A boot menu is displayed on a client computer when the client performs a Pre-Boot Execution Environment (PXE) boots and more than one boot image is available to that client. If only one boot image is available, the computer will automatically boot into that image. The boot images are ordered alphabetically, based on the file name of the .wim file that contains the image.

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Configuring the Boot Menu

Microsoft has completely reengineered the boot environment for Windows Vista and Windows Server® 2008 to address the increasing complexity and diversity of modern hardware and firmware. One aspect of this reengineering is a new firmware-independent data store that contains boot configuration data (BCD). The BCD store defines how the boot menu is configured. The store is a namespace container for BCD objects and elements that holds the information that is required to load Windows or run other boot applications. Physically, a BCD store is a binary file in the registry hive format. For more information about BCDs, see http://go.microsoft.com/fwlink/?LinkID=110353.

To customize the BCD store, see How to Modify the BCD Store Using Bcdedit. Note that when you modify the BCD store, you must force it to be recreated in order for your changes to take effect. To do this, either restart the WDSServer service (run wdsutil /stop-server and then run wdsutil /start-server) or run Sc control wdsserver 129. Because the menu exists outside of an operating system, there are certain limitations placed on the user interface (UI), including the following:

  • The screen size is 80x25 pixels, which means that approximately 13 images can be displayed on the page simultaneously. If more than 13 images are available, the display will scroll to support the additional images. The number of images that can be shown is dependent on several factors, including the number of images that need to be displayed to the client and the number of characters in the image name.

  • There is no mouse or Input Method Editor (IME) functionality.

  • There is no support for alternate keyboards, other than what the BIOS supports.

  • There is limited support for localization, other than what the BIOS supports.

  • There is limited support for accessibility.

Specifying Boot Images for Prestaged Clients

You can assign a boot image to a prestaged computer in Active Directory Domain Services (AD DS). For instructions, see the "Prestage Computers" section in How to Manage Client Computers. In these instances, Windows Deployment Services must dynamically create a BCD store for the booting client that has the assigned boot image selected as the default. Rather than generating a unique BCD store that contains only that operating system entry for each booting client (which, due to the BCD architecture may take several seconds), the existing BCD store for the client’s architecture (in RemoteInstall\Tmp) is copied and the default selection is modified to reflect the new default. In addition, other booting clients that have been assigned the same boot image can reuse this dynamically generated BCD store.

Considerations for x64-Based Clients

Because x64-based computers are capable of booting both x86-based and x64-based images, the default behavior is that x64-based users see a list of both x86-based and x64-based boot images when both are available on the server. This means that x64-based clients receive the x86x64.{GUID}.bcd store. For instructions on configuring the boot image policy that x64-based clients should see, see the "Boot Program and Boot Image" section in How to Manage Client Computers.

To work-around issues where the booting client may not be sending the correct architecture value in the initial PXE discovery packet, the Wdsnbp.com boot program will detect the architecture of the booting client and report that value back to the Windows Deployment Services server. For more information, see the "List of NBPs" section in Managing Network Boot Programs.