3 This is wimlib version 1.2.7 (March 2013). wimlib can be used to read,
4 write, and mount files in the Windows Imaging Format (WIM files). These files
5 are normally created by using the `imagex.exe' utility on Windows, but this
6 library provides a free implementation of imagex for UNIX-based systems.
10 A Windows Imaging (WIM) file is an archive. Like some other archive formats
11 such as ZIP, files in WIM archives may be compressed. WIM archives support two
12 Microsoft-specific compression formats: LZX and XPRESS. Both are based on LZ77
13 and Huffman encoding, and both are supported by wimlib.
15 Unlike ZIP files, WIM files can contain multiple independent toplevel directory
16 trees known as images. While each image has its own metadata describing a
17 directory tree and file access modes, files are not duplicated for each image;
18 instead, each file is included only once in the entire WIM. Microsoft did this
19 so that in one WIM file, they could do things like have 5 different versions of
20 Windows that are almost exactly the same.
22 Microsoft provides documentation for the WIM file format, XPRESS compression
23 format, and LZX compression format. The XPRESS documentation is acceptable, but
24 the LZX documentation is not entirely correct, and the WIM documentation itself
27 A WIM file may be either stand-alone or split into multiple parts.
31 wimlib provides a public API for other programs to use, but also comes with two
32 programs: `imagex' and `mkwinpeimg'.
34 `imagex' is intended to be like the imagex.exe program from Windows. `imagex'
35 can be used to create, extract, and mount WIM files. Both read-only and
36 read-write mounts are supported. See the man page `doc/imagex.1' for more
39 `mkwinpeimg' is shell script that makes it easy to create a customized bootable
40 image of Windows PE that can be put on a CD or USB drive, or published on a
41 server for PXE booting. See the main page `doc/mkwinpeimg.1' for more details.
43 There is an additional program, `wimapply', that is not installed by default.
44 It can be used to build a small executable with the ability to apply a WIM image
45 from a standalone WIM, without having to build the whole shared library. This
46 could be useful on Linux boot clients that only need to be able to apply a WIM,
47 not capture/split/join/append/export/mount a WIM. See `programs/wimapply.c'.
51 wimlib can create XPRESS or LZX compressed WIM archives. Currently, the XPRESS
52 compression ratio is slightly better than that provided by Microsoft's software,
53 while the LZX compression ratio is approaching that of Microsoft's software but
54 is not quite there yet. Running time is as good as or better than Microsoft's
55 software, especially with multithreaded compression, available in wimlib v1.1.0
58 The following tables compare the compression ratio and performance for creating
59 a compressed Windows PE image (disk usage of about 524 MB, uncompressed WIM size
64 XPRESS Compression LZX Compression
65 wimlib imagex (v1.2.1): 138,971,353 bytes 131,379,943 bytes
66 Microsoft imagex.exe: 140,406,981 bytes 127,249,176 bytes
68 Table 2. Time to create WIM
70 XPRESS Compression LZX Compression
71 wimlib imagex (v1.2.1, 2 threads): 11 sec 17 sec
72 Microsoft imagex.exe: 25 sec 89 sec
76 As of version 1.0.0, wimlib supports capturing and applying images directly to
77 NTFS volumes. This was made possible with the help of libntfs-3g from the
78 NTFS-3g project. This feature supports capturing and restoring NTFS-specific
79 data such as security descriptors, alternate data streams, and reparse point
82 The code for NTFS image capture and image application is complete enough that it
83 is possible to apply an image from the "install.wim" contained in recent Windows
84 installation media (Vista, Windows 7, or Windows 8) directly to a NTFS volume,
85 and then boot Windows from it after preparing the Boot Configuration Data. In
86 addition, a Windows installation can be captured (or backed up) into a WIM file,
87 and then re-applied later.
91 A major use for this library is to create customized images of Windows PE, the
92 Windows Preinstallation Environment, without having to rely on Windows. Windows
93 PE is a lightweight version of Windows that can run entirely from memory and can
94 be used to install Windows from local media or a network drive or perform
95 maintenance. Windows PE is the operating system that runs when you boot from
96 the Windows installation media.
98 You can find Windows PE on the installation DVD for Windows Vista, Windows 7, or
99 Windows 8, in the file `sources/boot.wim'. Windows PE can also be found in the
100 Windows Automated Installation Kit (WAIK), which is free to download from
101 Microsoft, inside the `WinPE.cab' file, which you can extract if you install
102 either the `cabextract' or `p7zip' programs.
104 In addition, Windows installations and recovery partitions frequently contain a
105 WIM containing an image of the Windows Recovery Environment, which is similar to
111 This is a commonly used free library to read and write XML files. You
112 likely already have it installed as a dependency for some other program.
113 For more information see http://xmlsoft.org/.
115 * libfuse (optional but highly recommended)
116 Unless configured with --without-fuse, wimlib requires a non-ancient
117 version of libfuse to be installed. Most GNU/Linux distributions
118 already include this, but make sure you have the libfuse package
119 installed, and also libfuse-dev if your distribution distributes header
120 files separately. FUSE also requires a kernel module. If the kernel
121 module is available it will automatically be loaded if you try to mount
122 a WIM file. For more information see http://fuse.sourceforge.net/.
123 FUSE is also available for FreeBSD.
125 * libntfs-3g (optional but highly recommended)
126 Unless configured with --without-ntfs-3g, wimlib requires the library
127 and headers for libntfs-3g version 2011-4-12 or later to be installed.
128 Versions dated 2010-3-6 and earlier do not work because they are missing
129 the header xattrs.h (and the file xattrs.c, which contains functions we
130 need). libntfs-3g version 2013-1-13 is compatible only with wimlib
133 * OpenSSL / libcrypto (optional)
134 wimlib can use the SHA1 message digest code from OpenSSL instead of
135 compiling in yet another SHA1 implementation. (See LICENSE section.)
139 * syslinux (optional)
140 * cabextract (optional)
141 The `mkwinpeimg' shell script will look for several other programs
142 depending on what options are given to it. Depending on your GNU/Linux
143 distribution, you may already have these programs installed, or they may
144 be in the software repository. Making an ISO filesystem requires
145 `mkisofs' from `cdrkit' (http://www.cdrkit.org). Making a disk image
146 requires `mtools' (http://www.gnu.org/software/mtools) and `syslinux'
147 (http://www.syslinux.org). Retrieving files from the Windows Automated
148 Installation Kit requires `cabextract' (http://www.cabextract.org.uk).
152 Besides the various well-known options, the following options can be passed to
153 wimlib's `configure' script:
156 If libntfs-3g is not available or is not version 2011-4-12 or later,
157 wimlib can be built without it, in which case it will not be possible to
158 apply or capture images directly to/from NTFS volumes.
161 If libfuse or the FUSE kernel module is not available, wimlib can be
162 compiled with --without-fuse. This will remove the ability to mount and
166 Build in functions for SHA1 rather than using external SHA1 functions
167 from libcrypto (part of OpenSSL). The default is to use libcrypto if it
168 is found on the system.
170 --enable-xattr, --disable-xattr
171 Enable or disable support for the extended-attributes interface to NTFS
172 alternate data streams in mounted WIMs. To support these, wimlib
173 requires that the setxattr() function and the attr/xattr.h header are
174 available. The default is to autodetect whether support is possible.
176 --disable-multithreaded-compression
177 By default, data will be compressed using multiple threads when writing
178 a WIM, unless only 1 processor is detected. Specify this option to
179 disable support for this.
182 Use a very fast assembly language implementation of SHA1 from Intel.
183 Only use this if the build target supports the SSSE3 instructions.
185 --disable-custom-memory-allocator
186 If this option is given, a very small amount of space will be saved by
187 removing support for the wimlib_set_memory_allocator() function. imagex
190 --disable-verify-compression
191 Unless this option is given, every time wimlib compresses a data block,
192 it will decompress it into a temporary buffer and abort the program with
193 an error message if the decompressed data does not exactly match the
194 original data. This only makes compression about 10% slower. However,
195 this checking can probably be safely disabled because there are no known
196 bugs in the compression code, and the SHA1 message digest of every
197 extracted file is checked anyway.
199 --disable-error-messages
200 Save some space by removing all error messages from the library.
203 Remove all assertions, even the ones that are included by default.
205 --enable-more-assertions
206 Enable assertions that are not included by default.
209 Include debugging messages. Only use this option if you have found a
213 Include more debugging messages. Only use this option if you have found
214 a bug in the library.
218 wimlib has mostly been developed and tested on x86_64 (64-bit) GNU/Linux.
220 It has been tested on x86 (32-bit) GNU/Linux occasionally.
222 wimlib may work on FreeBSD and Mac OS X. However, this is not well tested. If
223 you do not have libntfs-3g 2011-4-12 or later available, you must configure
224 wimlib with --without-ntfs-3g. On FreeBSD, before mounting a WIM you need to
225 load the POSIX message queue module (run `kldload mqueuefs').
227 The code pays attention to endianness, so it should work on big-endian
228 architectures, but I've never tested this so do not expect it to work.
230 There are no plans to port wimlib to Windows since the programming interface on
231 Windows is very different and Microsoft's imagex.exe is already available.
235 The WIM file format is specified in a document that can be found in the
236 Microsoft Download Center. There is a similar document that specifies the LZX
237 compression format, and a document that specifies the XPRESS compression format.
238 However, many parts of these formats are poorly documented, and some parts have
239 no documentation whatsoever. Some particularly poorly documented parts of the
240 formats have had comments added in various places in the library. Please see
241 the code and/or ask me if you have any questions about the WIM file format as it
242 exists in reality and not as it exists in Microsoft's poorly written
245 The code in ntfs-apply.c and ntfs-capture.c uses the NTFS-3g library, which is a
246 library for reading and writing to NTFS filesystems (the filesystem used by
247 recent versions of Windows). See
248 http://www.tuxera.com/community/ntfs-3g-download/ for more information.
250 lzx-decompress.c, the code to decompress WIM file resources that are compressed
251 using LZX compression, is originally based on code from the cabextract project
252 (http://www.cabextract.org.uk).
254 lzx-compress.c, the code to compress WIM file resources using LZX compression,
255 is originally based on code written by Matthew Russotto (www.russotto.net/chm/).
257 lz77.c, the code to find LZ77 matches (used for both XPRESS and LZX compression),
258 is based on code from zlib.
260 A very limited number of other free programs can handle some parts of the WIM
261 file format. 7-zip is able to extract and create WIMs (as well as files in many
262 other archive formats). However, wimlib is designed specifically to handle WIM
263 files and provides features previously only available in Microsoft's imagex.exe,
264 such as the ability to mount WIMs read-write as well as read-only, the ability
265 to create LZX or XPRESS compressed WIMs, and the correct handling of security
266 descriptors and hard links.
268 An earlier version of wimlib is being used to deploy Windows 7 from the Ultimate
269 Deployment Appliance. For more information see
270 http://www.ultimatedeployment.org/.
272 You can see the documentation about Microsoft's version of the imagex program at
273 http://technet.microsoft.com/en-us/library/cc749447(v=ws.10).aspx, so you can
274 see how it compares to the version provided by this library.
276 GNU/Linux equivalents of WIM format
278 What's the equivalent way to capture the filesystem of a GNU/Linux operating
279 system into an archive file? You have a few options:
282 SquashFS (http://squashfs.sourceforge.net/) provides a compressed,
283 read-only filesystem for Linux, and it's probably the closest equivalent
284 of the WIM format and better designed. Although you can't mount
285 SquashFS read-write, when wimlib does this for WIM files it's really an
286 illusion since the WIM isn't actually modified until the image is
287 unmounted. Multiple top-level images in SquashFS files are not
288 supported, although nothing stops you from just putting each image in a
292 FSArchiver (http://www.fsarchiver.org/Main_Page) is not widely used, but
293 it appears to have some features quite similar to the WIM format.
296 The well-known tar format can usually capture a UNIX filesystem just
297 fine, and compressing the tar file produces a good compression ratio
298 (better than WIM, especially if using XZ compression), but there is no
299 support for random access, file deduplication, multiple images per
300 archive, or extended attributes.
303 Zip shares some features with WIM but is not designed to store entire
307 The 7z format has some nice features but is unfortunately not designed
312 See the manual pages for `imagex', the manual pages for the subcommands of
313 `imagex', and the manual page for `mkwinpeimg'.
315 As of version 0.5.0, wimlib's public API is documented. Doxygen is required to
316 build the documentation. To build the documentation, run `configure', then
317 enter the directory `doc' and run `doxygen'. The HTML documentation will be
318 created in a directory named `html'.
322 As of version 1.0.0, wimlib is released under the GNU GPL version 3.0 or later.
323 This includes the files in the `programs' directory as well as the files in the
326 wimlib is independently developed and does not contain any code, data, or files
327 copyrighted by Microsoft. It is not known to be affected by any patents.
329 By default, wimlib will be linked to the system library "libcrypto", which
330 probably will be OpenSSL. Some people believe that GPL code cannot be linked to
331 OpenSSL without a linking exception. As far as I know, I cannot officially
332 include a linking exception with the license of this library because several
333 files could be considered derived works of code copyrighted by others. If you
334 believe this to be a problem, configure with --without-libcrypto to avoid
335 linking with OpenSSL. There is no difference in functionality--- there will
336 just be stand-alone SHA1 message digest code built into the library.
340 wimlib is experimental. Use Microsoft's `imagex.exe' if you want to make sure
341 your WIM files are made correctly (but beware: Microsoft's version contains some
344 Please submit a bug report (to ebiggers3@gmail.com) if you find a bug in wimlib.
346 Some parts of the WIM file format are poorly documented or even completely
347 undocumented, so I've just had to do the best I can to read and write WIMs that
348 appear to be compatible with Microsoft's software.
git://wimlib.net / wimlib / blob