Adding upstream version 1.13~rc1.
Signed-off-by: Daniel Baumann <daniel@debian.org>
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This is lziprecover.info, produced by makeinfo version 4.13 from
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lziprecover.texinfo.
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INFO-DIR-SECTION Data Compression
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START-INFO-DIR-ENTRY
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* Lziprecover: (lziprecover). Data recovery tool for lzipped files
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END-INFO-DIR-ENTRY
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File: lziprecover.info, Node: Top, Next: Introduction, Up: (dir)
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Lziprecover Manual
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******************
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This manual is for Lziprecover (version 1.13-rc1, 12 November 2011).
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* Menu:
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* Introduction:: Purpose and features of lziprecover
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* Invoking Lziprecover:: Command line interface
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* File Format:: Detailed format of the compressed file
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* Examples:: A small tutorial with examples
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* Problems:: Reporting bugs
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* Concept Index:: Index of concepts
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Copyright (C) 2009, 2010, 2011 Antonio Diaz Diaz.
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This manual is free documentation: you have unlimited permission to
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copy, distribute and modify it.
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File: lziprecover.info, Node: Introduction, Next: Invoking Lziprecover, Prev: Top, Up: Top
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1 Introduction
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**************
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Lziprecover is a data recovery tool and decompressor for files in the
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lzip compressed data format (.lz) able to repair slightly damaged files,
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recover badly damaged files from two or more copies, extract undamaged
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members from multi-member files, decompress files and test integrity of
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files.
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Lziprecover is able to recover or decompress files produced by any of
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the compressors in the lzip family; lzip, plzip, minilzip/lzlib, clzip
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and pdlzip. This recovery capability contributes to make the lzip format
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one of the best options for long-term data archiving.
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When recovering data, lziprecover takes as arguments the names of the
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damaged files and writes zero or more recovered files depending on the
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operation selected and whether the recovery succeeded or not. The
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damaged files themselves are never modified.
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When decompressing or testing file integrity, lziprecover behaves
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like lzip or lunzip.
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If the files are too damaged for lziprecover to repair them, data
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from damaged members can be partially recovered writing it to stdout as
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shown in the following example (the resulting file may contain some
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garbage data at the end):
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lziprecover -cd rec00001file.lz > rec00001file
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If the cause of file corruption is damaged media, the combination
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GNU ddrescue + lziprecover is the best option for recovering data from
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multiple damaged copies. *Note ddrescue-example::, for an example.
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Return values: 0 for a normal exit, 1 for environmental problems
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(file not found, invalid flags, I/O errors, etc), 2 to indicate a
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corrupt or invalid input file, 3 for an internal consistency error (eg,
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bug) which caused lziprecover to panic.
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File: lziprecover.info, Node: Invoking Lziprecover, Next: File Format, Prev: Introduction, Up: Top
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2 Invoking Lziprecover
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**********************
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The format for running lziprecover is:
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lziprecover [OPTIONS] [FILES]
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Lziprecover supports the following options:
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`-h'
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`--help'
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Print an informative help message describing the options and exit.
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`-V'
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`--version'
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Print the version number of lziprecover on the standard output and
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exit.
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`-c'
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`--stdout'
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Decompress to standard output. Needed when reading from a named
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pipe (fifo) or from a device. Use it to recover as much of the
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uncompressed data as possible when decompressing a corrupt file.
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`-d'
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`--decompress'
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Decompress.
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`-f'
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`--force'
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Force overwrite of output files.
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`-k'
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`--keep'
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Keep (don't delete) input files during decompression.
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`-m'
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`--merge'
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Try to produce a correct file merging the good parts of two or more
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damaged copies. The copies must be single-member files. The merge
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will fail if the copies have too many damaged areas or if the same
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byte is damaged in all copies. If successful, a repaired copy is
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written to the file `FILE_fixed.lz'. The exit status is 0 if the
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file could be repaired, 2 otherwise.
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To give you an idea of its possibilities, when merging two copies
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each of them with one damaged area affecting 1 percent of the
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copy, the probability of obtaining a correct file is about 98
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percent. With three such copies the probability rises to 99.97
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percent. For large files with small errors, the probability
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approaches 100 percent even with only two copies.
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`-o FILE'
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`--output=FILE'
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Place the output into `FILE' instead of into `FILE_fixed.lz'. If
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splitting, the names of the files produced are in the form
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`rec00001FILE', `rec00002FILE', etc. If decompressing from
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standard input and `--stdout' has not been specified, use `FILE'
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as the name of the decompressed file.
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`-q'
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`--quiet'
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Quiet operation. Suppress all messages.
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`-R'
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`--repair'
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Try to repair a small error, affecting only one byte, in a
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single-member FILE. If successful, a repaired copy is written to
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the file `FILE_fixed.lz'. `FILE' is not modified at all. The exit
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status is 0 if the file could be repaired, 2 otherwise.
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`-s'
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`--split'
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Search for members in `FILE' and write each member in its own
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`.lz' file. You can then use `lziprecover -t' to test the
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integrity of the resulting files, decompress those which are
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undamaged, and try to repair or partially decompress those which
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are damaged.
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The names of the files produced are in the form `rec00001FILE.lz',
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`rec00002FILE.lz', etc, and are designed so that the use of
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wildcards in subsequent processing, for example,
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`lziprecover -cd rec*FILE.lz > recovered_data', processes the
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files in the correct order.
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`-t'
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`--test'
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Check integrity of the specified file(s), but don't decompress
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them. This really performs a trial decompression and throws away
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the result. Use it together with `-v' to see information about
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the file.
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`-v'
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`--verbose'
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Verbose mode.
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When decompressing or testing, further -v's (up to 4) increase the
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verbosity level, showing status, dictionary size, compression
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ratio, trailer contents (CRC, data size, member size), and up to 6
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bytes of trailing garbage (if any).
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File: lziprecover.info, Node: File Format, Next: Examples, Prev: Invoking Lziprecover, Up: Top
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3 File Format
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*************
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In the diagram below, a box like this:
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+---+
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| | <-- the vertical bars might be missing
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+---+
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represents one byte; a box like this:
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+==============+
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+==============+
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represents a variable number of bytes.
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A lzip file consists of a series of "members" (compressed data sets).
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The members simply appear one after another in the file, with no
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additional information before, between, or after them.
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Each member has the following structure:
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+--+--+--+--+----+----+=============+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| ID string | VN | DS | Lzma stream | CRC32 | Data size | Member size |
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+--+--+--+--+----+----+=============+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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All multibyte values are stored in little endian order.
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`ID string'
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A four byte string, identifying the lzip format, with the value
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"LZIP".
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`VN (version number, 1 byte)'
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Just in case something needs to be modified in the future. Valid
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values are 0 and 1. Version 0 files are deprecated. They can
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contain only one member and lack the `Member size' field.
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`DS (coded dictionary size, 1 byte)'
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Bits 4-0 contain the base 2 logarithm of the base dictionary size.
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Bits 7-5 contain the number of "wedges" to substract from the base
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dictionary size to obtain the dictionary size. The size of a wedge
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is (base dictionary size / 16).
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Valid values for dictionary size range from 4KiB to 512MiB.
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`Lzma stream'
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The lzma stream, finished by an end of stream marker. Uses default
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values for encoder properties.
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`CRC32 (4 bytes)'
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CRC of the uncompressed original data.
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`Data size (8 bytes)'
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Size of the uncompressed original data.
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`Member size (8 bytes)'
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Total size of the member, including header and trailer. This
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facilitates safe recovery of undamaged members from multimember
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files.
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File: lziprecover.info, Node: Examples, Next: Problems, Prev: File Format, Up: Top
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4 A small tutorial with examples
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********************************
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Example 1: Restore a regular file from its compressed version
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`file.lz'. If the operation is successful, `file.lz' is removed.
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lziprecover -d file.lz
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Example 2: Verify the integrity of the compressed file `file.lz' and
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show status.
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lziprecover -tv file.lz
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Example 3: Decompress `file.lz' partially until 10KiB of decompressed
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data are produced.
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lziprecover -cd file.lz | dd bs=1024 count=10
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Example 4: Decompress `file.lz' partially from decompressed byte 10000
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to decompressed byte 15000 (5000 bytes are produced).
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lziprecover -cd file.lz | dd bs=1000 skip=10 count=5
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Example 5: Repair a one-byte corruption in the single-member file
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`file.lz'. (Indented lines are abridged error messages from
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lziprecover).
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lziprecover -v -R file.lz
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Copy of input file repaired successfully.
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mv file_fixed.lz file.lz
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Example 6: Split the multi-member file `file.lz' and write each member
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in its own `recXXXXXfile.lz' file. Then use `lziprecover -t' to test
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the integrity of the resulting files.
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lziprecover -s file.lz
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lziprecover -tv rec*file.lz
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Example 7: Recover a compressed backup from two copies on CD-ROM (see
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the GNU ddrescue manual for details about ddrescue)
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ddrescue -b2048 /dev/cdrom cdimage1 logfile1
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mount -t iso9660 -o loop,ro cdimage1 /mnt/cdimage
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cp /mnt/cdimage/backup.tar.lz rescued1.tar.lz
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umount /mnt/cdimage
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(insert second copy in the CD drive)
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ddrescue -b2048 /dev/cdrom cdimage2 logfile2
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mount -t iso9660 -o loop,ro cdimage2 /mnt/cdimage
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cp /mnt/cdimage/backup.tar.lz rescued2.tar.lz
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umount /mnt/cdimage
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lziprecover -m -v -o rescued.tar.lz rescued1.tar.lz rescued2.tar.lz
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Example 8: Recover the first volume of those created with the command
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`lzip -b 32MiB -S 650MB big_db' from two copies, `big_db1_00001.lz' and
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`big_db2_00001.lz', with member 00007 damaged in the first copy, member
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00018 damaged in the second copy, and member 00012 damaged in both
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copies. Two correct copies are produced and compared.
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lziprecover -s big_db1_00001.lz
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lziprecover -s big_db2_00001.lz
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lziprecover -t rec*big_db1_00001.lz
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rec00007big_db1_00001.lz: crc mismatch
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rec00012big_db1_00001.lz: crc mismatch
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lziprecover -t rec*big_db2_00001.lz
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rec00012big_db2_00001.lz: crc mismatch
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rec00018big_db2_00001.lz: crc mismatch
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lziprecover -m -v rec00012big_db1_00001.lz rec00012big_db2_00001.lz
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Input files merged successfully
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cp rec00007big_db2_00001.lz rec00007big_db1_00001.lz
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cp rec00012big_db1_00001_fixed.lz rec00012big_db1_00001.lz
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cp rec00012big_db1_00001_fixed.lz rec00012big_db2_00001.lz
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cp rec00018big_db1_00001.lz rec00018big_db2_00001.lz
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cat rec*big_db1_00001.lz > big_db3_00001.lz
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cat rec*big_db2_00001.lz > big_db4_00001.lz
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zcmp big_db3_00001.lz big_db4_00001.lz
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File: lziprecover.info, Node: Problems, Next: Concept Index, Prev: Examples, Up: Top
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5 Reporting Bugs
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****************
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There are probably bugs in lziprecover. There are certainly errors and
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omissions in this manual. If you report them, they will get fixed. If
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you don't, no one will ever know about them and they will remain unfixed
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for all eternity, if not longer.
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If you find a bug in lziprecover, please send electronic mail to
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<lzip-bug@nongnu.org>. Include the version number, which you can find
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by running `lziprecover --version'.
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File: lziprecover.info, Node: Concept Index, Prev: Problems, Up: Top
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Concept Index
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*************
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[index ]
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* Menu:
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* bugs: Problems. (line 6)
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* examples: Examples. (line 6)
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* file format: File Format. (line 6)
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* getting help: Problems. (line 6)
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* introduction: Introduction. (line 6)
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* invoking lziprecover: Invoking Lziprecover. (line 6)
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Tag Table:
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||||
Node: Top231
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Node: Introduction898
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Node: Invoking Lziprecover2684
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Node: File Format6150
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Node: Examples8156
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Ref: ddrescue-example9409
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Node: Problems11188
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Node: Concept Index11738
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End Tag Table
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