[PATCH 0/2] Introduce grub hybrid bootloader and use it.

Ok, it turns out that grub-mkrescue can create a hybrid bootloader that works

with both EFI and non-EFI systems.

For that, the contents of lib/grub/i386-pc has to be available to

grub-mkrescue. Then it will build a hybrid bootloader.

I've successfully tested it using:

$ qemu-system-x86_64 -bios $(guix build ovmf)/share/firmware/ovmf_x64.bin -m 1G -enable-kvm -cdrom ZZ -serial stdio

$ qemu-system-x86_64 -bios $(guix build ovmf)/share/firmware/ovmf_x64.bin -m 1G -enable-kvm -hda ZZ -serial stdio

$ qemu-system-x86_64 -m 1G -enable-kvm -cdrom ZZ -serial stdio

$ qemu-system-x86_64 -m 1G -enable-kvm -hda ZZ -serial stdio

and the patch from bug# 27690.

Danny Milosavljevic (2):

bootloader: Add grub-hybrid-bootloader.

install: Use grub-hybrid-bootloader.

gnu/bootloader/grub.scm | 7 +++++++

gnu/packages/bootloaders.scm | 20 ++++++++++++++++++++

gnu/system/install.scm | 3 ++-

3 files changed, 29 insertions(+), 1 deletion(-)

---

gnu/bootloader/grub.scm | 7 +++++++

gnu/packages/bootloaders.scm | 20 ++++++++++++++++++++

2 files changed, 27 insertions(+)

---

gnu/system/install.scm | 3 ++-

1 file changed, 2 insertions(+), 1 deletion(-)

On Fri, 14 Jul 2017 20:59:54 +0200

Danny Milosavljevic <dannym@scratchpost.org> wrote:

and the patch from bug# 27689.

To clarify: I've tested both

$ guix system disk-image gnu/system/install.scm

and

$ guix system disk-image -t iso9660 gnu/system/install.scm

- both successfully.

Hi,

Danny Milosavljevic <dannym@scratchpost.org> skribis:

[...]

^

Lower-case please.

Is it really all it takes to make a GRUB that can do both BIOS and UEFI?

I wonder why GRUB upstream doesn’t do it by default. Do you think we

should discuss it with them?

If that works, we might just as well make it the new “grub” package and

remove “grub-efi”. Or is there any downside?

Thanks,

Ludo’.

Hi Ludo,

On Thu, 20 Jul 2017 10:39:14 +0200

ludo@gnu.org (Ludovic Courtès) wrote:

I think they do, in a sense. In many other distributions the directory is common - so if you install both grub-pc and grub-efi on your disk then grub will indeed use both (for grub-mkrescue).

I only use this feature for grub-mkrescue right now. I know that it is supported *there* in the sense that there's explicit "if" blocks checking for both platforms (by literals) in the same function, but not exclusively (i.e. "if (efi) A; if (non efi) B;" without "else"). See main() in util/grub-mkrescue.c in grub 2.02 (lines 667ff for EFI, lines 571ff for "PC"). The EFI stuff has "_EFI" in the preprocessor definitions, so search for that.

Note that main() supports a command line option for getting the source files for ONE SINGLE platform, but when you don't specify that option then it uses multiple platforms (the ones it can find).

For using multiple platforms as a regular bootloader I do NOT know whether that works or makes sense at all. Maybe it does, I just didn't test it (and can't usefully).

That's why there's the alternative implementation that wouldn't add a Guix bootloader for it.

I hope someone else knows. I don't have EFI hardware so I'm really the wrong person to find out that stuff. Well I could try reading the documentation / asking and hoping that it's all correct, but ... you know... paper is patient :)

util/grub-install.c seems to use a case anaylsis with exclusive cases for finding out EFI or not *shrugs*.

I read up on EFI some more. Apparently EFI can load files from FAT partitions and execute them.

There's the tool "grub-mkstandalone" which will put the GRUB bootloader into an executable file that you can then put on the FAT partition - which the EFI system will later boot from.

So I guess we already do all that's required for installed-hybrid support because Marius already added the grub-mkstandalone invocation to gnu/build/vm.scm - and we install the traditional grub-pc otherwise. So isn't it already hybrid? Can't be far off.

Maybe I contributed to the confusion, but my meddling with grub-efi and grub-hybrid is really just to have grub-mkrescue build a hybrid ISO, nothing else. I don't use grub-install at all there (and I don't use grub-mkstandalone either).

I think the best way forward for the ISO image to do it like that:

That's it. I don't think we have to fiddle with the regular Guix bootloaders or even with the existing bootloader packages at all.

close 27695