Install all Apple software updates in a DeployStudio postinstall script. I wrote my own script because of a bug with the Software Update plugin in DeployStudio 1.6.12.

software_update.sh

#!/bin/bash

# https://gist.github.com/595c89076a8db738b8da

# DeployStudio postinstall script to install all available Apple software
# updates. I wrote this because of a bug with the Software Update plugin
# in DeployStudio 1.6.12 that causes an infinite loop in certain circumstances.

installed_updates=()

# Helper function since Bash 3 doesn't have associative arrays.
# Probably means I should be doing this in python.
function is_update_installed () {
  for installed in "${installed_updates[@]}"; do
    if [[ "$1" = "${installed}" ]]; then
      return 0
    fi
  done
  return 1
}

while true; do
  available_updates=()
  restart_required=false

  printf 'Checking if updates are available...\n'

  # Loop over the list of software updates.
  sus_output="$(/usr/sbin/softwareupdate --list 2>/dev/null)"
  while IFS= read -r line; do
    # If the line begins with three spaces and an asterisk then it is a
    # required update.
    if [[ "${line}" = '   *'* ]]; then
      name="${line:5}"
      if is_update_installed "${name}"; then
        printf 'Update "%s" has already been installed. Skipping.\n' "${name}"
      else
        printf 'Adding "%s" as an available update.\n' "${name}"
        available_updates+=("${name}")
      fi
    # If the line ends with the [restart] tag then a reboot will be required.
    elif [[ "${line}" = *'[restart]' ]]; then
      printf 'Update requires a restart.\n'
      restart_required=true
    fi
  done <<< "${sus_output}"

  printf '\nTo Be Installed:\n'
  printf '\t"%s"\n' "${available_updates[@]}"
  printf 'Available Updates: %s\nRestart Required: %s\n\n' ${#available_updates[@]} ${restart_required}

  # Install any available updates.
  if [[ ${#available_updates[@]} -gt 0 ]]; then
    printf 'Installing all available updates...\n'
    /usr/sbin/softwareupdate --install "${available_updates[@]}"
    if [[ ${restart_required} = true ]]; then
      printf 'Restart required. Exiting.\n'
      printf 'Ignore the warning that DeployStudio is about to give. This script is not failing.\n'
      exit 100
    fi
  else
    # Exit when we run out of updates to install.
    printf 'No available updates remaining. Exiting.\n'
    exit 0
  fi

  printf 'Remembering installed updates.\n\n'
  for update in "${available_updates[@]}"; do
    installed_updates+=("${update}")
  done
done

exit 0