[syslinux] chainload back pxelinux from Grub4DOS?

[H. Peter Anvin]

On 12/18/2009 08:04 AM, Frantisek Rysanek wrote:
> But, I can't seem to chainload pxelinux back.
> Even if I add "keeppxe" to my "screensaver" profile.
> Grub hangs while trying to load pxelinux.0 (the last message says 
> "asking for upper memory" or something like that, which is odd). 
> Seems to me that the pxelinux.0 binary doesn't have the right header 
> to appear as a "linux kernel".

That's right, it doesn't, because it isn't one... it's a PXE image.

> I've tried looking at how the memdisk binary is post-processed by the 
> makefile for chainloading (with an idea that I could re-apply the 
> same method on the pxelinux binary), but I couldn't figure it out.

The PXE loader just loads the straight binary at address 0x7c00 and
jumps to it.

> I assume that this could be useful for other purposes too, other than 
> the screensaver - such as: boot DOS, do some HW maintenance stuff, 
> tweak some config registers, and return to the boot menu without a 
> reboot... I know I've been in a similar situation before.

DOS tends to wreck the BIOS environment to shreds, so it is very
difficult to make that work right.

> Any ideas are welcome :-)
> 
> Frank Rysanek
> 
> P.S.: one other feature request: would it be possible to have two 
> different default profiles, one for timeout, another one for 
> "just <Enter>"?

Look for the ONTIMEOUT option.

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.