Comment 20 for bug 1575652

It worked.
Below is my grub.cfg

menuentry "Install Ubuntu" {
set gfxpayload=keep
linux /ubuntu-installer/amd64/linux live-installer/net-image=http://192.168.1.1/ubuntu/install/filesystem.squashfs hostname=unassigned netcfg/choose_interface=auto gfxpayload=800x600x16,800x600 --- auto=true url=http://192.168.1.1/preseed.cfg quiet
initrd /ubuntu-installer/amd64/initrd.gz
}