1 SQUASHFS 4.2 - A squashed read-only filesystem for Linux 2 3 Copyright 2002-2011 Phillip Lougher <phillip@lougher.demon.co.uk> 4 5 Released under the GPL licence (version 2 or later). 6 7Welcome to Squashfs 4.2. This is a tools only release, support for Squashfs 8filesystems is in mainline (2.6.29 and later). 9 10New features in Squashfs-tools 4.2 11---------------------------------- 12 13 1. Support for XZ compression 14 2. Support for compressor specific options 15 16Compatiblity 17------------ 18 19Mksquashfs 4.2 generates 4.0 filesystems. These filesystems are fully 20compatible/interchangable with filesystems generated by Mksquashfs 4.0 and are 21mountable on 2.6.29 and later kernels. 22 23XZ compression 24-------------- 25 26Squashfs now supports XZ compression. 27 28XZ support is in 2.6.38 and newer kernels. 29 30New Mksquashfs options 31---------------------- 32 33-X<compressor-option> 34 35 Compression algorithms can now support compression specific options. These 36options are prefixed by -X, and are passed to the compressor for handling. 37 38 The compression specific options supported by each compressor can be 39found by typing mksquashfs without any arguments. They are displayed at the 40end of the help message, e.g. 41 42Compressors available and compressor specific options: 43 gzip (no options) (default) 44 lzo (no options) 45 xz 46 -Xbcj filter1,filter2,...,filterN 47 Compress using filter1,filter2,...,filterN in turn 48 (in addition to no filter), and choose the best compression. 49 Available filters: x86, arm, armthumb, powerpc, sparc, ia64 50 -Xdict-size <dict-size> 51 Use <dict-size> as the XZ dictionary size. The dictionary size 52 can be specified as a percentage of the block size, or as an 53 absolute value. The dictionary size must be less than or equal 54 to the block size and 8192 bytes or larger. It must also be 55 storable in the xz header as either 2^n or as 2^n+2^(n+1). 56 Example dict-sizes are 75%, 50%, 37.5%, 25%, or 32K, 16K, 8K 57 etc. 58