subiquity/installer/resources/grub/grub.cfg

function scan_disk {
    # Scan the disk and create a menuentry to boot it if it contains a linux
    # install
    disk=$1
    if [ -e $disk/etc/lsb-release ]; then
        probe -s uuid -u $disk
        source $disk/etc/lsb-release
        menuentry "$DISTRIB_ID $DISTRIB_RELEASE $disk" $disk $uuid { 
            set root=$2
            linux /vmlinuz root=UUID=$3
            initrd /initrd.img
        }
    fi
}

# Load modules
insmod all_video
insmod gfxterm
insmod png
insmod regexp
insmod part_gpt
insmod part_msdos

# Set up display
set gfxmode=auto
terminal_output gfxterm serial_com0
terminal_input console serial_com0
background_image /boot/grub/splash.png
loadfont /boot/grub/unicode.pf2

# Scan all disks except for current root
for disk in (*); do
    if [ "$disk" != "(${root})" ]; then
        scan_disk $disk
    fi
done

# Create menuentry for installer
menuentry "Boot Installer - Graphical Console" {
    linux /vmlinuz ip=dhcp ro root=LABEL=cloudimg-rootfs overlayroot=tmpfs console=ttyS0 console=tty0 splash
    initrd /initrd.img
}
menuentry "Boot Installer - Serial Console" {
    linux /vmlinuz ip=dhcp ro root=LABEL=cloudimg-rootfs overlayroot=tmpfs console=tty0 console=ttyS0 splash
    initrd /initrd.img
}

set default=0
set timeout=50