The Windows Imaging Format (WIM) is a

file File or filing may refer to: Mechanical tools and processes * File (tool), a tool used to ''remove'' fine amounts of material from a workpiece **Filing (metalworking), a material removal process in manufacturing ** Nail file, a tool used to gent ...

-based

disk image A disk image, in computing, is a computer file containing the contents and structure of a disk volume or of an entire data storage device, such as a hard disk drive, tape drive, floppy disk, optical disc, or USB flash drive. A disk image is us ...

format Format may refer to: Printing and visual media * Text formatting, the typesetting of text elements * Paper formats, or paper size standards * Newspaper format, the size of the paper page Computing * File format, particular way that informatio ...

. It was developed by

Microsoft Microsoft Corporation is an American multinational technology corporation producing computer software, consumer electronics, personal computers, and related services headquartered at the Microsoft Redmond campus located in Redmond, Washing ...

to help deploy

Windows Vista Windows Vista is a major release of the Windows NT operating system developed by Microsoft. It was the direct successor to Windows XP, which was released five years before, at the time being the longest time span between successive releases of ...

and subsequent versions of the

Windows Windows is a group of several proprietary graphical operating system families developed and marketed by Microsoft. Each family caters to a certain sector of the computing industry. For example, Windows NT for consumers, Windows Server for serv ...

operating system An operating system (OS) is system software that manages computer hardware, software resources, and provides common services for computer programs. Time-sharing operating systems schedule tasks for efficient use of the system and may also in ...

family, as well as

Windows Fundamentals for Legacy PCs Windows Fundamentals for Legacy PCs ("WinFLP") is a thin client release of the Windows NT operating system developed by Microsoft and optimized for older, less powerful hardware. It was released on July 8, 2006, nearly two years after its Wind ...

Design

Like other

formats, a WIM

contains a set of files and associated

filesystem In computing, file system or filesystem (often abbreviated to fs) is a method and data structure that the operating system uses to control how data is stored and retrieved. Without a file system, data placed in a storage medium would be one larg ...

metadata Metadata is "data that provides information about other data", but not the content of the data, such as the text of a message or the image itself. There are many distinct types of metadata, including: * Descriptive metadata – the descriptive ...

. However, unlike

sector Sector may refer to: Places * Sector, West Virginia, U.S. Geometry * Circular sector, the portion of a disc enclosed by two radii and a circular arc * Hyperbolic sector, a region enclosed by two radii and a hyperbolic arc * Spherical sector, a p ...

-based formats (such as

ISO ISO is the most common abbreviation for the International Organization for Standardization. ISO or Iso may also refer to: Business and finance * Iso (supermarket), a chain of Danish supermarkets incorporated into the SuperBest chain in 2007 * Iso ...

or VHD), WIM is file-based: the fundamental unit of information in a WIM is a file. The primary advantages of being file-based is hardware independence and

single-instance storage Single-instance storage (SIS) is a system's ability to take multiple copies of content and replace them by a single shared copy. It is a means to eliminate data duplication and to increase efficiency. SIS is frequently implemented in file systems ...

of a file referenced multiple times in the filesystem tree. Since the files are stored inside a single WIM file, the overhead of opening and closing many individual files is reduced. The cost of reading or writing many thousands of individual files on the local disk is negated by hardware and software-based disk caching as well as sequential reading and writing of the data. WIM files can contain multiple disk images, which are referenced either by their numerical index or by their unique name. Due to the use of single-instance storage, the more each successive disk image has in common with previous images added to the WIM file, the less new data will be added. A WIM can also be split (spanned) into multiple parts, which have the extension. WIM images can be made

bootable In computing, booting is the process of starting a computer as initiated via hardware such as a button or by a software command. After it is switched on, a computer's central processing unit (CPU) has no software in its main memory, so some ...

and Windows

boot loader A bootloader, also spelled as boot loader or called boot manager and bootstrap loader, is a computer program that is responsible for booting a computer. When a computer is turned off, its softwareincluding operating systems, application code, a ...

supports booting Windows from a WIM file. Windows Setup DVD in Windows Vista and later use such WIM files. In this case, BOOT.WIM contains a bootable version of

Windows PE Windows Preinstallation Environment (also known as Windows PE and WinPE) is a lightweight version of Windows used for the deployment of PCs, workstations, and servers, or troubleshooting an operating system while it is offline. It is intended t ...

from which the installation is performed. Other setup files are held in the INSTALL.WIM. Since Windows 8.1, the size of Windows directory can be reduced by moving system files into compressed WIM images stored on a separate hidden partition ( WIMBoot).Windows Image File Boot (WIMBoot) Overview
/ref> Since

Windows 10 Windows 10 is a major release of Microsoft's Windows NT operating system. It is the direct successor to Windows 8.1, which was released nearly two years earlier. It was released to manufacturing on July 15, 2015, and later to retail on J ...

, system files can be compressed on the system disk ( CompactOS). WIM supports three families of

LZ77 LZ77 and LZ78 are the two lossless data compression algorithms published in papers by Abraham Lempel and Jacob Ziv in 1977 and 1978. They are also known as LZ1 and LZ2 respectively. These two algorithms form the basis for many variations includin ...

-based compression algorithms in ascending ratio and descending speed: XPRESS, LZX, and LZMS.wimlib: the open source Windows Imaging (WIM) library - Compression algorithm
/ref> The former two use

Huffman encoding In computer science and information theory, a Huffman code is a particular type of optimal prefix code that is commonly used for lossless data compression. The process of finding or using such a code proceeds by means of Huffman coding, an algor ...

, while the latter uses adaptive Huffman encoding with

range coding Range coding (or range encoding) is an entropy coding method defined by G. Nigel N. Martin in a 1979 paper,, 100000)) using the probability distribution . The encoder breaks down the range , 100000) into three subranges: A: [ ...

. There is also support for solid compression. Both solid compression and LZMS are introduced more recently, in WIMGAPI from Windows 8 and DISM from Windows 8.1.

Tools

ImageX

ImageX is the command-line tool used to create, edit and deploy

disk images in the Windows Imaging Format. Along with the underlying Windows Imaging Interface library (WIMGAPI), it is distributed as part of the free

Windows Automated Installation Kit Windows Assessment and Deployment Kit (Windows ADK), formerly Windows Automated Installation Kit (Windows AIK or WAIK), is a collection of tools and technologies produced by Microsoft designed to help deploy Microsoft Windows operating system imag ...

(WAIK/OPK). Starting with

, Windows Setup uses the WAIK API to install Windows. The first distributed prototype of ImageX was built 6.0.4007.0 (main.030212-2037). It allowed Microsoft

OEM An original equipment manufacturer (OEM) is generally perceived as a company that produces non-aftermarket parts and equipment that may be marketed by another manufacturer. It is a common industry term recognized and used by many professional or ...

partners to experiment with the imaging technology and was developed in parallel with Longhorn alpha prototypes. It was first introduced in Milestone 4 into the Longhorn project and used in later builds of Longhorn. Build 6.0.5384.4 added significant advantages over previous versions, like read-only and read/write folder mounting capabilities, splitting to multiple image files (SWM), a WIM filter driver and the latest compression algorithms. It has been used since pre-RC (release candidates) of Windows Vista.

DISM

Deployment Image Service and Management Tool (DISM) is a tool introduced in Windows 7 and Windows Server 2008 R2 that can perform servicing tasks on a Windows installation image, be it an online image (i.e. the one the user is running) or an offline image within a folder or WIM file. Its features include mounting and unmounting images, querying installed device drivers in an offline image, and adding a device driver to an offline image. It is now possible to repair with DISM any image using either a Windows Installation CD or

Windows Update Windows Update is a Microsoft service for the Windows 9x and Windows NT families of operating system, which automates downloading and installing Microsoft Windows software updates over the Internet. The service delivers software updates for Wind ...

. Before Windows Server 2012 and Windows 8, DISM had incorporated the majority of ImageX functions but not all; ImageX was still needed for image capture. However, DISM

deprecated In several fields, especially computing, deprecation is the discouragement of use of some terminology, feature, design, or practice, typically because it has been superseded or is no longer considered efficient or safe, without completely removing ...

ImageX in Windows 8.

Support in other operating systems

Since April 30, 2012, an open-source library for handling the WIM format is available. This library can be used on

Unix-like A Unix-like (sometimes referred to as UN*X or *nix) operating system is one that behaves in a manner similar to a Unix system, although not necessarily conforming to or being certified to any version of the Single UNIX Specification. A Unix-li ...

systems, as well as on Windows. Thanks to this project,

Linux Linux ( or ) is a family of open-source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically packaged as a Linux distribution, which ...

distributions now have their own imagex clone called ''wimlib-imagex'', which allows mounting WIM images and managing them (read/write) like any other block-storage provider. As WIM images use somewhat common compression algorithms, they can be accessed by using

file archiver A file archiver is a computer program that combines a number of files together into one archive file, or a series of archive files, for easier transportation or storage. File archivers may employ lossless data compression in their archive formats ...

s like

7-Zip 7-Zip is a free and open-source file archiver, a utility used to place groups of files within compressed containers known as "archives". It is developed by Igor Pavlov and was first released in 1999. 7-Zip has its own archive format called 7z, ...

. For other operating systems that might not support this format, it is still possible to convert .wim images to the more commonly used

ISO image An optical disc image (or ISO image, from the ISO 9660 file system used with CD-ROM media) is a disk image that contains everything that would be written to an optical disc, disk sector by disc sector, including the optical disc file system. ...

using the

Windows Assessment and Deployment Kit Windows Assessment and Deployment Kit (Windows ADK), formerly Windows Automated Installation Kit (Windows AIK or WAIK), is a collection of tools and technologies produced by Microsoft designed to help deploy Microsoft Windows operating system imag ...

on Windows.

References

External links

Windows Imaging Format Whitepaper that describes the internal file structure of WIM files

ImageX and WIM Image Format
at

Microsoft TechNet Microsoft TechNet was a Microsoft web portal and web service for IT professionals. It included a library containing documentation and technical resources for Microsoft products, a learning center which provides online training, discussion forums ...

{{Windows Components Archive formats Windows Vista Windows Server 2008 Disk images