Ubuntu netbooting needs a "new" kernel parameter

After a few hours spent trying to find why Ubuntu 12.04 would not download a preseed file while netbooting, I stumbled upon this bug https://bugs.launchpad.net/ubuntu/+source/casper/+bug/923219 .

I needed to add “IPAPPEND 2” after the APPEND directive in the pxelinux config file.

Great.