[syslinux] Booting legacy Linux kernel in EFI mode

[Gene Cumm]

On Sun, Sep 22, 2013 at 3:09 PM, Celelibi <celelibi at gmail.com> wrote:
> Hello,
>
> My question is quite straightforward, still I couldn't find an anwser
> on the interweb.
> Is it possible to boot the Linux kernels I used to boot in legacy
> mode, but now in EFI mode?

I believe unless the kernel specifically supports EFI boot, it can not
be booted.

> I mean, I would like to keep all my PXE settings with my menus and
> kernels and stuff, but now boot them in PXE-EFI mode.
>
> I've been able to boot on syslinux.efi and keep my config files, but
> when I try to boot on a linux kernel, I get an error like "no such
> file or directory" while I see it download the file from the tftp.
>
> Is this a bug in syslinux?
> Or is there a deep incompatibility?
> And (a bit out of scope) if I get my old kernel to boot in EFI mode,
> will the driver efivars have access to the EFI variables? Or does the
> kernel need to be recompiled specially for EFI?

Doubtful.  Yes (although I think most EFI kernels I've seen will
function for both).

--Gene