fixed for me with initrd.gz & linux file
http://archive.ubuntu.com/ubuntu/dists/xenial-updates/main/installer-amd64/current/images/netboot/ubuntu-installer/amd64/
fixed for me with initrd.gz & linux file
http:// archive. ubuntu. com/ubuntu/ dists/xenial- updates/ main/installer- amd64/current/ images/ netboot/ ubuntu- installer/ amd64/