subiquity/installer/resources/grub/grub.cfg

function strcontains {
    set str="$1"
    set pattern="$2"
    if regexp ".*${pattern}.*" "$str"; then
        return 0;
    else
        return 1;
    fi
}

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 "Discovered: $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 ext2
insmod gfxterm
insmod linux
insmod normal
insmod part_gpt
insmod part_msdos
insmod png
insmod probe
insmod regexp
insmod serial

# Set up display
set gfxmode=auto
terminal_output gfxterm
terminal_input console

# Set boot type
if [ x$grub_platform = xefi ]; then
set boottype=efi
else
set boottype=bios
fi

# Try to set up serial
serial --unit=0 --speed=9600
terminal_output --append serial
terminal_input --append serial

# Set up appearance
loadfont /boot/grub/unicode.pf2

regexp -s install_disk 'hd([0-9]+)' $root
# Scan all disks except for current root
for disk in (*); do
    if ! strcontains "$disk" $install_disk; then
        scan_disk $disk
    fi
done

# Create menuentry for installer
menuentry "Boot Installer - Graphical Console" {
    set root=(hd0,msdos2)
    linux /vmlinuz ro root=LABEL=cloudimg-rootfs overlayroot=device:dev=LABEL=overlay-rootfs console=ttyS0 console=tty0 quiet splash
    initrd /initrd.img
}
menuentry "Boot Installer - Serial Console" {
    set root=(hd0,msdos2)
    linux /vmlinuz ro root=LABEL=cloudimg-rootfs overlayroot=device:dev=LABEL=overlay-rootfs console=tty0 console=ttyS0
    initrd /initrd.img
}

set default=0
set timeout=50