[syslinux] pxelinux and UEFI laptops - broke everything which had worked with BIOS/pxelinux.0

Victor Sudakov vas at sibptus.ru
Sat Dec 19 21:16:56 PST 2020

Ady via Syslinux wrote:
> A minimal search and reading would be enough to understand the problem.

My primary reading has been https://wiki.syslinux.org/wiki/index.php?title=PXELINUX

It has a small and useful section on UEFI but does not cover any of the
caveats we discuss below.

> > A typical EFIx64/pxelinux.cfg/default entry looks like this:
> > 
> > label memtest2
> >   menu label ^8. Memtest86+ v4.20
> >   kernel memtest420
> Memtest86+ v4.20 is for BIOS (and/or CSM) only, not for UEFI.

All right, I have just extracted the "memtest" kernel from the
https://www.memtest86.com/download.htm (memtest86-usb-9.0-beta-1.zip
distribution) which is UEFI-only. 

The result? Still, an instant reboot after "memdisk" is downloaded by
the PXE client.

And generally, do you mean to say that if some "kernel" was compiled without
UEFI in mind, syslinux.efi will not be able to boot it? This cuts off about
1/2 of my collection of engineering utilites.

> > label memtest3
> >  menu label ^7. Memtest-86 v4.3
> >  kernel memdisk
> >  append initrd=memtest86-floppy.img
> memdisk (as of version 6.04-pre1) is for BIOS (and/or CSM) only, not 
> for UEFI.

Wait, do you mean to say that memdisk from the syslinux distribution (I'm
testing syslinux-6.03 now) is useless with syslinux.efi from the same

This cuts off about the other 1/2 of my collection of utilites in the form
of floppy and ISO images.

> So, for UEFI boot, you need tools/kernels that are compatible with 

It is sad news (especially about the memdisk "kernel" which is part of the
syslinux distribution). Probably it would be a good idea to mention this in
the PXELINUX wiki page (in a bold red font for people like me).

At present it looks like I'll be looking for some alternative to syslinux.

> BTW, some EFI binaries are compatible with Secure Boot, and some are 
> not - syslinux.efi 6.04-pre1 is/are in the latter group.

There is at least one good news: I don't use Secure Boot.

Therefore syslinux.efi 6.03 boots fine on the UEFI-only laptops, draws the
blue menu and can boot the OS from the local disk (which is the only thing
which it can do). Bummer!

Victor Sudakov,  VAS4-RIPE, VAS47-RIPN
2:5005/49 at fidonet http://vas.tomsk.ru/

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