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Diffstat (limited to 'README')
| -rw-r--r-- | README | 37 |
1 files changed, 19 insertions, 18 deletions
@@ -1,7 +1,7 @@ Description Tarlz is a massively parallel (multi-threaded) combined implementation of -the tar archiver and the lzip compressor. Tarlz creates, lists and extracts +the tar archiver and the lzip compressor. Tarlz creates, lists, and extracts archives in a simplified and safer variant of the POSIX pax format compressed with lzip, keeping the alignment between tar members and lzip members. The resulting multimember tar.lz archive is fully backward @@ -18,7 +18,8 @@ because it does not keep the members aligned. Tarlz can create tar archives with five levels of compression granularity; per file (--no-solid), per block (--bsolid, default), per directory -(--dsolid), appendable solid (--asolid), and solid (--solid). +(--dsolid), appendable solid (--asolid), and solid (--solid). It can also +create uncompressed tar archives. Of course, compressing each file (or each directory) individually can't achieve a compression ratio as high as compressing solidly the whole tar @@ -31,16 +32,16 @@ archive, but it has the following advantages: member), and unwanted members can be deleted from the archive. Just like an uncompressed tar archive. - * It is a safe POSIX-style backup format. In case of corruption, - tarlz can extract all the undamaged members from the tar.lz - archive, skipping over the damaged members, just like the standard - (uncompressed) tar. Moreover, the option '--keep-damaged' can be - used to recover as much data as possible from each damaged member, - and lziprecover can be used to recover some of the damaged members. + * It is a safe POSIX-style backup format. In case of corruption, tarlz + can extract all the undamaged members from the tar.lz archive, + skipping over the damaged members, just like the standard + (uncompressed) tar. Moreover, the option '--keep-damaged' can be used + to recover as much data as possible from each damaged member, and + lziprecover can be used to recover some of the damaged members. - * A multimember tar.lz archive is usually smaller than the - corresponding solidly compressed tar.gz archive, except when - individually compressing files smaller than about 32 KiB. + * A multimember tar.lz archive is usually smaller than the corresponding + solidly compressed tar.gz archive, except when compressing files + smaller than about 32 KiB individually. Note that the POSIX pax format has a serious flaw. The metadata stored in pax extended records are not protected by any kind of check sequence. @@ -54,19 +55,19 @@ Metadata like file name and file size must be always protected in an archive format because of the adverse effects of undetected corruption in them, potentially much worse that undetected corruption in the data. Even more so in the case of pax because the amount of metadata it stores is potentially -large, making undetected corruption more probable. +large, making undetected corruption and archiver misbehavior more probable. Headers and metadata must be protected separately from data because the integrity checking of lzip may not be able to detect the corruption before the metadata has been used, for example, to create a new file in the wrong place. -Because of the above, tarlz protects the extended records with a CRC in a -way compatible with standard tar tools. +Because of the above, tarlz protects the extended records with a Cyclic +Redundancy Check (CRC) in a way compatible with standard tar tools. Tarlz does not understand other tar formats like gnu, oldgnu, star or v7. -'tarlz -tf archive.tar.lz > /dev/null' can be used to verify that the format -of the archive is compatible with tarlz. +The command 'tarlz -tf archive.tar.lz > /dev/null' can be used to verify +that the format of the archive is compatible with tarlz. The diagram below shows the correspondence between each tar member (formed by one or two headers plus optional data) in the tar archive and each lzip @@ -84,10 +85,10 @@ tar.lz +===============+=================================================+========+ -Copyright (C) 2013-2019 Antonio Diaz Diaz. +Copyright (C) 2013-2020 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 |