XZ Utils for Debian =================== Contents: 1. History 2. Differences from standard XZ Utils 3. LZMA Utils compatibility 4. Configuration History ------- XZ Utils should have been called LZMA Utils 4.42, but it came too late. The old .lzma file format has some problems, worst of which is the lack of magic number, but it gets enough use to still need to be supported. See /usr/share/doc/xz-utils/history.txt.gz for the full story. Differences from standard XZ Utils ---------------------------------- XZ Utils 5.1.y has some experimental features which are disabled in Debian to allow interfaces to evolve. Debian liblzma is also modified to avoid breakage when the same process loads liblzma2 from Debian 6.0 (squeeze) and liblzma5. abi-threaded-encoder Disable threaded compression in liblzma and xz. abi-version-script liblzma: Do not pretend to satisfy dependencies on XZ_5.1.1alpha. abi-liblzma2-compat, configure-liblzma2-compat Do not check reserved fields past the historical end of the lzma_stream structure if liblzma.so.2 is loaded in the same process image. Likewise when linked statically. (See bug #649522.) man-date, man-xz-lvv-minver (from upstream) Document the "Minimum version required to decompress" field of "xz --robot -v -v --list" output. xz-lvv-empty-block-minver (from upstream) Fix the version number printed by "xz -lvv" for files with Blocks of zero uncompressed_size: the decoder bug preventing reading such files was fixed in xz 5.0.2, not 5.0.3. decoder-check-first-0x00 (from upstream) Check that the first byte of range encoded data is zero to catch broken files sooner. Changes in 5.1.2alpha not applied: Docs: Language fix to 01_compress_easy.c xz: Add incomplete support for --block-list INSTALL: Document --enable-symbol-versions configure: Add a comment about *-linux tuples for clarity TODO: Warn that threads and fork() do not mix well Bump the version number and update NEWS for 5.1.2alpha LZMA Utils compatibility ------------------------ To support old scripts and muscle memory, XZ Utils can emulate the legacy LZMA Utils interface. To use this feature, you can install some subset of the following list of symbolic links to your $PATH. lzma, unlzma, lzcat -> /usr/bin/xz lzgrep, lzegrep, lzfgrep -> /usr/bin/xzgrep lzless -> /usr/bin/xzless lzmore -> /usr/bin/xzmore lzdiff, lzcmp -> /usr/bin/xzdiff If you would like XZ Utils to provide these commands by default for all users, use "update-alternatives --config lzma". Configuration ------------- The memory usage of xz can vary from a few hundred kilobytes to several gigabytes depending on the compression settings. If you would like xz to automatically scale down its settings while compressing to decrease memory usage, you can declare so by adding an option like the following to your environment (e.g., in ~/.profile): XZ_DEFAULTS=--memlimit-compress=256MiB export XZ_DEFAULTS See the "Memory usage" section of the xz(1) manual page for details. -- Jonathan Nieder Mon, 10 Sep 2012 14:35:27 -0700