Grub configuration | Julien Guillod

The boot file bootx64.efi corresponds to the file grubnetx64.efi.signed present in the package grub-efi-amd64-signed.

Once the file bootx64.efi is received by the computer booting in UEFI netboot, the computer retrieve the following grub configuration file:

set default="1"
set timeout=10

set linux_gfx_mode=keep

menuentry 'Boot from next volume' {
	exit
}

menuentry 'Install Ubuntu {{ ubuntu_version }}' {

	echo '------------------------------------------------------------------------------'
	echo -n 'Interface:   '; net_ls_addr
	echo "HTTP Server: ${net_default_server}"
	echo '------------------------------------------------------------------------------'

	echo 'Loading vmlinuz...'
        linux (http)/netboot/vmlinuz ip=dhcp url=http://${net_default_server}/netboot/ubuntu-{{ ubuntu_version }}-desktop-amd64.iso url=http://${net_default_server}/netboot/preseed.cfg automatic-ubiquity
        echo 'Loading initrd...'
        initrd (http)/netboot/initrd

}

menuentry 'UEFI Firmware Settings' {
	fwsetup
}

This file define a grub entry to load the kernel located in /var/www/netboot/vmlinuz over HTTP.

The parameter url=http://${net_default_server}/netboot/ubuntu-{{ ubuntu_version }}-desktop-amd64.iso gives the location of the ISO image of Ubuntu (served by nginx over HTTP).

The second parameter url=http://${net_default_server}/netboot/preseed.cfg is to retrieve Debian preseed configuration file. Finally, automatic-ubiquity is here to tell Ubuntu Ubiquity installer to perform an automatic installation.