Provided by: lrzip_0.608-1_amd64 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)