Hi, thanks for all the details, but I have no time to look at every small detail. In the past, I sometime had a problems when som package depencies in testing were not yet correct, so creating the nfsroot with backports kernel failed. Maybe this is similar to your problems now.
Since FAI 6.2 it's possible to put .deb files into /srv/fai/config/pkgs/<CLASSNAME>/ Then FAI will install those .deb package via dpkg after using install_packages for the rest. But IIRC this is not used when creating the nfsroot. You way fi it by creating an nfsroot with some default kernel, then chroot into the nfsroot and manually add the backpots kernel, then don't forget to copy the kernel and initrd into the tftp directory. -- regards Thomas