INTRODUCTION This is wimlib version 1.7.1-BETA (June 2014). wimlib is a C library for creating, modifying, extracting, and mounting files in the Windows Imaging Format (WIM files). These files are normally created using the ImageX (imagex.exe) or Dism (Dism.exe) utilities on Windows, but wimlib is distributed with a free implementation of ImageX called "wimlib-imagex" for both UNIX-like systems and Windows. INSTALLATION To install wimlib and wimlib-imagex on Windows you simply need to download and extract the ZIP file containing the latest binaries from the SourceForge page (http://sourceforge.net/projects/wimlib/), which you may have already done. To install wimlib and wimlib-imagex on UNIX-like systems (with Linux being the primary supported and tested platform), you must compile the source code, which is also available at http://sourceforge.net/projects/wimlib/. Alternatively, check if a package has been prepared for your Linux distribution. Example files for Debian and RPM packaging are in the debian/ and rpm/ directories. WIM FILES A Windows Imaging (WIM) file is an archive designed primarily for archiving Windows filesystems. However, it can be used on other platforms as well, with some limitations. Like some other archive formats such as ZIP, files in WIM archives may be compressed. WIM files support multiple compression formats, including LZX, XPRESS, and LZMS. All these formats are supported by wimlib. A WIM file consists of one or more "images". Each image is an independent top-level directory structure and is logically separate from all other images in the WIM. Each image has a name as well as a 1-based index in the WIM file. To save space, WIM archives automatically combine all duplicate files across all images. A WIM file may be either stand-alone or split into multiple parts. Split WIMs are read-only and cannot be modified. Since version 1.6.0, wimlib also supports ESD (.esd) files, except when encrypted. These are still WIM files but they use a newer version of the file format. IMAGEX IMPLEMENTATION wimlib itself is a C library, and it provides a documented public API (See: http://wimlib.sourceforge.net) for other programs to use. However, it is also distributed with a command-line program called "wimlib-imagex" that uses this library to implement an imaging tool similar to Microsoft's ImageX. wimlib-imagex supports almost all the capabilities of Microsoft's ImageX as well as additional capabilities. wimlib-imagex works on both UNIX-like systems and Windows, although some features differ between the platforms. Run `wimlib-imagex' with no arguments to see an overview of the available commands and their syntax. For additional documentation: * If you have installed wimlib-imagex on a UNIX-like system, you will find further documentation in the man pages; run `man wimlib-imagex' to get started. * If you have downloaded the Windows binary distribution, you will find the documentation for wimlib-imagex in PDF format in the "doc" directory, ready for viewing with any PDF viewer. Please note that although the PDF files are converted from UNIX-style "man pages", they do document Windows-specific behavior when appropriate. COMPRESSION RATIO wimlib (and wimlib-imagex) can create XPRESS, LZX, or LZMS compressed WIM files. wimlib includes its own compression codecs and does not use the compression API available on some versions of Windows. I have gradually been improving the compression codecs in wimlib. For XPRESS and LZX, they now usually outperform and outcompress the equivalent Microsoft implementations. Although results will vary depending on the data being compressed, in the table below I present the results for a common use case: compressing an x86 Windows PE image. Each row displays the compression type, the size of the resulting WIM file in bytes, and how many seconds it took to create the file. When applicable, the results with the equivalent Microsoft implementation in WIMGAPI is included. ============================================================================= | Compression || wimlib (v1.7.1) | WIMGAPI (Windows 8.1) | ============================================================================= | None [1] || 361,182,560 in 3.7s | 361,183,674 in 4.4s | | XPRESS [2] || 138,349,798 in 5.8s | 140,416,657 in 6.8s | | XPRESS (slow) [3] || 135,234,072 in 19.5s | N/A | | LZX (quick) [4] || 131,816,279 in 6.7s | N/A | | LZX (normal) [5] || 126,808,347 in 28.3s | 127,259,566 in 31.4s | | LZX (slow) [6] || 126,199,523 in 61.4s | N/A | | LZMS (non-solid) [7] || 122,083,126 in 30.4s | N/A | | LZMS (solid) [8] || 93,752,206 in 84.3s | 88,742,238 in 156.1s | | "WIMBoot" [9] || 167,039,787 in 7.6s | 169,051,718 in 14.9s | | "WIMBoot" (slow) [10] || 165,141,503 in 15.8s | N/A | ============================================================================= Notes: [1] '--compress=none' for wimlib-imagex; '/compress:none' for DISM. [2] '--compress=XPRESS' for wimlib-imagex; '/compress:fast' for DISM. Compression chunk size defaults to 32768 bytes in both cases. [3] '--compress=XPRESS:80' for wimlib-imagex; no known equivalent for DISM. Compression chunk size defaults to 32768 bytes. [4] '--compress=LZX:20' for wimlib-imagex; no known equivalent for DISM. Compression chunk size defaults to 32768 bytes. [5] '--compress=LZX' or '--compress=LZX:50' or no option for wimlib-imagex; '/compress:maximum' for DISM. Compression chunk size defaults to 32768 bytes in both cases. [6] '--compress=LZX:100' for wimlib-imagex; no known equivalent for DISM. Compression chunk size defaults to 32768 bytes. [7] '--compress=LZMS' for wimlib-imagex; no known equivalent for DISM. Compression chunk size defaults to 131072 bytes. [8] '--solid' for wimlib-imagex. Should be '/compress:recovery' for DISM, but only works for /Export-Image, not /Capture-Image. Compression chunk size in solid blocks defaults to 33554432 for wimlib, 67108864 for DISM. [9] '--wimboot' for wimlib-imagex; '/wimboot' for DISM. This is really XPRESS compression with 4096 byte chunks, so the same as '--compress=XPRESS --chunk-size=4096'. [10] '--wimboot --compress=XPRESS:80' for wimlib-imagex; no known equivalent for DISM. Same format as [9], but trying harder to get a good compression ratio. Note: wimlib-imagex's --compress option also accepts the "fast", "maximum", and "recovery" aliases for XPRESS, LZX, and LZMS, respectively. Testing environment: - 64 bit binaries - Windows 8.1 virtual machine running on Linux with VT-x - 2 CPUs and 2 GiB memory given to virtual machine - SSD-backed virtual disk - All tests done with page cache warmed The compression ratio provided by wimlib is also competitive with commonly used archive formats. Below are file sizes that result when the Canterbury corpus is compressed with wimlib (v1.7.0), WIMGAPI (Windows 8), and some other formats/programs: ================================================= | Format | Size (bytes) | ================================================= | tar | 2,826,240 | | WIM (WIMGAPI, None) | 2,814,278 | | WIM (wimlib, None) | 2,813,856 | | WIM (WIMGAPI, XPRESS) | 825,410 | | WIM (wimlib, XPRESS) | 792,024 | | tar.gz (gzip, default) | 738,796 | | ZIP (Info-ZIP, default) | 735,334 | | tar.gz (gzip, -9) | 733,971 | | ZIP (Info-ZIP, -9) | 732,297 | | WIM (wimlib, LZX quick) | 722,196 | | WIM (WIMGAPI, LZX) | 651,766 | | WIM (wimlib, LZX normal) | 649,204 | | WIM (wimlib, LZX slow) | 639,618 | | WIM (wimlib, LZMS non-solid) | 592,136 | | tar.bz2 (bzip, default) | 565,008 | | tar.bz2 (bzip, -9) | 565,008 | | WIM (wimlib, LZMS solid) | 525,270 | | WIM (wimlib, LZMS solid, slow) | 521,700 | | WIM (WIMGAPI, LZMS solid) | 521,232 | | tar.xz (xz, default) | 486,916 | | tar.xz (xz, -9) | 486,904 | | 7z (7-zip, default) | 484,700 | | 7z (7-zip, -9) | 483,239 | ================================================= Note: WIM does even better on directory trees containing duplicate files, which the Canterbury corpus doesn't have. NTFS SUPPORT WIM images may contain data, such as alternate data streams and compression/encryption flags, that are best represented on the NTFS filesystem used on Windows. Also, WIM images may contain security descriptors which are specific to Windows and cannot be represented on other operating systems. wimlib handles this NTFS-specific or Windows-specific data in a platform-dependent way: * In the Windows version of wimlib and wimlib-imagex, NTFS-specific and Windows-specific data are supported natively. * In the UNIX version of wimlib and wimlib-imagex, NTFS-specific and Windows-specific data are ordinarily ignored; however, there is also special support for capturing and extracting images directly to/from unmounted NTFS volumes. This was made possible with the help of libntfs-3g from the NTFS-3g project. For both platforms the code for NTFS capture and extraction is complete enough that it is possible to apply an image from the "install.wim" contained in recent Windows installation media (Vista, Windows 7, or Windows 8) directly to an NTFS filesystem, and then boot Windows from it after preparing the Boot Configuration Data. In addition, a Windows installation can be captured (or backed up) into a WIM file, and then re-applied later. WINDOWS PE A major use for wimlib and wimlib-imagex is to create customized images of Windows PE, the Windows Preinstallation Environment, on either UNIX-like systems or Windows without having to rely on Microsoft's software and its restrictions and limitations. Windows PE is a lightweight version of Windows that can run entirely from memory and can be used to install Windows from local media or a network drive or perform maintenance. It is the operating system that runs when you boot from the Windows installation media. You can find Windows PE on the installation DVD for Windows Vista, Windows 7, or Windows 8, in the file `sources/boot.wim'. Windows PE can also be found in the Windows Automated Installation Kit (WAIK), which is free to download from Microsoft, inside the `WinPE.cab' file, which you can extract natively on Windows, or on UNIX-like systems if you install either the `cabextract' or `p7zip' programs. In addition, Windows installations and recovery partitions frequently contain a WIM containing an image of the Windows Recovery Environment, which is similar to Windows PE. A shell script `mkwinpeimg' is distributed with wimlib on UNIX-like systems to ease the process of creating and customizing a bootable Windows PE image. DEPENDENCIES This section documents the dependencies of wimlib and the programs distributed with it, when building for a UNIX-like system from source. If you have downloaded the Windows binary distribution of wimlib and wimlib-imagex then all dependencies were already included and this section is irrelevant. * libxml2 (required) This is a commonly used free library to read and write XML files. You likely already have it installed as a dependency for some other program. For more information see http://xmlsoft.org/. * libfuse (optional but highly recommended) Unless configured with --without-fuse, wimlib requires a non-ancient version of libfuse to be installed. Most Linux distributions already include this, but make sure you have the libfuse package installed, and also libfuse-dev if your distribution distributes header files separately. FUSE also requires a kernel module. If the kernel module is available it will automatically be loaded if you try to mount a WIM file. For more information see http://fuse.sourceforge.net/. FUSE is also available for FreeBSD. * libntfs-3g (optional but highly recommended) Unless configured with --without-ntfs-3g, wimlib requires the library and headers for libntfs-3g version 2011-4-12 or later to be installed. Versions dated 2010-3-6 and earlier do not work because they are missing the header xattrs.h (and the file xattrs.c, which contains functions we need). libntfs-3g version 2013-1-13 is compatible only with wimlib 1.2.4 and later. * OpenSSL / libcrypto (optional) wimlib can use the SHA1 message digest code from OpenSSL instead of compiling in yet another SHA1 implementation. (See LICENSE section.) * cdrkit (optional) * mtools (optional) * syslinux (optional) * cabextract (optional) The `mkwinpeimg' shell script will look for several other programs depending on what options are given to it. Depending on your Linux distribution, you may already have these programs installed, or they may be in the software repository. Making an ISO filesystem requires `mkisofs' from `cdrkit' (http://www.cdrkit.org). Making a disk image requires `mtools' (http://www.gnu.org/software/mtools) and `syslinux' (http://www.syslinux.org). Retrieving files from the Windows Automated Installation Kit requires `cabextract' (http://www.cabextract.org.uk). CONFIGURATION This section documents the most important options that may be passed to the "configure" script when building from source: --without-ntfs-3g If libntfs-3g is not available or is not version 2011-4-12 or later, wimlib can be built without it, in which case it will not be possible to apply or capture images directly to/from NTFS volumes. --without-fuse If libfuse or the FUSE kernel module is not available, wimlib can be compiled with --without-fuse. This will remove the ability to mount and unmount WIM files. --without-libcrypto Build in functions for SHA1 rather than using external SHA1 functions from libcrypto (part of OpenSSL). The default is to use libcrypto if it is found on the system. --disable-multithreaded-compression By default, data will be compressed using multiple threads when writing a WIM, unless only 1 processor is detected. Specify this option to disable support for this. --enable-ssse3-sha1 Use a very fast assembly language implementation of SHA1 from Intel. Only use this if the build target supports the SSSE3 instructions. --disable-error-messages Save some space by removing all error messages from the library. --disable-assertions Remove assertions included by default. PORTABILITY wimlib has primarily been tested on Linux and Windows (primarily Windows 7, but also Windows XP and Windows 8). wimlib may work on FreeBSD and Mac OS X. However, this is not well tested. If you do not have libntfs-3g 2011-4-12 or later available, you must configure wimlib with --without-ntfs-3g. On FreeBSD, before mounting a WIM you need to load the POSIX message queue module (run `kldload mqueuefs'). The code has primarily been tested on x86 and x86_64 CPUs, but it's written to be portable to other architectures and I've also tested it on ARM. However, although the code is written to correctly deal with endianness, it has not yet actually been tested on a big-endian architecture. REFERENCES The WIM file format is partially specified in a document that can be found in the Microsoft Download Center. However, this document really only provides an overview of the format and is not a formal specification. With regards to the supported compression formats: - Microsoft has official documentation for XPRESS that is of reasonable quality. - Microsoft has official documentation for LZX but it contains errors. - There does not seem to be any official documentation for LZMS, so my comments and code in src/lzms-decompress.c may in fact be the best documentation available for this particular compression format. The code in ntfs-3g_apply.c and ntfs-3g_capture.c uses the NTFS-3g library, which is a library for reading and writing to NTFS filesystems (the filesystem used by recent versions of Windows). See http://www.tuxera.com/community/ntfs-3g-download/ for more information. The LZX decompressor (lzx-decompress.c) was originally based on code from the cabextract project (http://www.cabextract.org.uk). The LZX compressor (lzx-compress.c) was originally based on code written by Matthew Russotto (www.russotto.net/chm/). However I have since rewritten and made many improvements to both the decompressor and compressor. lz_binary_trees.c contains LZ77 match-finding code that uses binary trees. It is based on code from liblzma but I have since rewritten it. A limited number of other free programs can handle some parts of the WIM file format: * 7-zip is able to extract and create WIMs (as well as files in many other archive formats). However, wimlib is designed specifically to handle WIM files and provides features previously only available in Microsoft's implementation, such as the ability to mount WIMs read-write as well as read-only, the ability to create compressed WIMs, and the correct handling of security descriptors and hard links. * ImagePyX (https://github.com/maxpat78/ImagePyX) is a Python program that provides similar capabilities to wimlib-imagex. One thing to note, though, is that it does not support compression and decompression by itself, but instead relies on external native code, such as the codecs from wimlib. If you are looking for an archive format that provides features similar to WIM but was designed primarily for UNIX, you may want to consider SquashFS (http://squashfs.sourceforge.net/). However, you may find that wimlib works surprisingly well on UNIX. It will store hard links and symbolic links, and it has optional support for storing UNIX owners, groups, modes, and special files such as device nodes and FIFOs. Actually, I use it to back up my own files on Linux! LICENSE AND DISCLAIMER See COPYING for information about the license. wimlib is independently developed and does not contain any code, data, or files copyrighted by Microsoft. It is not known to be affected by any patents. On UNIX-like systems, if you do not want wimlib to be dynamically linked with libcrypto (OpenSSL), configure with --without-libcrypto. This replaces the SHA1 implementation with built-in code and there will be no difference in functionality. wimlib comes with no warranty whatsoever. Please submit a bug report (to ebiggers3@gmail.com) if you find a bug in wimlib and/or wimlib-imagex. Be aware that some parts of the WIM file format are poorly documented or even completely undocumented, so I've just had to do the best I can to read and write WIMs that appear to be compatible with Microsoft's software.