Bug#731709: grub-efi UEFI support based on debian-cd work complete (repos)
El 18/01/16 a las 14:00, Thomas Schmitt escribió:
So any bootloader is made primary by leaving out -eltorito-alt-boot.
There is no "primary" or "secondary" on the level of boot images
and loaders. (Of course you may call them this way in your project.)
There are first, second, third ... El Torito boot images or MBR, GPT,
APM partition entries.
The sequence is just needed because not all can be first in the list.
The boot firmware inspects the medium for its known lures,
picks a tasty one, and follows it to the boot loader or kernel.
So, yes, I'm the one who invented the term primary for live-build.
Actually, it was not meant for alt El Torito boot entries (or non first
entries as you clarify).
The first idea was to add both syslinux and grub-pc in the same image.
Grub-pc would be the one installed to be boot but syslinux files would
be there for Multi-USB tools to know how to understand the iso and put
it into an USB.
The Grub-pc bits were thought in first place for Super Grub2 Disk (which
it is Grub2 cfg files mainly).
(Now that I think of the current 'check primary bootloader role'
functions unable me to perform that Super Grub2 Disk Debian Live that
included the Syslinux bits too. Anyways I'll find a workaround for that
in the future. Not a priority right now.)
Now primary means: "First lure" and secondary means "Second lure" by
your definition.
Currently there's no way to stop you from requesting:
--bootloaders="syslinux,grub-efi,syslinux-efi"
Given the way that both grub-efi and syslinux-efi use:
/efi/boot/bootia32.efi
and
/efi/boot/bootx64.efi
the last one to be run would overwrite the first one efi files.
You can probably use only one legacy bootloader but syslinux-efi and
grub-efi use different files so it should be possible to install both.
I am not sure how selecting one or the other would work, though.
You can offer several EL Torito boot images for BIOS, indeed.
It will depend on your BIOS what it does in this case.
Interesting.
There can be only one MBR, though. So you would have to hop
by MBR x86 code to a standalone program which chooses among
the BIOS suitable El Torito boot images.
With EFI it makes few sense to offer more than one El Torito
boot image or EFI System Partition. UEFI 2.4 rather prescribes to
handle all alternatives inside the FAT filesystem. The firmware
will start the \EFI\BOOT\BOOT*.EFI binary which it deems suitable
for its processor type.
This binary is quite free in its further proceedings.
So... How would you go about for a:
--bootloaders="syslinux,grub-efi,syslinux-efi"
to make sense if, as I have stated earlier (although I might have missed
something there) they would overwrite their /efi/boot/boot*efi files ?
adrian15
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