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diff --git a/doc/lzip.texinfo b/doc/lzip.texinfo index b86de34..190f20f 100644 --- a/doc/lzip.texinfo +++ b/doc/lzip.texinfo @@ -5,8 +5,8 @@ @finalout @c %**end of header -@set UPDATED 30 April 2011 -@set VERSION 1.12 +@set UPDATED 12 November 2011 +@set VERSION 1.13-rc1 @dircategory Data Compression @direntry @@ -39,8 +39,6 @@ This manual is for Lzip (version @value{VERSION}, @value{UPDATED}). * Invoking Lzip:: Command line interface * File Format:: Detailed format of the compressed file * Examples:: A small tutorial with examples -* Lziprecover:: Recovering data from damaged compressed files -* Invoking Lziprecover:: Command line interface * Problems:: Reporting bugs * Concept Index:: Index of concepts @end menu @@ -62,6 +60,9 @@ gzip or bzip2. Lzip decompresses almost as fast as gzip and compresses better than bzip2, which makes it well suited for software distribution and data archiving. +If you ever need to recover data from a damaged lzip file, try the +lziprecover program. + Lzip replaces every file given in the command line with a compressed version of itself, with the name "original_name.lz". Each compressed file has the same modification date, permissions, and, when possible, @@ -208,10 +209,10 @@ Print an informative help message describing the options and exit. @itemx --version Print the version number of lzip on the standard output and exit. -@item -b @var{size} -@itemx --member-size=@var{size} -Produce a multimember file and set the member size limit to @var{size} -bytes. Minimum member size limit is 100kB. Small member size may degrade +@item -b @var{bytes} +@itemx --member-size=@var{bytes} +Produce a multimember file and set the member size limit to @var{bytes}. +Minimum member size limit is 100kB. Small member size may degrade compression ratio, so use it only when needed. The default is to produce single-member files. @@ -227,7 +228,7 @@ Decompress. @item -f @itemx --force -Force overwrite of output file. +Force overwrite of output files. @item -F @itemx --recompress @@ -238,8 +239,8 @@ Force recompression of files whose name already has the @samp{.lz} or @itemx --keep Keep (don't delete) input files during compression or decompression. -@item -m @var{length} -@itemx --match-length=@var{length} +@item -m @var{bytes} +@itemx --match-length=@var{bytes} Set the match length limit in bytes. After a match this long is found, the search is finished. Valid values range from 5 to 273. Larger values usually give better compression ratios but longer compression times. @@ -257,25 +258,25 @@ compressing and splitting the output in volumes. @itemx --quiet Quiet operation. Suppress all messages. -@item -s @var{size} -@itemx --dictionary-size=@var{size} +@item -s @var{bytes} +@itemx --dictionary-size=@var{bytes} Set the dictionary size limit in bytes. Valid values range from 4KiB to 512MiB. Lzip will use the smallest possible dictionary size for each member without exceeding this limit. Note that dictionary sizes are quantized. If the specified size does not match one of the valid sizes, -it will be rounded upwards by adding up to (@var{size} / 16) to it. +it will be rounded upwards by adding up to (@var{bytes} / 16) to it. For maximum compression you should use a dictionary size limit as large as possible, but keep in mind that the decompression memory requirement is affected at compression time by the choice of dictionary size limit. -@item -S @var{size} -@itemx --volume-size=@var{size} +@item -S @var{bytes} +@itemx --volume-size=@var{bytes} Split the compressed output into several volume files with names @samp{original_name00001.lz}, @samp{original_name00002.lz}, etc, and set -the volume size limit to @var{size} bytes. Each volume is a complete, -maybe multimember, lzip file. Minimum volume size limit is 100kB. Small -volume size may degrade compression ratio, so use it only when needed. +the volume size limit to @var{bytes}. Each volume is a complete, maybe +multimember, lzip file. Minimum volume size limit is 100kB. Small volume +size may degrade compression ratio, so use it only when needed. @item -t @itemx --test @@ -285,8 +286,8 @@ Use it together with @samp{-v} to see information about the file. @item -v @itemx --verbose -Verbose mode. -When compressing, show the compression ratio for each file processed. +Verbose mode.@* +When compressing, show the compression ratio for each file processed.@* When decompressing or testing, further -v's (up to 4) increase the verbosity level, showing status, dictionary size, compression ratio, trailer contents (CRC, data size, member size), and up to 6 bytes of @@ -422,8 +423,8 @@ file.lz | cmp file -}}. @sp 1 @noindent -Example 1: Replace a regular file with its compressed version file.lz -and show the compression ratio. +Example 1: Replace a regular file with its compressed version +@samp{file.lz} and show the compression ratio. @example lzip -v file @@ -431,8 +432,8 @@ lzip -v file @sp 1 @noindent -Example 2: Like example 1 but the created file.lz is multimember with a -member size of 1MiB. The compression ratio is not shown. +Example 2: Like example 1 but the created @samp{file.lz} is multimember +with a member size of 1MiB. The compression ratio is not shown. @example lzip -b 1MiB file @@ -440,8 +441,9 @@ lzip -b 1MiB file @sp 1 @noindent -Example 3: Restore a regular file from its compressed version file.lz. -If the operation is successful, file.lz is removed. +Example 3: Restore a regular file from its compressed version +@samp{file.lz}. If the operation is successful, @samp{file.lz} is +removed. @example lzip -d file.lz @@ -449,8 +451,8 @@ lzip -d file.lz @sp 1 @noindent -Example 4: Verify the integrity of the compressed file file.lz and show -status. +Example 4: Verify the integrity of the compressed file @samp{file.lz} +and show status. @example lzip -tv file.lz @@ -459,7 +461,7 @@ lzip -tv file.lz @sp 1 @noindent Example 5: Compress a whole floppy in /dev/fd0 and send the output to -file.lz. +@samp{file.lz}. @example lzip -c /dev/fd0 > file.lz @@ -467,8 +469,8 @@ lzip -c /dev/fd0 > file.lz @sp 1 @noindent -Example 6: Decompress file.lz partially until 10KiB of decompressed data -are produced. +Example 6: Decompress @samp{file.lz} partially until 10KiB of +decompressed data are produced. @example lzip -cd file.lz | dd bs=1024 count=10 @@ -476,184 +478,40 @@ lzip -cd file.lz | dd bs=1024 count=10 @sp 1 @noindent -Example 7: Create a multivolume compressed tar archive with a volume -size of 1440KiB. - -@example -tar -c some_directory | lzip -S 1440KiB -o volume_name -@end example - -@sp 1 -@noindent -Example 8: Extract a multivolume compressed tar archive. +Example 7: Decompress @samp{file.lz} partially from decompressed byte +10000 to decompressed byte 15000 (5000 bytes are produced). @example -lzip -cd volume_name*.lz | tar -xf - +lzip -cd file.lz | dd bs=1000 skip=10 count=5 @end example @sp 1 @noindent -Example 9: Create a multivolume compressed backup of a big database file -with a volume size of 650MB, where each volume is a multimember file -with a member size of 32MiB. +Example 8: Create a multivolume compressed tar archive with a volume +size of 1440KiB. @example -lzip -b 32MiB -S 650MB big_db +tar -c some_directory | lzip -S 1440KiB -o volume_name @end example @sp 1 -@anchor{ddrescue-example} @noindent -Example 10: Recover a compressed backup from two copies on CD-ROM (see -the GNU ddrescue manual for details about ddrescue) +Example 9: Extract a multivolume compressed tar archive. @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 rescued.tar.lz rescued1.tar.lz rescued2.tar.lz +lzip -cd volume_name*.lz | tar -xf - @end example @sp 1 @noindent -Example 11: Recover the first volume of those created in example 9 from -two copies, @samp{big_db1_00001.lz} and @samp{big_db2_00001.lz}, with -member 00007 damaged in the first copy, member 00018 damaged in the -second copy, and member 00012 damaged in both copies. (Indented lines -are abridged error messages from lzip/lziprecover). Two correct copies -are produced and compared. - -@example -lziprecover -s big_db1_00001.lz -lziprecover -s big_db2_00001.lz -lzip -t rec*big_db1_00001.lz - rec00007big_db1_00001.lz: crc mismatch - rec00012big_db1_00001.lz: crc mismatch -lzip -t rec*big_db2_00001.lz - rec00012big_db2_00001.lz: crc mismatch - rec00018big_db2_00001.lz: crc mismatch -lziprecover -m -v rec00012big_db1_00001.lz rec00012big_db2_00001.lz - Input files merged successfully -cp rec00007big_db2_00001.lz rec00007big_db1_00001.lz -cp rec00012big_db1_00001_fixed.lz rec00012big_db1_00001.lz -cp rec00012big_db1_00001_fixed.lz rec00012big_db2_00001.lz -cp rec00018big_db1_00001.lz rec00018big_db2_00001.lz -cat rec*big_db1_00001.lz > big_db3_00001.lz -cat rec*big_db2_00001.lz > big_db4_00001.lz -zcmp big_db3_00001.lz big_db4_00001.lz -@end example - - -@node Lziprecover -@chapter Lziprecover -@cindex lziprecover - -Lziprecover is a data recovery tool for lzip compressed files able to -repair slightly damaged files, recover badly damaged files from two or -more copies, and extract undamaged members from multi-member files. - -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. - -If the files are too damaged for lziprecover to repair them, data from -damaged members can be partially recovered writing it to stdout as shown -in the following example (the resulting file may contain garbage data at -the end): - -@example -lzip -cd rec00001file.lz > rec00001file -@end example - -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. @xref{ddrescue-example}, for an example. - - -@node Invoking Lziprecover -@chapter Invoking Lziprecover -@cindex invoking lziprecover - -The format for running lziprecover is: +Example 10: Create a multivolume compressed backup of a big database +file with a volume size of 650MB, where each volume is a multimember +file with a member size of 32MiB. @example -lziprecover [@var{options}] [@var{files}] +lzip -b 32MiB -S 650MB big_db @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 -f -@itemx --force -Force overwrite of output file. - -@item -m -@itemx --merge -Try to produce a correct file merging the good parts of two or more -damaged copies. The copies must be single-member files. The merge will -fail if the copies have too many damaged areas or if the same byte is -damaged in all copies. If successful, a repaired copy is written to the -file @samp{@var{file}_fixed.lz}. - -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 with -small errors, the probability approaches 100 percent even with only two -copies. - -@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{rec00001@var{file}}, etc. - -@item -q -@itemx --quiet -Quiet operation. Suppress all messages. - -@item -R -@itemx --repair -Try to repair a small error, affecting only one byte, in a single-member -@var{file}. If successful, a repaired copy is written to the file -@samp{@var{file}_fixed.lz}. @samp{@var{file}} is not modified at all. - -@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{lzip -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{rec00001@var{file}.lz}, @samp{rec00002@var{file}.lz}, etc, and are -designed so that the use of wildcards in subsequent processing, for -example, @w{@samp{lzip -cd rec*@var{file}.lz > recovered_data}}, -processes the files in the correct order. - -@item -v -@itemx --verbose -Verbose mode. Further -v's increase the verbosity level. - -@end table - @node Problems @chapter Reporting Bugs |