text: #!/bin/bash
   
  ####################
  # Notes            #                 
  ####################
  #
  # Created 20200625 by Nathan Worster
  #
  # This script assumes that the macOS Beta installer is already staged in the Applications folder, and will convert that .app installer into a bootable .dmg.
  # To download the latest macOS beta, go to https://developer.apple.com/download/ or, if applicable, https://appleseed.apple.com/.
  # The .dmg file will be placed in ~/Downloads.
  # This script must be run with sudo using "sudo bash <filename>" if run outside of an MDM.
  # 
  ####################
  # Variables        #
  ####################
   
  dmgName=$"macOS11BigSurBeta"
   
  ####################
  # Script           #
  ####################
   
  cd ~/Downloads
   
  # Create and mount sparse volume:
  hdiutil create -o install_container -size 15G -layout SPUD -fs HFS+J -type SPARSE
  hdiutil attach install_container.sparseimage -noverify -mountpoint /Volumes/install_build
   
  # Copy contents of installer .app into mounted volume:
  /Applications/Install\ macOS\ Beta.app/Contents/Resources/createinstallmedia --nointeraction --volume /Volumes/install_build
   
  # Detach the completed image:
  hdiutil detach -force /Volumes/Install\ macOS\ Beta
   
  # Convert and rename the image:
  hdiutil convert install_container.sparseimage -format UDZO -o $dmgName.dmg
   
  # Cleanup
   
  rm install_container.sparseimage
   
  exit 0