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diff --git a/debian/lzip.README.Debian b/debian/lzip.README.Debian new file mode 100644 index 0000000..ba77528 --- /dev/null +++ b/debian/lzip.README.Debian @@ -0,0 +1,112 @@ +Lzip for Debian +=============== + +1. Lzip implementations +----------------------- + +Lzip is available in different implementations: + + lzip original C++ implementation + plzip parallel C++ implementation + + lziprecover C++ implementation with extra recovery functionality + clzip C implementation + + lunzip C implementation, decompressor only + xlunzip C implementation using lzip_decompress kernel module, decompressor only + + lzd simple C implementation, decompressor only, educational purpose + minilzip simple C implementation using lzlib library + pdlzip simple C implementation, Public Domain + +All Lzip implementations are fully compatible (files can be compressed and +decompressed with any implementation interchangeably). + +All Lzip implementations support the same command line switches (except for lzd): +if an option is not implemented it is silently ignored (e.g. the -n option to set +the number of threads is accepted by all implementations but only plzip makes +use of it). + + +2. update-alternatives +---------------------- + +On Debian based systems all Lzip implementations are installed as +lzip.$implementation (e.g. /usr/bin/lzip.plzip) and /usr/bin/lzip is a symlink +managed by update-altenatives to point to the currently selected +implementation. All Lzip packages provide the virtual lzip-alternatives package. + +The following automatic priorities are used: + + Decompressors: + xlunzip -2000 + lunzip -1000 + + Compressor and decompressors: + minilzip 1000 + pdlzip 2000 + clzip 3000 + lziprecover 4000 + lzip 5000 + plzip 6000 + + +This allows: + + * users to manually switch the implementation conveniently with: + + sudo update-alternative --config lzip + + if more than one Lzip imlementation is installed. + + * automatically have the system use the 'best' implementation installed + (using the priorities listed above, e.g. installing plzip will superseed + lzip automatically). + + * switching transparently between implementations, e.g. globally using + the multi-threaded plzip instead of the single-threaded lzip requires only + one command: + + sudo update-alternatives --set lzip /usr/bin/lzip.plzip + + No scripts or commands need to be changed. If you were using lzip + before, install plzip and all your Lzip operations are now parallelized + automatically. + +Additional lzip-compressor and lzip-decompressor are provided, both as virtual +packages as well as alternatives in /usr/bin. This allows one to use a mixed +mode of setting lzip alternatives globally, such as using plzip for +decompression and lzip for compression. + +Note: lzd (decompressor only, educational purpose) doesn't provide the '--test' +parameter to verify compressed file integrity (which now is the base-line +requirement for all lzip variants providing alternatives) and is therefore +not providing any update-alternative handling. + + +3. Best practice +---------------- + +To make the best use of Lzip, the following should be considered: + + * use lzip in scripts and commands, don't hardcode a specific implementation + (e.g. use lzip, not plzip). + + * use alternative depends in debian packages, don't depend on a specific + implementation (e.g. use 'Depends: lzip-alternative | lzip' or + 'Depends: lzip-alternative | plzip', not 'Depends: lzip'). + + * use compressor or decompressor explicitly (e.g. use + 'Depends: lzip-decompressor | lunzip' if you don't need to compress files). + + +4. See also +----------- + + * tarlz: archiver with multimember lzip compression + * zutils: utilities for dealing with compressed files transparently + + * Xz format inadequate for long-term archiving + http://lzip.nongnu.org/xz_inadequate.html + + -- Daniel Baumann <daniel.baumann@progress-linux.org> Sun, 26 Aug 2018 11:06:17 +0200 |