OS X: How to backup the Mac OS X Install DVD?

ToastI recently decided to make some Mac OS X installation tests, and, to avoid destroying the original Apple Install DVDs, I thought it would be great to first make some backups of the disks.

And so I discovered the intricacies of the Apple hybrid disks…

Problem

My first choice was to use the standard Disk Utility application. Obviously it recognised the disk and reported it as a 6.74 GB volume, formatted as Mac OS Extended (HFS+).

Disk UtilityIt even allowed me to create a Disk Image from the content of this disk (Disk Utility Menu -> File -> New -> Disk Image from “Mac OS X Install DVD”, resulting a .cdr file, described as a “DVD/CD master”).

Disk Image SaveOne would expect from such a image to be an exact copy of the original disk. Not really…

Surprise

To my big surprise, I plugged the same Mac OS X disk into a Windows machine, and it showed a completely different picture:

Windows Support PropertiesWow! The same disk was a CDFS 936 MB volume, named WindowsSupport and containing Boot Camp related Windows stuff:

Windows Support After some research I understood that the Apple install disk is a hybrid volume, containing both a ISO part (above), and a HFS+ part:

Mac Install DVDThe ISO part not only provides divers for the Boot Camp Windows partition, but also allows to remotely install DVD-less devices like the MacBook Air, in a network where there are no other Mac OS X computers. For this, run the Setup.exe on a Windows machine and you’ll installs a special DVD sharing server. While booting the MacBook Air, if a special key is pressed, the network boot mode is selected, and a list of shared DVDs is displayed for selection. (On Mac OS X, this functionality is provided by the Remote Install Mac OS X application).

Solution

Once I understood the hybrid nature of the Apple Install DVD, I also understood that regular Windows or Mac tools will probably not be able to backup both parts of the disk; Apple Disk Utility offered to create a  “DVD/CD master” of the Mac part, while the Windows tools are able to create a ISO file with the Windows part.

Further research revealed that a possible solution to backup the Mac Install DVD is the Disk Copy function from the (quite extensive) package Roxio Toast 10 Titanium.

Toast Disc CopyThis time the DVD was reported to be a 7.24 GB volume, the sum of the Mac and Windows parts. From this window it is possible to  either directly create a DVD DL, or to save the content as a Disk Image, using Roxio’s custom .toast format, that can be later burned to disk.

Conclusion

Although initially confusing and frustrating by it’s dual appearance, the Apple Mac OS X Install DVD is in fact a quite interesting design, packing two disks into a single hybrid one. It’s nothing magic, and can be copied with existing tools, like Roxio Toast.

Critics? Well, if I would not expect Windows DVD tools to recognise the Mac part, I would expect the Mac OS Disk Utilities to be able to mount, or at least to report the existence of the Windows part, and properly duplicate the entire disk.

About Liviu Ionescu (ilg)
Hi! My name is Liviu Ionescu (ilg, ilegeul or eunete for colleagues and friends) and I’m a senior IT engineer. Or should I say a real programmer?

One Response to OS X: How to backup the Mac OS X Install DVD?

  1. TheJackRackham says:

    At the time of my writing, the cheapest license of Roxio Toast is on sale for 79.99 USD. You can buy at least 3 other OSX DVDs from the Apple Store with that money!

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: