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@@ -3,8 +3,9 @@ Description Lziprecover is a data recovery tool and decompressor for files in the lzip compressed data format (.lz). Lziprecover is able to repair slightly damaged files, produce a correct file by merging the good parts of two or more -damaged copies, extract data from damaged files, decompress files and test -integrity of files. +damaged copies, reproduce a missing (zeroed) sector using a reference file, +extract data from damaged files, decompress files, and test integrity of +files. Lziprecover can remove the damaged members from multimember files, for example multimember tar.lz archives. @@ -22,68 +23,71 @@ The lzip file format is designed for data sharing and long-term 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 source 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. + recovery means. The program lziprecover 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 source 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 the lzip reference implementation is copylefted, which guarantees that it will remain free forever. -A nice feature of the lzip format is that a corrupt byte is easier to -repair the nearer it is from the beginning of the file. Therefore, with -the help of lziprecover, losing an entire archive just because of a -corrupt byte near the beginning is a thing of the past. +A nice feature of the lzip format is that a corrupt byte is easier to repair +the nearer it is from the beginning of the file. Therefore, with the help of +lziprecover, losing an entire archive just because of a corrupt byte near +the beginning is a thing of the past. -For compressible data, multiple lzip-compressed copies have a better -chance of surviving intact than one uncompressed copy using the same -amount of storage space. +Compression may be good for long-term archiving. For compressible data, +multiple compressed copies may provide redundancy in a more useful form and +may have a better chance of surviving intact than one uncompressed copy +using the same amount of storage space. This is specially true if the format +provides recovery capabilities like those of lziprecover, which is able to +find and combine the good parts of several damaged copies. -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 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 -GNU ddrescue + lziprecover is the best option for recovering data from -multiple damaged copies. +If the cause of file corruption is a damaged medium, the combination +GNU ddrescue + lziprecover is the recommended option for recovering data +from damaged lzip files. -If a file is too damaged for lziprecover to repair it, all the -recoverable data in all members of the file can be extracted in one step -with the '-D' option. +If a file is too damaged for lziprecover to repair it, all the recoverable +data in all members of the file can be extracted in one step with the +command 'lziprecover -cd -i file.lz > file'. 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 kept unchanged. +operation selected and whether the recovery succeeded or not. The damaged +files themselves are kept unchanged. -When decompressing or testing file integrity, lziprecover behaves like -lzip or lunzip. +When decompressing or testing file integrity, lziprecover behaves like lzip +or lunzip. -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. (Supposing that the -errors are randomly located inside each copy). +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. (Supposing that the errors are randomly located +inside each copy). -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 -lziprecover source directory to build it. Then try 'unzcrash --help'. +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 lziprecover source +directory to build it. Then try 'unzcrash --help'. -Copyright (C) 2009-2019 Antonio Diaz Diaz. +Copyright (C) 2009-2021 Antonio Diaz Diaz. This file is free documentation: you have unlimited permission to copy, -distribute and modify it. +distribute, and modify it. The file Makefile.in is a data file used by configure to produce the Makefile. It has the same copyright owner and permissions that configure |