Windows Image File Boot (WIMBoot) Overview
Applies To: Windows 8.1
Windows image file boot (WIMBoot) lets you set up a PC so that it runs directly from a compressed Windows image file (WIM file).
WIMBoot can significantly reduce the amount of space used by Windows files. This helps you provide more free space to users, and helps you manufacture Windows on PCs with smaller drives.
WIMBoot can also help reduce manufacturing time:
You can deploy Windows with fewer compression/decompression steps.
You can make updates to the image on the factory floor faster by using a separate customized image file.
You can refresh a PC or restore it to its factory state faster. This reduces the need to create a separate partition for testing a PC on the factory floor, and can also help reduce PC support calls.
WIMBoot is available for client editions of Windows 8.1 with Windows 8.1 Update only (not server versions). All architectures are supported, including amd64, x86, and ARM. Some enterprise deployment tools do not support WIMBoot.
WIMBoot is available only for UEFI-based PCs running in UEFI mode (legacy BIOS-compatibility mode isn't supported).
WIMBoot is supported for solid-state drives and eMMC (Windows HCK compliant) drives. WIMBoot isn't supported on traditional drives that contain rotational components, or on hybrid drives that contain both solid-state and rotational drive components. WIMBoot works by taking advantage of the capability of solid-state drives to access different areas of the hard drive quickly.
It's OK to have a secondary drive attached to the PC, and the secondary drive can contain rotational components. But the WIMBoot image and pointer files must all be located on the primary solid-state or eMMC drive.
Some backup, antivirus, and encryption tools aren’t compatible with WIMBoot images.
In bare metal recovery scenarios (booting windows RE from an external hard drive) on a WIMBoot-configured PC, the only supported push button reset option is to reset the PC by wiping and recreating partitions. For more information, see Push-Button Reset Overview and Bare Metal Reset/Recovery: Enable Your Users to Create Media and to Recover Hard Drive Space.
November 2014: Windows 8.1 Update PCs configured with WIMBoot will not receive November Update (KB3000850).
To save drive space, we’ve limited offering only the following types of updates from Windows Update to WIMBoot devices with 32GB or less of storage space:
Critical updates that keep the system or programs running.
Security updates and security advisory updates.
Users can still manually download and install updates from the Microsoft Download Center.
WIMBoot is not recommended on systems with fixed internal storage of more than 32GB.
How does it work?
In a standard Windows installation (without WIMBoot), every file is written to disk at least twice: once in the compressed form for recovery, and once in the uncompressed form in the applied image. When the push-button reset feature is included, the compressed image remains on the PC. Having both the Windows installation and recovery image on the device can take up a lot of disk space.
When installing Windows with WIMBoot, you write the files to the disk only once, in compressed format. Next, you apply a set of pointer files onto the Windows partition that point back to the compressed files in the Images partition. When the user adds files, apps, or updates, they're added onto the Windows partition.
In WIMBoot, your WIMBoot image is also used as the recovery image, saving disk space.
New partition layout
WIMBoot uses a new partition layout.
Standard partition layout (without WIMBoot):
- The Windows 8.1 partition layout includes two system partitions (ESP and MSR), a Windows partition, and two separate recovery partitions:
The Images partition contains the compressed images of the Windows files (install.wim), the Windows RE recovery tools (winre.wim), and other factory floor customizations (custom.wim).
The Windows partition contains the pointer files to the compressed image, plus free space for any new files created by the end user, including registry files, page files, hibernation files, user data, and user-installed apps and updates.
For more info, see Deploy WIMBoot Images: If you know the size of the images upfront.
Factory floor customizations
The WIMBoot process supports creating a separate custom.wim file for final customizations, such as Windows updates, build-to-order apps and drivers, or other changes that typically happen on the factory floor. This means you don't have to recapture these updates into the fully-loaded install.wim. This change can potentially save time during the manufacturing process.
If the user refreshes the image, the push-button reset tools refresh the pointers to both the install.wim and the custom.wim file.
For more info, see Create WIMBoot Images and Deploy WIMBoot Images: If you know the size of the images upfront.
Security with WIMBoot
WIMBoot is compatible with Secure Boot.
We don’t recommend that you use encryption tools, such as BitLocker, on the Images partition because this might reduce system performance. If you have sensitive apps or data to preinstall, install them to the Windows partition.
To deploy Windows using the WIMBoot, you'll need the Windows 8.1 Update version of the Windows Assessment and Deployment Kit (Windows ADK), with the following tools.
You'll need the updated version of DISM to capture and apply the installation files. For more info, see What's New in DISM.
To capture and apply the installation files, you'll need Windows PE 5.1, which includes the updated version of DISM. For more info, see Update WinPE 5.0 to WinPE 5.1.
Windows RE / Push-button reset
For WIMBoot PCs:
The push-button reset feature is enabled automatically for client editions of Windows and cannot be disabled or opted out of. You don't need to register your push-button reset WIM file (install.wim).
You'll still need to register the Windows RE file (winre.wim). For more info, see Deploy WIMBoot Images: If you know the size of the images upfront.
The built-in recovery drive creator (bare metal reset) is enabled automatically for client editions of Windows, using the WIMBoot hard drive partition layout. If you're using a non-standard partition configuration, you'll need to update your ResetConfig.xml file and add the new WIMBoot parameter. For more info, see ResetConfig XML Reference.
WIMBoot doesn't support split WIM (.swm) files. If you need to create bare metal reset media on a WIMBoot configuration with a WIM file that is larger than 4GB, use the Create a recovery drive feature, which splits the WIM using an internal format. For more info, see Bare Metal Reset/Recovery: Enable Your Users to Create Media and to Recover Hard Drive Space.