3 This is wimlib version 1.7.1-BETA (June 2014). wimlib is a C library for
4 creating, modifying, extracting, and mounting files in the Windows Imaging
5 Format (WIM files). These files are normally created using the ImageX
6 (imagex.exe) or Dism (Dism.exe) utilities on Windows, but wimlib is distributed
7 with a free implementation of ImageX called "wimlib-imagex" for both UNIX-like
12 To install wimlib and wimlib-imagex on Windows you simply need to download and
13 extract the ZIP file containing the latest binaries from the SourceForge page
14 (http://sourceforge.net/projects/wimlib/), which you may have already done.
16 To install wimlib and wimlib-imagex on UNIX-like systems (with Linux being the
17 primary supported and tested platform), you must compile the source code, which
18 is also available at http://sourceforge.net/projects/wimlib/. Alternatively,
19 check if a package has been prepared for your Linux distribution. Example files
20 for Debian and RPM packaging are in the debian/ and rpm/ directories.
24 A Windows Imaging (WIM) file is an archive designed primarily for archiving
25 Windows filesystems. However, it can be used on other platforms as well, with
26 some limitations. Like some other archive formats such as ZIP, files in WIM
27 archives may be compressed. WIM files support multiple compression formats,
28 including LZX, XPRESS, and LZMS. All these formats are supported by wimlib.
30 A WIM file consists of one or more "images". Each image is an independent
31 top-level directory structure and is logically separate from all other images in
32 the WIM. Each image has a name as well as a 1-based index in the WIM file. To
33 save space, WIM archives automatically combine all duplicate files across all
36 A WIM file may be either stand-alone or split into multiple parts. Split WIMs
37 are read-only and cannot be modified.
39 Since version 1.6.0, wimlib also supports ESD (.esd) files, except when
40 encrypted. These are still WIM files but they use a newer version of the file
45 wimlib itself is a C library, and it provides a documented public API (See:
46 http://wimlib.sourceforge.net) for other programs to use. However, it is also
47 distributed with a command-line program called "wimlib-imagex" that uses this
48 library to implement an imaging tool similar to Microsoft's ImageX.
49 wimlib-imagex supports almost all the capabilities of Microsoft's ImageX as well
50 as additional capabilities. wimlib-imagex works on both UNIX-like systems and
51 Windows, although some features differ between the platforms.
53 Run `wimlib-imagex' with no arguments to see an overview of the available
54 commands and their syntax. For additional documentation:
56 * If you have installed wimlib-imagex on a UNIX-like system, you will find
57 further documentation in the man pages; run `man wimlib-imagex' to get
60 * If you have downloaded the Windows binary distribution, you will find the
61 documentation for wimlib-imagex in PDF format in the "doc" directory,
62 ready for viewing with any PDF viewer. Please note that although the PDF
63 files are converted from UNIX-style "man pages", they do document
64 Windows-specific behavior when appropriate.
68 wimlib (and wimlib-imagex) can create XPRESS, LZX, or LZMS compressed WIM files.
69 wimlib includes its own compression codecs and does not use the compression API
70 available on some versions of Windows.
72 I have gradually been improving the compression codecs in wimlib. For XPRESS
73 and LZX, they now usually outperform and outcompress the equivalent Microsoft
74 implementations. Although results will vary depending on the data being
75 compressed, in the table below I present the results for a common use case:
76 compressing an x86 Windows PE image. Each row displays the compression type,
77 the size of the resulting WIM file in bytes, and how many seconds it took to
78 create the file. When applicable, the results with the equivalent Microsoft
79 implementation in WIMGAPI is included.
81 =============================================================================
82 | Compression || wimlib (v1.7.1) | WIMGAPI (Windows 8.1) |
83 =============================================================================
84 | None [1] || 361,182,560 in 3.7s | 361,183,674 in 4.4s |
85 | XPRESS [2] || 138,349,798 in 5.8s | 140,416,657 in 6.8s |
86 | XPRESS (slow) [3] || 135,234,072 in 19.5s | N/A |
87 | LZX (quick) [4] || 131,816,279 in 6.7s | N/A |
88 | LZX (normal) [5] || 126,808,347 in 28.3s | 127,259,566 in 31.4s |
89 | LZX (slow) [6] || 126,199,523 in 61.4s | N/A |
90 | LZMS (non-solid) [7] || 122,083,126 in 30.4s | N/A |
91 | LZMS (solid) [8] || 93,752,206 in 84.3s | 88,742,238 in 156.1s |
92 | "WIMBoot" [9] || 167,039,787 in 7.6s | 169,051,718 in 14.9s |
93 | "WIMBoot" (slow) [10] || 165,141,503 in 15.8s | N/A |
94 =============================================================================
97 [1] '--compress=none' for wimlib-imagex; '/compress:none' for DISM.
99 [2] '--compress=XPRESS' for wimlib-imagex; '/compress:fast' for DISM.
100 Compression chunk size defaults to 32768 bytes in both cases.
102 [3] '--compress=XPRESS:80' for wimlib-imagex; no known equivalent for DISM.
103 Compression chunk size defaults to 32768 bytes.
105 [4] '--compress=LZX:20' for wimlib-imagex; no known equivalent for DISM.
106 Compression chunk size defaults to 32768 bytes.
108 [5] '--compress=LZX' or '--compress=LZX:50' or no option for wimlib-imagex;
109 '/compress:maximum' for DISM.
110 Compression chunk size defaults to 32768 bytes in both cases.
112 [6] '--compress=LZX:100' for wimlib-imagex; no known equivalent for DISM.
113 Compression chunk size defaults to 32768 bytes.
115 [7] '--compress=LZMS' for wimlib-imagex; no known equivalent for DISM.
116 Compression chunk size defaults to 131072 bytes.
118 [8] '--solid' for wimlib-imagex. Should be '/compress:recovery' for DISM,
119 but only works for /Export-Image, not /Capture-Image. Compression chunk
120 size in solid blocks defaults to 33554432 for wimlib, 67108864 for DISM.
122 [9] '--wimboot' for wimlib-imagex; '/wimboot' for DISM.
123 This is really XPRESS compression with 4096 byte chunks, so the same as
124 '--compress=XPRESS --chunk-size=4096'.
126 [10] '--wimboot --compress=XPRESS:80' for wimlib-imagex;
127 no known equivalent for DISM.
128 Same format as [9], but trying harder to get a good compression ratio.
130 Note: wimlib-imagex's --compress option also accepts the "fast", "maximum", and
131 "recovery" aliases for XPRESS, LZX, and LZMS, respectively.
136 - Windows 8.1 virtual machine running on Linux with VT-x
137 - 2 CPUs and 2 GiB memory given to virtual machine
138 - SSD-backed virtual disk
139 - All tests done with page cache warmed
141 The compression ratio provided by wimlib is also competitive with commonly used
142 archive formats. Below are file sizes that result when the Canterbury corpus is
143 compressed with wimlib (v1.7.0), WIMGAPI (Windows 8), and some other
146 =================================================
147 | Format | Size (bytes) |
148 =================================================
150 | WIM (WIMGAPI, None) | 2,814,278 |
151 | WIM (wimlib, None) | 2,813,856 |
152 | WIM (WIMGAPI, XPRESS) | 825,410 |
153 | WIM (wimlib, XPRESS) | 792,024 |
154 | tar.gz (gzip, default) | 738,796 |
155 | ZIP (Info-ZIP, default) | 735,334 |
156 | tar.gz (gzip, -9) | 733,971 |
157 | ZIP (Info-ZIP, -9) | 732,297 |
158 | WIM (wimlib, LZX quick) | 722,196 |
159 | WIM (WIMGAPI, LZX) | 651,766 |
160 | WIM (wimlib, LZX normal) | 649,204 |
161 | WIM (wimlib, LZX slow) | 639,618 |
162 | WIM (wimlib, LZMS non-solid) | 592,136 |
163 | tar.bz2 (bzip, default) | 565,008 |
164 | tar.bz2 (bzip, -9) | 565,008 |
165 | WIM (wimlib, LZMS solid) | 525,270 |
166 | WIM (wimlib, LZMS solid, slow) | 521,700 |
167 | WIM (WIMGAPI, LZMS solid) | 521,232 |
168 | tar.xz (xz, default) | 486,916 |
169 | tar.xz (xz, -9) | 486,904 |
170 | 7z (7-zip, default) | 484,700 |
171 | 7z (7-zip, -9) | 483,239 |
172 =================================================
174 Note: WIM does even better on directory trees containing duplicate files, which
175 the Canterbury corpus doesn't have.
179 WIM images may contain data, such as alternate data streams and
180 compression/encryption flags, that are best represented on the NTFS filesystem
181 used on Windows. Also, WIM images may contain security descriptors which are
182 specific to Windows and cannot be represented on other operating systems.
183 wimlib handles this NTFS-specific or Windows-specific data in a
184 platform-dependent way:
186 * In the Windows version of wimlib and wimlib-imagex, NTFS-specific and
187 Windows-specific data are supported natively.
189 * In the UNIX version of wimlib and wimlib-imagex, NTFS-specific and
190 Windows-specific data are ordinarily ignored; however, there is also special
191 support for capturing and extracting images directly to/from unmounted NTFS
192 volumes. This was made possible with the help of libntfs-3g from the
195 For both platforms the code for NTFS capture and extraction is complete enough
196 that it is possible to apply an image from the "install.wim" contained in recent
197 Windows installation media (Vista, Windows 7, or Windows 8) directly to an NTFS
198 filesystem, and then boot Windows from it after preparing the Boot Configuration
199 Data. In addition, a Windows installation can be captured (or backed up) into a
200 WIM file, and then re-applied later.
204 A major use for wimlib and wimlib-imagex is to create customized images of
205 Windows PE, the Windows Preinstallation Environment, on either UNIX-like systems
206 or Windows without having to rely on Microsoft's software and its restrictions
209 Windows PE is a lightweight version of Windows that can run entirely from memory
210 and can be used to install Windows from local media or a network drive or
211 perform maintenance. It is the operating system that runs when you boot from
212 the Windows installation media.
214 You can find Windows PE on the installation DVD for Windows Vista, Windows 7, or
215 Windows 8, in the file `sources/boot.wim'. Windows PE can also be found in the
216 Windows Automated Installation Kit (WAIK), which is free to download from
217 Microsoft, inside the `WinPE.cab' file, which you can extract natively on
218 Windows, or on UNIX-like systems if you install either the `cabextract' or
221 In addition, Windows installations and recovery partitions frequently contain a
222 WIM containing an image of the Windows Recovery Environment, which is similar to
225 A shell script `mkwinpeimg' is distributed with wimlib on UNIX-like systems to
226 ease the process of creating and customizing a bootable Windows PE image.
230 This section documents the dependencies of wimlib and the programs distributed
231 with it, when building for a UNIX-like system from source. If you have
232 downloaded the Windows binary distribution of wimlib and wimlib-imagex then all
233 dependencies were already included and this section is irrelevant.
236 This is a commonly used free library to read and write XML files. You
237 likely already have it installed as a dependency for some other program.
238 For more information see http://xmlsoft.org/.
240 * libfuse (optional but highly recommended)
241 Unless configured with --without-fuse, wimlib requires a non-ancient
242 version of libfuse to be installed. Most Linux distributions already
243 include this, but make sure you have the libfuse package installed, and
244 also libfuse-dev if your distribution distributes header files
245 separately. FUSE also requires a kernel module. If the kernel module
246 is available it will automatically be loaded if you try to mount a WIM
247 file. For more information see http://fuse.sourceforge.net/. FUSE is
248 also available for FreeBSD.
250 * libntfs-3g (optional but highly recommended)
251 Unless configured with --without-ntfs-3g, wimlib requires the library
252 and headers for libntfs-3g version 2011-4-12 or later to be installed.
253 Versions dated 2010-3-6 and earlier do not work because they are missing
254 the header xattrs.h (and the file xattrs.c, which contains functions we
255 need). libntfs-3g version 2013-1-13 is compatible only with wimlib
258 * OpenSSL / libcrypto (optional)
259 wimlib can use the SHA1 message digest code from OpenSSL instead of
260 compiling in yet another SHA1 implementation. (See LICENSE section.)
264 * syslinux (optional)
265 * cabextract (optional)
266 The `mkwinpeimg' shell script will look for several other programs
267 depending on what options are given to it. Depending on your Linux
268 distribution, you may already have these programs installed, or they may
269 be in the software repository. Making an ISO filesystem requires
270 `mkisofs' from `cdrkit' (http://www.cdrkit.org). Making a disk image
271 requires `mtools' (http://www.gnu.org/software/mtools) and `syslinux'
272 (http://www.syslinux.org). Retrieving files from the Windows Automated
273 Installation Kit requires `cabextract' (http://www.cabextract.org.uk).
277 This section documents the most important options that may be passed to the
278 "configure" script when building from source:
281 If libntfs-3g is not available or is not version 2011-4-12 or later,
282 wimlib can be built without it, in which case it will not be possible to
283 apply or capture images directly to/from NTFS volumes.
286 If libfuse or the FUSE kernel module is not available, wimlib can be
287 compiled with --without-fuse. This will remove the ability to mount and
291 Build in functions for SHA1 rather than using external SHA1 functions
292 from libcrypto (part of OpenSSL). The default is to use libcrypto if it
293 is found on the system.
295 --disable-multithreaded-compression
296 By default, data will be compressed using multiple threads when writing
297 a WIM, unless only 1 processor is detected. Specify this option to
298 disable support for this.
301 Use a very fast assembly language implementation of SHA1 from Intel.
302 Only use this if the build target supports the SSSE3 instructions.
304 --disable-error-messages
305 Save some space by removing all error messages from the library.
308 Remove assertions included by default.
312 wimlib has primarily been tested on Linux and Windows (primarily Windows 7, but
313 also Windows XP and Windows 8).
315 wimlib may work on FreeBSD and Mac OS X. However, this is not well tested. If
316 you do not have libntfs-3g 2011-4-12 or later available, you must configure
317 wimlib with --without-ntfs-3g. On FreeBSD, before mounting a WIM you need to
318 load the POSIX message queue module (run `kldload mqueuefs').
320 The code has primarily been tested on x86 and x86_64 CPUs, but it's written to
321 be portable to other architectures and I've also tested it on ARM. However,
322 although the code is written to correctly deal with endianness, it has not yet
323 actually been tested on a big-endian architecture.
327 The WIM file format is partially specified in a document that can be found in
328 the Microsoft Download Center. However, this document really only provides an
329 overview of the format and is not a formal specification.
331 With regards to the supported compression formats:
333 - Microsoft has official documentation for XPRESS that is of reasonable quality.
334 - Microsoft has official documentation for LZX but it contains errors.
335 - There does not seem to be any official documentation for LZMS, so my comments
336 and code in src/lzms-decompress.c may in fact be the best documentation
337 available for this particular compression format.
339 The code in ntfs-3g_apply.c and ntfs-3g_capture.c uses the NTFS-3g library,
340 which is a library for reading and writing to NTFS filesystems (the filesystem
341 used by recent versions of Windows). See
342 http://www.tuxera.com/community/ntfs-3g-download/ for more information.
344 The LZX decompressor (lzx-decompress.c) was originally based on code from the
345 cabextract project (http://www.cabextract.org.uk). The LZX compressor
346 (lzx-compress.c) was originally based on code written by Matthew Russotto
347 (www.russotto.net/chm/). However I have since rewritten and made many
348 improvements to both the decompressor and compressor.
350 lz_binary_trees.c contains LZ77 match-finding code that uses binary trees. It
351 is based on code from liblzma but I have since rewritten it.
353 A limited number of other free programs can handle some parts of the WIM
356 * 7-zip is able to extract and create WIMs (as well as files in many
357 other archive formats). However, wimlib is designed specifically to handle
358 WIM files and provides features previously only available in Microsoft's
359 implementation, such as the ability to mount WIMs read-write as well as
360 read-only, the ability to create compressed WIMs, and the correct handling
361 of security descriptors and hard links.
362 * ImagePyX (https://github.com/maxpat78/ImagePyX) is a Python program that
363 provides similar capabilities to wimlib-imagex. One thing to note, though,
364 is that it does not support compression and decompression by itself, but
365 instead relies on external native code, such as the codecs from wimlib.
367 If you are looking for an archive format that provides features similar to WIM
368 but was designed primarily for UNIX, you may want to consider SquashFS
369 (http://squashfs.sourceforge.net/). However, you may find that wimlib works
370 surprisingly well on UNIX. It will store hard links and symbolic links, and it
371 has optional support for storing UNIX owners, groups, modes, and special files
372 such as device nodes and FIFOs. Actually, I use it to back up my own files on
375 LICENSE AND DISCLAIMER
377 See COPYING for information about the license.
379 wimlib is independently developed and does not contain any code, data, or files
380 copyrighted by Microsoft. It is not known to be affected by any patents.
382 On UNIX-like systems, if you do not want wimlib to be dynamically linked with
383 libcrypto (OpenSSL), configure with --without-libcrypto. This replaces the SHA1
384 implementation with built-in code and there will be no difference in
387 wimlib comes with no warranty whatsoever. Please submit a bug report (to
388 ebiggers3@gmail.com) if you find a bug in wimlib and/or wimlib-imagex.
390 Be aware that some parts of the WIM file format are poorly documented or even
391 completely undocumented, so I've just had to do the best I can to read and write
392 WIMs that appear to be compatible with Microsoft's software.