58 lines
2.6 KiB
Markdown
58 lines
2.6 KiB
Markdown
# Overview
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System compression, also known as "Compact OS", is a Windows feature that allows
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rarely modified files to be compressed using the XPRESS or LZX compression
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formats. It is not built directly into NTFS but rather is implemented using
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reparse points. This feature appeared in Windows 10 and it appears that many
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Windows 10 systems have been using it by default.
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This repository contains a plugin which enables the NTFS-3G FUSE driver to
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transparently read from system-compressed files. It must be built against
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NTFS-3G version 2016.2.22AR.1 or later, since that was the first version to
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include support for reparse point plugins.
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Currently, only reading is supported. Compressing an existing file may be done
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by using the "compact" utility on Windows, with one of the options below
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("xpress4k" is the weakest and fastest, "lzx" is the strongest and slowest):
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/exe:xpress4k
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/exe:xpress8k
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/exe:xpress16k
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/exe:lzx
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# Installation
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The plugin can be built by running `./configure && make`. The build system must
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be able to find the NTFS-3G library and headers. On some platforms this may
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require that the "ntfs-3g-dev" package or similar be installed in addition to
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the main "ntfs-3g" package.
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After compiling, run `make install` to install the plugin to the NTFS-3G plugin
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directory, which will be a subdirectory "ntfs-3g" of the system library
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directory (`$libdir`). An example full path to the installed plugin is
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`/usr/lib/ntfs-3g/ntfs-plugin-80000017.so`. It may differ slightly on different
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platforms. `make install` will create the plugin directory if it does not
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already exist.
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# Implementation note
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The XPRESS and LZX decompression formats used in system-compressed files are
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identical to the formats used in Windows Imaging (WIM) archives. Therefore, for
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the system compression plugin I borrowed the XPRESS and LZX decompressors I had
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already written for the wimlib project (https://wimlib.net/). I made some
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slight modifications for integration purposes. The code in wimlib is currently
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licensed LGPLv3+, but I have relicensed the version in this plugin to GPLv2+ for
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consistency with NTFS-3G's license. (Public domain portions remain public
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domain.)
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# Notices
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The NTFS-3G system compression plugin was written by Eric Biggers, with
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contributions from Jean-Pierre André. You can contact the author at
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ebiggers3@gmail.com.
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This software may be redistributed and/or modified under the terms of the GNU
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General Public License as published by the Free Software Foundation, either
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version 2 of the License, or (at your option) any later version. There is NO
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WARRANY, to the extent permitted by law. See the COPYING file for details.
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