[syslinux] Chain-loading from WDS to PXELinux on a different tftp server

[Gene Cumm]

On Dec 25, 2014 2:11 AM, "Luke Ledgerd" <luke.ledgerd at niteco.se> wrote:
>
> Hey guys,
>
> We are going with WDS to fire up first to get the benefits of targeted M$
deployments. If you have the "handle unknown computers" off on your M$
Distribution point, then you can still use regular WDS which runs next as a
PXE filter (DLL linked into WDS) to fire off anything you want to including
PXELinux.
>
> The stuff I was talking about before with PXELinux not working in EFI-64
was related to the EFI Network Boot Rom trying to connect to the DHCP
server on Port 4011 (PXE server). I could have kept hacking around with
DHCP options, or forced DHCPD to listen on that port, or set up a proper
PXEServer that complies with 3.X of the PXE spec, but it wasn't required
for what we wanted in this environment so I moved on, and let WDS
workaround the problem with EFI + PXELinux I had.
>
> Question.
> 1) Can you kick off PXELinux without a Unix DHCP Server (WDS), and make
it jump to a different tftp server from WDS? That's what I'm going for. I
want the default PATH to include the IP address of a different TFTP server
in PXE Linux.

Certainly though the choices on how depend on BIOS versus EFI.   If loaded
properly from the second tftpd, this should set siaddr/sname to the second
server. If you need to load the Syslinux binary from the first then use the
second for the rest, you'll need option 210 (forced by DHCP or built-in
options; no client normal would request this option from a DHCP).

> The new implementation will have to have a separate folder for EFI64,
EFI32, PXE 2.1 because that's what I think WDS demands - or at least for
whatever chainloads the PXELinux off another TFTP server.
>
> 2) As a fallback, PXEChain as I understand requires another DHCP server

Not necessarily but "the devil is in the details".

>
http://www.vcritical.com/2011/06/peaceful-coexistence-wds-and-linux-pxe-servers/
>http://www.syslinux.org/wiki/index.php/Common_Problems#pxechain.com-2

This was a possible workaround I came up with to avoid pxechain.com after
the timer bug was discovered and I resolved for 4.04-pre1 and won't work
with Syslinux -5.00+.

Side note: pxechain.com is unusable in Syslinux 6.00+ and pxechn.c32 is
BIOS only.

> These docs look good by they don't explain how it all plays together with
PXELinux dual booting with EFI/Non EFI shared configuration.

SYSLINUX for EFI is new compared to those docs.

> Does PXEChain do everything I want? Can it even a pass configuration file
for PXELinux to start with.pxechain

pxechain.com only allows one required parameter, the file.  pxechn.c32
allows you to specify a strings to change behaviors.

> This looks very interesting - This Russian knows what he is doing....
>http://sysmagazine.com/posts/175669/
>
> I'll let you know how I go today with it. We are going for the perfect
setup where SCCM does it's thing if it needs to - else throws back to WDS
-> PXELinux for a computer not targeted for any SCCM PXE Deployment task
sequences, so it's going to be a bit different from the above article.
>
> Why a different TFTP server? We have a NAS that is already setup and
tested and it does a good job of mounting lots of loopback ISO's and
sharing them on TFTP, even if it doesn't support MTFTP and all that.

Syslinux won't directly use MTFTP anyways.

--Gene