simpleiso

#!/bin/bash
#
# Generate a basic ISO boot image from vmlinuz & initramfs. The resulting image
# should be bootable by BIOS or UEFI systems.

set -euxo pipefail

# Optional parameters.
INITRAMFS=
BOOT_PARAMS=

# From xorriso package.
MKISOFS=/usr/bin/xorriso
# From the isolinux package.
ISOLINUX_BIN=/usr/lib/ISOLINUX/isolinux.bin
# From the syslinux-common package.
LDLINUX_C32=/usr/lib/syslinux/modules/bios/ldlinux.c32


function help() {
  echo "usage: ${0} [OPTIONS] vmlinuz isoname"
  echo
  echo "where OPTIONS are:"
  echo " -h       show this help"
  echo " -i FILE  initramfs filesystem image for kernel"
  echo " -x ARGS  extra kernel command line args"
}


# Check for required binaries.
if [ ! -f "${MKISOFS}" ]; then
  echo "Error: mkisofs not found, please install or update PATH"
  exit 1
fi

# Parse command line parameters.
while getopts "hi:x:" opt; do
  case ${opt} in
    h)
      help
      exit 0
      ;;
    i)
      INITRAMFS="${OPTARG}"
      ;;
    x)
      BOOT_PARAMS="${OPTARG}"
      ;;
  esac
done

# Adjust positional parameters after processing with getopts.
shift $((OPTIND - 1))

# Assign positional parameters.
VMLINUZ=${1:?Error: Please provide a vmlinuz image}
ISO_NAME=${2:?Error: Please provide an ISO output file name}


function setup_isofs() {
  local isofs_dir=$1
  local efiboot_img=$2
  local vmlinuz=$3
  local initramfs=$4
  local boot_params=$5

  local initramfs_config=
  local initramfs_config_efi=

  # Setup the mkisofs filesystem.
  cp $vmlinuz ${isofs_dir}/vmlinuz
  if test -f "$initramfs" ; then
    cp $initramfs ${isofs_dir}/initramfs
    initramfs_config="INITRD initramfs"
    initramfs_config_efi="initrdefi /initramfs"
  fi

  # Generate isolinux.cfg
  cat > ${isofs_dir}/isolinux.cfg <<EOF
SAY ePoxy ISO boot image: $ISO_NAME
SAY Kernel parameters: $boot_params
TIMEOUT 30
DEFAULT linux

LABEL linux
 KERNEL vmlinuz
 APPEND $boot_params
 $initramfs_config
EOF
  cat > ${isofs_dir}/grub.cfg <<EOF
set timeout=5
set color_highlight=black/light-magenta

menuentry 'linux: ${ISO_NAME}' {
    linuxefi  /vmlinuz $boot_params
    $initramfs_config_efi
}
EOF

  make_bootefi_img ${efiboot_img} ${isofs_dir}

  # Copy isolinux bootloader.
  install -D -m 644 ${ISOLINUX_BIN} ${isofs_dir}/isolinux/isolinux.bin
  touch ${isofs_dir}/$( date +%Y%m%d-%H%M%S )

  # Syslinux 6.x requires the LDLINUX_C32 file.
  cp ${LDLINUX_C32} ${isofs_dir}
}

function make_bootefi_img() {
  local bootefi_img=$1
  local isofs_dir=$2
  local tmp=$( mktemp --directory )

  local raw_size_k=$(
    du --dereference --summarize --block-size=1K ${isofs_dir} \
      | awk '{ print $1; }'
  )

  local size=$(( $raw_size_k + 4096 ))

  # Make the grub efi boot loader image.
  grub-mkimage -o ${tmp}/bootx64.efi -p / -O x86_64-efi fat iso9660 part_gpt \
      part_msdos normal boot linux linuxefi efinet lsefi lsefisystab lsefimmap \
      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 udf

  # Ignore meaningless sector alignment failures.
  export MTOOLS_SKIP_CHECK=1

  # Creates an empty fat16 disk image. NB: fat32 min size is 256MB.
  truncate --size ${size}K ${tmp}/data.fat16
  mkfs.vfat ${tmp}/data.fat16 -F16

  # Creates the necessary subdirectories.
  mmd -i ${tmp}/data.fat16 ::/efi ::/efi/boot
  mcopy -bsQ -i ${tmp}/data.fat16 ${tmp}/bootx64.efi ::/efi/boot
  mcopy -bsQ -i ${tmp}/data.fat16 ${isofs_dir}/grub.cfg ::/
  mcopy -bsQ -i ${tmp}/data.fat16 ${isofs_dir}/vmlinuz ::/
  mcopy -bsQ -i ${tmp}/data.fat16 ${isofs_dir}/initramfs ::/

  # Copy the fat16 formatted data as the complete bootefi img file.
  cp ${tmp}/data.fat16 ${bootefi_img}

  # Clean up temporary directory.
  rm -rf ${tmp}
}


function main() {
  local isodir=$( mktemp -d /tmp/iso.dir.XXXXXX )

  setup_isofs $isodir ${isodir}/efiboot.img "$VMLINUZ" "$INITRAMFS" "${BOOT_PARAMS}"

  # Generate the ISO image. File paths are relative to the ${isodir}.
  ${MKISOFS} -as mkisofs \
      -isohybrid-mbr /usr/lib/ISOLINUX/isohdpfx.bin \
      -c isolinux/boot.cat \
      -b isolinux/isolinux.bin \
      -no-emul-boot \
      -boot-load-size 4 \
      -boot-info-table \
      -eltorito-alt-boot \
      -e efiboot.img \
      -no-emul-boot \
      -isohybrid-gpt-basdat \
      -output ${ISO_NAME} \
      ${isodir}

  # Clean up temporary directory.
  rm -fr ${isodir}
}

main