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Mac OS X Deployment v10.6: Creating System Images

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This chapter will show you how to select a system imaging technique that meets your deployment needs, integrate advanced Mac OS X managed preferences with your system image, create a cloned system image using Disk Utility, create basic network disk images using System Image Utility, and build a modular NetRestore image using System Image Utility.

Chapter Files

Deployment Planning Template.pdf, available at www.peachpit.com/acsa.deployment

Mac OS X v10.6 installation media

Time

This chapter usually takes approximately 4 hours to complete, but it could take much longer depending on the complexity of your deployment.

Goals

  • Select a system imaging technique that meets your deployment needs
  • Integrate advanced Mac OS X managed preferences with your system image
  • Create a cloned system image using Disk Utility
  • Create basic network disk images using System Image Utility
  • Build a modular NetRestore image using System Image Utility

For many deployments, the best solution is a unified system disk image, which involves creating an ideal system, saving it to a disk image, and then deploying that system to all your computers. A unified system image requires a significant time investment up front, but it saves a great deal of time in the long run. Computers with identical configurations are much easier to manage; the fewer the differences between your deployed systems, the more uniform their performance and the less time spent diagnosing problems, updating software, and reconfiguring hardware.

A unified system image also greatly accelerates the deployment process for any deployment larger than a dozen computers. Once you have fully configured, tested, and created a custom system image on one computer, it can take as little as five minutes to copy it to another machine. Compare this with the time needed to deploy the system individually on every computer, and it’s easy to see the benefit of a deployable system disk image. In this chapter you will learn two general methods for creating deployable system disk images: cloning from a model system and building a modular system.

Understanding System Image Creation

Before starting the process of creating a system image, you must consider your deployment requirements: what software and configuration settings will be part of your system image? Consider your users, your systems, and the limitations of identical-system deployment on multiple computers. You also need to consider which of the two image creation methodologies will best suit your needs and abilities. The choices you make while planning your system image will affect every computer on which this system is deployed.

Defining System Image Requirements

When identifying all the specific items and configuration settings that you want to include in your system image, you must take into consideration the requirements of your users, the technical requirements of your systems, and the limitations of deploying an identical system on multiple computers.

User Requirements

Your primary focus when developing system image requirements should be on maximizing system usability, for both users and administrators. In some cases your target audience or usage policies may require tighter system control. This is often the case when users are inexperienced or cannot be trusted to manage any part of their systems. In this scenario you would limit application access and lock down as many system configuration settings as possible. You would also want to make things easy for the user by preconfiguring any system setting you can. In scenarios where you will be performing a significant amount of client management, you should incorporate directory services–based managed preferences.

In professional or creative environments, you may not need to be as restrictive in the application or settings, but you should still make sure to prepare the system based on the users’ needs; for instance, install third-party applications and peripheral drivers for inclusion with your system image.

No matter the level of your users, your system image should be as fully configured as possible, with both Apple and third-party software installed and updated, any necessary support files such as third-party drivers and fonts installed, and any systemwide configuration settings implemented. Note, though, that many settings are not well suited to deployment via a unified system image—more on this topic later in this section.

Computer-Specific System Requirements

Before you create your system image, you must determine which version of Mac OS X you intend to use. A major administrative advantage of using Mac OS X v10.6 and Mac OS X Server v10.6 is that they include all the hardware drivers necessary to work with any Mac that meets the minimum system requirements, allowing you to build a single system image that can work on any Mac.

Although creating a unified system image for computers that support Mac OS X v10.6 is simple, creating a system image for brand-new Macs can present a significant problem. In many cases, because the release of new Mac computers is not in sync with the release of the retail version of Mac OS X, a custom intermediate version of Mac OS X is created just to support the new hardware. However, new Macs cannot run versions of Mac OS X released prior to their introduction—that is, the oldest version of Mac OS X supported by a new Mac computer is the version that it ships with from the factory.

Thus, a previously created system image will not work on new Mac computers, and you will have to create a new system image based on the version of Mac OS X that shipped with the new Macs. Further, these custom intermediate versions of Mac OS X may technically work with older Mac computers, but they are not officially supported by Apple to do so, presenting a problem when you are trying to build a single unified system image.

Fortunately, every general Mac OS X version update includes support for all Mac computers introduced prior to the update. For example, if you were to acquire new Macs that were introduced this week, the next general update of Mac OS X will include support for those new Macs and will support older hardware as well. Therefore, if you can wait to build your system image until you can base it on the next general update for Mac OS X, you can create a single system image for all your Macs. If you can’t wait that long, you will need to create a separate system image just for your new Macs.

It’s important to note that custom intermediate versions of Mac OS X for new computers do not use different version numbers from the general releases. They do, however, have different build numbers, which can be identified by clicking once on the version number from the About This Mac window.

Software Update Requirements

You should strive to build your system image using the latest versions of your selected software. To do this, you’ll need to collect and keep track of all the necessary software update installers that you’ll apply when building your system image.

First you need to determine and acquire the latest version updates for Apple software. Apple’s downloads website, www.apple.com/downloads/, lists all the latest updates and can be searched and browsed so you can locate and then download specific Apple software updates. However, it may not seem obvious which Apple updates are needed; for this reason you can open Software Update from the Apple menu.

Apple Software Update will compare your Mac’s current installed software with the latest versions available from Apple. Obviously, you should run this on one of your test deployment systems to verify exactly which updates are necessary. The Mac OS X v10.6 version of Software Update no longer allows you to download updates without installing them. Thus, if you want to acquire the updates for later installation or deployment, you will have to do so from Apple’s downloads website.

You should also verify that you are using the latest versions of third-party applications and drivers. Many third-party products feature a built-in automatic update system that will check online for updates. However, few of these third-party update systems will allow you to download the individual update installer so that you can later use it to build your system image. Again, in this case, visit the software developer’s website to download the individual update installers.

Limitations of a Unified System Image

You should include as many configured settings as possible with your system image so you don’t have to spend time setting these items on each individual computer. However, there are many settings that you should not, or cannot, deploy with the same configuration to every computer.

For example, in most cases, user-specific settings should not be included with your system image. Computer-specific settings also should not be configured on the system image. For instance, a unique IP address and network name needs to be set for every Mac. Both user- and computer-specific settings are best handled using dedicated client management tools and techniques.

In deploying a Mac OS X Server system image, your primary goal will be to strike a balance between what you can safely configure as part of the generic server system image and what settings you must leave for after deployment.

Choosing a System Image Methodology

When using the tools built into Mac OS X to create a deployable system disk image, you have a choice between two different methodologies: cloned system images and modular system images.

With a cloned system image, you first set up a model computer that is configured with all the software and settings you intend to deploy. Then you create a duplicate copy of the system volume saved to a disk image that has been specially prepared for deployment.

The modular system image methodology, a newer method, requires a bit more work up front, but it has several advantages over the older method and is the Apple-recommended best practice. With this method you build a fresh system by installing a series of installation packages to a sparse disk image. The installations include the full Mac OS X system, any software updates, any additional Apple software, any third-party software, and any custom installation packages that you have created to set up your system image. This sparse image is then converted to a disk image that has been prepared for deployment.

Cloned System Image Pros and Cons

  • Pro—Easier workflow for novice administrators

  • Pro—Less time spent creating initial system images

  • Con—Requires that the model computer be purged of any unnecessary or troublesome files

  • Con—Prone to issues if model not properly “cleaned”

  • Con—Prone to more issues when deploying to different models

  • Con—Increased workload when creating multiple system images

  • Con—Increased workload when it’s time to update system images

  • Con—New system images are never consistent with prior images

  • Con—Difficult to document and audit system image configurations

  • Con—Increased workload to test system image modifications

Modular System Image Pros and Cons

  • Pro—System images are clean because they have never been booted.

  • Pro—System images have no model-specific settings.

  • Pro—Apple updates won’t interfere with your customizations because they are always applied before your customizations.

  • Pro—Your workload is lighter when creating multiple system images that require unique software and configurations.

  • Pro—Your workload is decreased when it’s time to update system images.

  • Pro—Multiple and updated system images are perfectly consistent for similar items every single time.

  • Pro—All configurations are easily documented and easily audited.

  • Pro—Testing of updates and image modifications are simpler.

  • Pro—System image creation process is automated.

  • Pro—It’s easy to integrate modular system images with system maintenance workflows and third-party deployment tools.

  • Con—Workflow is more difficult for novice administrators.

  • Con—You must create custom installation packages for some third-party items and any configuration settings.

  • Con—You will spend more time creating an initial system image.

The cloned system image methodology requires less effort up front, and you can get your first image set up quickly. However, in the long run you’ll have to spend much more time fixing bugs, updating software, and adding modifications than with a modular system image. The modular system image methodology requires more initial effort to properly configure your first system image, but maintaining your systems will be much easier because you’ll be able to build new modular images with additional items and updated software.

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