mkbiosefi

#!/bin/bash

# https://blog.heckel.xyz/2017/05/28/creating-a-bios-gpt-and-uefi-gpt-grub-bootable-linux-system/#mkbiosefi.sh

DISK=$1
BOOTLABEL=$2
ROOTDIR=$3

if [ -z "$DISK" -o -z "$BOOTLABEL" ]; then
  echo "Syntax: $0 <image|disk> <root-label> [<chroot-dir>]"
  exit 1
fi

if [ "$UID" != "0" ]; then
  echo "Must be root."
  exit 1
fi

# Exit on errors
set -xe

# Install dependencies
apt-get install -y --force-yes \
  debootstrap \
  gdisk \
  rsync \
  grub-efi-amd64-bin \
  e2fsprogs

# Create chroot (if requested)
if [ -z "$ROOTDIR" ]; then
  ROOTDIR=chroot/

  # Bootstrap minimal system
  debootstrap --variant=minbase xenial chroot

  # Install kernel and grub
  for d in dev sys proc; do mount --bind /$d chroot/$d; done
  DEBIAN_FRONTEND=noninteractive chroot chroot apt-get install linux-image-generic grub-pc -y --force-yes
  umount chroot/{dev,proc,sys}
fi

# Create sparse file (if we're not dealing with a block device)
if [ ! -b "${DISK}" ]; then
  truncate --size 30G $DISK
fi

# Create partition layout
sgdisk --clear \
  --new 1::+1M --typecode=1:ef02 --change-name=1:'BIOS boot partition' \
  --new 2::+100M --typecode=2:ef00 --change-name=2:'EFI System' \
  --new 3::-0 --typecode=3:8300 --change-name=3:'Linux root filesystem' \
  $DISK

# Loop sparse file
LOOPDEV=$(losetup --find --show $DISK)
partprobe ${LOOPDEV}

# Create filesystems
mkfs.fat -F32 ${LOOPDEV}p2
mkfs.ext4 -F -L "${BOOTLABEL}" ${LOOPDEV}p3

# Mount OS partition, copy chroot, install grub
MOUNTDIR=$(mktemp -d -t demoXXXXXX)
mount ${LOOPDEV}p3 ${MOUNTDIR}

rsync -a ${ROOTDIR}/ ${MOUNTDIR}/

for d in dev sys proc; do mount --bind /$d ${MOUNTDIR}/$d; done
chroot ${MOUNTDIR}/ grub-install --modules="ext2 part_gpt" ${LOOPDEV}
chroot ${MOUNTDIR}/ update-grub

umount $MOUNTDIR/{dev,proc,sys,}
rmdir $MOUNTDIR

# Mount EFI partition
MOUNTDIR=$(mktemp -d -t demoXXXXXX)
mount ${LOOPDEV}p2 $MOUNTDIR

mkdir -p ${MOUNTDIR}/EFI/BOOT
grub-mkimage \
  -d /usr/lib/grub/x86_64-efi \
  -o ${MOUNTDIR}/EFI/BOOT/bootx64.efi \
  -p /efi/boot \
  -O x86_64-efi \
    fat iso9660 part_gpt part_msdos normal boot linux configfile loopback chain efifwsetup efi_gop \
    efi_uga ls search search_label search_fs_uuid search_fs_file gfxterm gfxterm_background \
    gfxterm_menu test all_video loadenv exfat ext2 ntfs btrfs hfsplus udf

# Create grub config
cat <<GRUBCFG > ${MOUNTDIR}/EFI/BOOT/grub.cfg
search --label "${BOOTLABEL}" --set prefix
configfile (\$prefix)/boot/grub/grub.cfg
GRUBCFG

umount $MOUNTDIR
rmdir $MOUNTDIR

# Remove loop device
sync ${LOOPDEV}
losetup -d ${LOOPDEV}

echo "Done. ${DISK} is ready to be booted via BIOS and UEFI."