simpleusb

#!/bin/bash
#
# simpleusb generates a UEFI boot image suitable for USB media.

set -uex

# Optional parameters.
INITRAMFS=
BOOT_PARAMS=

# Constants
FREE_SPACE_K=4096
boot_params=
initramfs_config=


function help() {
  echo "usage: ${0} [OPTIONS] vmlinuz usbname"
  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"
}


# 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=${1:?Error: Please provide a vmlinuz image}
USB_NAME=${2:?Error: Please provide a USB output file name}


function setup_usbfs() {
  local usbfs_dir=$1
  local vmlinuz=$2
  local initramfs=$3
  local boot_params=$4

  local initramfs_config=

  # Setup the filesystem.
  cp $vmlinuz ${usbfs_dir}/vmlinuz.efi
  if test -f "$initramfs" ; then
      cp $initramfs ${usbfs_dir}/initramfs
      initramfs_config="initrdefi /efi/boot/initramfs"
  fi

  # Generate default grub config using images and boot params.
  cat >$usbfs_dir/grub.cfg<<EOF
set timeout=5
set color_highlight=black/light-magenta

menuentry 'stage1: ${USB_NAME}' {
    linuxefi /efi/boot/vmlinuz.efi $boot_params
    $initramfs_config
}
menuentry 'Firmware Setup' {
    fwsetup
}
EOF

}

function make_efi_usb() {
  local usbdir=$1
  local usbfile=$2
  local tmp=$( mktemp --directory )
  local raw_size_k=$(
    du --dereference --summarize --block-size=1K ${usbdir} \
      | awk '{ print $1; }'
  )
  local size=$(( $raw_size_k + $FREE_SPACE_K ))

  # 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

  # Make the grub efi boot loader image.
  grub-mkimage -o bootx64.efi -p /efi/boot -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

  echo " Copying files to FAT16 image... "
  # Creates the necessary subdirectories.
  mmd -i ${tmp}/data.fat16 ::/efi
  mmd -i ${tmp}/data.fat16 ::/efi/boot
  mcopy -bsQ -i ${tmp}/data.fat16 bootx64.efi ::/efi/boot
  mcopy -bsQ -i ${tmp}/data.fat16 "${usbdir}"/* ::/efi/boot

  # Create 1M GPT header file. Use 1M to keep resulting image 1M aligned.
  local offset=$(( 1048576 ))
  truncate --size ${offset} ${usbfile}

  # Append fat16 data to the GPT header.
  cat ${tmp}/data.fat16 >> ${usbfile}

  echo " Formatting GPT header... "
  # Finally format the blank GPT header with the one fat16 partition.
  parted --script ${usbfile} \
    mktable gpt \
    mkpart primary fat16 ${offset}B 100% \
    name 1 UEFI \
    quit

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

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

  # Generate the USB image.
  setup_usbfs ${usbdir} ${VMLINUZ} "${INITRAMFS}" "${BOOT_PARAMS}"
  make_efi_usb "${usbdir}" "${USB_NAME}"

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

main