Provided by: lrzip_0.608-1_i386 bug

NAME

       lrzip - a large-file compression program

SYNOPSIS

       lrzip [OPTIONS] <file>
       lrzip -d [OPTIONS] <file>
       lrunzip [OPTIONS] <file>
       lrzcat [OPTIONS] <file>
       lrztar [lrzip options] <directory>
       lrztar -d [lrzip options] <directory>
       lrzuntar [lrzip options] <directory>
       LRZIP=NOCONFIG [lrzip|lrunzip] [OPTIONS] <file>

DESCRIPTION

       LRZIP is a file compression program designed to do particularly well on
       very large files containing long  distance  redundancy.   lrztar  is  a
       wrapper   for  LRZIP  to  simplify  compression  and  decompression  of
       directories.

OPTIONS SUMMARY

       Here is a summary of the options to lrzip.

       General options:
         -c            check integrity of file written on decompression
         -d            decompress
         -e            password protected sha512/aes128 encryption on compression
         -h|-?         show help
         -H            display md5 hash integrity information
         -i            show compressed file information
         -q            don't show compression progress
         -t            test compressed file integrity
         -v[v]         Increase verbosity
         -V            show version
       Options affecting output:
         -D            delete existing files
         -f            force overwrite of any existing files
         -k            keep broken or damaged output files
         -o filename   specify the output file name and/or path
         -O directory  specify the output directory when -o is not used
         -S suffix     specify compressed suffix (default '.lrz')
       Options affecting compression:
         -b            bzip2 compression
         -g            gzip compression using zlib
         -l            lzo compression (ultra fast)
         -n            no backend compression - prepare for other compressor
         -z            zpaq compression (best, extreme compression, extremely slow)
       Low level options:
         -L level      set lzma/bzip2/gzip compression level (1-9, default 7)
         -N value      Set nice value to value (default 19)
         -p value      Set processor count to override number of threads
         -T            Disable LZO compressibility testing
         -U            Use unlimited window size beyond ramsize (potentially much slower)
         -w size       maximum compression window in hundreds of MB
                       default chosen by heuristic dependent on ram and chosen compression

       LRZIP=NOCONFIG environment variable setting can be used to bypass lrzip.conf.
       TMP environment variable will be used for storage of temporary files when needed.
       TMPDIR may also be stored in lrzip.conf file.

       If no filenames or "-" is specified, stdin/out will be used.

OPTIONS

General options

       -c     This option enables integrity checking of the  file  written  to
              disk on decompression. All decompression is tested internally in
              lrzip with either crc32 or md5 hash checking  depending  on  the
              version  of  the  archive  already.  However the file written to
              disk may be  corrupted  for  other  reasons  to  do  with  other
              userspace  problems  such  as  faulty library versions, drivers,
              hardware failure and so on. Enabling this option will make lrzip
              perform  an  md5  hash check on the file that's written to disk.
              When the archive has the md5 value stored in it, it is  compared
              to  this. Otherwise it is compard to the value calculated during
              decompression. This offers an  extra  guarantee  that  the  file
              written is the same as the original archived.

       -d     Decompress.  If  this option is not used then lrzip looks at the
              name used to launch the  program.  If  it  contains  the  string
              "lrunzip"  then  the  -d  option  is  automatically  set.  If it
              contains the string "lrzcat"  then  the  -d  -o  -  options  are
              automatically set.

       -e     Encrypt.  This  option  enables  high  grade password encryption
              using a combination of multiply sha512 hashed  password,  random
              salt  and aes128 CBC encryption.  Passwords up to 500 characters
              long are supported, and the encryption mechanism used  virtually
              guarantees  that  the  same  file created with the same password
              will never be the same. Furthermore,  the  password  hashing  is
              increased   according   to  the  date  the  file  is  encrypted,
              increasing the number of CPU cycles required for  each  password
              attempt   in  accordance  with  Moore's  law,  thus  making  the
              difficulty of attempting brute force attacks proportional to the
              power of modern computers.

       -h|-?  Print an options summary page

       -H     This  shows  the  md5  hash  value  calculated on compressing or
              decompressing an lrzip archive. By default all  compression  has
              the  md5  value  calculated  and  stored  in  all archives since
              version 0.560. On decompression, when  an  md5  value  has  been
              found,  it  will  be calculated and used for integrity checking.
              If the md5 value is not stored in the archive, it  will  not  be
              calcuated unless explicitly specified with this option, or check
              integrity (see below) has been requested.

       -i     This shows information about a compressed  file.  It  shows  the
              compressed  size,  the decompressed size, the compression ratio,
              what compression was used and what hash checking  will  be  used
              for internal integrity checking.  Note that the compression mode
              is detected from the first  block  only  and  it  will  show  no
              compression  used if the first block was incompressible, even if
              later blocks were compressible. If verbose options -v or -vv are
              added,  a breakdown of all the internal blocks and progressively
              more information pertaining to them will also be shown.

       -q     If this option  is  specified  then  lrzip  will  not  show  the
              percentage  progress  while  compressing.  Note that compression
              happens in bursts with lzma compression  which  is  the  default
              compression.  This  means that it will progress very rapidly for
              short periods and then stop for long periods.

       -t     This tests the  compressed  file  integrity.  It  does  this  by
              decompressing it to a temporary file and then deleting it.

       -v[v]  Increases verbosity. -vv will print more messages than -v.

       -V     Print the lrzip version number

Options affecting output

       -D     If  this  option  is specified then lrzip will delete the source
              file after successful compression or  decompression.  When  this
              option is not specified then the source files are not deleted.

       -f     If  this  option  is not specified (Default) then lrzip will not
              overwrite any existing files. If you set this option  then  rzip
              will silently overwrite any files as needed.

       -k     This  option  will  keep  broken  or  damaged  files  instead of
              deleting them.  When compression or decompression is interrupted
              either  by  user  or  error,  or  a  file  decompressed fails an
              integrity check, it is normally deleted by LRZIP.

       -o     Set the output file name. If this option is  not  set  then  the
              output  file  name  is  chosen  based  on the input name and the
              suffix. The -o option cannot be used if more than one file  name
              is specified on the command line.

       -O     Set  the  output directory for the default filename. This option
              cannot be combined with -o.

       -S     Set the compression suffix. The default is '.lrz'.

Options affecting compression

       -b     Bzip2 compression. Uses bzip2 compression  for  the  2nd  stage,
              much like the original rzip does.

       -g     Gzip  compression. Uses gzip compression for the 2nd stage. Uses
              libz compress and uncompress functions.

       -l     LZO Compression. If this option is set then lrzip will  use  the
              ultra  fast  lzo  compression  algorithm for the 2nd stage. This
              mode of compression gives bzip2 like compression at the speed it
              would  normally  take  to simply copy the file, giving excellent
              compression/time value.

       -n     No 2nd stage compression. If this option is set then lrzip  will
              only perform the long distance redundancy 1st stage compression.
              While this does not compress any faster than LZO compression, it
              produces  a  smaller  file  that then responds better to further
              compression (by  eg  another  application),  also  reducing  the
              compression time substantially.

       -z     ZPAQ  compression.  Uses  ZPAQ compression which is from the PAQ
              family of compressors known  for  having  some  of  the  highest
              compression  ratios  possible but at the cost of being extremely
              slow on both compress and decompress (4x slower than lzma  which
              is the default).

Low level options

       -L 1..9
              Set  the  compression  level  from 1 to 9. The default is to use
              level 7, which gives good all round compression. The compression
              level  is  also  strongly related to how much memory lrzip uses.
              See the -w option for details.

       -N value
              The default nice value is 19. This option can be used to set the
              priority scheduling for the lrzip backup or decompression. Valid
              nice values are from -20 to 19. Note this does NOT speed  up  or
              slow down compression.

       -p value
              Set  the  number  of  processor count to determine the number of
              threads to run.  Normally lrzip  will  scale  according  to  the
              number of CPUs it detects. Using this will override the value in
              case you wish to use less CPUs to either decrease  the  load  on
              your  machine,  or  to improve compression. Setting it to 1 will
              maximise compression but will not attempt to use more  than  one
              CPU.

       -T     Disables the LZO compressibility threshold testing when a slower
              compression back-end is used. LZO testing is normally  performed
              for  the  slower  back-end  compression  of  LZMA  and ZPAQ. The
              reasoning is that if it is completely incompressible by LZO then
              it will also be incompressible by them. Thus if a block fails to
              be compressed by the very fast LZO, lrzip will  not  attempt  to
              compress  that  block with the slower compressor, thereby saving
              time. If this option is enabled, it will bypass the LZO  testing
              and attempt to compress each block regardless.

       -U     Unlimited window size. If this option is set, and the file being
              compressed does not fit into the available ram, lrzip will use a
              moving  second  buffer as a "sliding mmap" which emulates having
              infinite ram. This will provide the most possible compression in
              the  first rzip stage which can improve the compression of ultra
              large files when they're bigger than the available ram.  However
              it  runs  progressively slower the larger the difference between
              ram and the file size, so is best reserved for when the smallest
              possible  size  is  desired  on  a very large file, and the time
              taken is not important.

       -w n   Set the maximum  allowable  compression  window  size  to  n  in
              hundreds  of megabytes.  This is the amount of memory lrzip will
              search during its first stage of pre-compression and is the main
              thing  that  will  determine how much benefit lrzip will provide
              over ordinary compression with the 2nd stage algorithm.  If  not
              set  (recommended),  the  value  chosen will be determined by an
              internal heuristic in lrzip which uses the most memory  that  is
              reasonable,  without  any hard upper limit. It is limited to 2GB
              on 32bit machines. lrzip will always reduce the window  size  to
              the biggest it can be without running out of memory.

INSTALLATION

       "make install" or just install lrzip somewhere in your search path.

COMPRESSION ALGORITHM

       LRZIP  operates  in two stages. The first stage finds and encodes large
       chunks of duplicated data over potentially very long distances  in  the
       input  file.  The  second  stage  is  to use a compression algorithm to
       compress the output of the first stage. The compression  algorithm  can
       be  chosen  to  be  optimised  for  extreme  size  (zpaq), size (lzma -
       default), speed (lzo),  legacy  (bzip2  or  gzip)  or  can  be  omitted
       entirely  doing  only the first stage. A one stage only compressed file
       can almost always improve both the compression size and speed done by a
       subsequent compression program.

       The  key  difference  between  lrzip  and  other well known compression
       algorithms is its ability to  take  advantage  of  very  long  distance
       redundancy.  The  well  known  deflate  algorithm  used  in gzip uses a
       maximum history buffer of 32k. The  block  sorting  algorithm  used  in
       bzip2 is limited to 900k of history. The history buffer in lrzip can be
       any size long, not even limited by available ram.

       It is quite common these days to need to compress  files  that  contain
       long distance redundancies. For example, when compressing a set of home
       directories several users might have copies of the  same  file,  or  of
       quite  similar  files.  It  is  also  common to have a single file that
       contains large duplicated chunks over long distances, such as pdf files
       containing repeated copies of the same image. Most compression programs
       won't be able to take advantage of  this  redundancy,  and  thus  might
       achieve a much lower compression ratio than lrzip can achieve.

FILES

       LRZIP  recognises  a configuration file that contains default settings.
       This  configuration  is  searched  for  in   the   current   directory,
       /etc/lrzip,  and  $HOME/.lrzip.  The  configuration  filename  must  be
       lrzip.conf.

ENVIRONMENT

       By default, lrzip  will  search  for  and  use  a  configuration  file,
       lrzip.conf.   If  the  user  wishes  to  bypass the file, a startup ENV
       variable may be set.
       LRZIP = NOCONFIG [lrzip|lrunzip] [OPTIONS] <file>
       which will force lrzip to ignore the configuration file.

HISTORY - Notes on rzip by Andrew Tridgell

       The ideas behind rzip were  first  implemented  in  1998  while  I  was
       working  on  rsync.  That version was too slow to be practical, and was
       replaced by this version in 2003.  LRZIP was created by the  desire  to
       have  better  compression  and/or  speed by Con Kolivas on blending the
       lzma and lzo compression algorithms with  the  rzip  first  stage,  and
       extending the compression windows to scale with increasing ram sizes.

BUGS

       Nil known.

SEE ALSO

       lrzip.conf(5), lrunzip(1), lrzcat(1), lrztar(1), lrzuntar(1), bzip2(1),
       gzip(1), lzop(1), rzip(1), zip(1)

AUTHOR and CREDITS

       lrzip is being extensively bastardised from rzip by Con Kolivas.
       rzip was written by Andrew Tridgell.
       lzma was written by Igor Pavlov.
       lzo was written by Markus Oberhumer.
       zpaq was written by Matt Mahoney.
       Peter Hyman added informational output, updated  LZMA  SDK,  and  added
       lzma multi-threading capabilities.

       If  you  wish  to  report  a problem, or make a suggestion, then please
       email Con at kernel@kolivas.org

       lrzip is released under the  GNU  General  Public  License  version  2.
       Please see the file COPYING for license details.

                                   May 2011                           lrzip(1)