INTRODUCTION
-This is wimlib version 1.5.3 (December 2013). wimlib is a C library for
+This is wimlib version 1.7.0-BETA (May 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
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 two compression formats: LZX and
-XPRESS *. Both are supported by wimlib.
+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
A WIM file may be either stand-alone or split into multiple parts. Split WIMs
are read-only and cannot be modified.
-* Note: The Windows 8 WIMGAPI apparently adds a third format, LZMS, but it is
- not documented and is incompatible with ImageX and Dism. It is unclear if
- this new format is actually being used for anything.
+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 These are still WIM files but they use a newer version of the file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
COMPRESSION RATIO
-wimlib (and wimlib-imagex) can create XPRESS or LZX compressed WIM archives.
-The following tables compare the compression ratio and performance for creating
-a compressed x86_64 Windows PE image. Note: these timings were done on Windows
-so that the times would be fully comparable; however, wimlib may have even
-better performance on other operating systems such as Linux. Timings were done
-with 2 CPUs available, both of which automatically are used by wimlib for both
-XPRESS and LZX, and also by imagex.exe but apparently only for LZX.
-
- Table 1. WIM size
-
- XPRESS Compression LZX Compression
- wimlib-imagex (v1.5.3): 207,444,390 bytes 188,106,091 bytes
- Microsoft imagex.exe (Windows 7): 209,960,209 bytes 188,224,481 bytes
-
- Table 2. Time to create WIM
-
- XPRESS Compression LZX Compression
- wimlib-imagex (v1.5.3): 73 sec 202 sec
- Microsoft imagex.exe (Windows 7): 90 sec 149 sec
-
-The above LZX data are using explicitly specified maximum compression
-('--compress=maximum') as of wimlib v1.5.3. If `wimlib-imagex capture' or
-`wimlib-imagex capture' is instead run with no '--compress' argument, then a
-faster LZX compressor is used; it will produce results in between those given
-for XPRESS and LZX above.
-
-Note: if the absolute maximum compression ratio is desired, `wimlib-imagex
-optimize WIMFILE --recompress --compress-slow' on one of the above
-LZX-compressed WIMs produces a WIM of 187,089,943 bytes in about 400 seconds.
+wimlib (and wimlib-imagex) can create XPRESS, LZX, or LZMS compressed WIM
+archives. wimlib includes its own compression codecs and does not use the
+compression API available on some versions of Windows. The below table provides
+the results (file size, in bytes, and time to create, in seconds) of capturing a
+WIM containing an x86 Windows PE image, using various compression types and
+options. When applicable, the results with the equivalent Microsoft
+implementation in WIMGAPI, which is the library used by ImageX and Dism, are
+included.
+
+ ===========================================================================
+ | Compression type || wimlib (v1.6.1) | WIMGAPI (Windows 8) |
+ ===========================================================================
+ | None [1] || 531,979,435 in 18s | 531,980,333 in 24s |
+ | XPRESS [2] || 207,369,912 in 22s | 209,886,010 in 39s |
+ | LZX (quick) [3] || 194,876,901 in 29s | N/A |
+ | LZX (normal) [4] || 187,962,713 in 158s | 188,163,523 in 125s |
+ | LZX (slow) [5] || 186,913,423 in 358s | N/A |
+ | LZMS (non-solid) [6] || 176,880,594 in 182s | N/A |
+ | LZMS (solid) [7] || 136,507,304 in 494s | 126,735,608 in 623s |
+ ===========================================================================
+
+Notes:
+ [1] '--compress=none' for wimlib-imagex;
+ '/compress none' or no option for ImageX.
+
+ [2] '--compress=fast' or '--compress=XPRESS' for wimlib-imagex;
+ '/compress fast' or no option for ImageX.
+ Compression chunk size is 32768 (the default for XPRESS).
+
+ [3] No compression option specified to wimlib-imagex; no known equivalent for
+ WIMGAPI (ImageX uses XPRESS compression if no option specified).
+ Compression chunk size is 32768 (the default for LZX).
+
+ [4] '--compress=maximum' or '--compress=LZX' for wimlib-imagex;
+ '/compress maximum' for ImageX.
+ Compression chunk size is 32768 (the default for LZX).
+
+ [5] '--compress=maximum --compress-slow' for wimlib-imagex;
+ no known equivalent for WIMGAPI.
+ Compression chunk size is 32768 (the default for LZX).
+
+ [6] '--compress=recovery' or '--compress=LZMS' for wimlib-imagex;
+ no known way to create the equivalent with WIMGAPI.
+ Compression chunk size is 131072 (the default for LZMS). Note: this
+ compression type is not generally recommended due to its limited
+ compatibility with the MS implementations.
+
+ [7] '--compress=recovery --solid' or '--compress=LZMS --solid' for
+ wimlib-imagex; WIMCreateFile with WIM_COMPRESSION_LZMS and flag
+ 0x20000000 for WIMGAPI. Compression chunk size in packed resources is
+ 33554432 for wimlib, 67108864 for WIMGAPI. Note: this compression type
+ is not generally recommended due to its limited compatibility with the MS
+ implementations. Also, due to the large chunk size, wimlib uses about
+ 500MB of memory per thread when compressing in this format.
+
+The above timings were done on Windows 8 (x86) so that side-by-side comparisons
+with the Microsoft implementation would be possible; however, wimlib may have
+even better performance on other operating systems such as Linux. The system
+had 2 CPUs and 2 GiB of memory available. All times were done with the page
+cache warmed, so the times primarily measure the performance of the compression
+algorithms and not the time to read data from disk, which presumably is similar
+in each implementation.
+
+Below are results for compressing the Canterbury corpus using wimlib (v1.6.1),
+WIMGAPI (Windows 8), and some other formats/programs, including the archive size
+only. Note that the Canterbury corpus includes no duplicate files or hard
+links, which WIM handles better than most other formats by storing only distinct
+data streams.
+
+ =================================================
+ | 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) | 639,464 |
+ | WIM (wimlib, LZX slow) | 633,144 |
+ | WIM (wimlib, LZMS non-solid) | 590,252 |
+ | tar.bz2 (bzip, default) | 565,008 |
+ | tar.bz2 (bzip, -9) | 565,008 |
+ | WIM (wimlib, LZMS solid) | 534,218 |
+ | WIM (wimlib, LZMS solid, slow) | 529,904 |
+ | 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 |
+ =================================================
NTFS SUPPORT
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 a NTFS
+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.
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
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 code. 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 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.
-lzx-decompress.c, the code to decompress WIM file resources that are compressed
-using LZX compression, was originally based on code from the cabextract project
-(http://www.cabextract.org.uk) but has been rewritten.
+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.
-lzx-compress.c, the code to compress WIM file resources using LZX compression,
-was originally based on code written by Matthew Russotto (www.russotto.net/chm/)
-but has been rewritten.
+lz_hash.c contains LZ77 match-finding code that uses hash chains. It is based
+on code from zlib but I have since rewritten it.
-lz77.c, the code to find LZ77 matches (used for both XPRESS and LZX
-compression), is based on code from zlib but has been rewritten.
+lz_bt.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
- 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.
+ 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
Ultimate Deployment Appliance. For more information see
http://www.ultimatedeployment.org/.
-You can see the documentation about Microsoft's version of ImageX at
-http://technet.microsoft.com/en-us/library/cc749447(v=ws.10).aspx, so you can
-see how it compares to wimlib-imagex.
-
If you are looking for a UNIX archive format that provides features similar to
WIM, I recommend you take a look at SquashFS (http://squashfs.sourceforge.net/).
LICENSE
As of version 1.0.0, wimlib and all programs and scripts distributed with it are
-released under the GNU GPL version 3.0 or later.
+released under the GNU GPL version 3.0 or later. See COPYING for details.
+Some individual source files are also released under more permissive licenses.
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.
DISCLAIMER
-wimlib comes with no warranty whatsoever. 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
-and/or wimlib-imagex.
+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
git://wimlib.net / wimlib / blobdiff