I guess you do not have installed any linux-image package inside the nfsroot. Try:
grep linux-image /var/log/fai/fai-make-nfsroot.log Since you have installed the Ubuntu version of the FAI packages, your /etc/fai/NFSROOT may not work for a Debian nfsroot. Please check the diff of your NFSROOT to this version: https://github.com/faiproject/fai/blob/master/conf/NFSROOT In Ubuntu the kernel package ist called linux-image...-generic in Debian it's linux-image-amd64. I guess this is the problem you have. -- regards Thomas