Booting Windows PE from RAM Disk

Published: February 29, 2012

Updated: May 31, 2012

Applies To: Windows 8, Windows Server 2008 R2, Windows Server 2012

After you create a custom Windows® Preinstallation Environment (Windows PE) image, you must decide how the image will boot and where it will run from. There are several ways to boot Windows PE by using a RAM disk.

You can create bootable Windows PE RAM disk images on:

  • A CD-ROM or DVD-ROM.

  • A USB flash drive.

  • A hard drive.

  • A Windows Deployment Services server. You can access the image by using the Pre-Boot Execution Environment (PXE) boot.

  • A supported PXE server. You can access the image by using PXE boot.

For more information on methods of creating and booting to RAM disk, see Walkthrough: Install Windows PE to CD, USB Flash Drive, or USB Hard Drive.

The small size of Windows PE enables the complete Windows PE operating system image to load into random access memory (RAM) and to start the computer from a RAM disk. The RAM disk boot feature provides a virtual CD file system in memory.

Booting Windows PE from a RAM disk enables you to do the following:

  • Swap the removable media that is used to start the computer and insert different media to add drivers, utilities, applications, or a Windows operating-system image.

  • Start the computer from a Windows Deployment Services PXE server, which can disconnect from the network after Windows PE has loaded. After the initial download of the Windows PE image, there are no dependencies on network resources.

  • Delete and repartition the hard disk from which Windows PE has started.

  • Decrease total boot time.

The following items are required for starting Windows PE by using a RAM disk:

  • An x86-based or x64-based computer.

  • A bootable Windows PE image that is created from a Windows PE base image.

  • A minimum of 512 megabytes (MB) of RAM when you use the default Windows PE disk image.

Windows PE assigns drive letters to partitions alphabetically, starting with C. Be aware that Windows PE assigns drive letters that differ from the drive letters that Windows assigns to partitions. When you create deployment scripts based on these drives, assign drive partitions to letters M through Z of the alphabet to avoid drive lettering conflicts. Do not use drive X in deployment scripts. By default, Windows PE assigns X as the drive letter of any media that it boots from.You can change the drive location by using the Dism /Set-TargetPath command. To re-letter drives in Windows, either manually update the lettering in audit mode or use the Microsoft-Windows-Setup | DiskConfiguration Disk | ModifyPartitions | ModifyPartition | Letter answer file setting. For more information, see, Hard Drives and Partitions Overview.

See Also