Bug#922251: live-build: support syslinux-efi as (additional) bootloader
Hi,
Steve McIntyre wrote:
> Ady on the syslinux list has repeatedly argued against people
> suggesting that syslinux-efi will work for disk/CD hybrid media.
Ady emphasized that it does work with HDD. It was others and me who
pointed out that nobody ever could show success with CD-ROM on real iron.
For a short while Klaus Knopper convinced me that his complete mini-GNU/Linux
inside the EFI partition could solve the problem. But then appeared
negative reports on the german support forum and no positive ones.
It does work from USB stick but still not from DVD.
I wrote:
> > > Maybe Steve McIntyre can contribute an anecdote how he came to the
> > > decision in debian-cd to use GRUB2 for EFI
Andreas Heinlein wrote:
> > I am only taking a guess here, but maybe he just took over something
> > that was already done in Ubuntu. IIRC, Ubuntu 12.04 was the first distro
> > to support EFI booting
ubuntu-12.04-server-amd64.iso indeed has an EFI boot image in its El Torito
catalog. The MBR partition table does not have an entry of type 0xef, though.
So it was not treated by isohybrid option --uefi.
The boot image has the path "/boot/grub/efi.img", a FAT filesystem with
only one data file
/EFI/BOOT/BOOTX64.EFI
of which the end looks much like Debian's BOOTX64.EFI when it tries to hop
from EFI partition to ISO filesystem:
search --file --set=root /.disk/info
set prefix=($root)/boot/grub/x86_64-efi
source $prefix/grub.cfg
In debian-9.3.0-amd64-netinst.iso we can see:
search --file --set=root /.disk/info
set prefix=($root)/boot/grub
source $prefix/x86_64-efi/grub.cfg
(memdisk)/boot/grub
So possibly Colin Watson was the one who first used this GRUB gesture
within the EFI partition / boot image.
Steve McIntyre wrote:
> We already had working isohybrid media and I didn't want to drop that
> - in my opinion it's a very important feature.
> [...]
> In fact, one of the projects I've been trying to get to for a couple
> of years now is simplifying things by going the other way: using GRUB
> for everything and dropping syslinux on Debian media.
See results of program grub-mkrescue when grub-pc and grub-efi-ia32-bin or
grub-efi-amd64-bin are installed.
The main disadvantage of grub-mkrescue ISOs with EFI partition is the
lack of a mountable ISO partition. For exploring other layouts, i made a
man-in-the-middle script to be run as
grub-mkrescue --xorriso=frontend/grub-mkrescue-sed.sh ...
which manipulates the xorrisofs options before running the real xorriso.
I like the result of its default mode "mbr_only" and of mode "gpt_appended"
both with -partition_offset 16.
See
https://dev.lovelyhq.com/libburnia/libisoburn/raw/master/frontend/grub-mkrescue-sed.sh
Have a nice day :)
Thomas
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