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
----------------------------------

The Debian package modifies liblzma to produce a more readable build
log and to avoid breakage when a binary links indirectly to liblzma
from Debian 6.0 (squeeze) and 7.0 (wheezy) at the same time.

Patches applied:

 silent-rules:
   build: Use AM_SILENT_RULES if requested.

 xz-block-list:
   xz: Remove support for the --block-list option.

 abi-liblzma2-compat, configure-liblzma2-compat:
   liblzma: Do not check reserved space past the historical end of
   the lzma_stream structure if liblzma.so.2 is loaded in the same
   process image.  Likewise when building statically.
   (See bug #649522.)

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 <jrnieder@gmail.com>  Sat, 18 Aug 2012 03:18:42 -0700