[syslinux] PXELINUX, pxechain.com and Etherboot

[Jeffrey Hutzelman]

--On Wednesday, May 13, 2009 01:46:06 PM -0700 "H. Peter Anvin" 
<hpa at zytor.com> wrote:

> Joyce Yu wrote:
>> Hi,
>>
>> Anyone has tried to use pxechain with Etherboot? Here is my problem:
>>
>> The Etherboot client had no problem to get the list of install servers
>> manual from the pxechain. But didn't matter which server was chosen,
>> Etherboot client always tried to use the first server to do the
>> installation.  Etherboot 5.4 was used.
>>
>> What the problem may be? PXEchain or Etherboot?
>>
>
> I seem to vaguely recall that Etherboot doesn't preserve changes to the
> in-memory copy of the DHCP packet.  gPXE fixes this, I believe.  Anyone
> remember?

I'm sure this has come up before, but I don't recall.  I'm very interested 
in knowing exactly what the failure mode was.

[most of the rest of this is for the OP]

- did it fetch the wrong file?
- did it fetch the right file from the wrong server?
- did it fetch the right file, then the new program proceeded to use the
  wrong server?

The first two shouldn't happen -- PXECHAIN should correctly fetch the next 
NBP, from the correct server, even if nothing we do to the in-memory DHCP 
response has any effect.


Other things that might be useful:

- Build a copy of PXECHAIN.COM with DEBUG set, and post the resulting
  output.  This might be easier to capture if you use a serial console.
- Build a copy of PXECHAIN.COM with LOADER set to PXELINUX instead of PXE.
  This will cause it to use an alternate method of passing control, which
  may or may not have an effect.

But before going to all that trouble, posting the config and answering the 
questions above will go a long way toward helping to diagnose the problem.