WIMLIB This is wimlib version 1.2.7 (March 2013). wimlib can be used to read, write, and mount files in the Windows Imaging Format (WIM files). These files are normally created by using the `imagex.exe' utility on Windows, but this library provides a free implementation of imagex for UNIX-based systems. WIM FILES A Windows Imaging (WIM) file is an archive. Like some other archive formats such as ZIP, files in WIM archives may be compressed. WIM archives support two Microsoft-specific compression formats: LZX and XPRESS. Both are based on LZ77 and Huffman encoding, and both are supported by wimlib. Unlike ZIP files, WIM files can contain multiple independent toplevel directory trees known as images. While each image has its own metadata describing a directory tree and file access modes, files are not duplicated for each image; instead, each file is included only once in the entire WIM. Microsoft did this so that in one WIM file, they could do things like have 5 different versions of Windows that are almost exactly the same. Microsoft provides documentation for the WIM file format, XPRESS compression format, and LZX compression format. The XPRESS documentation is acceptable, but the LZX documentation is not entirely correct, and the WIM documentation itself is incomplete. A WIM file may be either stand-alone or split into multiple parts. PROGRAMS wimlib provides a public API for other programs to use, but also comes with two programs: `imagex' and `mkwinpeimg'. `imagex' is intended to be like the imagex.exe program from Windows. `imagex' can be used to create, extract, and mount WIM files. Both read-only and read-write mounts are supported. See the man page `doc/imagex.1' for more details. `mkwinpeimg' is shell script that makes it easy to create a customized bootable image of Windows PE that can be put on a CD or USB drive, or published on a server for PXE booting. See the main page `doc/mkwinpeimg.1' for more details. There is an additional program, `wimapply', that is not installed by default. It can be used to build a small executable with the ability to apply a WIM image from a standalone WIM, without having to build the whole shared library. This could be useful on Linux boot clients that only need to be able to apply a WIM, not capture/split/join/append/export/mount a WIM. See `programs/wimapply.c'. COMPRESSION RATIO wimlib can create XPRESS or LZX compressed WIM archives. Currently, the XPRESS compression ratio is slightly better than that provided by Microsoft's software, while the LZX compression ratio is approaching that of Microsoft's software but is not quite there yet. Running time is as good as or better than Microsoft's software, especially with multithreaded compression, available in wimlib v1.1.0 and later. The following tables compare the compression ratio and performance for creating a compressed Windows PE image (disk usage of about 524 MB, uncompressed WIM size 361 MB): Table 1. WIM size XPRESS Compression LZX Compression wimlib imagex (v1.2.1): 138,971,353 bytes 131,379,943 bytes Microsoft imagex.exe: 140,406,981 bytes 127,249,176 bytes Table 2. Time to create WIM XPRESS Compression LZX Compression wimlib imagex (v1.2.1, 2 threads): 11 sec 17 sec Microsoft imagex.exe: 25 sec 89 sec NTFS SUPPORT As of version 1.0.0, wimlib supports capturing and applying images directly to NTFS volumes. This was made possible with the help of libntfs-3g from the NTFS-3g project. This feature supports capturing and restoring NTFS-specific data such as security descriptors, alternate data streams, and reparse point data. The code for NTFS image capture and image application 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 a NTFS volume, 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 this library is to create customized images of Windows PE, the Windows Preinstallation Environment, without having to rely on Windows. 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. Windows PE 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 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. DEPENDENCIES * 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 GNU/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 GNU/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 Besides the various well-known options, the following options can be passed to wimlib's `configure' script: --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. --enable-xattr, --disable-xattr Enable or disable support for the extended-attributes interface to NTFS alternate data streams in mounted WIMs. To support these, wimlib requires that the setxattr() function and the attr/xattr.h header are available. The default is to autodetect whether support is possible. --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-custom-memory-allocator If this option is given, a very small amount of space will be saved by removing support for the wimlib_set_memory_allocator() function. imagex will be unaffected. --disable-verify-compression Unless this option is given, every time wimlib compresses a data block, it will decompress it into a temporary buffer and abort the program with an error message if the decompressed data does not exactly match the original data. This only makes compression about 10% slower. However, this checking can probably be safely disabled because there are no known bugs in the compression code, and the SHA1 message digest of every extracted file is checked anyway. --disable-error-messages Save some space by removing all error messages from the library. --disable-assertions Remove all assertions, even the ones that are included by default. --enable-more-assertions Enable assertions that are not included by default. --enable-debug Include debugging messages. Only use this option if you have found a bug in the library. --enable-more-debug Include more debugging messages. Only use this option if you have found a bug in the library. PORTABILITY wimlib has mostly been developed and tested on x86_64 (64-bit) GNU/Linux. It has been tested on x86 (32-bit) GNU/Linux occasionally. 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 pays attention to endianness, so it should work on big-endian architectures, but I've never tested this so do not expect it to work. There are no plans to port wimlib to Windows since the programming interface on Windows is very different and Microsoft's imagex.exe is already available. REFERENCES The WIM file format is specified in a document that can be found in the Microsoft Download Center. There is a similar document that specifies the LZX compression format, and a document that specifies the XPRESS compression format. However, many parts of these formats are poorly documented, and some parts have no documentation whatsoever. Some particularly poorly documented parts of the formats have had comments added in various places in the library. Please see the code and/or ask me if you have any questions about the WIM file format as it exists in reality and not as it exists in Microsoft's poorly written documentation. The code in ntfs-apply.c and ntfs-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. lzx-decompress.c, the code to decompress WIM file resources that are compressed using LZX compression, is originally based on code from the cabextract project (http://www.cabextract.org.uk). lzx-compress.c, the code to compress WIM file resources using LZX compression, is originally based on code written by Matthew Russotto (www.russotto.net/chm/). lz77.c, the code to find LZ77 matches (used for both XPRESS and LZX compression), is based on code from zlib. A very 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 imagex.exe, such as the ability to mount WIMs read-write as well as read-only, the ability to create LZX or XPRESS compressed WIMs, and the correct handling of security descriptors and hard links. An earlier version of wimlib is being used to deploy Windows 7 from the Ultimate Deployment Appliance. For more information see http://www.ultimatedeployment.org/. You can see the documentation about Microsoft's version of the imagex program at http://technet.microsoft.com/en-us/library/cc749447(v=ws.10).aspx, so you can see how it compares to the version provided by this library. GNU/Linux equivalents of WIM format What's the equivalent way to capture the filesystem of a GNU/Linux operating system into an archive file? You have a few options: SquashFS: SquashFS (http://squashfs.sourceforge.net/) provides a compressed, read-only filesystem for Linux, and it's probably the closest equivalent of the WIM format and better designed. Although you can't mount SquashFS read-write, when wimlib does this for WIM files it's really an illusion since the WIM isn't actually modified until the image is unmounted. Multiple top-level images in SquashFS files are not supported, although nothing stops you from just putting each image in a separate directory. FSArchiver: FSArchiver (http://www.fsarchiver.org/Main_Page) is not widely used, but it appears to have some features quite similar to the WIM format. Tar: The well-known tar format can usually capture a UNIX filesystem just fine, and compressing the tar file produces a good compression ratio (better than WIM, especially if using XZ compression), but there is no support for random access, file deduplication, multiple images per archive, or extended attributes. Zip: Zip shares some features with WIM but is not designed to store entire filesystems. 7z: The 7z format has some nice features but is unfortunately not designed with UNIX in mind. MORE INFORMATION See the manual pages for `imagex', the manual pages for the subcommands of `imagex', and the manual page for `mkwinpeimg'. As of version 0.5.0, wimlib's public API is documented. Doxygen is required to build the documentation. To build the documentation, run `configure', then enter the directory `doc' and run `doxygen'. The HTML documentation will be created in a directory named `html'. LICENSE As of version 1.0.0, wimlib is released under the GNU GPL version 3.0 or later. This includes the files in the `programs' directory as well as the files in the `src' directory. 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. By default, wimlib will be linked to the system library "libcrypto", which probably will be OpenSSL. Some people believe that GPL code cannot be linked to OpenSSL without a linking exception. As far as I know, I cannot officially include a linking exception with the license of this library because several files could be considered derived works of code copyrighted by others. If you believe this to be a problem, configure with --without-libcrypto to avoid linking with OpenSSL. There is no difference in functionality--- there will just be stand-alone SHA1 message digest code built into the library. DISCLAIMER wimlib is experimental. Use Microsoft's `imagex.exe' if you want to make sure your WIM files are made correctly (but beware: Microsoft's version contains some bugs). Please submit a bug report (to ebiggers3@gmail.com) if you find a bug in wimlib. 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.