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). wimlib and its command-line frontend 'wimlib-imagex'
6 provide a free and cross-platform alternative to Microsoft's WIMGAPI, ImageX,
11 To install wimlib and wimlib-imagex on Windows, simply download and extract the
12 ZIP file containing the latest binaries from the SourceForge page
13 (http://sourceforge.net/projects/wimlib/). You probably have already done this!
15 To install wimlib and wimlib-imagex on UNIX-like systems (with Linux being the
16 primary supported and tested platform), you must compile the source code, which
17 is also available at http://sourceforge.net/projects/wimlib/. Alternatively,
18 check if a package has been prepared for your Linux distribution. Example files
19 for Debian and RPM packaging are in the debian/ and rpm/ directories.
23 A Windows Imaging (WIM) file is an archive designed primarily for archiving
24 Windows filesystems. However, it can be used on other platforms as well, with
25 some limitations. Like some other archive formats such as ZIP, files in WIM
26 archives may be compressed. WIM files support multiple compression formats,
27 including LZX, XPRESS, and LZMS. All these formats are supported by wimlib.
29 A WIM file consists of one or more "images". Each image is an independent
30 top-level directory structure and is logically separate from all other images in
31 the WIM. Each image has a name as well as a 1-based index in the WIM file. To
32 save space, WIM archives automatically combine all duplicate files across all
35 A WIM file may be either stand-alone or split into multiple parts. Split WIMs
36 are read-only and cannot be modified.
38 Since version 1.6.0, wimlib also supports ESD (.esd) files, except when
39 encrypted. These are still WIM files but they use a newer version of the file
44 wimlib itself is a C library, and it provides a documented public API (See:
45 http://wimlib.sourceforge.net) for other programs to use. However, it is also
46 distributed with a command-line program called "wimlib-imagex" that uses this
47 library to implement an imaging tool similar to Microsoft's ImageX.
48 wimlib-imagex supports almost all the capabilities of Microsoft's ImageX as well
49 as additional capabilities. wimlib-imagex works on both UNIX-like systems and
50 Windows, although some features differ between the platforms.
52 Run `wimlib-imagex' with no arguments to see an overview of the available
53 commands and their syntax. For additional documentation:
55 * If you have installed wimlib-imagex on a UNIX-like system, you will find
56 further documentation in the man pages; run `man wimlib-imagex' to get
59 * If you have downloaded the Windows binary distribution, you will find the
60 documentation for wimlib-imagex in PDF format in the "doc" directory,
61 ready for viewing with any PDF viewer. Please note that although the PDF
62 files are converted from UNIX-style "man pages", they do document
63 Windows-specific behavior when appropriate.
67 wimlib (and wimlib-imagex) can create XPRESS, LZX, or LZMS compressed WIM files.
68 wimlib includes its own compression codecs and does not use the compression API
69 available on some versions of Windows.
71 I have gradually been improving the compression codecs in wimlib. For XPRESS
72 and LZX, they now usually outperform and outcompress the equivalent Microsoft
73 implementations. Although results will vary depending on the data being
74 compressed, in the table below I present the results for a common use case:
75 compressing an x86 Windows PE image. Each row displays the compression type,
76 the size of the resulting WIM file in bytes, and how many seconds it took to
77 create the file. When applicable, the results with the equivalent Microsoft
78 implementation in WIMGAPI is included.
80 =============================================================================
81 | Compression || wimlib (v1.7.1) | WIMGAPI (Windows 8.1) |
82 =============================================================================
83 | None [1] || 361,182,560 in 3.7s | 361,183,674 in 4.4s |
84 | XPRESS [2] || 138,349,798 in 5.8s | 140,416,657 in 6.8s |
85 | XPRESS (slow) [3] || 135,234,072 in 19.5s | N/A |
86 | LZX (quick) [4] || 131,816,279 in 6.7s | N/A |
87 | LZX (normal) [5] || 126,808,347 in 28.3s | 127,259,566 in 31.4s |
88 | LZX (slow) [6] || 126,199,523 in 61.4s | N/A |
89 | LZMS (non-solid) [7] || 122,083,126 in 30.4s | N/A |
90 | LZMS (solid) [8] || 93,752,206 in 84.3s | 88,742,238 in 156.1s |
91 | "WIMBoot" [9] || 167,039,787 in 7.6s | 169,051,718 in 14.9s |
92 | "WIMBoot" (slow) [10] || 165,141,503 in 15.8s | N/A |
93 =============================================================================
96 [1] '--compress=none' for wimlib-imagex; '/compress:none' for DISM.
98 [2] '--compress=XPRESS' for wimlib-imagex; '/compress:fast' for DISM.
99 Compression chunk size defaults to 32768 bytes in both cases.
101 [3] '--compress=XPRESS:80' for wimlib-imagex; no known equivalent for DISM.
102 Compression chunk size defaults to 32768 bytes.
104 [4] '--compress=LZX:20' for wimlib-imagex; no known equivalent for DISM.
105 Compression chunk size defaults to 32768 bytes.
107 [5] '--compress=LZX' or '--compress=LZX:50' or no option for wimlib-imagex;
108 '/compress:maximum' for DISM.
109 Compression chunk size defaults to 32768 bytes in both cases.
111 [6] '--compress=LZX:100' for wimlib-imagex; no known equivalent for DISM.
112 Compression chunk size defaults to 32768 bytes.
114 [7] '--compress=LZMS' for wimlib-imagex; no known equivalent for DISM.
115 Compression chunk size defaults to 131072 bytes.
117 [8] '--solid' for wimlib-imagex. Should be '/compress:recovery' for DISM,
118 but only works for /Export-Image, not /Capture-Image. Compression chunk
119 size in solid blocks defaults to 33554432 for wimlib, 67108864 for DISM.
121 [9] '--wimboot' for wimlib-imagex; '/wimboot' for DISM.
122 This is really XPRESS compression with 4096 byte chunks, so the same as
123 '--compress=XPRESS --chunk-size=4096'.
125 [10] '--wimboot --compress=XPRESS:80' for wimlib-imagex;
126 no known equivalent for DISM.
127 Same format as [9], but trying harder to get a good compression ratio.
129 Note: wimlib-imagex's --compress option also accepts the "fast", "maximum", and
130 "recovery" aliases for XPRESS, LZX, and LZMS, respectively.
135 - Windows 8.1 virtual machine running on Linux with VT-x
136 - 2 CPUs and 2 GiB memory given to virtual machine
137 - SSD-backed virtual disk
138 - All tests done with page cache warmed
140 The compression ratio provided by wimlib is also competitive with commonly used
141 archive formats. Below are file sizes that result when the Canterbury corpus is
142 compressed with wimlib (v1.7.0), WIMGAPI (Windows 8), and some other
145 =================================================
146 | Format | Size (bytes) |
147 =================================================
149 | WIM (WIMGAPI, None) | 2,814,278 |
150 | WIM (wimlib, None) | 2,813,856 |
151 | WIM (WIMGAPI, XPRESS) | 825,410 |
152 | WIM (wimlib, XPRESS) | 792,024 |
153 | tar.gz (gzip, default) | 738,796 |
154 | ZIP (Info-ZIP, default) | 735,334 |
155 | tar.gz (gzip, -9) | 733,971 |
156 | ZIP (Info-ZIP, -9) | 732,297 |
157 | WIM (wimlib, LZX quick) | 722,196 |
158 | WIM (WIMGAPI, LZX) | 651,766 |
159 | WIM (wimlib, LZX normal) | 649,204 |
160 | WIM (wimlib, LZX slow) | 639,618 |
161 | WIM (wimlib, LZMS non-solid) | 592,136 |
162 | tar.bz2 (bzip, default) | 565,008 |
163 | tar.bz2 (bzip, -9) | 565,008 |
164 | WIM (wimlib, LZMS solid) | 525,270 |
165 | WIM (wimlib, LZMS solid, slow) | 521,700 |
166 | WIM (WIMGAPI, LZMS solid) | 521,232 |
167 | tar.xz (xz, default) | 486,916 |
168 | tar.xz (xz, -9) | 486,904 |
169 | 7z (7-zip, default) | 484,700 |
170 | 7z (7-zip, -9) | 483,239 |
171 =================================================
173 Note: WIM does even better on directory trees containing duplicate files, which
174 the Canterbury corpus doesn't have.
178 WIM images may contain data, such as alternate data streams and
179 compression/encryption flags, that are best represented on the NTFS filesystem
180 used on Windows. Also, WIM images may contain security descriptors which are
181 specific to Windows and cannot be represented on other operating systems.
182 wimlib handles this NTFS-specific or Windows-specific data in a
183 platform-dependent way:
185 * In the Windows version of wimlib and wimlib-imagex, NTFS-specific and
186 Windows-specific data are supported natively.
188 * In the UNIX version of wimlib and wimlib-imagex, NTFS-specific and
189 Windows-specific data are ordinarily ignored; however, there is also special
190 support for capturing and extracting images directly to/from unmounted NTFS
191 volumes. This was made possible with the help of libntfs-3g from the
194 For both platforms the code for NTFS capture and extraction is complete enough
195 that it is possible to apply an image from the "install.wim" contained in recent
196 Windows installation media (Vista, Windows 7, or Windows 8) directly to an NTFS
197 filesystem, and then boot Windows from it after preparing the Boot Configuration
198 Data. In addition, a Windows installation can be captured (or backed up) into a
199 WIM file, and then re-applied later.
203 A major use for wimlib and wimlib-imagex is to create customized images of
204 Windows PE, the Windows Preinstallation Environment, on either UNIX-like systems
205 or Windows without having to rely on Microsoft's software and its restrictions
208 Windows PE is a lightweight version of Windows that can run entirely from memory
209 and can be used to install Windows from local media or a network drive or
210 perform maintenance. It is the operating system that runs when you boot from
211 the Windows installation media.
213 You can find Windows PE on the installation DVD for Windows Vista, Windows 7, or
214 Windows 8, in the file `sources/boot.wim'. Windows PE can also be found in the
215 Windows Automated Installation Kit (WAIK), which is free to download from
216 Microsoft, inside the `WinPE.cab' file, which you can extract natively on
217 Windows, or on UNIX-like systems if you install either the `cabextract' or
220 In addition, Windows installations and recovery partitions frequently contain a
221 WIM containing an image of the Windows Recovery Environment, which is similar to
224 A shell script `mkwinpeimg' is distributed with wimlib on UNIX-like systems to
225 ease the process of creating and customizing a bootable Windows PE image.
229 This section documents the dependencies of wimlib and the programs distributed
230 with it, when building for a UNIX-like system from source. If you have
231 downloaded the Windows binary distribution of wimlib and wimlib-imagex then all
232 dependencies were already included and this section is irrelevant.
235 This is a commonly used free library to read and write XML files. You
236 likely already have it installed as a dependency for some other program.
237 For more information see http://xmlsoft.org/.
239 * libfuse (optional but highly recommended)
240 Unless configured with --without-fuse, wimlib requires a non-ancient
241 version of libfuse to be installed. Most Linux distributions already
242 include this, but make sure you have the libfuse package installed, and
243 also libfuse-dev if your distribution distributes header files
244 separately. FUSE also requires a kernel module. If the kernel module
245 is available it will automatically be loaded if you try to mount a WIM
246 file. For more information see http://fuse.sourceforge.net/. FUSE is
247 also available for FreeBSD.
249 * libntfs-3g (optional but highly recommended)
250 Unless configured with --without-ntfs-3g, wimlib requires the library
251 and headers for libntfs-3g version 2011-4-12 or later to be installed.
252 Versions dated 2010-3-6 and earlier do not work because they are missing
253 the header xattrs.h (and the file xattrs.c, which contains functions we
254 need). libntfs-3g version 2013-1-13 is compatible only with wimlib
257 * OpenSSL / libcrypto (optional)
258 wimlib can use the SHA1 message digest code from OpenSSL instead of
259 compiling in yet another SHA1 implementation. (See LICENSE section.)
263 * syslinux (optional)
264 * cabextract (optional)
265 The `mkwinpeimg' shell script will look for several other programs
266 depending on what options are given to it. Depending on your Linux
267 distribution, you may already have these programs installed, or they may
268 be in the software repository. Making an ISO filesystem requires
269 `mkisofs' from `cdrkit' (http://www.cdrkit.org). Making a disk image
270 requires `mtools' (http://www.gnu.org/software/mtools) and `syslinux'
271 (http://www.syslinux.org). Retrieving files from the Windows Automated
272 Installation Kit requires `cabextract' (http://www.cabextract.org.uk).
276 This section documents the most important options that may be passed to the
277 "configure" script when building from source:
280 If libntfs-3g is not available or is not version 2011-4-12 or later,
281 wimlib can be built without it, in which case it will not be possible to
282 apply or capture images directly to/from NTFS volumes.
285 If libfuse or the FUSE kernel module is not available, wimlib can be
286 compiled with --without-fuse. This will remove the ability to mount and
290 Build in functions for SHA1 rather than using external SHA1 functions
291 from libcrypto (part of OpenSSL). The default is to use libcrypto if it
292 is found on the system.
294 --disable-multithreaded-compression
295 By default, data will be compressed using multiple threads when writing
296 a WIM, unless only 1 processor is detected. Specify this option to
297 disable support for this.
300 Use a very fast assembly language implementation of SHA1 from Intel.
301 Only use this if the build target supports the SSSE3 instructions.
303 --disable-error-messages
304 Save some space by removing all error messages from the library.
307 Remove assertions included by default.
311 wimlib works on both UNIX-like systems (Linux, Mac OS X, FreeBSD, etc.) and
312 Windows (XP and later).
314 On UNIX-like systems other than Linux, you must compile --without-fuse.
315 In addition, --without-ntfs-3g and --without-libcrypto are needed if the
316 corresponding libraries are not available on your system.
318 wimlib works on x86 and x86_64, but it should work on any other GCC-supported
319 32-bit or 64-bit architecture.
323 The WIM file format is partially specified in a document that can be found in
324 the Microsoft Download Center. However, this document really only provides an
325 overview of the format and is not a formal specification. It also does not
326 cover later extensions of the format, such as solid blocks.
328 With regards to the supported compression formats:
330 - Microsoft has official documentation for XPRESS that is of reasonable quality.
331 - Microsoft has official documentation for LZX, but in two different documents,
332 neither of which is completely applicable to its use in the WIM format, and
333 the first of which contains multiple errors.
334 - There does not seem to be any official documentation for LZMS, so my comments
335 and code in src/lzms-decompress.c may in fact be the best documentation
336 available for this particular compression format.
338 The algorithms used by wimlib's compression and decompression codecs are
339 inspired by a variety of sources, including open source projects and computer
342 The code in ntfs-3g_apply.c and ntfs-3g_capture.c uses the NTFS-3g library,
343 which is a library for reading and writing to NTFS filesystems (the filesystem
344 used by recent versions of Windows). See
345 http://www.tuxera.com/community/ntfs-3g-download/ for more information.
347 A limited number of other free programs can handle some parts of the WIM
350 * 7-zip is able to extract and create WIMs (as well as files in many
351 other archive formats). However, wimlib is designed specifically to handle
352 WIM files and provides features previously only available in Microsoft's
353 implementation, such as the ability to mount WIMs read-write as well as
354 read-only, the ability to create compressed WIMs, the correct handling of
355 security descriptors and hard links, support for LZMS compression, and
356 support for solid archives.
357 * ImagePyX (https://github.com/maxpat78/ImagePyX) is a Python program that
358 provides similar capabilities to wimlib-imagex. One thing to note, though,
359 is that it does not support compression and decompression by itself, but
360 instead relies on external native code, such as the codecs from wimlib.
362 If you are looking for an archive format that provides features similar to WIM
363 but was designed primarily for UNIX, you may want to consider SquashFS
364 (http://squashfs.sourceforge.net/). However, you may find that wimlib works
365 surprisingly well on UNIX. It will store hard links and symbolic links, and it
366 has optional support for storing UNIX owners, groups, modes, and special files
367 such as device nodes and FIFOs. Actually, I use it to back up my own files on
370 LICENSE AND DISCLAIMER
372 See COPYING for information about the license.
374 wimlib is independently developed and does not contain any code, data, or files
375 copyrighted by Microsoft. It is not known to be affected by any patents.
377 On UNIX-like systems, if you do not want wimlib to be dynamically linked with
378 libcrypto (OpenSSL), configure with --without-libcrypto. This replaces the SHA1
379 implementation with built-in code and there will be no difference in
382 wimlib comes with no warranty whatsoever. Please submit a bug report (to
383 ebiggers3@gmail.com) if you find a bug in wimlib and/or wimlib-imagex.