bug#26815: [PATCH 3/3] vm: Support EFI boot in base image.

[Marius Bakke]

Hi Danny, thanks for the quick feedback!

Danny Milosavljevic <address@hidden> writes:

>> +      (system* "grub-mkstandalone" "-O" "x86_64-efi" "-o"
>> +               (string-append efi-directory "/EFI/BOOT/BOOTX64.EFI")
>> +               ;; Embed the contents of grubdisk.cfg.
>> +               (string-append "boot/grub/grub.cfg=" target
>> +                              "/tmp/grubdisk.cfg"))
>
> Check return value of system* ?

Good point. Will wrap it in an (unless (zero? ...) (error ...)).

>>                    (partitions (list (partition
>>                                       (size #$(- disk-image-size
>> -                                                (* 10 (expt 2 20))))
>> +                                                (* 50 (expt 2 20))))
>
> <https://wiki.archlinux.org/index.php/EFI_System_Partition> says:
>
>>According to a Microsoft note[2], the minimum size for the EFI System 
>>Partition (ESP) would be 100 MB, though this is not stated in the UEFI 
>>Specification. Note that for Advanced Format 4K Native drives 
>>(4-KB-per-sector) drives, the size is at least 256 MiB, because it is the 
>>minimum partition size of FAT32 drives (calculated as sector size (4KB) x 
>>65527 = 256 MiB), due to a limitation of the FAT32 file format. 

I have no idea what happens if you dd this image onto a 4k drive, only
tested with a 512B flash drive.

> Is this relevant for us?
>
> Also, <https://gist.github.com/Apsu/4108795> says that F32 is not required 
> for most UEFI firmwares. FAT12, FAT32 usually work.  But better be safe than 
> sorry, I guess.

If FAT32 may cause problems on some install media, perhaps it's better
to rely on the calculated allocation tables and "hope for the best". I
don't have a spare 4k drive to test with, though.

>> +                                     (size (* 40 (expt 2 20)))
>> +                                     (label "gnu-esp")
>> +                                     (file-system "vfat")
>
> Is it really vfat with long file names and everything? Or only FAT32 (with 
> short file names)?

Good catch. I think it should be FAT32 indeed, according to parted from
a prepared disk image. AFAIK parted does not actually use this flag for
anything, but it's good to be accurate.

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