Adding upstream version 1.15~rc1.
Signed-off-by: Daniel Baumann <daniel@debian.org>
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20 changed files with 439 additions and 219 deletions
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@ -6,19 +6,19 @@
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@finalout
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@c %**end of header
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@set UPDATED 17 June 2013
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@set VERSION 1.15-pre1
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@set UPDATED 29 July 2013
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@set VERSION 1.15-rc1
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@dircategory Data Compression
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@direntry
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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 direntry
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@ifnothtml
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@titlepage
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@title Lziprecover
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@subtitle Data recovery tool for lzipped files
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@subtitle Data recovery tool for lzip files
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@subtitle for Lziprecover version @value{VERSION}, @value{UPDATED}
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@author by Antonio Diaz Diaz
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@ -36,13 +36,14 @@ This manual is for Lziprecover (version @value{VERSION}, @value{UPDATED}).
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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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@end menu
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@sp 1
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@ -57,16 +58,34 @@ to copy, distribute and modify it.
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@cindex introduction
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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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@w{GNU ddrescue + lziprecover} is the best option for recovering data
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from multiple damaged copies. @xref{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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@example
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lziprecover -D0 -i -o file -q file.lz
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@end example
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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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@ -83,25 +102,12 @@ damaged files themselves are never modified.
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When decompressing or testing file integrity, lziprecover behaves like
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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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@example
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lziprecover -D0 -i -o file -q file.lz
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@end example
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If the cause of file corruption is damaged media, the combination
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@w{GNU ddrescue + lziprecover} is the best option for recovering data
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from multiple damaged copies. @xref{ddrescue-example}, for an example.
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Lziprecover is not a replacement for regular backups, but a last line of
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defense for the case where the backups are also damaged.
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@node Invoking Lziprecover
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@chapter Invoking Lziprecover
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@node Invoking lziprecover
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@chapter Invoking lziprecover
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@cindex invoking
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The format for running lziprecover is:
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@ -172,8 +178,8 @@ information about the members in the file.
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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 file
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@samp{@var{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 (@pxref{Merging
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Files}) for a complete description of the merge mode.
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be produced, 2 otherwise. See the chapter @samp{Merging files}
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(@pxref{Merging files}) for a complete description of the merge mode.
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@item -o @var{file}
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@itemx --output=@var{file}
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@ -190,11 +196,11 @@ Quiet operation. Suppress all messages.
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@item -R
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@itemx --repair
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Try to repair a file with small errors (up to one byte error per member).
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If successful, a repaired copy is written to the file
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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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@samp{@var{file}_fixed.lz}. @samp{@var{file}} is not modified at all.
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The exit status is 0 if the file could be repaired, 2 otherwise.
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See the chapter Repairing Files (@pxref{Repairing Files}) for a complete
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The exit status is 0 if the file could be repaired, 2 otherwise. See the
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chapter @samp{Repairing files} (@pxref{Repairing files}) for a complete
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description of the repair mode.
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@item -s
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@ -221,13 +227,12 @@ Use it together with @samp{-v} to see information about the file.
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@itemx --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 ratio,
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verbosity level, showing status, compression ratio, dictionary size,
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trailer contents (CRC, data size, member size), and up to 6 bytes of
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trailing garbage (if any).
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@end table
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@sp 1
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Numbers given as arguments to options may be followed by a multiplier
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and an optional @samp{B} for "byte".
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@ -252,8 +257,8 @@ invalid input file, 3 for an internal consistency error (eg, bug) which
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caused lziprecover to panic.
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@node Repairing Files
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@chapter Repairing Files
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@node Repairing files
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@chapter Repairing files
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@cindex repairing files
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Lziprecover is able to repair files with small errors (up to one byte
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@ -268,12 +273,12 @@ versa. It may be caused by bad RAM or even by natural radiation. I have
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seen a case of bit-flip in a file stored in an USB flash drive.
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@node Merging Files
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@chapter Merging Files
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@node Merging files
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@chapter Merging files
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@cindex merging files
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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 (@pxref{Repairing Files}), lziprecover can try to produce a
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repair them (@pxref{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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@ -285,16 +290,33 @@ The merge will fail if the damaged areas overlap (at least one byte is
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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 each
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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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@example
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ddrescue --extend-outfile=<correct_size> small_file.lz extended_file.lz
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@end example
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If some of the copies have got garbage data at the end and are therefore
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larger than they should, you can reduce their sizes to the correct value
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with the following command before merging them with the other copies:
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@example
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ddrescue --size=<correct_size> large_file.lz reduced_file.lz
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@end example
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To give you an idea of its possibilities, when merging two copies, each
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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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@node File Format
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@chapter File Format
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@node File format
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@chapter File format
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@cindex file format
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Perfection is reached, not when there is no longer anything to add, but
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@ -421,7 +443,7 @@ mv file_fixed.lz file.lz
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@sp 1
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@noindent
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Example 6: Split the multi-member file @samp{file.lz} and write each
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member in its own @samp{recXXXXXfile.lz} file. Then use
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member in its own @samp{recXXXfile.lz} file. Then use
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@w{@samp{lziprecover -t}} to test the integrity of the resulting files.
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@example
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@ -453,13 +475,13 @@ ddrescue -b2048 /dev/cdrom cdimage2 logfile2
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mount -t iso9660 -o loop,ro cdimage2 /mnt/cdimage
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cp /mnt/cdimage/backup.tar.lz rescued2.tar.lz
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umount /mnt/cdimage
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lziprecover -m -v -o rescued.tar.lz rescued1.tar.lz rescued2.tar.lz
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lziprecover -m -v -o backup.tar.lz rescued1.tar.lz rescued2.tar.lz
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@end example
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@sp 1
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@noindent
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Example 8: Recover the first volume of those created with the command
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@w{@code{lzip -b 32MiB -S 650MB big_db}} from two copies,
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@w{@samp{lzip -b 32MiB -S 650MB big_db}} from two copies,
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@samp{big_db1_00001.lz} and @samp{big_db2_00001.lz}, with member 07
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damaged in the first copy, member 18 damaged in the second copy, and
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member 12 damaged in both copies. The correct file produced is saved in
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@ -471,8 +493,80 @@ lziprecover -m -v -o big_db_00001.lz big_db1_00001.lz big_db2_00001.lz
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@end example
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@node Unzcrash
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@chapter Testing the robustness of decompressors
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@cindex unzcrash
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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 @samp{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 it,
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increasing 256 times each byte of the compressed data, so as to test all
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possible one-byte errors. This should not cause any invalid memory
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accesses. If it does, please, report it as a bug.
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Unzcrash really executes as a subprocess the shell command specified in
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the first non-option argument, and then writes the file specified in the
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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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@example
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unzcrash [@var{options}] "lzip -tv" @var{filename}.lz
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@end example
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Unzcrash supports the following options:
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@table @samp
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@item -h
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@itemx --help
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Print an informative help message describing the options and exit.
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@item -V
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@itemx --version
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Print the version number of lziprecover on the standard output and exit.
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@item -b @var{range}
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@itemx --bits=@var{range}
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Test N-bit errors only, instead of testing all the 255 wrong values for
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each byte. @samp{N-bit error} means any value differing from the
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original value in N bit positions, not a value differing from the
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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 28 8 1@*
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Examples of @var{range}: 1 1,2,3 1-4 1,3-5,8 1-3,5-8
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@item -p @var{bytes}
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@itemx --position=@var{bytes}
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First byte position to test in the file. Defaults to 0.
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@item -q
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@itemx --quiet
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Quiet operation. Suppress all messages.
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@item -s @var{bytes}
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@itemx --size=@var{bytes}
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Number of byte positions to test. If not specified, the whole file is
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tested.
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@item -v
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@itemx --verbose
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Verbose mode.
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@end table
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Exit status: 0 for a normal exit, 1 for environmental problems (file not
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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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@node Problems
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@chapter Reporting Bugs
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@chapter Reporting bugs
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@cindex bugs
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@cindex getting help
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@ -486,8 +580,8 @@ If you find a bug in lziprecover, please send electronic mail to
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find by running @w{@samp{lziprecover --version}}.
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@node Concept Index
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@unnumbered Concept Index
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@node Concept index
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@unnumbered Concept index
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@printindex cp
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