Patch RHEL5 derived ISOs isolinux config file

isolinux-patch.rb

#!/usr/bin/env ruby  
require 'tmpdir'
require 'fileutils'
require 'thread'

def progress_loop(thread , msg = "Working... " , step_lag = 0.1)
  $stdout.sync = true
  line_reset = "\r\e[0K" + msg
  while thread.status
    print line_reset + "|"
    sleep step_lag
    print line_reset + "/"
    sleep step_lag
    print line_reset + "-"
    sleep step_lag
    print line_reset + '\\'
    sleep step_lag
  end
end


def patch_isolinux(iso, cfg, tmpdir = nil, debug = false)
  tmpdir = Dir.mktmpdir if tmpdir.nil?
  FileUtils.mkdir_p tmpdir + '/iso'
  `mount -o loop #{iso} #{tmpdir}/iso`
  if $? != 0
    $stderr.puts "ERROR: Mounting ISO (#{iso}) failed."
    return false 
  end
  begin
    FileUtils.cp_r "#{tmpdir}/iso", "#{tmpdir}/newiso"
    FileUtils.cp cfg, "#{tmpdir}/newiso/isolinux/isolinux.cfg"
    isoout = File.basename(iso, File.extname(iso)) + '-patched.iso'
    `mkisofs -R -J -T -b isolinux/isolinux.bin -c isolinux/boot.cat -no-emul-boot -boot-load-size 4 -boot-info-table -o #{isoout} #{tmpdir}/newiso > /dev/null 2>&1`
    if $? != 0
      $stderr.puts "ERROR: mkisofs failed."
      return false 
    end
  rescue Exception => e
    $stderr.puts "ERROR: #{e.message}"
    return false
  ensure
    `umount #{tmpdir}/iso`
    if not debug
      FileUtils.rm_rf tmpdir + '/iso'
      FileUtils.rm_rf tmpdir + '/newiso'
    end
  end
  true
end

def usage 
$stderr.puts """
Usage: isolinux-patch isofile isolinux-cfg [tmpdir]

"""
end

iso = ARGV[0]
cfg = ARGV[1]
temp = ARGV[2]

if `whoami`.strip.chomp != 'root'
  $stderr.puts 'Run this script as root.'
  exit 1
end

if iso.nil? or cfg.nil?
  usage 
  exit 1
end

if `which mkisofs`.strip.chomp.empty?
  $stderr.puts "ERROR: mkisofs command not found."
  exit
end

if not File.exist?(iso)
  $stderr.puts "ERROR: #{iso} is not a valid file."
  exit
end

if not File.exist?(cfg)
  $stderr.puts "ERROR: #{cfg} is not a valid file."
end

t = Thread.new do
  if not temp.nil? and File.directory?(temp)
    patch_isolinux(iso, cfg, temp)
  else
    patch_isolinux(iso, cfg)
  end
end
progress_loop t, "Patching ISO (this will take some time)... "
puts "Done."