Windows Imaging Format

Like other disk image formats, WIM includes a set of files and their associated file system metadata . However, unlike sector- oriented formats (such as .ISO and .CUE / .BIN , most often used for CD and DVD images), WIM is a file-oriented format, that is, the smallest logical element is a file . The advantage of this approach is the hardware independence of the format and the ability to store only one copy of a file that has many links in the file system tree ( single instance storage ).

Although the format architecture is considered file-oriented, the files are stored inside a separate WIM database, which reduces the costs for SMB when opening and closing many separate files at the end of the data transfer process. The cost of reading or writing many thousands of individual files on a local disk is leveled out by hardware and software disk caching as well as sequential reading or writing of data.

A WIM file can include several images that are identified by a numerical index or a unique name. Single instance storage technology, when adding a new image to existing ones, allows to reduce the size of the WIM database if matching elements are present. A WIM image can also be split into several files that are assigned the .swm extension

One WIM file may link to another. For example, in WDS (Windows Deployment Services), the contents of the files are stored in the Res.rwm file, and in the Image_Name.wim files, a link to Res.rwm plus the folder structure and access rights. ^[2]

Dism - A standard Windows program (starting with Vista ) with wide functionality ^[3] , designed for servicing and preparing Windows images, including, can be used to service a Windows image (WIM file) or virtual hard disk ( VHD file or VHDX file).

Imagex is a command-line utility included with microsoft WAIK for creating, editing, and deploying Windows image files in WIM format. Starting with Windows Vista, the Windows Installer uses the WAIK API to install a new or cloned copy of Windows. The first ImageX implementation had build number 6.0.4007.0 (main.030212-2037). It was used by Microsoft OEM Partners to test Microsoft image technology and was being developed in parallel with the alpha versions of Longhorn . In assembly 6.0.5384.4, various innovations were added: read-write status demarcation, image splitting (SWM), WIM filter driver, and LZX compression algorithms. This build was used in pre-release candidates for Windows Vista .

GImagex - Third-party utility, implementation of ImageX functionality in a graphical interface ( GUI ). It implements all the same functions as ImageX, but in a more user-friendly window view, it does not require either WAIK installed in the system or ImageX executable files.

Developer's site: http://www.autoitscript.com/gimagex/

Wimlib - A third-party open and cross-platform utility with a command line interface and syntax similar to Imagex , as well as a library for creating, extracting and modifying WIM images. Wimlib contains advanced implementations of the compression algorithms XPRESS, LZX and LZMS, as a result of which, greater compression is achieved compared to similar technologies from microsoft. In addition, wimlib can be used to work with ESD archives (Electronic Software Download). ESD archives are WIM archives that use LZMS compression in continuous mode and therefore are usually much smaller than regular WIM archives. Microsoft sometimes distributes ESD archives with encrypted content, wimlib cannot independently decrypt such archives.

Developer site: https://wimlib.net/

A WIM image can also be mounted on a logical drive under Windows with a drive letter assigned to facilitate editing its contents (thanks to this, a WIM image can be easily converted to an ISO image ). It should be noted that the WimFltr.sys driver must be loaded before mounting the WIM image using ImageX.

Subsequently, APIs for working with WIM images were also published. Their functionality is implemented through the WIMGAPI.DLL library. In this way, independent developers can create their own software tools.

WIM images can be bootable . In this case, the BOOT.WIM file contains the bootable version of the Windows PE environment from which the installation process is performed. The remaining installation files are included in INSTALL.WIM.

In addition to the standard Microsoft utilities, you can also extract files from a WIM image using the free 7-Zip file archiver. However, he will not open some files.

• Windows Preinstallation Environment
• en: System Deployment Image

• Windows Imaging Format Whitepaper describing the internal structure of WIM files
• ImageX and the WIM image format on en: Microsoft TechNet (Russian)
• File Extension Details for .WIM at filext.com
• DISM on technet.microsoft.com (Russian)