legacy-bios and uefi boot work.
>> 
Affirmative :)