System images basically consist of the capture of a preconfigured computer into a single image that is then deployed to every other system. The preconfigured computer is usually called the reference computer. The reference computer is prepared, then depersonalized through a process called system preparationusually through the use of the Microsoft Sysprep tool which prepares an image for mass reproductionand finally, captured as a system image.
System images originated from the use of disk imaging software. This software would be designed to capture the disk of the reference computer sector by sector into an image which would then be used to reproduce the entire contents of the disk to other systems. Perhaps the most famous disk imaging tool is Symantec Ghost which is now integrated to the Symantec Ghost Solution Suite. Several other manufacturers offer disk imaging technologies: Altiris, Arconis, LANDesk, and more.
In the recent past, manufacturers have changed this sector-based disk image to a file-based image, capturing all of the files that are required to reproduce the reference computer onto others. File-based images are better than sector-based images since they are independent of the disk structure and can therefore be applied to a wider variety of systems. Most people use system images for PCs, but they can also be used for servers.
When it comes to Windows Vista, several changes have been introduced to make this process as simple as possible.
Vista installs through a new process called Image-Based Setup (IBS). Thats because Microsoft introduced a new system image format with the delivery of Vista: the WIM format. Each DVD that includes Vista includes at least two WIM files: one for Vista itself and one for the Windows Preinstallation Environment (Windows PE) which is a version of Windows that runs in memory only and can be used to install operating systems (OS) on bare metal machines or machines that do not include an OS.
Because it uses single instance storeit stores only one single copy of any given filethe file-based WIM image format can include several different editions of Vista; the edition you install is determined by the product key you type in during installation. In order to work with WIM images, Microsoft has introduced ImageX, a command-line tool that generates and manipulates WIM images. Other manufacturers have also updated their tools to work with Vista images, both disk and file-based.
Image-Based Setup basically copies the Vista WIM to a computer and then expands it to perform the installation. This IBS process is the same whether you perform an upgrade over an existing operating system or a new installation on a bare metal machine. In the latter case, the installation first boots into Windows PE, then copies the Vista WIM and expands it.
Other installation changes include the ability to install to different hardware without using a different image. Hardware specific installations are tied to the Windows Hardware Abstraction Layer (HAL). The HAL is the component that will make Windows work with specific hardware. Different vendors often require different HALs. In previous versions of Windows, you needed one image for each HAL in your network.
With Vista, the image is HAL-independent, reducing the need for multiple images. In addition, Vista is language agnostic. This means that it installs without any language; language packs are applied at installation and used to personalize the installation to your requirements. Because of this, it is possible to include multiple language packs in the same image and determine which applies during installation. These features bring the concept of one single worldwide image much closer to reality.