https://github.com/geerlingguy/macos-virtualbox-vm/issues/28 work in progress

prepare-iso.sh

#!/bin/bash

#
# Create a bootable ISO image from Apple's installer application for 
# OS X Yosemite (10.10.x), OS X El Capitan (10.11.x), 
# macOS Sierra (10.12.x) or pre-release macOS High Sierra (10.13).
# 
# Notes, including credits: 
# https://github.com/geerlingguy/macos-virtualbox-vm/blob/master/README.md
# 
# Updating for 10.13: 
# https://github.com/geerlingguy/macos-virtualbox-vm/issues/28
#

#
# createISO
#
# This function creates the ISO image for the user.
# Inputs:  $1 = The name of the installer - located in your Applications folder or in your local folder/PATH.
#          $2 = The name that you want to give to the ISO file.
#
function createISO()
{
  if [ $# -eq 2 ] ; then
    local installerAppName=${1}
    local isoName=${2}
    local error=0

    # echo Debug: installerAppName = ${installerAppName} , isoName = ${isoName}

    # =======================================
    # Producing an ISO from Apple's installer
    # =======================================
    echo
    echo Mount the electronic software distribution (ESD) at /Volumes/install_app
    echo --------------------------------------------------------------------------------

    if [ -e "${installerAppName}" ] ; then
      echo $ hdiutil attach "${installerAppName}"/Contents/SharedSupport/InstallESD.dmg -noverify -nobrowse -mountpoint /Volumes/install_app
      hdiutil attach "${installerAppName}"/Contents/SharedSupport/InstallESD.dmg -noverify -nobrowse -mountpoint /Volumes/install_app
      error=$?
    elif [ -e /Applications/"${installerAppName}" ] ; then
      echo $ hdiutil attach /Applications/"${installerAppName}"/Contents/SharedSupport/InstallESD.dmg -noverify -nobrowse -mountpoint /Volumes/install_app
      hdiutil attach /Applications/"${installerAppName}"/Contents/SharedSupport/InstallESD.dmg -noverify -nobrowse -mountpoint /Volumes/install_app
      error=$?
    else
      echo "A compatible installer was not found."
      error=1
    fi

    if [ ${error} -ne 0 ] ; then
      echo "Failed to mount the InstallESD.dmg from within the installer at ${installerAppName}. Exiting. (${error})"
      return ${error}
    fi

    echo
    echo Create ${isoName} – an empty disk image with an Apple partition map (APM) 
    echo --------------------------------------------------------------------------------
    echo $ hdiutil create -o /tmp/${isoName} -size 8g -layout SPUD -fs HFS+J -type SPARSE
    hdiutil create -o /tmp/${isoName} -size 8g -layout SPUD -fs HFS+J -type SPARSE

    echo
    echo Mount ${isoName} for package addition at /Volumes/install_build
    echo --------------------------------------------------------------------------------
    echo $ hdiutil attach /tmp/${isoName}.sparseimage -noverify -nobrowse -mountpoint /Volumes/install_build
    hdiutil attach /tmp/${isoName}.sparseimage -noverify -nobrowse -mountpoint /Volumes/install_build

    echo
    echo Write the base system to /Volumes/install_build
    echo --------------------------------------------------------------------------------
    # echo $ asr restore -source /Volumes/install_app/BaseSystem.dmg -target /Volumes/install_build -noprompt -noverify -erase
    # asr restore -source /Volumes/install_app/BaseSystem.dmg -target /Volumes/install_build -noprompt -noverify -erase
    echo $ time asr restore -source "${installerAppName}"/Contents/SharedSupport/BaseSystem.dmg -target /Volumes/install_build -noprompt -noverify -erase
    time asr restore -source "${installerAppName}"/Contents/SharedSupport/BaseSystem.dmg -target /Volumes/install_build -noprompt -noverify -erase

    echo
    echo Remove a link (if present), copy packages
    echo --------------------------------------------------------------------------------
    # echo $ rm /Volumes/OS\ X\ Base\ System/System/Installation/Packages
    # rm /Volumes/OS\ X\ Base\ System/System/Installation/Packages
    echo $ time ditto -V /Volumes/install_app/Packages /Volumes/OS\ X\ Base\ System/System/Installation/
    time ditto -V /Volumes/install_app/Packages /Volumes/OS\ X\ Base\ System/System/Installation/

    echo
    echo Copy dependencies
    echo --------------------------------------------------------------------------------
    # echo $ cp -rp /Volumes/install_app/BaseSystem.chunklist /Volumes/OS\ X\ Base\ System/BaseSystem.chunklist
    # cp -rp /Volumes/install_app/BaseSystem.chunklist /Volumes/OS\ X\ Base\ System/BaseSystem.chunklist
    echo $ ditto -V "${installerAppName}"/Contents/SharedSupport/BaseSystem.chunklist /Volumes/OS\ X\ Base\ System/BaseSystem.chunklist
    ditto -V "${installerAppName}"/Contents/SharedSupport/BaseSystem.chunklist /Volumes/OS\ X\ Base\ System/BaseSystem.chunklist
    # echo $ cp -rp /Volumes/install_app/BaseSystem.dmg /Volumes/OS\ X\ Base\ System/BaseSystem.dmg
    # cp -rp /Volumes/install_app/BaseSystem.dmg /Volumes/OS\ X\ Base\ System/BaseSystem.dmg
    echo $ time ditto -V "${installerAppName}"/Contents/SharedSupport/BaseSystem.dmg /Volumes/OS\ X\ Base\ System/BaseSystem.dmg
    time ditto -V "${installerAppName}"/Contents/SharedSupport/BaseSystem.dmg /Volumes/OS\ X\ Base\ System/BaseSystem.dmg

    echo
    echo Unmount an image from /Volumes/install_app
    echo --------------------------------------------------------------------------------
    echo $ hdiutil detach /Volumes/install_app
    hdiutil detach /Volumes/install_app

    echo
    echo Unmount the image of the base system
    echo --------------------------------------------------------------------------------
    echo $ hdiutil detach /Volumes/OS\ X\ Base\ System/
    hdiutil detach /Volumes/OS\ X\ Base\ System/

    echo
    echo Resize the partition in ${isoName} – remove free space
    echo --------------------------------------------------------------------------------
    echo $ hdiutil resize -size `hdiutil resize -limits /tmp/${isoName}.sparseimage | tail -n 1 | awk '{ print $1 }'`b /tmp/${isoName}.sparseimage
    hdiutil resize -size `hdiutil resize -limits /tmp/${isoName}.sparseimage | tail -n 1 | awk '{ print $1 }'`b /tmp/${isoName}.sparseimage

    echo
    echo Convert ${isoName} to UDTO (DVD/CD-R master for export)
    echo --------------------------------------------------------------------------------
    echo $ time hdiutil convert /tmp/${isoName}.sparseimage -format UDTO -o /tmp/${isoName}
    time hdiutil convert /tmp/${isoName}.sparseimage -format UDTO -o /tmp/${isoName}

    echo
    echo Remove the temporary .sparseimage file 
    echo --------------------------------------------------------------------------------
    echo $ rm /tmp/${isoName}.sparseimage
    rm /tmp/${isoName}.sparseimage

    echo
    echo Rename the .iso file, move it to the desktop
    echo --------------------------------------------------------------------------------
    echo $ mv /tmp/${isoName}.cdr ~/Desktop/${isoName}.iso
    mv /tmp/${isoName}.cdr ~/Desktop/${isoName}.iso
  fi
}

#
# installerExists
#
# Returns 0 if the installer was found either locally or in the /Applications directory.  1 if not.
#
function installerExists()
{
  local installerAppName=$1
  local result=1
  if [ -e "${installerAppName}" ] ; then
    result=0
  elif [ -e /Applications/"${installerAppName}" ] ; then
    result=0
  fi
  return ${result}
}

#
# Main script code
#
# Eject installer disk in case it was opened after download from App Store
hdiutil info | grep /dev/disk | grep partition | cut -f 1 | xargs hdiutil detach -force

# Seek a compatible installer.
# If found, then begin the ISO production routine. 

installerExists "Install macOS Sierra.app"
result=$?
if [ ${result} -eq 0 ] ; then
  createISO "Install macOS 10.13 Beta.app" "10.13"
else
  installerExists "Install macOS Sierra.app"
  result=$?
  if [ ${result} -eq 0 ] ; then
    createISO "Install macOS Sierra.app" "Sierra"
  else
    installerExists "Install OS X El Capitan.app"
    result=$?
    if [ ${result} -eq 0 ] ; then
      createISO "Install OS X El Capitan.app" "El Capitan"
    else
      installerExists "Install OS X Yosemite.app"
      result=$?
      if [ ${result} -eq 0 ] ; then
        createISO "Install OS X Yosemite.app" "Yosemite"
      else
        echo "A compatible installer was not found."
      fi
    fi
  fi
fi