[ipxe-devel] iPXE (undionly.kpxe) chain load to WDS server

Alex Davies alex at davz.net
Tue May 15 10:08:15 UTC 2012

Hi All,

I am using iPXE undionly.kpxe to divert to chain load various Linux
bootloaders and its works perfectly. We have a legacy Windows setup which
initially acted as the TFTP server for undionly, and I was able to get our
iPXE/Linux environment totally decoupled (at the moment we are putting
undionly.kpxe in the legacy TFTP directory on the WDS TFTP servers). I am
using this iPXE command:

chain tftp://ip.of.tftp/Boot/x86/wdsnbp.0

This works even if I pointed to a different network's TFTP server, which is

What happens (from packet captures) is that wdsnbp.0 downloads and does
another DHCP request. It seems to take the next-server value from this but
ignore the filename value, to download wdsnbp.com from the next-server. If
I "set next-server xxx" above the chain, this is ignored - the new DHCP
value takes priority. This is annoying, because the DNS system we are using
does not easily support returning different options to different types of

wdsnbp.0 seems does various things but ends up downloading pxeboot.n12,
which goes off and downloads bootmgr.exe. This downloads some other files,
 but also some 'hidden' files such as \tmp\x86\64{A_UUID} which I think is
some sort of API for settings used by MS TFTP WDS servers. This does not
work unless the DHCP next-server is the WDS server, i.e. unless the
original undionly.kpxe is served up from the Windows WDS TFTP server.
Ideally I would like to get rid of this and use these WDS servers only for
Windows builds.

If I point iPXE directly to tftp://ip.of.wds/pxelinux.n12 I just see "TFTP
download failed", and looking at the packet capture it is attempting to
download bootmgr.exe from the next-server IP. However, in this case, there
is no new DHCP request so I would have thought that I should be able to
override this in iPXE with a set command. Does anyone know if this is
possible and if so what to 'set'?



Alex Davies

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