Merging upstream version 1.15~rc1.
Signed-off-by: Daniel Baumann <daniel@debian.org>
This commit is contained in:
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20 changed files with 439 additions and 219 deletions
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@ -3,7 +3,7 @@ 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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* Lziprecover: (lziprecover). Data recovery tool for lzip files
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END-INFO-DIR-ENTRY
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@ -12,18 +12,19 @@ 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 1.15-pre1, 17 June 2013).
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This manual is for Lziprecover (version 1.15-rc1, 29 July 2013).
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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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* Repairing Files:: Fixing bit-flip and similar errors
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* Merging Files:: Fixing several damaged copies
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* File Format:: Detailed format of the compressed file
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* Invoking lziprecover:: Command line interface
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* Repairing files:: Fixing bit-flip and similar errors
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* Merging files:: Fixing several damaged copies
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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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* Unzcrash:: Testing the robustness of decompressors
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* Problems:: Reporting bugs
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* Concept Index:: Index of concepts
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* Concept index:: Index of concepts
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Copyright (C) 2009, 2010, 2011, 2012, 2013 Antonio Diaz Diaz.
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@ -32,22 +33,38 @@ This manual is for Lziprecover (version 1.15-pre1, 17 June 2013).
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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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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 data from
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damaged files, decompress files and test integrity of files.
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lzip compressed data format (.lz), able to repair slightly damaged
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files, recover badly damaged files from two or more copies, extract data
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from damaged files, decompress files and test integrity of files.
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The lzip file format is designed for long-term data archiving. It is
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clean, provides very safe 4 factor integrity checking, and is backed by
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the recovery capabilities of lziprecover.
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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. It makes lzip files resistant to bit-flip, one of the most
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common forms of data corruption, and its recovery capabilities
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contribute to make of the lzip format one of the best options for
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long-term data archiving.
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and pdlzip.
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Lziprecover makes lzip files resistant to bit-flip (one of the most
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common forms of data corruption), and can safely merge multiple damaged
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backup copies.
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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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If a file is too damaged for lziprecover to repair it, all the
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recoverable data in all members of the file can be extracted with the
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following command (the resulting file may contain errors and some
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garbage data may be produced at the end of each member):
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lziprecover -D0 -i -o file -q file.lz
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Lziprecover is able to efficiently extract a range of bytes from a
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multi-member file, because it only decompresses the members containing
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@ -64,24 +81,13 @@ 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 a file is too damaged for lziprecover to repair it, all the
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recoverable data in all members of the file can be extracted with the
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following command (the resulting file may contain errors and some
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garbage data may be produced at the end of each member):
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lziprecover -D0 -i -o file -q file.lz
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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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Lziprecover is not a replacement for regular backups, but a last
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line of defense for the case where the backups are also damaged.
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File: lziprecover.info, Node: Invoking Lziprecover, Next: Repairing Files, Prev: Introduction, Up: Top
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File: lziprecover.info, Node: Invoking lziprecover, Next: Repairing files, Prev: Introduction, Up: Top
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2 Invoking Lziprecover
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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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@ -149,8 +155,8 @@ The format for running lziprecover is:
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Try to produce a correct file merging the good parts of two or more
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damaged copies. If successful, a repaired copy is written to the
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file `FILE_fixed.lz'. The exit status is 0 if a correct file could
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be produced, 2 otherwise. See the chapter Merging Files (*note
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Merging Files::) for a complete description of the merge mode.
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be produced, 2 otherwise. See the chapter `Merging files' (*note
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Merging files::) for a complete description of the merge mode.
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`-o FILE'
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`--output=FILE'
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@ -167,10 +173,10 @@ The format for running lziprecover is:
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`-R'
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`--repair'
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Try to repair a file with small errors (up to one byte error per
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member). If successful, a repaired copy is written to the file
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member). If successful, a repaired copy is written to the file
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`FILE_fixed.lz'. `FILE' is not modified at all. The exit status
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is 0 if the file could be repaired, 2 otherwise. See the chapter
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Repairing Files (*note Repairing Files::) for a complete
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is 0 if the file could be repaired, 2 otherwise. See the chapter
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`Repairing files' (*note Repairing files::) for a complete
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description of the repair mode.
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`-s'
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@ -199,12 +205,11 @@ The format for running lziprecover is:
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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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verbosity level, showing status, compression ratio, dictionary
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size, 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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Numbers given as arguments to options may be followed by a multiplier
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and an optional `B' for "byte".
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@ -227,9 +232,9 @@ invalid input file, 3 for an internal consistency error (eg, bug) which
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caused lziprecover to panic.
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File: lziprecover.info, Node: Repairing Files, Next: Merging Files, Prev: Invoking Lziprecover, Up: Top
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File: lziprecover.info, Node: Repairing files, Next: Merging files, Prev: Invoking lziprecover, Up: Top
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3 Repairing Files
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3 Repairing files
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*****************
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Lziprecover is able to repair files with small errors (up to one byte
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@ -244,13 +249,13 @@ vice versa. It may be caused by bad RAM or even by natural radiation. I
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have seen a case of bit-flip in a file stored in an USB flash drive.
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File: lziprecover.info, Node: Merging Files, Next: File Format, Prev: Repairing Files, Up: Top
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File: lziprecover.info, Node: Merging files, Next: File format, Prev: Repairing files, Up: Top
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4 Merging Files
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4 Merging files
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***************
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If you have several copies of a file but all of them are too damaged to
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repair them (*note Repairing Files::), lziprecover can try to produce a
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repair them (*note Repairing files::), lziprecover can try to produce a
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correct file merging the good parts of the damaged copies.
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The merge may succeed even if some copies of the file have all the
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@ -262,17 +267,31 @@ the file.
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is damaged in all copies), or are adjacent and the boundary can't be
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determined, or if the copies have too many damaged areas.
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To give you an idea of its possibilities, when merging two copies
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All the copies must have the same size. If some of them have been
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truncated and are therefore smaller than they should, you can extend
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them to the correct size with the following command before merging them
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with the other copies:
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ddrescue --extend-outfile=<correct_size> small_file.lz extended_file.lz
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If some of the copies have got garbage data at the end and are
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therefore larger than they should, you can reduce their sizes to the
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correct value with the following command before merging them with the
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other copies:
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ddrescue --size=<correct_size> large_file.lz reduced_file.lz
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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 copy, the
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probability of obtaining a correct file is about 98 percent. With three
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such copies the probability rises to 99.97 percent. For large files with
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small errors, the probability approaches 100 percent even with only two
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copies.
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such copies the probability rises to 99.97 percent. For large files (a
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few MB) with small errors (one sector damaged per copy), the probability
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approaches 100 percent even with only two copies.
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File: lziprecover.info, Node: File Format, Next: Examples, Prev: Merging Files, Up: Top
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File: lziprecover.info, Node: File format, Next: Examples, Prev: Merging files, Up: Top
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5 File Format
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5 File format
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*************
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Perfection is reached, not when there is no longer anything to add, but
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@ -343,7 +362,7 @@ additional information before, between, or after them.
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File: lziprecover.info, Node: Examples, Next: Problems, Prev: File Format, Up: Top
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File: lziprecover.info, Node: Examples, Next: Unzcrash, Prev: File format, Up: Top
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6 A small tutorial with examples
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********************************
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@ -381,8 +400,8 @@ are abridged diagnostic messages from lziprecover).
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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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in its own `recXXXfile.lz' file. Then use `lziprecover -t' to test the
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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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@ -401,7 +420,7 @@ error-checked merging of copies (*Note GNU ddrescue manual:
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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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lziprecover -m -v -o backup.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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@ -414,9 +433,80 @@ correct file produced is saved in `big_db_00001.lz'.
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Input files merged successfully
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File: lziprecover.info, Node: Problems, Next: Concept Index, Prev: Examples, Up: Top
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File: lziprecover.info, Node: Unzcrash, Next: Problems, Prev: Examples, Up: Top
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7 Reporting Bugs
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7 Testing the robustness of decompressors
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*****************************************
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The lziprecover package also includes unzcrash, a program written to
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test robustness to decompression of corrupted data, inspired by
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unzcrash.c from Julian Seward's bzip2. Type `make unzcrash' in the
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lziprecover source directory to build it.
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Unzcrash reads the specified file and then repeatedly decompresses
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it, increasing 256 times each byte of the compressed data, so as to
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test all possible one-byte errors. This should not cause any invalid
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memory accesses. If it does, please, report it as a bug.
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Unzcrash really executes as a subprocess the shell command specified
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in the first non-option argument, and then writes the file specified in
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the second non-option argument to the standard input of the subprocess,
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modifying the corresponding byte each time. Therefore you can use
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unzcrash to test any decompressor (not only lzip), or even other decoder
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programs with a suitable command line syntax.
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The format for running unzcrash is:
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unzcrash [OPTIONS] "lzip -tv" FILENAME.lz
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Unzcrash 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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`-b RANGE'
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`--bits=RANGE'
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Test N-bit errors only, instead of testing all the 255 wrong
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values for each byte. `N-bit error' means any value differing from
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the original value in N bit positions, not a value differing from
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the original value in the bit position N.
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The number of N-bit errors per byte (N = 1 to 8) is: 8 28 56 70 56
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28 8 1
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Examples of RANGE: 1 1,2,3 1-4 1,3-5,8 1-3,5-8
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`-p BYTES'
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`--position=BYTES'
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First byte position to test in the file. Defaults to 0.
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`-q'
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`--quiet'
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Quiet operation. Suppress all messages.
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`-s BYTES'
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`--size=BYTES'
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Number of byte positions to test. If not specified, the whole file
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is tested.
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`-v'
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`--verbose'
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Verbose mode.
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Exit status: 0 for a normal exit, 1 for environmental problems (file
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not found, invalid flags, I/O errors, etc), 2 to indicate a corrupt or
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invalid input file, 3 for an internal consistency error (eg, bug) which
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caused unzcrash to panic.
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File: lziprecover.info, Node: Problems, Next: Concept index, Prev: Unzcrash, Up: Top
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8 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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@ -429,9 +519,9 @@ for all eternity, if not longer.
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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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File: lziprecover.info, Node: Concept index, Prev: Problems, Up: Top
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Concept Index
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Concept index
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*************
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[index ]
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@ -439,26 +529,28 @@ Concept Index
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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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* 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: Invoking Lziprecover. (line 6)
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* merging files: Merging Files. (line 6)
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* repairing files: Repairing Files. (line 6)
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* invoking: Invoking lziprecover. (line 6)
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* merging files: Merging files. (line 6)
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* repairing files: Repairing files. (line 6)
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* unzcrash: Unzcrash. (line 6)
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Tag Table:
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Node: Top231
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Node: Introduction1032
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Node: Invoking Lziprecover3052
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Node: Repairing Files8489
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Node: Merging Files9208
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Node: File Format10338
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Node: Examples12822
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Ref: ddrescue-example14024
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Node: Problems15134
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Node: Concept Index15684
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Node: Top228
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Node: Introduction1095
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Node: Invoking lziprecover3248
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Node: Repairing files8686
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Node: Merging files9405
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Node: File format11176
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Node: Examples13660
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Ref: ddrescue-example14860
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Node: Unzcrash15969
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Node: Problems18344
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Node: Concept index18894
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End Tag Table
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