[syslinux] Chainloading from one PXELINUX to another (with some iPXE in the mix)?

[Mike Sollanych]

----- Original Message -----
> From: "Jeffrey Hutzelman" <jhutz at cmu.edu>
> To: "For discussion of Syslinux and tftp-hpa" <syslinux at zytor.com>
> Cc: jhutz at cmu.edu
> Sent: Wednesday, June 8, 2011 2:04:03 PM
> Subject: Re: [syslinux] Chainloading from one PXELINUX to another (with some iPXE in the mix)?
>
> I admit there's not a whole lot of documentation, but there's also
> not really much to document.

Fair enough, I guess it either works for what you want or it doesnt! :-)
 
> > "pxechain.com [FOG SERVER FQDN]::pxelinux.0"
> 
> Yup, that's what should happen.  Assuming, of course, that you don't
> actually have brackets in your config file.

Yep, didn't think it was necessary to give out my server name.

> PXECHAIN should do that for you; in fact, that's its main purpose.
> It works by updating the PXE stack's cached DHCP reply, which works
> with the Intel reference stack and with every PXE stack I've seen on real
> hardware, but might _not_ work with software stacks like gpxe/ipxe.

Can you elaborate on this? From what I can tell, the pxelinux.0 loaded from
the FOG server is executing, but then it's trying to get its config file via
TFTP from the original master server. 

If I understand you correctly, you're saying that the PXECHAIN.COM module
edits the name of the TFTP server in memory, loads the provided file via
TFTP, and then runs it; and that the newly running file (the FOG pxelinux, 
in my case) should use the now-edited TFTP server name to fetch its config.

If that's the case, and it should be loading configs from the FOG server,
then that's not working here.

> We've had it work on pretty much every PXE-capable box we've seen in
> the last few years.  But, again, without first loading an alternate PXE
> stack.

I guess iPXE could be getting in the way, but it's a requirement of our 
setup here to have iPXE first - there are other things it can load up instead
of SYSLINUX depending on the configuration in a specific department.

> > Seeing as how I've had luck with that CONFIG directive (config.c32)
> > at loading the default file, it makes sense (to me anyway) that a 
> > modification of that module to support loading PXELINUX config files 
> > using the same precedence as the initial load would do the trick quite
> > nicely.
> 
> I don't believe there's currently a way to do that.  It's possible
> there's something new, though; I haven't looked at recent code in a
> while.
> 
> -- Jeff

Do you know who the maintainer is for that particular module? I wouldn't mind
getting into contact with him/her to see if they'd be interested in adding
the functionality I'm looking for. I can't see it being that complicated.

There does seem to be some work on a chain com32 that is more powerful:
http://syslinux.zytor.com/archives/2010-November/015571.html

The author is Gene Cumm, who I'm CC'ing on this message in the hopes
that he notices and lets me know where he's at with pxechn.c32.

I don't seem to have that in my distribution of PXELINUX, though I
presently rely on someone else to build PXELINUX for me on the master 
server as I don't have the rights to do it at the present time :-P

Thanks much,
Mike