From 2085b1344e4c2b3c4a3d21d4bc10227679a55507 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sat, 7 Nov 2015 12:45:12 +0100 Subject: Merging upstream version 1.16~pre1. Signed-off-by: Daniel Baumann --- doc/lziprecover.1 | 12 +- doc/lziprecover.info | 233 ++++++++++--------- doc/lziprecover.texi | 606 ++++++++++++++++++++++++++++++++++++++++++++++++ doc/lziprecover.texinfo | 589 ---------------------------------------------- 4 files changed, 734 insertions(+), 706 deletions(-) create mode 100644 doc/lziprecover.texi delete mode 100644 doc/lziprecover.texinfo (limited to 'doc') diff --git a/doc/lziprecover.1 b/doc/lziprecover.1 index cda6779..3a6300f 100644 --- a/doc/lziprecover.1 +++ b/doc/lziprecover.1 @@ -1,7 +1,7 @@ .\" DO NOT MODIFY THIS FILE! It was generated by help2man 1.37.1. -.TH LZIPRECOVER "1" "September 2013" "Lziprecover 1.15" "User Commands" +.TH LZIPRECOVER "1" "April 2014" "lziprecover 1.16-pre1" "User Commands" .SH NAME -Lziprecover \- recovers data from damaged lzip files +lziprecover \- recovers data from damaged lzip files .SH SYNOPSIS .B lziprecover [\fIoptions\fR] [\fIfiles\fR] @@ -69,20 +69,20 @@ Report bugs to lzip\-bug@nongnu.org .br Lziprecover home page: http://www.nongnu.org/lzip/lziprecover.html .SH COPYRIGHT -Copyright \(co 2013 Antonio Diaz Diaz. +Copyright \(co 2014 Antonio Diaz Diaz. License GPLv3+: GNU GPL version 3 or later .br This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. .SH "SEE ALSO" The full documentation for -.B Lziprecover +.B lziprecover is maintained as a Texinfo manual. If the .B info and -.B Lziprecover +.B lziprecover programs are properly installed at your site, the command .IP -.B info Lziprecover +.B info lziprecover .PP should give you access to the complete manual. diff --git a/doc/lziprecover.info b/doc/lziprecover.info index 5f8ad08..1248e6f 100644 --- a/doc/lziprecover.info +++ b/doc/lziprecover.info @@ -1,5 +1,5 @@ -This is lziprecover.info, produced by makeinfo version 4.13 from -lziprecover.texinfo. +This is lziprecover.info, produced by makeinfo version 4.13+ from +lziprecover.texi. INFO-DIR-SECTION Data Compression START-INFO-DIR-ENTRY @@ -12,7 +12,7 @@ File: lziprecover.info, Node: Top, Next: Introduction, Up: (dir) Lziprecover Manual ****************** -This manual is for Lziprecover (version 1.15, 14 September 2013). +This manual is for Lziprecover (version 1.16-pre1, 5 April 2014). * Menu: @@ -27,7 +27,7 @@ This manual is for Lziprecover (version 1.15, 14 September 2013). * Concept index:: Index of concepts - Copyright (C) 2009, 2010, 2011, 2012, 2013 Antonio Diaz Diaz. + Copyright (C) 2009, 2010, 2011, 2012, 2013, 2014 Antonio Diaz Diaz. This manual is free documentation: you have unlimited permission to copy, distribute and modify it. @@ -43,18 +43,29 @@ lzip compressed data format (.lz), able to repair slightly damaged files, recover badly damaged files from two or more copies, extract data from damaged files, decompress files and test integrity of files. - The lzip file format is designed for long-term data archiving. It is -clean, provides very safe 4 factor integrity checking, and is backed by -the recovery capabilities of lziprecover. + The lzip file format is designed for long-term data archiving, taking +into account both data integrity and decoder availability: + + * The lzip format provides very safe integrity checking and some data + recovery means. The lziprecover program can repair bit-flip errors + (one of the most common forms of data corruption) in lzip files, + and provides data recovery capabilities, including error-checked + merging of damaged copies of a file. + + * The lzip format is as simple as possible (but not simpler). The + lzip manual provides the code of a simple decompressor along with + a detailed explanation of how it works, so that with the only help + of the lzip manual it would be possible for a digital + archaeologist to extract the data from a lzip file long after + quantum computers eventually render LZMA obsolete. + + * Additionally lzip is copylefted, which guarantees that it will + remain free forever. Lziprecover is able to recover or decompress files produced by any of the compressors in the lzip family; lzip, plzip, minilzip/lzlib, clzip and pdlzip. - Lziprecover makes lzip files resistant to bit-flip (one of the most -common forms of data corruption), and can safely merge multiple damaged -backup copies. - If the cause of file corruption is damaged media, the combination GNU ddrescue + lziprecover is the best option for recovering data from multiple damaged copies. *Note ddrescue-example::, for an example. @@ -96,113 +107,113 @@ The format for running lziprecover is: Lziprecover supports the following options: -`-h' -`--help' +'-h' +'--help' Print an informative help message describing the options and exit. -`-V' -`--version' +'-V' +'--version' Print the version number of lziprecover on the standard output and exit. -`-c' -`--stdout' +'-c' +'--stdout' Decompress to standard output. Needed when reading from a named pipe (fifo) or from a device. Use it to recover as much of the uncompressed data as possible when decompressing a corrupt file. -`-d' -`--decompress' +'-d' +'--decompress' Decompress. -`-D RANGE' -`--range-decompress=RANGE' +'-D RANGE' +'--range-decompress=RANGE' Decompress only a range of bytes starting at decompressed byte - position `BEGIN' and up to byte position `END - 1'. Three formats - of RANGE are recognized, `BEGIN', `BEGIN-END', and `BEGIN,SIZE'. + position 'BEGIN' and up to byte position 'END - 1'. Three formats + of RANGE are recognized, 'BEGIN', 'BEGIN-END', and 'BEGIN,SIZE'. If only BEGIN is specified, END is taken as the end of the file. The produced bytes are sent to standard output unless the - `--output' option is used. In order to guarantee the correctness + '--output' option is used. In order to guarantee the correctness of the data produced, all members containing any part of the desired data are decompressed and their integrity is verified. This operation is more efficient in multi-member files because it only decompresses the members containing the desired data. -`-f' -`--force' +'-f' +'--force' Force overwrite of output files. -`-i' -`--ignore-errors' - Make `--range-decompress' ignore data errors and continue +'-i' +'--ignore-errors' + Make '--range-decompress' ignore data errors and continue decompressing the remaining members in the file. For example, - `lziprecover -i -D0 file.lz > file' decompresses all the - recoverable data in all members of `file.lz' without having to + 'lziprecover -i -D0 file.lz > file' decompresses all the + recoverable data in all members of 'file.lz' without having to split it first. -`-k' -`--keep' +'-k' +'--keep' Keep (don't delete) input files during decompression. -`-l' -`--list' +'-l' +'--list' Print total file sizes and ratios. The values produced are correct - even for multi-member files. Use it together with `-v' to see + even for multi-member files. Use it together with '-v' to see information about the members in the file. -`-m' -`--merge' +'-m' +'--merge' Try to produce a correct file merging the good parts of two or more damaged copies. If successful, a repaired copy is written to the - file `FILE_fixed.lz'. The exit status is 0 if a correct file could - be produced, 2 otherwise. See the chapter `Merging files' (*note + file 'FILE_fixed.lz'. The exit status is 0 if a correct file could + be produced, 2 otherwise. See the chapter 'Merging files' (*note Merging files::) for a complete description of the merge mode. -`-o FILE' -`--output=FILE' - Place the output into `FILE' instead of into `FILE_fixed.lz'. If +'-o FILE' +'--output=FILE' + Place the output into 'FILE' instead of into 'FILE_fixed.lz'. If splitting, the names of the files produced are in the form - `rec01FILE', `rec02FILE', etc. If decompressing from standard - input and `--stdout' has not been specified, use `FILE' as the + 'rec01FILE', 'rec02FILE', etc. If decompressing from standard + input and '--stdout' has not been specified, use 'FILE' as the name of the decompressed file. -`-q' -`--quiet' +'-q' +'--quiet' Quiet operation. Suppress all messages. -`-R' -`--repair' +'-R' +'--repair' Try to repair a file with small errors (up to one byte error per member). If successful, a repaired copy is written to the file - `FILE_fixed.lz'. `FILE' is not modified at all. The exit status + 'FILE_fixed.lz'. 'FILE' is not modified at all. The exit status is 0 if the file could be repaired, 2 otherwise. See the chapter - `Repairing files' (*note Repairing files::) for a complete + 'Repairing files' (*note Repairing files::) for a complete description of the repair mode. -`-s' -`--split' - Search for members in `FILE' and write each member in its own - `.lz' file. You can then use `lziprecover -t' to test the +'-s' +'--split' + Search for members in 'FILE' and write each member in its own + '.lz' file. You can then use 'lziprecover -t' to test the integrity of the resulting files, decompress those which are undamaged, and try to repair or partially decompress those which are damaged. - The names of the files produced are in the form `rec01FILE.lz', - `rec02FILE.lz', etc, and are designed so that the use of wildcards + The names of the files produced are in the form 'rec01FILE.lz', + 'rec02FILE.lz', etc, and are designed so that the use of wildcards in subsequent processing, for example, - `lziprecover -cd rec*FILE.lz > recovered_data', processes the + 'lziprecover -cd rec*FILE.lz > recovered_data', processes the files in the correct order. The number of digits used in the names - varies depending on the number of members in `FILE'. + varies depending on the number of members in 'FILE'. -`-t' -`--test' +'-t' +'--test' Check integrity of the specified file(s), but don't decompress them. This really performs a trial decompression and throws away - the result. Use it together with `-v' to see information about + the result. Use it together with '-v' to see information about the file. -`-v' -`--verbose' +'-v' +'--verbose' Verbose mode. When decompressing or testing, further -v's (up to 4) increase the verbosity level, showing status, compression ratio, dictionary @@ -211,7 +222,7 @@ The format for running lziprecover is: Numbers given as arguments to options may be followed by a multiplier -and an optional `B' for "byte". +and an optional 'B' for "byte". Table of SI and binary prefixes (unit multipliers): @@ -239,7 +250,7 @@ File: lziprecover.info, Node: Repairing files, Next: Merging files, Prev: Inv Lziprecover is able to repair files with small errors (up to one byte error per member). The error may be located anywhere in the file except -in the header (first 6 bytes of each member) or in the `Member size' +in the header (first 6 bytes of each member) or in the 'Member size' field of the trailer (last 8 bytes of each member). This makes lzip files resistant to bit-flip, one of the most common forms of data corruption. @@ -323,15 +334,15 @@ additional information before, between, or after them. All multibyte values are stored in little endian order. -`ID string' +'ID string' A four byte string, identifying the lzip format, with the value "LZIP" (0x4C, 0x5A, 0x49, 0x50). -`VN (version number, 1 byte)' +'VN (version number, 1 byte)' Just in case something needs to be modified in the future. 1 for now. -`DS (coded dictionary size, 1 byte)' +'DS (coded dictionary size, 1 byte)' Lzip divides the distance between any two powers of 2 into 8 equally spaced intervals, named "wedges". The dictionary size is calculated by taking a power of 2 (the base size) and substracting @@ -343,18 +354,18 @@ additional information before, between, or after them. Example: 0xD3 = 2^19 - 6 * 2^15 = 512 KiB - 6 * 32 KiB = 320 KiB Valid values for dictionary size range from 4 KiB to 512 MiB. -`Lzma stream' +'Lzma stream' The lzma stream, finished by an end of stream marker. Uses default values for encoder properties. See the lzip manual for a full description. -`CRC32 (4 bytes)' +'CRC32 (4 bytes)' CRC of the uncompressed original data. -`Data size (8 bytes)' +'Data size (8 bytes)' Size of the uncompressed original data. -`Member size (8 bytes)' +'Member size (8 bytes)' Total size of the member, including header and trailer. This field acts as a distributed index, allows the verification of stream integrity, and facilitates safe recovery of undamaged members from @@ -368,30 +379,30 @@ File: lziprecover.info, Node: Examples, Next: Unzcrash, Prev: File format, U ******************************** Example 1: Restore a regular file from its compressed version -`file.lz'. If the operation is successful, `file.lz' is removed. +'file.lz'. If the operation is successful, 'file.lz' is removed. lziprecover -d file.lz -Example 2: Verify the integrity of the compressed file `file.lz' and +Example 2: Verify the integrity of the compressed file 'file.lz' and show status. lziprecover -tv file.lz -Example 3: Decompress `file.lz' partially until 10 KiB of decompressed +Example 3: Decompress 'file.lz' partially until 10 KiB of decompressed data are produced. lziprecover -D 0,10KiB file.lz -Example 4: Decompress `file.lz' partially from decompressed byte 10000 +Example 4: Decompress 'file.lz' partially from decompressed byte 10000 to decompressed byte 15000 (5000 bytes are produced). lziprecover -D 10000-15000 file.lz -Example 5: Repair small errors in the file `file.lz'. (Indented lines +Example 5: Repair small errors in the file 'file.lz'. (Indented lines are abridged diagnostic messages from lziprecover). lziprecover -v -R file.lz @@ -399,8 +410,8 @@ are abridged diagnostic messages from lziprecover). mv file_fixed.lz file.lz -Example 6: Split the multi-member file `file.lz' and write each member -in its own `recXXXfile.lz' file. Then use `lziprecover -t' to test the +Example 6: Split the multi-member file 'file.lz' and write each member +in its own 'recXXXfile.lz' file. Then use 'lziprecover -t' to test the integrity of the resulting files. lziprecover -s file.lz @@ -424,10 +435,10 @@ error-checked merging of copies (*Note GNU ddrescue manual: Example 8: Recover the first volume of those created with the command -`lzip -b 32MiB -S 650MB big_db' from two copies, `big_db1_00001.lz' and -`big_db2_00001.lz', with member 07 damaged in the first copy, member 18 +'lzip -b 32MiB -S 650MB big_db' from two copies, 'big_db1_00001.lz' and +'big_db2_00001.lz', with member 07 damaged in the first copy, member 18 damaged in the second copy, and member 12 damaged in both copies. The -correct file produced is saved in `big_db_00001.lz'. +correct file produced is saved in 'big_db_00001.lz'. lziprecover -m -v -o big_db_00001.lz big_db1_00001.lz big_db2_00001.lz Input files merged successfully @@ -440,7 +451,7 @@ File: lziprecover.info, Node: Unzcrash, Next: Problems, Prev: Examples, Up: The lziprecover package also includes unzcrash, a program written to test robustness to decompression of corrupted data, inspired by -unzcrash.c from Julian Seward's bzip2. Type `make unzcrash' in the +unzcrash.c from Julian Seward's bzip2. Type 'make unzcrash' in the lziprecover source directory to build it. Unzcrash reads the specified file and then repeatedly decompresses @@ -461,40 +472,40 @@ programs with a suitable command line syntax. Unzcrash supports the following options: -`-h' -`--help' +'-h' +'--help' Print an informative help message describing the options and exit. -`-V' -`--version' +'-V' +'--version' Print the version number of unzcrash on the standard output and exit. -`-b RANGE' -`--bits=RANGE' +'-b RANGE' +'--bits=RANGE' Test N-bit errors only, instead of testing all the 255 wrong - values for each byte. `N-bit error' means any value differing from + values for each byte. 'N-bit error' means any value differing from the original value in N bit positions, not a value differing from the original value in the bit position N. The number of N-bit errors per byte (N = 1 to 8) is: 8 28 56 70 56 28 8 1 Examples of RANGE: 1 1,2,3 1-4 1,3-5,8 1-3,5-8 -`-p BYTES' -`--position=BYTES' +'-p BYTES' +'--position=BYTES' First byte position to test in the file. Defaults to 0. -`-q' -`--quiet' +'-q' +'--quiet' Quiet operation. Suppress all messages. -`-s BYTES' -`--size=BYTES' +'-s BYTES' +'--size=BYTES' Number of byte positions to test. If not specified, the whole file is tested. -`-v' -`--verbose' +'-v' +'--verbose' Verbose mode. @@ -516,7 +527,7 @@ for all eternity, if not longer. If you find a bug in lziprecover, please send electronic mail to . Include the version number, which you can find -by running `lziprecover --version'. +by running 'lziprecover --version'.  File: lziprecover.info, Node: Concept index, Prev: Problems, Up: Top @@ -540,17 +551,17 @@ Concept index  Tag Table: -Node: Top228 -Node: Introduction1096 -Node: Invoking lziprecover3249 -Node: Repairing files8687 -Node: Merging files9406 -Node: File format11177 -Node: Examples13687 -Ref: ddrescue-example14888 -Node: Unzcrash15997 -Node: Problems18369 -Node: Concept index18919 +Node: Top226 +Node: Introduction1100 +Node: Invoking lziprecover3858 +Node: Repairing files9296 +Node: Merging files10015 +Node: File format11786 +Node: Examples14296 +Ref: ddrescue-example15497 +Node: Unzcrash16606 +Node: Problems18978 +Node: Concept index19528  End Tag Table diff --git a/doc/lziprecover.texi b/doc/lziprecover.texi new file mode 100644 index 0000000..be4fc27 --- /dev/null +++ b/doc/lziprecover.texi @@ -0,0 +1,606 @@ +\input texinfo @c -*-texinfo-*- +@c %**start of header +@setfilename lziprecover.info +@documentencoding ISO-8859-15 +@settitle Lziprecover Manual +@finalout +@c %**end of header + +@set UPDATED 5 April 2014 +@set VERSION 1.16-pre1 + +@dircategory Data Compression +@direntry +* Lziprecover: (lziprecover). Data recovery tool for lzip files +@end direntry + + +@ifnothtml +@titlepage +@title Lziprecover +@subtitle Data recovery tool for lzip files +@subtitle for Lziprecover version @value{VERSION}, @value{UPDATED} +@author by Antonio Diaz Diaz + +@page +@vskip 0pt plus 1filll +@end titlepage + +@contents +@end ifnothtml + +@node Top +@top + +This manual is for Lziprecover (version @value{VERSION}, @value{UPDATED}). + +@menu +* Introduction:: Purpose and features of lziprecover +* Invoking lziprecover:: Command line interface +* Repairing files:: Fixing bit-flip and similar errors +* Merging files:: Fixing several damaged copies +* File format:: Detailed format of the compressed file +* Examples:: A small tutorial with examples +* Unzcrash:: Testing the robustness of decompressors +* Problems:: Reporting bugs +* Concept index:: Index of concepts +@end menu + +@sp 1 +Copyright @copyright{} 2009, 2010, 2011, 2012, 2013, 2014 +Antonio Diaz Diaz. + +This manual is free documentation: you have unlimited permission +to copy, distribute and modify it. + + +@node Introduction +@chapter Introduction +@cindex introduction + +Lziprecover is a data recovery tool and decompressor for files in the +lzip compressed data format (.lz), able to repair slightly damaged +files, recover badly damaged files from two or more copies, extract data +from damaged files, decompress files and test integrity of files. + +The lzip file format is designed for long-term data archiving, taking +into account both data integrity and decoder availability: + +@itemize @bullet +@item +The lzip format provides very safe integrity checking and some data +recovery means. The lziprecover program can repair bit-flip errors (one +of the most common forms of data corruption) in lzip files, and provides +data recovery capabilities, including error-checked merging of damaged +copies of a file. + +@item +The lzip format is as simple as possible (but not simpler). The lzip +manual provides the code of a simple decompressor along with a detailed +explanation of how it works, so that with the only help of the lzip +manual it would be possible for a digital archaeologist to extract the +data from a lzip file long after quantum computers eventually render +LZMA obsolete. + +@item +Additionally lzip is copylefted, which guarantees that it will remain +free forever. +@end itemize + +Lziprecover is able to recover or decompress files produced by any of +the compressors in the lzip family; lzip, plzip, minilzip/lzlib, clzip +and pdlzip. + +If the cause of file corruption is damaged media, the combination +@w{GNU ddrescue + lziprecover} is the best option for recovering data +from multiple damaged copies. @xref{ddrescue-example}, for an example. + +If a file is too damaged for lziprecover to repair it, all the +recoverable data in all members of the file can be extracted with the +following command (the resulting file may contain errors and some +garbage data may be produced at the end of each member): + +@example +lziprecover -D0 -i -o file -q file.lz +@end example + +Lziprecover is able to efficiently extract a range of bytes from a +multi-member file, because it only decompresses the members containing +the desired data. + +Lziprecover can print correct total file sizes and ratios even for +multi-member files. + +When recovering data, lziprecover takes as arguments the names of the +damaged files and writes zero or more recovered files depending on the +operation selected and whether the recovery succeeded or not. The +damaged files themselves are never modified. + +When decompressing or testing file integrity, lziprecover behaves like +lzip or lunzip. + +Lziprecover is not a replacement for regular backups, but a last line of +defense for the case where the backups are also damaged. + + +@node Invoking lziprecover +@chapter Invoking lziprecover +@cindex invoking + +The format for running lziprecover is: + +@example +lziprecover [@var{options}] [@var{files}] +@end example + +Lziprecover supports the following options: + +@table @samp +@item -h +@itemx --help +Print an informative help message describing the options and exit. + +@item -V +@itemx --version +Print the version number of lziprecover on the standard output and exit. + +@item -c +@itemx --stdout +Decompress to standard output. Needed when reading from a named pipe +(fifo) or from a device. Use it to recover as much of the uncompressed +data as possible when decompressing a corrupt file. + +@item -d +@itemx --decompress +Decompress. + +@item -D @var{range} +@itemx --range-decompress=@var{range} +Decompress only a range of bytes starting at decompressed byte position +@samp{@var{begin}} and up to byte position @w{@samp{@var{end} - 1}}. +Three formats of @var{range} are recognized, @samp{@var{begin}}, +@samp{@var{begin}-@var{end}}, and @samp{@var{begin},@var{size}}. If only +@var{begin} is specified, @var{end} is taken as the end of the file. The +produced bytes are sent to standard output unless the @samp{--output} +option is used. In order to guarantee the correctness of the data +produced, all members containing any part of the desired data are +decompressed and their integrity is verified. This operation is more +efficient in multi-member files because it only decompresses the members +containing the desired data. + +@item -f +@itemx --force +Force overwrite of output files. + +@item -i +@itemx --ignore-errors +Make @samp{--range-decompress} ignore data errors and continue +decompressing the remaining members in the file. For example, +@w{@samp{lziprecover -i -D0 file.lz > file}} decompresses all the +recoverable data in all members of @samp{file.lz} without having to +split it first. + +@item -k +@itemx --keep +Keep (don't delete) input files during decompression. + +@item -l +@itemx --list +Print total file sizes and ratios. The values produced are correct even +for multi-member files. Use it together with @samp{-v} to see +information about the members in the file. + +@item -m +@itemx --merge +Try to produce a correct file merging the good parts of two or more +damaged copies. If successful, a repaired copy is written to the file +@samp{@var{file}_fixed.lz}. The exit status is 0 if a correct file could +be produced, 2 otherwise. See the chapter @samp{Merging files} +(@pxref{Merging files}) for a complete description of the merge mode. + +@item -o @var{file} +@itemx --output=@var{file} +Place the output into @samp{@var{file}} instead of into +@samp{@var{file}_fixed.lz}. If splitting, the names of the files +produced are in the form @samp{rec01@var{file}}, @samp{rec02@var{file}}, +etc. If decompressing from standard input and @samp{--stdout} has not +been specified, use @samp{@var{file}} as the name of the decompressed +file. + +@item -q +@itemx --quiet +Quiet operation. Suppress all messages. + +@item -R +@itemx --repair +Try to repair a file with small errors (up to one byte error per +member). If successful, a repaired copy is written to the file +@samp{@var{file}_fixed.lz}. @samp{@var{file}} is not modified at all. +The exit status is 0 if the file could be repaired, 2 otherwise. See the +chapter @samp{Repairing files} (@pxref{Repairing files}) for a complete +description of the repair mode. + +@item -s +@itemx --split +Search for members in @samp{@var{file}} and write each member in its own +@samp{.lz} file. You can then use @samp{lziprecover -t} to test the +integrity of the resulting files, decompress those which are undamaged, +and try to repair or partially decompress those which are damaged. + +The names of the files produced are in the form +@samp{rec01@var{file}.lz}, @samp{rec02@var{file}.lz}, etc, and are +designed so that the use of wildcards in subsequent processing, for +example, @w{@samp{lziprecover -cd rec*@var{file}.lz > recovered_data}}, +processes the files in the correct order. The number of digits used in +the names varies depending on the number of members in @samp{@var{file}}. + +@item -t +@itemx --test +Check integrity of the specified file(s), but don't decompress them. +This really performs a trial decompression and throws away the result. +Use it together with @samp{-v} to see information about the file. + +@item -v +@itemx --verbose +Verbose mode.@* +When decompressing or testing, further -v's (up to 4) increase the +verbosity level, showing status, compression ratio, dictionary size, +trailer contents (CRC, data size, member size), and up to 6 bytes of +trailing garbage (if any). + +@end table + +Numbers given as arguments to options may be followed by a multiplier +and an optional @samp{B} for "byte". + +Table of SI and binary prefixes (unit multipliers): + +@multitable {Prefix} {kilobyte (10^3 = 1000)} {|} {Prefix} {kibibyte (2^10 = 1024)} +@item Prefix @tab Value @tab | @tab Prefix @tab Value +@item k @tab kilobyte (10^3 = 1000) @tab | @tab Ki @tab kibibyte (2^10 = 1024) +@item M @tab megabyte (10^6) @tab | @tab Mi @tab mebibyte (2^20) +@item G @tab gigabyte (10^9) @tab | @tab Gi @tab gibibyte (2^30) +@item T @tab terabyte (10^12) @tab | @tab Ti @tab tebibyte (2^40) +@item P @tab petabyte (10^15) @tab | @tab Pi @tab pebibyte (2^50) +@item E @tab exabyte (10^18) @tab | @tab Ei @tab exbibyte (2^60) +@item Z @tab zettabyte (10^21) @tab | @tab Zi @tab zebibyte (2^70) +@item Y @tab yottabyte (10^24) @tab | @tab Yi @tab yobibyte (2^80) +@end multitable + +@sp 1 +Exit status: 0 for a normal exit, 1 for environmental problems (file not +found, invalid flags, I/O errors, etc), 2 to indicate a corrupt or +invalid input file, 3 for an internal consistency error (eg, bug) which +caused lziprecover to panic. + + +@node Repairing files +@chapter Repairing files +@cindex repairing files + +Lziprecover is able to repair files with small errors (up to one byte +error per member). The error may be located anywhere in the file except +in the header (first 6 bytes of each member) or in the @samp{Member +size} field of the trailer (last 8 bytes of each member). This makes +lzip files resistant to bit-flip, one of the most common forms of data +corruption. + +Bit-flip happens when one bit in the file is changed from 0 to 1 or vice +versa. It may be caused by bad RAM or even by natural radiation. I have +seen a case of bit-flip in a file stored in an USB flash drive. + + +@node Merging files +@chapter Merging files +@cindex merging files + +If you have several copies of a file but all of them are too damaged to +repair them (@pxref{Repairing files}), lziprecover can try to produce a +correct file merging the good parts of the damaged copies. + +The merge may succeed even if some copies of the file have all the +headers and trailers damaged, as long as there is at least one copy of +every header and trailer intact, even if they are in different copies of +the file. + +The merge will fail if the damaged areas overlap (at least one byte is +damaged in all copies), or are adjacent and the boundary can't be +determined, or if the copies have too many damaged areas. + +All the copies must have the same size. If some of them have been +truncated and are therefore smaller than they should, you can extend +them to the correct size with the following command before merging them +with the other copies: + +@example +ddrescue --extend-outfile= small_file.lz extended_file.lz +@end example + +If some of the copies have got garbage data at the end and are therefore +larger than they should, you can reduce their sizes to the correct value +with the following command before merging them with the other copies: + +@example +ddrescue --size= large_file.lz reduced_file.lz +@end example + +To give you an idea of its possibilities, when merging two copies, each +of them with one damaged area affecting 1 percent of the copy, the +probability of obtaining a correct file is about 98 percent. With three +such copies the probability rises to 99.97 percent. For large files (a +few MB) with small errors (one sector damaged per copy), the probability +approaches 100 percent even with only two copies. + + +@node File format +@chapter File format +@cindex file format + +Perfection is reached, not when there is no longer anything to add, but +when there is no longer anything to take away.@* +--- Antoine de Saint-Exupery + +@sp 1 +In the diagram below, a box like this: +@verbatim ++---+ +| | <-- the vertical bars might be missing ++---+ +@end verbatim + +represents one byte; a box like this: +@verbatim ++==============+ +| | ++==============+ +@end verbatim + +represents a variable number of bytes. + +@sp 1 +A lzip file consists of a series of "members" (compressed data sets). +The members simply appear one after another in the file, with no +additional information before, between, or after them. + +Each member has the following structure: +@verbatim ++--+--+--+--+----+----+=============+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +| ID string | VN | DS | Lzma stream | CRC32 | Data size | Member size | ++--+--+--+--+----+----+=============+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +@end verbatim + +All multibyte values are stored in little endian order. + +@table @samp +@item ID string +A four byte string, identifying the lzip format, with the value "LZIP" +(0x4C, 0x5A, 0x49, 0x50). + +@item VN (version number, 1 byte) +Just in case something needs to be modified in the future. 1 for now. + +@item DS (coded dictionary size, 1 byte) +Lzip divides the distance between any two powers of 2 into 8 equally +spaced intervals, named "wedges". The dictionary size is calculated by +taking a power of 2 (the base size) and substracting from it a number of +wedges between 0 and 7. The size of a wedge is (base_size / 16).@* +Bits 4-0 contain the base 2 logarithm of the base size (12 to 29).@* +Bits 7-5 contain the number of wedges (0 to 7) to substract from the +base size to obtain the dictionary size.@* +Example: 0xD3 = 2^19 - 6 * 2^15 = 512 KiB - 6 * 32 KiB = 320 KiB@* +Valid values for dictionary size range from 4 KiB to 512 MiB. + +@item Lzma stream +The lzma stream, finished by an end of stream marker. Uses default values +for encoder properties. See the lzip manual for a full description. + +@item CRC32 (4 bytes) +CRC of the uncompressed original data. + +@item Data size (8 bytes) +Size of the uncompressed original data. + +@item Member size (8 bytes) +Total size of the member, including header and trailer. This field acts +as a distributed index, allows the verification of stream integrity, and +facilitates safe recovery of undamaged members from multi-member files. + +@end table + + +@node Examples +@chapter A small tutorial with examples +@cindex examples + +Example 1: Restore a regular file from its compressed version +@samp{file.lz}. If the operation is successful, @samp{file.lz} is +removed. + +@example +lziprecover -d file.lz +@end example + +@sp 1 +@noindent +Example 2: Verify the integrity of the compressed file @samp{file.lz} +and show status. + +@example +lziprecover -tv file.lz +@end example + +@sp 1 +@noindent +Example 3: Decompress @samp{file.lz} partially until 10 KiB of +decompressed data are produced. + +@example +lziprecover -D 0,10KiB file.lz +@end example + +@sp 1 +@noindent +Example 4: Decompress @samp{file.lz} partially from decompressed byte +10000 to decompressed byte 15000 (5000 bytes are produced). + +@example +lziprecover -D 10000-15000 file.lz +@end example + +@sp 1 +@noindent +Example 5: Repair small errors in the file @samp{file.lz}. (Indented +lines are abridged diagnostic messages from lziprecover). + +@example +lziprecover -v -R file.lz + Copy of input file repaired successfully. +mv file_fixed.lz file.lz +@end example + +@sp 1 +@noindent +Example 6: Split the multi-member file @samp{file.lz} and write each +member in its own @samp{recXXXfile.lz} file. Then use +@w{@samp{lziprecover -t}} to test the integrity of the resulting files. + +@example +lziprecover -s file.lz +lziprecover -tv rec*file.lz +@end example + +@sp 1 +@anchor{ddrescue-example} +@noindent +Example 7: Recover a compressed backup from two copies on CD-ROM with +error-checked merging of copies +@ifnothtml +(@xref{Top,GNU ddrescue manual,,ddrescue}, +@end ifnothtml +@ifhtml +(See the +@uref{http://www.gnu.org/software/ddrescue/manual/ddrescue_manual.html,,ddrescue manual} +@end ifhtml +for details about ddrescue). + +@example +ddrescue -b2048 /dev/cdrom cdimage1 logfile1 +mount -t iso9660 -o loop,ro cdimage1 /mnt/cdimage +cp /mnt/cdimage/backup.tar.lz rescued1.tar.lz +umount /mnt/cdimage + (insert second copy in the CD drive) +ddrescue -b2048 /dev/cdrom cdimage2 logfile2 +mount -t iso9660 -o loop,ro cdimage2 /mnt/cdimage +cp /mnt/cdimage/backup.tar.lz rescued2.tar.lz +umount /mnt/cdimage +lziprecover -m -v -o backup.tar.lz rescued1.tar.lz rescued2.tar.lz +@end example + +@sp 1 +@noindent +Example 8: Recover the first volume of those created with the command +@w{@samp{lzip -b 32MiB -S 650MB big_db}} from two copies, +@samp{big_db1_00001.lz} and @samp{big_db2_00001.lz}, with member 07 +damaged in the first copy, member 18 damaged in the second copy, and +member 12 damaged in both copies. The correct file produced is saved in +@samp{big_db_00001.lz}. + +@example +lziprecover -m -v -o big_db_00001.lz big_db1_00001.lz big_db2_00001.lz + Input files merged successfully +@end example + + +@node Unzcrash +@chapter Testing the robustness of decompressors +@cindex unzcrash + +The lziprecover package also includes unzcrash, a program written to +test robustness to decompression of corrupted data, inspired by +unzcrash.c from Julian Seward's bzip2. Type @samp{make unzcrash} in the +lziprecover source directory to build it. + +Unzcrash reads the specified file and then repeatedly decompresses it, +increasing 256 times each byte of the compressed data, so as to test all +possible one-byte errors. This should not cause any invalid memory +accesses. If it does, please, report it as a bug. + +Unzcrash really executes as a subprocess the shell command specified in +the first non-option argument, and then writes the file specified in the +second non-option argument to the standard input of the subprocess, +modifying the corresponding byte each time. Therefore you can use +unzcrash to test any decompressor (not only lzip), or even other decoder +programs with a suitable command line syntax. + +The format for running unzcrash is: + +@example +unzcrash [@var{options}] "lzip -tv" @var{filename}.lz +@end example + +Unzcrash supports the following options: + +@table @samp +@item -h +@itemx --help +Print an informative help message describing the options and exit. + +@item -V +@itemx --version +Print the version number of unzcrash on the standard output and exit. + +@item -b @var{range} +@itemx --bits=@var{range} +Test N-bit errors only, instead of testing all the 255 wrong values for +each byte. @samp{N-bit error} means any value differing from the +original value in N bit positions, not a value differing from the +original value in the bit position N.@* +The number of N-bit errors per byte (N = 1 to 8) is: 8 28 56 70 56 28 8 1@* +Examples of @var{range}: 1 1,2,3 1-4 1,3-5,8 1-3,5-8 + +@item -p @var{bytes} +@itemx --position=@var{bytes} +First byte position to test in the file. Defaults to 0. + +@item -q +@itemx --quiet +Quiet operation. Suppress all messages. + +@item -s @var{bytes} +@itemx --size=@var{bytes} +Number of byte positions to test. If not specified, the whole file is +tested. + +@item -v +@itemx --verbose +Verbose mode. + +@end table + +Exit status: 0 for a normal exit, 1 for environmental problems (file not +found, invalid flags, I/O errors, etc), 2 to indicate a corrupt or +invalid input file, 3 for an internal consistency error (eg, bug) which +caused unzcrash to panic. + + +@node Problems +@chapter Reporting bugs +@cindex bugs +@cindex getting help + +There are probably bugs in lziprecover. There are certainly errors and +omissions in this manual. If you report them, they will get fixed. If +you don't, no one will ever know about them and they will remain unfixed +for all eternity, if not longer. + +If you find a bug in lziprecover, please send electronic mail to +@email{lzip-bug@@nongnu.org}. Include the version number, which you can +find by running @w{@samp{lziprecover --version}}. + + +@node Concept index +@unnumbered Concept index + +@printindex cp + +@bye diff --git a/doc/lziprecover.texinfo b/doc/lziprecover.texinfo deleted file mode 100644 index 3dbceb9..0000000 --- a/doc/lziprecover.texinfo +++ /dev/null @@ -1,589 +0,0 @@ -\input texinfo @c -*-texinfo-*- -@c %**start of header -@setfilename lziprecover.info -@documentencoding ISO-8859-15 -@settitle Lziprecover Manual -@finalout -@c %**end of header - -@set UPDATED 14 September 2013 -@set VERSION 1.15 - -@dircategory Data Compression -@direntry -* Lziprecover: (lziprecover). Data recovery tool for lzip files -@end direntry - - -@ifnothtml -@titlepage -@title Lziprecover -@subtitle Data recovery tool for lzip files -@subtitle for Lziprecover version @value{VERSION}, @value{UPDATED} -@author by Antonio Diaz Diaz - -@page -@vskip 0pt plus 1filll -@end titlepage - -@contents -@end ifnothtml - -@node Top -@top - -This manual is for Lziprecover (version @value{VERSION}, @value{UPDATED}). - -@menu -* Introduction:: Purpose and features of lziprecover -* Invoking lziprecover:: Command line interface -* Repairing files:: Fixing bit-flip and similar errors -* Merging files:: Fixing several damaged copies -* File format:: Detailed format of the compressed file -* Examples:: A small tutorial with examples -* Unzcrash:: Testing the robustness of decompressors -* Problems:: Reporting bugs -* Concept index:: Index of concepts -@end menu - -@sp 1 -Copyright @copyright{} 2009, 2010, 2011, 2012, 2013 Antonio Diaz Diaz. - -This manual is free documentation: you have unlimited permission -to copy, distribute and modify it. - - -@node Introduction -@chapter Introduction -@cindex introduction - -Lziprecover is a data recovery tool and decompressor for files in the -lzip compressed data format (.lz), able to repair slightly damaged -files, recover badly damaged files from two or more copies, extract data -from damaged files, decompress files and test integrity of files. - -The lzip file format is designed for long-term data archiving. It is -clean, provides very safe 4 factor integrity checking, and is backed by -the recovery capabilities of lziprecover. - -Lziprecover is able to recover or decompress files produced by any of -the compressors in the lzip family; lzip, plzip, minilzip/lzlib, clzip -and pdlzip. - -Lziprecover makes lzip files resistant to bit-flip (one of the most -common forms of data corruption), and can safely merge multiple damaged -backup copies. - -If the cause of file corruption is damaged media, the combination -@w{GNU ddrescue + lziprecover} is the best option for recovering data -from multiple damaged copies. @xref{ddrescue-example}, for an example. - -If a file is too damaged for lziprecover to repair it, all the -recoverable data in all members of the file can be extracted with the -following command (the resulting file may contain errors and some -garbage data may be produced at the end of each member): - -@example -lziprecover -D0 -i -o file -q file.lz -@end example - -Lziprecover is able to efficiently extract a range of bytes from a -multi-member file, because it only decompresses the members containing -the desired data. - -Lziprecover can print correct total file sizes and ratios even for -multi-member files. - -When recovering data, lziprecover takes as arguments the names of the -damaged files and writes zero or more recovered files depending on the -operation selected and whether the recovery succeeded or not. The -damaged files themselves are never modified. - -When decompressing or testing file integrity, lziprecover behaves like -lzip or lunzip. - -Lziprecover is not a replacement for regular backups, but a last line of -defense for the case where the backups are also damaged. - - -@node Invoking lziprecover -@chapter Invoking lziprecover -@cindex invoking - -The format for running lziprecover is: - -@example -lziprecover [@var{options}] [@var{files}] -@end example - -Lziprecover supports the following options: - -@table @samp -@item -h -@itemx --help -Print an informative help message describing the options and exit. - -@item -V -@itemx --version -Print the version number of lziprecover on the standard output and exit. - -@item -c -@itemx --stdout -Decompress to standard output. Needed when reading from a named pipe -(fifo) or from a device. Use it to recover as much of the uncompressed -data as possible when decompressing a corrupt file. - -@item -d -@itemx --decompress -Decompress. - -@item -D @var{range} -@itemx --range-decompress=@var{range} -Decompress only a range of bytes starting at decompressed byte position -@samp{@var{begin}} and up to byte position @w{@samp{@var{end} - 1}}. -Three formats of @var{range} are recognized, @samp{@var{begin}}, -@samp{@var{begin}-@var{end}}, and @samp{@var{begin},@var{size}}. If only -@var{begin} is specified, @var{end} is taken as the end of the file. The -produced bytes are sent to standard output unless the @samp{--output} -option is used. In order to guarantee the correctness of the data -produced, all members containing any part of the desired data are -decompressed and their integrity is verified. This operation is more -efficient in multi-member files because it only decompresses the members -containing the desired data. - -@item -f -@itemx --force -Force overwrite of output files. - -@item -i -@itemx --ignore-errors -Make @samp{--range-decompress} ignore data errors and continue -decompressing the remaining members in the file. For example, -@w{@samp{lziprecover -i -D0 file.lz > file}} decompresses all the -recoverable data in all members of @samp{file.lz} without having to -split it first. - -@item -k -@itemx --keep -Keep (don't delete) input files during decompression. - -@item -l -@itemx --list -Print total file sizes and ratios. The values produced are correct even -for multi-member files. Use it together with @samp{-v} to see -information about the members in the file. - -@item -m -@itemx --merge -Try to produce a correct file merging the good parts of two or more -damaged copies. If successful, a repaired copy is written to the file -@samp{@var{file}_fixed.lz}. The exit status is 0 if a correct file could -be produced, 2 otherwise. See the chapter @samp{Merging files} -(@pxref{Merging files}) for a complete description of the merge mode. - -@item -o @var{file} -@itemx --output=@var{file} -Place the output into @samp{@var{file}} instead of into -@samp{@var{file}_fixed.lz}. If splitting, the names of the files -produced are in the form @samp{rec01@var{file}}, @samp{rec02@var{file}}, -etc. If decompressing from standard input and @samp{--stdout} has not -been specified, use @samp{@var{file}} as the name of the decompressed -file. - -@item -q -@itemx --quiet -Quiet operation. Suppress all messages. - -@item -R -@itemx --repair -Try to repair a file with small errors (up to one byte error per -member). If successful, a repaired copy is written to the file -@samp{@var{file}_fixed.lz}. @samp{@var{file}} is not modified at all. -The exit status is 0 if the file could be repaired, 2 otherwise. See the -chapter @samp{Repairing files} (@pxref{Repairing files}) for a complete -description of the repair mode. - -@item -s -@itemx --split -Search for members in @samp{@var{file}} and write each member in its own -@samp{.lz} file. You can then use @samp{lziprecover -t} to test the -integrity of the resulting files, decompress those which are undamaged, -and try to repair or partially decompress those which are damaged. - -The names of the files produced are in the form -@samp{rec01@var{file}.lz}, @samp{rec02@var{file}.lz}, etc, and are -designed so that the use of wildcards in subsequent processing, for -example, @w{@samp{lziprecover -cd rec*@var{file}.lz > recovered_data}}, -processes the files in the correct order. The number of digits used in -the names varies depending on the number of members in @samp{@var{file}}. - -@item -t -@itemx --test -Check integrity of the specified file(s), but don't decompress them. -This really performs a trial decompression and throws away the result. -Use it together with @samp{-v} to see information about the file. - -@item -v -@itemx --verbose -Verbose mode.@* -When decompressing or testing, further -v's (up to 4) increase the -verbosity level, showing status, compression ratio, dictionary size, -trailer contents (CRC, data size, member size), and up to 6 bytes of -trailing garbage (if any). - -@end table - -Numbers given as arguments to options may be followed by a multiplier -and an optional @samp{B} for "byte". - -Table of SI and binary prefixes (unit multipliers): - -@multitable {Prefix} {kilobyte (10^3 = 1000)} {|} {Prefix} {kibibyte (2^10 = 1024)} -@item Prefix @tab Value @tab | @tab Prefix @tab Value -@item k @tab kilobyte (10^3 = 1000) @tab | @tab Ki @tab kibibyte (2^10 = 1024) -@item M @tab megabyte (10^6) @tab | @tab Mi @tab mebibyte (2^20) -@item G @tab gigabyte (10^9) @tab | @tab Gi @tab gibibyte (2^30) -@item T @tab terabyte (10^12) @tab | @tab Ti @tab tebibyte (2^40) -@item P @tab petabyte (10^15) @tab | @tab Pi @tab pebibyte (2^50) -@item E @tab exabyte (10^18) @tab | @tab Ei @tab exbibyte (2^60) -@item Z @tab zettabyte (10^21) @tab | @tab Zi @tab zebibyte (2^70) -@item Y @tab yottabyte (10^24) @tab | @tab Yi @tab yobibyte (2^80) -@end multitable - -@sp 1 -Exit status: 0 for a normal exit, 1 for environmental problems (file not -found, invalid flags, I/O errors, etc), 2 to indicate a corrupt or -invalid input file, 3 for an internal consistency error (eg, bug) which -caused lziprecover to panic. - - -@node Repairing files -@chapter Repairing files -@cindex repairing files - -Lziprecover is able to repair files with small errors (up to one byte -error per member). The error may be located anywhere in the file except -in the header (first 6 bytes of each member) or in the @samp{Member -size} field of the trailer (last 8 bytes of each member). This makes -lzip files resistant to bit-flip, one of the most common forms of data -corruption. - -Bit-flip happens when one bit in the file is changed from 0 to 1 or vice -versa. It may be caused by bad RAM or even by natural radiation. I have -seen a case of bit-flip in a file stored in an USB flash drive. - - -@node Merging files -@chapter Merging files -@cindex merging files - -If you have several copies of a file but all of them are too damaged to -repair them (@pxref{Repairing files}), lziprecover can try to produce a -correct file merging the good parts of the damaged copies. - -The merge may succeed even if some copies of the file have all the -headers and trailers damaged, as long as there is at least one copy of -every header and trailer intact, even if they are in different copies of -the file. - -The merge will fail if the damaged areas overlap (at least one byte is -damaged in all copies), or are adjacent and the boundary can't be -determined, or if the copies have too many damaged areas. - -All the copies must have the same size. If some of them have been -truncated and are therefore smaller than they should, you can extend -them to the correct size with the following command before merging them -with the other copies: - -@example -ddrescue --extend-outfile= small_file.lz extended_file.lz -@end example - -If some of the copies have got garbage data at the end and are therefore -larger than they should, you can reduce their sizes to the correct value -with the following command before merging them with the other copies: - -@example -ddrescue --size= large_file.lz reduced_file.lz -@end example - -To give you an idea of its possibilities, when merging two copies, each -of them with one damaged area affecting 1 percent of the copy, the -probability of obtaining a correct file is about 98 percent. With three -such copies the probability rises to 99.97 percent. For large files (a -few MB) with small errors (one sector damaged per copy), the probability -approaches 100 percent even with only two copies. - - -@node File format -@chapter File format -@cindex file format - -Perfection is reached, not when there is no longer anything to add, but -when there is no longer anything to take away.@* ---- Antoine de Saint-Exupery - -@sp 1 -In the diagram below, a box like this: -@verbatim -+---+ -| | <-- the vertical bars might be missing -+---+ -@end verbatim - -represents one byte; a box like this: -@verbatim -+==============+ -| | -+==============+ -@end verbatim - -represents a variable number of bytes. - -@sp 1 -A lzip file consists of a series of "members" (compressed data sets). -The members simply appear one after another in the file, with no -additional information before, between, or after them. - -Each member has the following structure: -@verbatim -+--+--+--+--+----+----+=============+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ -| ID string | VN | DS | Lzma stream | CRC32 | Data size | Member size | -+--+--+--+--+----+----+=============+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ -@end verbatim - -All multibyte values are stored in little endian order. - -@table @samp -@item ID string -A four byte string, identifying the lzip format, with the value "LZIP" -(0x4C, 0x5A, 0x49, 0x50). - -@item VN (version number, 1 byte) -Just in case something needs to be modified in the future. 1 for now. - -@item DS (coded dictionary size, 1 byte) -Lzip divides the distance between any two powers of 2 into 8 equally -spaced intervals, named "wedges". The dictionary size is calculated by -taking a power of 2 (the base size) and substracting from it a number of -wedges between 0 and 7. The size of a wedge is (base_size / 16).@* -Bits 4-0 contain the base 2 logarithm of the base size (12 to 29).@* -Bits 7-5 contain the number of wedges (0 to 7) to substract from the -base size to obtain the dictionary size.@* -Example: 0xD3 = 2^19 - 6 * 2^15 = 512 KiB - 6 * 32 KiB = 320 KiB@* -Valid values for dictionary size range from 4 KiB to 512 MiB. - -@item Lzma stream -The lzma stream, finished by an end of stream marker. Uses default values -for encoder properties. See the lzip manual for a full description. - -@item CRC32 (4 bytes) -CRC of the uncompressed original data. - -@item Data size (8 bytes) -Size of the uncompressed original data. - -@item Member size (8 bytes) -Total size of the member, including header and trailer. This field acts -as a distributed index, allows the verification of stream integrity, and -facilitates safe recovery of undamaged members from multi-member files. - -@end table - - -@node Examples -@chapter A small tutorial with examples -@cindex examples - -Example 1: Restore a regular file from its compressed version -@samp{file.lz}. If the operation is successful, @samp{file.lz} is -removed. - -@example -lziprecover -d file.lz -@end example - -@sp 1 -@noindent -Example 2: Verify the integrity of the compressed file @samp{file.lz} -and show status. - -@example -lziprecover -tv file.lz -@end example - -@sp 1 -@noindent -Example 3: Decompress @samp{file.lz} partially until 10 KiB of -decompressed data are produced. - -@example -lziprecover -D 0,10KiB file.lz -@end example - -@sp 1 -@noindent -Example 4: Decompress @samp{file.lz} partially from decompressed byte -10000 to decompressed byte 15000 (5000 bytes are produced). - -@example -lziprecover -D 10000-15000 file.lz -@end example - -@sp 1 -@noindent -Example 5: Repair small errors in the file @samp{file.lz}. (Indented -lines are abridged diagnostic messages from lziprecover). - -@example -lziprecover -v -R file.lz - Copy of input file repaired successfully. -mv file_fixed.lz file.lz -@end example - -@sp 1 -@noindent -Example 6: Split the multi-member file @samp{file.lz} and write each -member in its own @samp{recXXXfile.lz} file. Then use -@w{@samp{lziprecover -t}} to test the integrity of the resulting files. - -@example -lziprecover -s file.lz -lziprecover -tv rec*file.lz -@end example - -@sp 1 -@anchor{ddrescue-example} -@noindent -Example 7: Recover a compressed backup from two copies on CD-ROM with -error-checked merging of copies -@ifnothtml -(@xref{Top,GNU ddrescue manual,,ddrescue}, -@end ifnothtml -@ifhtml -(See the -@uref{http://www.gnu.org/software/ddrescue/manual/ddrescue_manual.html,,ddrescue manual} -@end ifhtml -for details about ddrescue). - -@example -ddrescue -b2048 /dev/cdrom cdimage1 logfile1 -mount -t iso9660 -o loop,ro cdimage1 /mnt/cdimage -cp /mnt/cdimage/backup.tar.lz rescued1.tar.lz -umount /mnt/cdimage - (insert second copy in the CD drive) -ddrescue -b2048 /dev/cdrom cdimage2 logfile2 -mount -t iso9660 -o loop,ro cdimage2 /mnt/cdimage -cp /mnt/cdimage/backup.tar.lz rescued2.tar.lz -umount /mnt/cdimage -lziprecover -m -v -o backup.tar.lz rescued1.tar.lz rescued2.tar.lz -@end example - -@sp 1 -@noindent -Example 8: Recover the first volume of those created with the command -@w{@samp{lzip -b 32MiB -S 650MB big_db}} from two copies, -@samp{big_db1_00001.lz} and @samp{big_db2_00001.lz}, with member 07 -damaged in the first copy, member 18 damaged in the second copy, and -member 12 damaged in both copies. The correct file produced is saved in -@samp{big_db_00001.lz}. - -@example -lziprecover -m -v -o big_db_00001.lz big_db1_00001.lz big_db2_00001.lz - Input files merged successfully -@end example - - -@node Unzcrash -@chapter Testing the robustness of decompressors -@cindex unzcrash - -The lziprecover package also includes unzcrash, a program written to -test robustness to decompression of corrupted data, inspired by -unzcrash.c from Julian Seward's bzip2. Type @samp{make unzcrash} in the -lziprecover source directory to build it. - -Unzcrash reads the specified file and then repeatedly decompresses it, -increasing 256 times each byte of the compressed data, so as to test all -possible one-byte errors. This should not cause any invalid memory -accesses. If it does, please, report it as a bug. - -Unzcrash really executes as a subprocess the shell command specified in -the first non-option argument, and then writes the file specified in the -second non-option argument to the standard input of the subprocess, -modifying the corresponding byte each time. Therefore you can use -unzcrash to test any decompressor (not only lzip), or even other decoder -programs with a suitable command line syntax. - -The format for running unzcrash is: - -@example -unzcrash [@var{options}] "lzip -tv" @var{filename}.lz -@end example - -Unzcrash supports the following options: - -@table @samp -@item -h -@itemx --help -Print an informative help message describing the options and exit. - -@item -V -@itemx --version -Print the version number of unzcrash on the standard output and exit. - -@item -b @var{range} -@itemx --bits=@var{range} -Test N-bit errors only, instead of testing all the 255 wrong values for -each byte. @samp{N-bit error} means any value differing from the -original value in N bit positions, not a value differing from the -original value in the bit position N.@* -The number of N-bit errors per byte (N = 1 to 8) is: 8 28 56 70 56 28 8 1@* -Examples of @var{range}: 1 1,2,3 1-4 1,3-5,8 1-3,5-8 - -@item -p @var{bytes} -@itemx --position=@var{bytes} -First byte position to test in the file. Defaults to 0. - -@item -q -@itemx --quiet -Quiet operation. Suppress all messages. - -@item -s @var{bytes} -@itemx --size=@var{bytes} -Number of byte positions to test. If not specified, the whole file is -tested. - -@item -v -@itemx --verbose -Verbose mode. - -@end table - -Exit status: 0 for a normal exit, 1 for environmental problems (file not -found, invalid flags, I/O errors, etc), 2 to indicate a corrupt or -invalid input file, 3 for an internal consistency error (eg, bug) which -caused unzcrash to panic. - - -@node Problems -@chapter Reporting bugs -@cindex bugs -@cindex getting help - -There are probably bugs in lziprecover. There are certainly errors and -omissions in this manual. If you report them, they will get fixed. If -you don't, no one will ever know about them and they will remain unfixed -for all eternity, if not longer. - -If you find a bug in lziprecover, please send electronic mail to -@email{lzip-bug@@nongnu.org}. Include the version number, which you can -find by running @w{@samp{lziprecover --version}}. - - -@node Concept index -@unnumbered Concept index - -@printindex cp - -@bye -- cgit v1.2.3