Understanding Windows Imaging

When you update Windows 7 by adding or removing features, applying hotfixes, or installing service packs, you are simply modifying the set of modules available. And because these modules are independent, you can make these changes without impacting the system as a whole. Because language packs are separate modules as well, you can easily implement different language configurations without needing separate installations for each language.

Microsoft distributes Windows 7 on media with Windows Imaging Format (WIM) disk images. WIM uses compression and single-instance storage to dramatically reduce the size of image files. Compression reduces the size of the image in much the same way that Zip compression reduces the size of files. Using single-instance storage reduces the size of the image because only one physical copy of a file is stored for each instance of that file in the disk image. Because WIM is hardware independent, Microsoft can ship one binary for 32-bit architectures and one binary for 64-bit architectures. A separate binary is available for Itanium-based computers.

Windows 7 can be installed through either automated or interactive setup. You can automate the installation of Windows 7 in several ways. You can:

• Create an unattended installation answer file Windows 7 uses a standards-based single-format answer file. This file, called Unattend.xml, is written in XML, making it easier to process using standard tools. By creating a custom answer file and then running Setup using this answer file, you can perform unattended installations of Windows 7. The Setup program can then install the operating system from a distribution share or from media.
• Use Sysprep image-based installation Requires running the System Preparation command-line tool (Sysprep.exe) on a computer that you want to use as the master deployment computer and then creating a disk image of this computer's configuration. Sysprep is stored in the %SystemRoot%\ System32\Sysprep folder. The Windows Automated Installation Kit (Windows AIK) includes Windows System Image Manager and ImageX to help you use Sysprep for deployments. You use Windows System Image Manager to create answer files for unattended installations. You use ImageX to create and manage disk images.

By using WIM as its disk-imaging format and taking advantage of the modular design of Windows 7, ImageX significantly reduces the number of disk images that must be maintained. You no longer need to maintain multiple hardware-dependent disk images or multiple language-dependent disk images. Instead, you typically need only a single disk image for each chip architecture used in your organization. You can then use different installation scripts to customize the operating system installation as necessary.

WIM has other advantages over earlier disk image formats as well. WIM enables you to modify and maintain disk images offline, which means you can add or remove optional components and drivers or perform updates without having to create a new disk image. To do this, you mount the disk image as a folder and then use Windows Explorer or other tools to update, manage, or remove files as necessary.

Windows System Image Manager, ImageX, and Sysprep provide several different ways to automate deployment. Here are the basic steps:

1. Set up and configure Windows 7 on a computer not being used for normal operations, and then install and configure any necessary components and applications.
2. Run Sysprep to prepare the computer for capture. Sysprep removes unique identifiers from the computer and designates it as a master deployment computer. At the end of this process, the computer no longer has identifying information that allows it to be logged on to and used within a domain or workgroup.
3. Use the ImageX /Capture option to capture the disk image and store this image on media or in a distribution share. The image can be maintained offline by using the ImageX /Mountrw option to mount the image in read/ write mode so that you can make any necessary changes. Use the ImageX /Unmount command to unmount the image when you are finished making changes.
   You also can mount images using DISM /Mount-WIM and unmount images using DISM /Unmount-WIM. DISM provides functionality for manipulating images. You can set product keys, perform upgrades, add or remove drivers, set language and locale information, add or remove packages and features, and clean up images.
4. Use Windows System Image Manager to create your unattended installation answer files. You can then create deployment scripts that configure the computer, run Setup using the answer file, and apply the disk image you've previously created.
5. Run your deployment script to configure the computer and install the operating system.