WIMBoot is a new feature, currently only available on the desktop side of Windows 8.1 Update, that lets computers boot directly off a Windows image file, or WIM file.
Why would you want this?
WIM files are tremendously compressed. They have been used in the last few releases of Windows as the method by which the operating system was distributed—on the DVDs and ISO files, you would see boot.wim and install.wim, two files that contained essentially the entire Windows system, highly compressed. What the installer was doing during the first phase was simply extracting the full set of files from these compressed WIM files, and then moving on into the next phase of registering DLLs and doing the housekeeping necessary to get from bare metal to a working Windows machine. Interestingly, the compressed WIM file stays on the Windows machine to allow for system file recovery, so you’re paying the disk space price twice: once to store the compressed version of all of the files, and a second time to store the fully expanded version of the files for normal daily use.
WIMBoot turns this on its head, at least on PCs with solid state drives and UEFI firmware—in other words, no traditional or legacy machines with rotating platters for disk drives you boot from, and BIOS chips. It lays down a copy of the compressed WIM file on a special imaging partition, and then during installation, Windows just creates pointers on the operating partition to the compressed files in the partition where the WIM file is stored. The imaging partition is also used as the recovery partition, so it does double duty.
By enabling a scenario where you can boot into Windows directly off of a WIM file, you gain the ability to:
- Have PCs that can use push-button restore while maintaining much more free disk space across the entire device.
- Install Windows on devices with very small, fast drives like tablets, hybrid PCs, and repurposed machines to use as thin clients.
- Install Windows much more quickly by eliminating a time consuming phase of the setup process.
How Do You Create WIMBoot Files?
You can use the Deployment Image Servicing and Management (DISM) tool to create WIMBoot images. Here is a procedure you can use to get started.
- Install Windows 8.1 Update on a PC.
- If you have Windows 8.1 imagines and Windows RE (Recovery Environment) images, stream in the Windows 8.1 Update to those source files, too, so that you are working from the latest version of the operating system.
- Install the Windows Assessment and Deployment Kit Windows 8.1 Updater version.
- Create a boot drive in Windows PE by following the instructions at http://technet.microsoft.com/en-us/library/dn613859.aspx.
- Copy the existing install.wim file into a new temporary file that you will use to create the WIMBoot image.
copy c:\images\install.wim c:\images\install_wimboot.wim
- Mount the image.
dism /mount-image /imagefile:”C:\images\install_wimboot.wim /Index:1 /MountDir:c:\mnt\win
- Grab the hidden Windows RE image and unhide it so you can separate it out to save even more space.
attrib –s –h c:\mnt\win\windows\system32\recovery\winre.wim
move c:\mnt\win\windows\system32\recovery\winre.wim c:\images\winre.wim
- Unmount the image and save your changes with the commit command.
dism /unmount-image /mountdir:c:\mnt\win /commit
- Boot into Windows PE (the boot drive you created in step four), apply the Windows image you just created, and then reboot. When Windows starts the out of box experience upon that next boot, hit Control, Shift, and F3 at the same time to get into audit mode.
- Clean up the image to save even more disk space.
Dism /cleanup-image /online /startcomponentcleanup
- Sysprep the PC as you normally would to scrub SIDs and make the PC ready for imaging.
c:\windows\system32\sysprep\sysprep /generalize /shutdown /oobe
- When the PC reboots, boot into Windows PE again and then recapture the image, which will include the applied updates and remove superseded files to save space. Note the new WIMBoot switch, which instructs DISM to save the image in a format compatible with WIMBoot.
DISM /Capture-Image /WIMBoot /ImageFile:”X:\Images\install_wimboot.wim” /CaptureDir:C: /Name:”WIMBoot Enterprise_x64 8.1 Update”
How do I Deploy WIMBoot into Production?
To use the WIMBoot image you created above, you need to boot your target PCs into Windows PE and then create a partition layout that includes a system partition, a Windows partition, and the image partition. Here is a sample diskpart script to create the required layout.
select disk 0
create partition efi size=100
format quick fs=fat32 label="System"
create partition msr size=128
create partition primary
format quick fs=ntfs label="Windows"
create partition primary
format quick fs=ntfs label="Images"
You can use the guidance at http://technet.microsoft.com/en-us/library/dn605112.aspx for very detailed sequences of deploying WIMBoot images to different devices based on whether or not you know how big the images will be in advance.
This article originally appeared, with edits, at SearchEnterpriseDesktop.com.