Hi,
René Rebe wrote:
> In general I do not like messing with and duplicating packages, but
> given the i386 vintage legacy I might add an option (maybe even
> defaulting to yes) to build grub2 twice, once for vintage BIOS, and
> once for UEFI to allow creating such hybrid ISOs just for the sake
> of greatest backward compatibility.
At least the developer of GRUB2 intended to combine bootloaders for
PC-BIOS and EFI in one ISO (plus software for some HFS+ addicted Mac
firmware). So i doubt that duplication of GRUB2 is absolutely necessary
for that task.
On a Debian "amd64" system it suffices to install the GRUB2 binary package
for "pc" BIOS and the packages for "ia32" and "amd64" EFI. Then a run of
program grub-mkrescue produces an ISO with BIOS MBR and an EFI partition
with the start-up programs for both 32-bit and 64-bit Intel:
/efi
/efi/boot
/efi/boot/bootx64.efi
/efi/boot/bootia32.efi
/efi/boot/boot.efi
/NvVars
The data files have these byte counts:
132608 /efi/boot/bootx64.efi
95744 /efi/boot/bootia32.efi
95744 /efi/boot/boot.efi
1759 /NvVars
That's obviously not enough for a full-fledged GRUB2. So i assume this stuff
hops as soon as possible into the ISO and its 14 MB of GRUB2 files, where
it joins the code path after the MBR code and the El Torito boot image
program on BIOS. (I understand MBR code hops on the El Torito program which
then boots GRUB2.)
A look at the buildd log on "amd64"
https://buildd.debian.org/status/fetch.php?pkg=grub2&arch=amd64&ver=2.02%2Bdfsg1-11&stamp=1549836961&raw=0
gives the impression that all three needed binary Debian packages
grub-pc-bin grub-efi-ia32-bin grub-efi-amd64-bin
get built in one sweep.
(I myself am not into building bootloaders from source ... :))
Have a nice day :)
Thomas
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