xz

       .lzma files

SYNOPSIS
       xz [option]...  [file]...

       unxz is equivalent to xz --decompress.
       xzcat is equivalent to xz --decompress --stdout.
       lzma is equivalent to xz --format=lzma.
       unlzma is equivalent to xz --format=lzma --decompress.
       lzcat is equivalent to xz --format=lzma --decompress --stdout.

       When writing scripts that need to decompress files, it  is  recommended
       to  always use the name xz with appropriate arguments (xz -d or xz -dc)
       instead of the names unxz and xzcat.

DESCRIPTION
       xz is a general-purpose data compression tool with command line  syntax
       similar  to  gzip(1)  and  bzip2(1).  The native file format is the .xz
       format, but also the legacy .lzma format  and  raw  compressed  streams
       with no container format headers are supported.

       xz compresses or decompresses each file according to the selected oper-
       ation mode.  If no files are given or file is -, xz reads from standard
       input and writes the processed data to standard output.  xz will refuse
       (display an error and skip the file) to write compressed data to  stan-
       dard output if it is a terminal. Similarly, xz will refuse to read com-
       pressed data from standard input if it is a terminal.

       Unless --stdout is specified, files other than - are written to  a  new
       file whose name is derived from the source file name:

       o  When  compressing,  the  suffix  of  the  target file format (.xz or
          .lzma) is appended to the source filename to get  the  target  file-
          name.

       o  When  decompressing,  the  .xz  or  .lzma suffix is removed from the
          filename to get the target filename.  xz also  recognizes  the  suf-
          fixes .txz and .tlz, and replaces them with the .tar suffix.

       If  the  target file already exists, an error is displayed and the file
       is skipped.

       Unless writing to standard output, xz will display a warning  and  skip
       the file if any of the following applies:

       o  File  is  not  a regular file. Symbolic links are not followed, thus
          they are never considered to be regular files.

       o  File has more than one hardlink.

       o  File has setuid, setgid, or sticky bit set.

       o  The operation mode is set to compress, and the file  already  has  a
          suffix  of  the  target file format (.xz or .txz when compressing to

       support copying other metadata like access control  lists  or  extended
       attributes yet.

       Once  the  target file has been successfully closed, the source file is
       removed unless --keep was specified. The source file is  never  removed
       if the output is written to standard output.

       Sending  SIGINFO  or  SIGUSR1 to the xz process makes it print progress
       information to standard error.  This has only limited  use  since  when
       standard error is a terminal, using --verbose will display an automati-
       cally updating progress indicator.

   Memory usage
       The memory usage of xz varies from a few hundred kilobytes  to  several
       gigabytes depending on the compression settings. The settings used when
       compressing a file affect also the memory usage  of  the  decompressor.
       Typically  the decompressor needs only 5 % to 20 % of the amount of RAM
       that the compressor needed when creating the file.  Still,  the  worst-
       case memory usage of the decompressor is several gigabytes.

       To  prevent uncomfortable surprises caused by huge memory usage, xz has
       a built-in memory usage limiter. The default limit is  40  %  of  total
       physical  RAM. While operating systems provide ways to limit the memory
       usage of processes, relying on it wasn't deemed to be flexible enough.

       When compressing, if the selected compression settings exceed the  mem-
       ory  usage limit, the settings are automatically adjusted downwards and
       a notice about this is displayed. As an exception, if the memory  usage
       limit  is exceeded when compressing with --format=raw, an error is dis-
       played and xz will exit with exit status 1.

       If source file cannot be  decompressed  without  exceeding  the  memory
       usage  limit,  an  error  message is displayed and the file is skipped.
       Note that compressed files may contain many blocks, which may have been
       compressed  with  different  settings.  Typically  all blocks will have
       roughly the same memory requirements, but it is possible that  a  block
       later  in  the  file  will  exceed the memory usage limit, and an error
       about too low memory usage limit gets displayed  after  some  data  has
       already been decompressed.

       The  absolute  value  of the active memory usage limit can be seen with
       --info-memory or near the bottom of the  output  of  --long-help.   The
       default limit can be overriden with --memory=limit.

OPTIONS
   Integer suffixes and special values
       In  most places where an integer argument is expected, an optional suf-
       fix is supported to easily indicate large integers. There  must  be  no
       space between the integer and the suffix.

       k or kB
              The  integer  is  multiplied by 1,000 (10^3). For example, 5k or
              5kB equals 5000.

       Gi or GiB
              The integer is multiplied by 1,073,741,824 (2^30).

       A special value max can be used to indicate the maximum  integer  value
       supported by the option.

   Operation mode
       If  multiple  operation  mode  options  are  given,  the last one takes
       effect.

       -z, --compress
              Compress. This is the default operation mode when  no  operation
              mode option is specified, and no other operation mode is implied
              from the command name (for example, unxz implies --decompress).

       -d, --decompress, --uncompress
              Decompress.

       -t, --test
              Test the integrity of compressed files.  No files are created or
              removed.  This  option  is  equivalent  to --decompress --stdout
              except that the decompressed data is discarded instead of  being
              written to standard output.

       -l, --list
              View  information  about  the  compressed files. No uncompressed
              output is produced, and no files are created or removed. In list
              mode,  the program cannot read the compressed data from standard
              input or from other unseekable sources.

              This feature has not been implemented yet.

   Operation modifiers
       -k, --keep
              Keep (don't delete) the input files.

       -f, --force
              This option has several effects:

              o  If the target file already exists, delete it before compress-
                 ing or decompressing.

              o  Compress  or  decompress  even  if the input is not a regular
                 file, has more than one hardlink, or has setuid,  setgid,  or
                 sticky  bit set.  The setuid, setgid, and sticky bits are not
                 copied to the target file.

              o  If combined with --decompress --stdout and xz doesn't  recog-
                 nize  the  type  of  the source file, xz will copy the source
                 file as is  to  standard  output.  This  allows  using  xzcat
                 --force  like  cat(1) for files that have not been compressed
                 with xz.  Note that in future,  xz  might  support  new  com-
                 pressed file formats, which may make xz decompress more types
                 of files instead of copying them as is  to  standard  output.

              instead  of .xz or .lzma.  If not writing to standard output and
              the source file already has the suffix .suf, a warning  is  dis-
              played and the file is skipped.

              When decompressing, recognize also files with the suffix .suf in
              addition to files with the .xz, .txz, .lzma, or .tlz suffix.  If
              the  source  file  has the suffix .suf, the suffix is removed to
              get the target filename.

              When compressing or decompressing  raw  streams  (--format=raw),
              the  suffix  must always be specified unless writing to standard
              output, because there is no default suffix for raw streams.

       --files[=file]
              Read the filenames to process from file;  if  file  is  omitted,
              filenames are read from standard input. Filenames must be termi-
              nated with the newline character. A dash (-) is taken as a regu-
              lar  filename; it doesn't mean standard input.  If filenames are
              given also as command line arguments, they are processed  before
              the filenames read from file.

       --files0[=file]
              This  is  identical  to --files[=file] except that the filenames
              must be terminated with the null character.

   Basic file format and compression options
       -F format, --format=format
              Specify the file format to compress or decompress:

              o  auto: This is the default. When compressing, auto is  equiva-
                 lent to xz.  When decompressing, the format of the input file
                 is autodetected. Note that raw streams (created  with  --for-
                 mat=raw) cannot be autodetected.

              o  xz: Compress to the .xz file format, or accept only .xz files
                 when decompressing.

              o  lzma or alone: Compress to the legacy .lzma file  format,  or
                 accept  only  .lzma files when decompressing. The alternative
                 name alone is provided for backwards compatibility with  LZMA
                 Utils.

              o  raw:  Compress  or uncompress a raw stream (no headers). This
                 is meant for advanced users only. To decode raw streams,  you
                 need to set not only --format=raw but also specify the filter
                 chain, which would normally be stored in the container format
                 headers.

       -C check, --check=check
              Specify  the  type  of  the integrity check, which is calculated
              from the uncompressed data. This option has an effect only  when
              compressing  into  the .xz format; the .lzma format doesn't sup-
              port integrity checks.  The integrity check (if any) is verified
              when the .xz file is decompressed.
                 at detecting damaged files and the speed difference is negli-
                 gible.

              o  sha256: Calculate SHA-256. This is somewhat slower than CRC32
                 and CRC64.

              Integrity of the .xz headers is always verified with  CRC32.  It
              is not possible to change or disable it.

       -0 ... -9
              Select compression preset. If a preset level is specified multi-
              ple times, the last one takes effect.

              The compression preset levels can be  categorised  roughly  into
              three categories:

              -0 ... -2
                     Fast presets with relatively low memory usage.  -1 and -2
                     should give compression speed and  ratios  comparable  to
                     bzip2 -1 and bzip2 -9, respectively.  Currently -0 is not
                     very good (not much faster than -1 but  much  worse  com-
                     pression).  In future, -0 may be indicate some fast algo-
                     rithm instead of LZMA2.

              -3 ... -5
                     Good compression ratio with low to medium  memory  usage.
                     These are significantly slower than levels 0-2.

              -6 ... -9
                     Excellent  compression  with medium to high memory usage.
                     These are also slower than the lower preset  levels.  The
                     default  is -6.  Unless you want to maximize the compres-
                     sion ratio, you probably don't want a higher preset level
                     than -7 due to speed and memory usage.

              The  exact compression settings (filter chain) used by each pre-
              set may vary between xz versions. The  settings  may  also  vary
              between  files  being compressed, if xz determines that modified
              settings will probably give  better  compression  ratio  without
              significantly affecting compression time or memory usage.

              Because  the  settings  may vary, the memory usage may vary too.
              The following table lists the maximum memory usage of each  pre-
              set  level,  which  won't be exceeded even in future versions of
              xz.

              FIXME: The table below is just a rough idea.

                     Preset   Compression   Decompression
                       -0         6 MiB         1 MiB
                       -1         6 MiB         1 MiB
                       -2        10 MiB         1 MiB
                       -3        20 MiB         2 MiB
                       -4        30 MiB         3 MiB

              These  are  somewhat  misleading  aliases for -0 and -9, respec-
              tively.  These are provided  only  for  backwards  compatibility
              with LZMA Utils.  Avoid using these options.

              Especially the name of --best is misleading, because the defini-
              tion of best depends on the input data, and that usually  people
              don't  want  the  very best compression ratio anyway, because it
              would be very slow.

       -e, --extreme
              Modify the compression preset (-0 ... -9) so that a  little  bit
              better compression ratio can be achieved without increasing mem-
              ory usage of the compressor or decompressor (exception: compres-
              sor  memory usage may increase a little with presets -0 ... -2).
              The downside is that the compression time will increase dramati-
              cally (it can easily double).

       -M limit, --memory=limit
              Set  the  memory usage limit. If this option is specied multiple
              times, the last one takes effect. The limit can be specified  in
              multiple ways:

              o  The limit can be an absolute value in bytes. Using an integer
                 suffix like MiB can be useful. Example: --memory=80MiB

              o  The limit can be specified as a percentage of  physical  RAM.
                 Example: --memory=70%

              o  The  limit  can be reset back to its default value (currently
                 40 % of physical RAM) by setting it to 0.

              o  The memory usage limiting can be effectively disabled by set-
                 ting limit to max.  This isn't recommended. It's usually bet-
                 ter to use, for example, --memory=90%.

              The current limit can be seen near the bottom of the  output  of
              the --long-help option.

       -T threads, --threads=threads
              Specify the maximum number of worker threads to use. The default
              is the number of available CPU cores. You can  see  the  current
              value  of  threads near the end of the output of the --long-help
              option.

              The actual number of worker threads can be less than threads  if
              using  more  threads  would  exceed  the memory usage limit.  In
              addition to CPU-intensive worker threads, xz may use a few  aux-
              iliary threads, which don't use a lot of CPU time.

              Multithreaded  compression and decompression are not implemented
              yet, so this option has no effect for now.

   Custom compressor filter chains
       A custom filter chain allows specifying  the  compression  settings  in
       some  filters  can work only as the last filter in the chain, some only
       as a non-last filter, and some work  in  any  position  in  the  chain.
       Depending on the filter, this limitation is either inherent to the fil-
       ter design or exists to prevent security issues.

       A custom filter chain is specified by using one or more filter  options
       in the order they are wanted in the filter chain. That is, the order of
       filter options  is  significant!  When  decoding  raw  streams  (--for-
       mat=raw),  the  filter  chain  is specified in the same order as it was
       specified when compressing.

       Filters take filter-specific options as a comma-separated  list.  Extra
       commas in options are ignored. Every option has a default value, so you
       need to specify only those you want to change.

       --lzma1[=options], --lzma2[=options]
              Add LZMA1 or LZMA2 filter to the filter chain. These filter  can
              be used only as the last filter in the chain.

              LZMA1  is  a legacy filter, which is supported almost solely due
              to the legacy .lzma file  format,  which  supports  only  LZMA1.
              LZMA2  is  an  updated  version  of  LZMA1 to fix some practical
              issues of LZMA1. The .xz format uses LZMA2, and doesn't  support
              LZMA1  at  all.  Compression speed and ratios of LZMA1 and LZMA2
              are practically the same.

              LZMA1 and LZMA2 share the same set of options:

              preset=preset
                     Reset all LZMA1 or LZMA2 options to preset.  Preset  con-
                     sist  of an integer, which may be followed by single-let-
                     ter preset modifiers. The integer can be  from  0  to  9,
                     matching  the  command  line options -0 ... -9.  The only
                     supported  modifier  is  currently   e,   which   matches
                     --extreme.

                     The  default  preset  is 6, from which the default values
                     for the rest of the LZMA1 or LZMA2 options are taken.

              dict=size
                     Dictionary (history buffer) size indicates how many bytes
                     of  the  recently  processed uncompressed data is kept in
                     memory. One method to reduce  size  of  the  uncompressed
                     data  is  to  store distance-length pairs, which indicate
                     what data to repeat from the dictionary buffer. The  big-
                     ger the dictionary, the better the compression ratio usu-
                     ally is, but dictionaries bigger  than  the  uncompressed
                     data are waste of RAM.

                     Typical  dictionary  size  is  from 64 KiB to 64 MiB. The
                     minimum is 4 KiB.  The maximum for  compression  is  cur-
                     rently 1.5 GiB. The decompressor already supports dictio-
                     naries up to one byte less than 4 GiB, which is the maxi-
                     mum for LZMA1 and LZMA2 stream formats.

              lp=lp  Specify  the number of literal position bits. The minimum
                     is 0 and the maximum is 4; the default is 0.

              pb=pb  Specify the number of position bits. The minimum is 0 and
                     the maximum is 4; the default is 2.

              mode=mode
                     Compression  mode  specifies the function used to analyze
                     the data produced by the match finder.   Supported  modes
                     are fast and normal.  The default is fast for presets 0-2
                     and normal for presets 3-9.

              mf=mf  Match finder has a major effect on encoder speed,  memory
                     usage,  and  compression  ratio. Usually Hash Chain match
                     finders are faster than Binary Tree match  finders.  Hash
                     Chains  are  usually  used  together  with  mode=fast and
                     Binary Trees with mode=normal.  The memory usage formulas
                     are  only  rough  estimates, which are closest to reality
                     when dict is a power of two.

                     hc3    Hash Chain with 2- and 3-byte hashing
                            Minimum value for nice: 3
                            Memory usage: dict * 7.5 (if dict <= 16 MiB);
                            dict * 5.5 + 64 MiB (if dict > 16 MiB)

                     hc4    Hash Chain with 2-, 3-, and 4-byte hashing
                            Minimum value for nice: 4
                            Memory usage: dict * 7.5

                     bt2    Binary Tree with 2-byte hashing
                            Minimum value for nice: 2
                            Memory usage: dict * 9.5

                     bt3    Binary Tree with 2- and 3-byte hashing
                            Minimum value for nice: 3
                            Memory usage: dict * 11.5 (if dict <= 16 MiB);
                            dict * 9.5 + 64 MiB (if dict > 16 MiB)

                     bt4    Binary Tree with 2-, 3-, and 4-byte hashing
                            Minimum value for nice: 4
                            Memory usage: dict * 11.5

              nice=nice
                     Specify what is considered to be  a  nice  length  for  a
                     match.  Once a match of at least nice bytes is found, the
                     algorithm stops looking for possibly better matches.

                     nice can be 2-273 bytes. Higher values tend to give  bet-
                     ter  compression  ratio  at expense of speed. The default
                     depends on the preset level.

              depth=depth
                     Specify the maximum search depth in the match finder. The

       --powerpc[=options]

       --ia64[=options]

       --arm[=options]

       --armthumb[=options]

       --sparc[=options]
              Add a branch/call/jump (BCJ) filter to the filter  chain.  These
              filters can be used only as non-last filter in the filter chain.

              A  BCJ filter converts relative addresses in the machine code to
              their absolute counterparts. This doesn't change the size of the
              data,  but  it  increases redundancy, which allows e.g. LZMA2 to
              get better compression ratio.

              The BCJ filters are always reversible, so using a BCJ filter for
              wrong  type of data doesn't cause any data loss. However, apply-
              ing a BCJ filter for wrong type of data is a bad  idea,  because
              it tends to make the compression ratio worse.

              Different instruction sets have have different alignment:

                     Filter      Alignment   Notes
                     x86             1       32-bit and 64-bit x86
                     PowerPC         4       Big endian only
                     ARM             4       Little endian only
                     ARM-Thumb       2       Little endian only
                     IA-64          16       Big or little endian
                     SPARC           4       Big or little endian

              Since  the  BCJ-filtered  data is usually compressed with LZMA2,
              the compression ratio may be  improved  slightly  if  the  LZMA2
              options  are set to match the alignment of the selected BCJ fil-
              ter. For example, with the IA-64 filter, it's good to  set  pb=4
              with  LZMA2  (2^4=16). The x86 filter is an exception; it's usu-
              ally good to stick to LZMA2's default four-byte  alignment  when
              compressing x86 executables.

              All BCJ filters support the same options:

              start=offset
                     Specify  the  start  offset  that is used when converting
                     between relative and absolute addresses.  The offset must
                     be a multiple of the alignment of the filter (see the ta-
                     ble above).   The  default  is  zero.  In  practice,  the
                     default  is  good;  specifying  a custom offset is almost
                     never useful.

                     Specifying a non-zero start  offset  is  probably  useful
                     only  if  the executable has multiple sections, and there
                     are many cross-section jumps or  calls.  Applying  a  BCJ

              images or uncompressed PCM audio. However, special purpose algo-
              rithms may give significantly better results than Delta + LZMA2.
              This is true especially with audio, which compresses faster  and
              better e.g. with FLAC.

              Supported options:

              dist=distance
                     Specify  the  distance of the delta calculation as bytes.
                     distance must be 1-256. The default is 1.

                     For example, with dist=2 and eight-byte input A1 B1 A2 B3
                     A3 B5 A4 B7, the output will be A1 B1 01 02 01 02 01 02.

   Other options
       -q, --quiet
              Suppress  warnings  and  notices. Specify this twice to suppress
              errors too.  This option has no effect on the exit status.  That
              is,  even  if a warning was suppressed, the exit status to indi-
              cate a warning is still used.

       -v, --verbose
              Be verbose. If standard error is connected  to  a  terminal,  xz
              will  display  a progress indicator.  Specifying --verbose twice
              will give even more verbose output  (useful  mostly  for  debug-
              ging).

              The progress indicator shows the following information:

              o  Completion  percentage is shown if the size of the input file
                 is known.  That is, percentage cannot be shown in pipes.

              o  Amount of compressed data produced (compressing) or  consumed
                 (decompressing).

              o  Amount  of  uncompressed  data consumed (compressing) or pro-
                 duced (decompressing).

              o  Compression ratio, which is calculated by dividing the amount
                 of  compressed  data processed so far by the amount of uncom-
                 pressed data processed so far.

              o  Compression or decompression speed. This is measured  as  the
                 amount  of  uncompressed  data consumed (compression) or pro-
                 duced (decompression) per second. It is shown once a few sec-
                 onds have passed since xz started processing the file.

              o  Elapsed  time  or  estimated time remaining.  Elapsed time is
                 displayed in the  format  M:SS  or  H:MM:SS.   The  estimated
                 remaining  time  is  displayed in a less precise format which
                 never has colons, for example, 2 min 30 s. The  estimate  can
                 be  shown only when the size of the input file is known and a
                 couple of seconds have already passed since xz  started  pro-
                 cessing the file.

              ing  was  detected.  This  option  doesn't  affect the verbosity
              level, thus both --quiet and --no-warn have to be  used  to  not
              display warnings and to not alter the exit status.

       --robot
              Print messages in a machine-parsable format. This is intended to
              ease writing frontends that want to use xz instead  of  liblzma,
              which may be the case with various scripts. The output with this
              option enabled is meant to be stable across  xz  releases.  Cur-
              rently  --robot is implemented only for --info-memory and --ver-
              sion, but the idea is to make it usable for  actual  compression
              and decompression too.

       --info-memory
              Display  the current memory usage limit in human-readable format
              on a single line, and exit successfully. To see how much RAM  xz
              thinks your system has, use --memory=100% --info-memory.  To get
              machine-parsable output (memory usage  limit  as  bytes  without
              thousand separators), specify --robot before --info-memory.

       -h, --help
              Display  a  help  message  describing  the  most  commonly  used
              options, and exit successfully.

       -H, --long-help
              Display a help message describing all features of xz,  and  exit
              successfully

       -V, --version
              Display  the  version number of xz and liblzma in human readable
              format. To get machine-parsable output, specify  --robot  before
              --version.

EXIT STATUS
       0      All is good.

       1      An error occurred.

       2      Something  worth  a  warning  occurred,  but  no  actual  errors
              occurred.

       Notices (not warnings or errors) printed on standard error don't affect
       the exit status.

ENVIRONMENT
       XZ_OPT A  space-separated  list of options is parsed from XZ_OPT before
              parsing the options given on the command line.  Note  that  only
              options  are  parsed  from  XZ_OPT; all non-options are silently
              ignored. Parsing is done with getopt_long(3) which is used  also
              for the command line arguments.

LZMA UTILS COMPATIBILITY
       The  command  line  syntax  of  xz  is  practically a superset of lzma,
       unlzma, and lzcat as found from LZMA Utils 4.32.x. In most cases, it is
               -2     512 KiB      1 MiB
               -3       1 MiB    512 KiB
               -4       2 MiB      1 MiB
               -5       4 MiB      2 MiB
               -6       8 MiB      4 MiB
               -7      16 MiB      8 MiB
               -8      32 MiB     16 MiB
               -9      64 MiB     32 MiB

       The dictionary size differences affect the compressor memory usage too,
       but  there  are some other differences between LZMA Utils and XZ Utils,
       which make the difference even bigger:

              Level     xz      LZMA Utils 4.32.x
               -1       2 MiB          2 MiB
               -2       5 MiB         12 MiB
               -3      13 MiB         12 MiB
               -4      25 MiB         16 MiB
               -5      48 MiB         26 MiB
               -6      94 MiB         45 MiB
               -7     186 MiB         83 MiB
               -8     370 MiB        159 MiB
               -9     674 MiB        311 MiB

       The default preset level in LZMA Utils is -7 while in XZ  Utils  it  is
       -6, so both use 8 MiB dictionary by default.

   Streamed vs. non-streamed .lzma files
       Uncompressed  size  of the file can be stored in the .lzma header. LZMA
       Utils does that when compressing regular files.  The alternative is  to
       mark that uncompressed size is unknown and use end of payload marker to
       indicate where the decompressor should  stop.   LZMA  Utils  uses  this
       method  when uncompressed size isn't known, which is the case for exam-
       ple in pipes.

       xz supports decompressing .lzma files with or without  end  of  payload
       marker,  but  all  .lzma  files  created  by xz will use end of payload
       marker and have uncompressed  size  marked  as  unknown  in  the  .lzma
       header.  This may be a problem in some (uncommon) situations. For exam-
       ple, a .lzma decompressor in an embedded device might  work  only  with
       files  that  have known uncompressed size. If you hit this problem, you
       need to use LZMA Utils or LZMA SDK to create  .lzma  files  with  known
       uncompressed size.

   Unsupported .lzma files
       The  .lzma format allows lc values up to 8, and lp values up to 4. LZMA
       Utils can decompress files with any lc and lp, but always creates files
       with  lc=3  and  lp=0.  Creating files with other lc and lp is possible
       with xz and with LZMA SDK.

       The implementation of the LZMA1 filter in liblzma requires that the sum
       of  lc  and  lp  must not exceed 4. Thus, .lzma files which exceed this
       limitation, cannot be decompressed with xz.

       first  .lzma stream. In most situations, this is a bug. This also means
       that LZMA Utils don't support decompressing concatenated .lzma files.

       If there is data left after the first .lzma stream,  xz  considers  the
       file  to  be corrupt. This may break obscure scripts which have assumed
       that trailing garbage is ignored.

NOTES
   Compressed output may vary
       The exact compressed output produced from the same  uncompressed  input
       file may vary between XZ Utils versions even if compression options are
       identical.  This is because the encoder can be improved (faster or bet-
       ter compression) without affecting the file format. The output can vary
       even between different builds of the same XZ Utils version, if  differ-
       ent build options are used.

       The  above  means that implementing --rsyncable to create rsyncable .xz
       files is not going to happen without freezing a  part  of  the  encoder
       implementation, which can then be used with --rsyncable.

   Embedded .xz decompressors
       Embedded .xz decompressor implementations like XZ Embedded don't neces-
       sarily support files created with  check  types  other  than  none  and
       crc32.   Since  the default is --check=crc64, you must use --check=none
       or --check=crc32 when creating files for embedded systems.

       Outside embedded systems, all .xz format decompressors support all  the
       check  types, or at least are able to decompress the file without veri-
       fying the integrity check if the particular check is not supported.

       XZ Embedded supports BCJ filters, but only with the default start  off-
       set.

SEE ALSO
       xzdec(1), gzip(1), bzip2(1)

       XZ Utils: <http://tukaani.org/xz/>
       XZ Embedded: <http://tukaani.org/xz/embedded.html>
       LZMA SDK: <http://7-zip.org/sdk.html>



Tukaani                           2009-11-16                             XZ(1)
Man Pages Copyright Respective Owners. Site Copyright (C) 1994 - 2014 Hurricane Electric. All Rights Reserved.