[syslinux] Even more (U)EFI questions

Mattias Schlenker ms at mattiasschlenker.de
Wed Jan 22 06:47:56 PST 2014


Am 22.01.2014 15:25, schrieb Dean Graff:
> I have not looked into it all that much. But seems that UEFI basically
> allows booting without a bootloader.

It does. In fact I usually use preloader.efi (with keytool.efi and 
hashtool.efi for secure boot) and gummiboot.x64.efi to boot EFI stub 
kernels on x86_64. But until short time a go I had no idea someone would 
try to sell 32 bit UEFI on computers with 64 bit processors.

> I am looking forward to making a little HOWTO, for this subject and also
> for using `mkdiskimage' with syslinux and vfat ( which i had a lot of fun
> playing with last night).

On most UEFI implementations EFI boot from USB works from a thumb drive 
that has a single FAT partition and that even might be bootable on BIOS. 
Just /efi/boot/bootx64.efi has to be present, EFI reads the FAT filesystem.

However, not every UEFI implementation likes this setup. For those 
machines "my distribution" LessLinux partitions the thumb drive with a 
GPT partition table and a legacy boot partition and an UEFI boot 
partition (and several data partitions). Together with gptmbr.bin the 
thumb drive is bootable on BIOS and UEFI. A big advantage of this layout 
is that it can also be used on hard disks that can be booted either via 
eSATA or USB-SATA adapter.

If requested I'll write a tutorial on this kind of layout.

But so far I have absolutely no experience with 32 bit EFI. In the past 
I could simply declare Macs with 32 bit UEFI as "unsupported" or "might 
work - untested", but with clover trail/bay trail my customers will ask 
for 32 bit UEFI support.

Regards,
Mattias


-- 
Mattias Schlenker - Redaktion + EDV-Beratung + Linux-CD/DVD-Konzepte
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