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<sect1 id="pre-why">
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  <title>Rationale for Packages in the Book</title>

    <para>The goal of LFS is to build a complete and usable
    foundation-level system&mdash;including all the packages needed to replicate
    itself&mdash;and providing a relatively minimal base from which to customize
    a more complete system based on the user's choices.  This does not
    mean that LFS is the smallest system possible.  Several important packages
    are included that are not, strictly speaking, required.  The list below documents the
    reasons each package in the book has been included.</para>

    <itemizedlist>

      <listitem>
        <para>Acl</para>

        <para>This package contains utilities to administer Access
        Control Lists, which are used to define fine-grained
        discretionary access rights for files and directories.
        </para>
      </listitem>

      <listitem>
        <para>Attr</para>

        <para>This package contains programs for managing
        extended attributes on file system objects.
        </para>
      </listitem>

      <listitem>
        <para>Autoconf</para>

        <para>This package supplies programs for producing shell scripts that
        can automatically configure source code from a developer's
        template. It is often needed to rebuild a package after
        the build procedure has been updated.</para>
      </listitem>

      <listitem>
        <para>Automake</para>

        <para>This package contains programs for generating Make files from
        a template. It is often needed to rebuild a package after
        the build procedure has been updated.</para>
      </listitem>

      <listitem>
        <para>Bash</para>

        <para>This package satisfies an LSB core requirement to provide
        a Bourne Shell interface to the system.  It was chosen over
        other shell packages because of its common usage and extensive
        capabilities.</para>
      </listitem>

      <listitem>
        <para>Bc</para>

        <para>This package provides an arbitrary precision numeric processing language.
        It satisfies a requirement for building the Linux kernel.</para>
      </listitem>

      <listitem>
        <para>Binutils</para>

        <para>This package supplies a linker, an assembler, and other
        tools for handling object files. The programs in this package are
        needed to compile most of the packages in an LFS system.</para>
      </listitem>

      <listitem>
        <para>Bison</para>

        <para>This package contains the GNU version of yacc (Yet Another
        Compiler Compiler) needed to build several of the LFS programs.</para>
      </listitem>

      <listitem>
        <para>Bzip2</para>

        <para>This package contains programs for compressing and decompressing
        files.  It is required to decompress many LFS packages.</para>
      </listitem>

      <listitem>
        <para>Check</para>

        <para>This package provides a test harness for other programs.</para>
      </listitem>

      <listitem>
        <para>Coreutils</para>

        <para>This package contains a number of essential programs for viewing
        and manipulating files and directories. These programs are needed for
        command line file management, and are necessary for the installation
        procedures of every package in LFS.</para>
      </listitem>

      <listitem revision="systemd">
        <para>D-Bus</para>

        <para>This package contains programs to implement a message bus system,
        a simple way for applications to talk to one another.
        </para>
      </listitem>

      <listitem>
        <para>DejaGNU</para>

        <para>This package supplies a framework for testing other programs.</para>
      </listitem>

      <listitem>
        <para>Diffutils</para>

        <para>This package contains programs that show the differences
        between files or directories. These programs can be used to create
        patches, and are also used in many packages' build procedures.</para>
      </listitem>

      <listitem>
        <para>E2fsprogs</para>

        <para>This package supplies utilities for handling the ext2, ext3
        and ext4 file systems.  These are the most common and thoroughly
        tested file systems that Linux supports.</para>
      </listitem>

      <listitem revision="sysv">
        <para>Udev</para>

        <para>This package is a device manager.  It dynamically controls the ownership,
        permissions, names, and symbolic links of device nodes in the /dev directory when
        devices are added to or removed from the system.
        </para>
      </listitem>

      <listitem>
        <para>Expat</para>

        <para>This package yields a relatively small XML parsing library.  It
        is required by the XML::Parser Perl module.</para>
      </listitem>

      <listitem>
        <para>Expect</para>

        <para>This package contains a program for carrying out scripted
        dialogues with other interactive programs.  It is commonly used
        for testing other packages.</para>
      </listitem>

      <listitem>
        <para>File</para>

        <para>This package contains a utility for determining the type of a
        given file or files. A few packages need it in their build scripts.</para>
      </listitem>

      <listitem>
        <para>Findutils</para>

        <para>This package provides programs to find files in a file system.
        It is used in many packages' build scripts.</para>
      </listitem>

      <listitem>
        <para>Flex</para>

        <para>This package contains a utility for generating programs that
        recognize patterns in text.  It is the GNU version of the lex
        (lexical analyzer) program.  It is required to build several
        LFS packages.</para>
      </listitem>

      <listitem>
        <para>Gawk</para>

        <para>This package supplies programs for manipulating text files.
        It is the GNU version of awk (Aho-Weinberg-Kernighan). It is used in
        many other packages' build scripts.</para>
      </listitem>

      <listitem>
        <para>GCC</para>

        <para>This is the Gnu Compiler Collection.  It contains the
        C and C++ compilers as well as several others not built by LFS.
        </para>
      </listitem>

      <listitem>
        <para>GDBM</para>

        <para>This package contains the GNU Database Manager library.  It
        is used by one other LFS package, Man-DB.</para>
      </listitem>

      <listitem>
        <para>Gettext</para>

        <para>This package provides utilities and libraries for
        the internationalization and localization of many packages.</para>
      </listitem>

      <listitem>
        <para>Glibc</para>

        <para>This package contains the main C library.  Linux programs will
        not run without it.</para>
      </listitem>

      <listitem>
        <para>GMP</para>

        <para>This package supplies math libraries that provide useful functions
        for arbitrary precision arithmetic.  It is needed to build GCC.</para>
      </listitem>

      <listitem>
        <para>Gperf</para>

        <para>This package produces a program that generates a perfect hash
        function from a set of keys. It is required by
        <phrase revision='sysv'>Udev</phrase>
        <phrase revision='systemd'>Systemd</phrase>.</para>
      </listitem>

      <listitem>
        <para>Grep</para>

        <para>This package contains programs for searching through files. These
        programs are used by most packages' build scripts.</para>
      </listitem>

      <listitem>
        <para>Groff</para>

        <para>This package contributes programs for processing and formatting text.
        One important function of these programs is to format man pages.</para>
      </listitem>

      <listitem>
        <para>GRUB</para>

        <para>This is the Grand Unified Boot Loader.  It is 
        the most flexible of several boot loaders available.
        </para>
      </listitem>

      <listitem>
        <para>Gzip</para>

        <para>This package contains programs for compressing and
        decompressing files. It is needed to decompress many packages
        in LFS.</para>
      </listitem>

      <listitem>
        <para>Iana-etc</para>

        <para>This package provides data for network services and protocols.
        It is needed to enable proper networking capabilities.</para>
      </listitem>

      <listitem>
        <para>Inetutils</para>

        <para>This package supplies programs for basic network
        administration.</para>
      </listitem>

      <listitem>
        <para>Intltool</para>

        <para>This package contributes tools for extracting translatable
        strings from source files.</para>
      </listitem>

      <listitem>
        <para>IProute2</para>

        <para>This package contains programs for basic and advanced IPv4 and
        IPv6 networking.  It was chosen over the other common network
        tools package (net-tools) for its IPv6 capabilities.  </para>
      </listitem>

      <listitem revision="systemd">
        <para>Jinja2</para>

        <para>This package is a Python module for text templating.
        It's required to build Systemd.</para>
      </listitem>

      <listitem>
        <para>Kbd</para>

        <para>This package produces key-table files, keyboard utilities
        for non-US keyboards, and a number of console fonts.</para>
      </listitem>

      <listitem>
        <para>Kmod</para>

        <para>This package supplies programs needed to administer Linux
        kernel modules.</para>
      </listitem>

      <listitem>
        <para>Less</para>

        <para>This package contains a very nice text file viewer that
        allows scrolling up or down when viewing a file.
        Many packages use it for paging the output.</para>
      </listitem>

      <listitem>
        <para>Libcap</para>

        <para>This package implements the userspace interfaces to
        the POSIX 1003.1e capabilities available in Linux kernels.
        </para>
      </listitem>

      <listitem>
        <para>Libelf</para>

        <para>The elfutils project provides libraries and tools for ELF files
        and DWARF data.  Most utilities in this package are available in
        other packages, but the library is needed to build the Linux
        kernel using the default (and most efficient) configuration.</para>

      </listitem>

      <listitem>
        <para>Libffi</para>

        <para>This package implements a portable, high level programming
        interface to various calling conventions.  Some programs may not know
        at the time of compilation what arguments are to be passed to a
        function. For instance, an interpreter may be told at run-time about
        the number and types of arguments used to call a given function. Libffi
        can be used in such programs to provide a bridge from the interpreter
        program to compiled code.</para>

      </listitem>

      <listitem>
        <para>Libpipeline</para>

        <para>The Libpipeline package supplies a library for manipulating
        pipelines of subprocesses in a flexible and convenient way. It is
        required by the Man-DB package.</para>
      </listitem>

      <listitem>
        <para>Libtool</para>

        <para>This package contains the GNU generic library support
        script. It wraps the complexity of using shared libraries into a
        consistent, portable interface.  It is needed by the test
        suites in other LFS packages.</para>
      </listitem>

      <listitem>
        <para>Libxcrypt</para>

        <para>This package provides the
        <systemitem class='library'>libcrypt</systemitem> library
        needed by various packages (notably, Shadow) for hashing passwords.
        It replaces the obsolete
        <systemitem class='library'>libcrypt</systemitem> implmentation in
        Glibc.</para>
      </listitem>

      <listitem>
        <para>Linux Kernel</para>

        <para>This package is the Operating System.  It is the Linux in
        the GNU/Linux environment.</para>
      </listitem>

      <listitem>
        <para>M4</para>

        <para>This package provides a general text macro processor useful
        as a build tool for other programs.</para>
      </listitem>

      <listitem>
        <para>Make</para>

        <para>This package contains a program for directing the building
        of packages.  It is required by almost every package in LFS.</para>
      </listitem>

      <listitem revision="systemd">
        <para>MarkupSafe</para>

        <para>This package is a Python module for processing strings in
        HTML/XHTML/XML safely.  Jinja2 requires this package.</para>
      </listitem>

      <listitem>
        <para>Man-DB</para>

        <para>This package contains programs for finding and viewing man pages.
        It was chosen instead of the <application>man</application> package
        because of its superior internationalization capabilities.  It supplies
        the man program.</para>
      </listitem>

      <listitem>
        <para>Man-pages</para>

        <para>This package provides the actual contents of the basic
        Linux man pages.</para>
      </listitem>

      <listitem>
        <para>Meson</para>

        <para>This package provides a software tool for automating the building
        of software. The main goal of Meson is to minimize the amount of time
        that software developers need to spend configuring a build
        system.  It's required to build Systemd, as well as many BLFS
        packages.</para>

      </listitem>

      <listitem>
        <para>MPC</para>

        <para>This package supplies arithmetic functions for complex
        numbers. It is required by GCC.</para>
      </listitem>

      <listitem>
        <para>MPFR</para>

        <para>This package contains functions for multiple precision
        arithmetic.  It is required by GCC.</para>
      </listitem>

      <listitem>
        <para>Ninja</para>

        <para>This package furnishes a small build system with a focus on speed.
        It is designed to have its input files generated by a higher-level build
        system, and to run builds as fast as possible.
        This package is required by Meson.</para>

      </listitem>

      <listitem>
        <para>Ncurses</para>

        <para>This package contains libraries for terminal-independent
        handling of character screens.  It is often used to provide
        cursor control for a menuing system. It is needed by a number of
        the packages in LFS.</para>
      </listitem>

      <listitem>
        <para>Openssl</para>

        <para>This package provides management tools and libraries relating to
        cryptography. These supply cryptographic functions to
        other packages, including the Linux kernel.</para>
      </listitem>

      <listitem>
        <para>Patch</para>

        <para>This package contains a program for modifying or creating files by
        applying a <emphasis>patch</emphasis> file typically created
        by the <application>diff</application> program.  It is needed by
        the build procedure for several LFS packages.</para>
      </listitem>

      <listitem>
        <para>Perl</para>

        <para>This package is an interpreter for the runtime language
        PERL. It is needed for the installation and test suites of several LFS
        packages.</para>
      </listitem>

      <listitem>
        <para>Pkgconf</para>

        <para>This package contains a program which helps to configure
        compiler and linker flags for development libraries.  The program
        can be used as a drop-in replacement of
        <command>pkg-config</command>, which is needed by the building
        system of many packages.  It's maintained more actively and slightly
        faster than the original Pkg-config package.</para>
      </listitem>

      <listitem>
        <para>Procps-NG</para>

        <para>This package contains programs for monitoring processes. These
        programs are useful for system administration, and are also used by
        the LFS Bootscripts.</para>
      </listitem>

      <listitem>
        <para>Psmisc</para>

        <para>This package produces programs for displaying information
        about running processes. These programs are useful for system
        administration.</para>
      </listitem>

      <listitem>
        <para>Python 3</para>

        <para>This package provides an interpreted language that has a design
        philosophy emphasizing code readability.</para>

      </listitem>

      <listitem>
        <para>Readline</para>

        <para>This package is a set of libraries that offer command-line
        editing and history capabilities.  It is used by Bash.</para>
      </listitem>

      <listitem>
        <para>Sed</para>

        <para>This package allows editing of text without opening it in a
        text editor. It is also needed by many LFS packages' configure
        scripts.</para>
      </listitem>

      <listitem>
        <para>Shadow</para>

        <para>This package contains programs for handling passwords
        securely.</para>
      </listitem>

      <listitem revision="sysv">
        <para>Sysklogd</para>

        <para>This package supplies programs for logging system messages,
        such as those emitted by the kernel or daemon processes when unusual
        events occur.</para>
      </listitem>

      <listitem revision="systemd">
        <para>Systemd</para>

        <para>This package provides an <application>init</application> program
        and several additional boot and system control capabilities as an
        alternative to Sysvinit.  It is used by many Linux distributions.
        </para>
      </listitem>

      <listitem revision="sysv">
        <para>Sysvinit</para>

        <para>This package provides the <application>init</application>
        program, the parent of all the other processes on a running Linux
        system. </para>
      </listitem>

      <listitem>
        <para>Tar</para>

        <para>This package provides archiving and extraction capabilities
        of virtually all the packages used in LFS.</para>
      </listitem>

      <listitem>
        <para>Tcl</para>

        <para>This package contains the Tool Command Language used
        in many test suites.</para>
      </listitem>

      <listitem>
        <para>Texinfo</para>

        <para>This package supplies programs for reading, writing, and
        converting info pages.  It is used in the installation
        procedures of many LFS packages.</para>
      </listitem>

      <listitem>
        <para>Util-linux</para>

        <para>This package contains miscellaneous utility programs.
        Among them are utilities for handling file systems, consoles,
        partitions, and messages.</para>
      </listitem>

      <listitem>
        <para>Vim</para>

        <para>This package provides an editor. It was chosen because of its
        compatibility with the classic vi editor and its huge number of powerful
        capabilities.  An editor is a very personal choice for
        many users. Any other editor can be substituted, if you wish.</para>
      </listitem>
      
      <listitem>
        <para>Wheel</para>

        <para>This package supplies a Python module that is the
        reference implementation of the Python wheel packaging standard.
        </para>
      </listitem>

      <listitem>
        <para>XML::Parser</para>

        <para>This package is a Perl module that interfaces with Expat.</para>
      </listitem>

      <listitem>
        <para>XZ Utils</para>

        <para>This package contains programs for compressing and decompressing
        files.  It provides the highest compression generally available
        and is useful for decompressing packages in XZ or LZMA format.</para>
      </listitem>

      <listitem>
        <para>Zlib</para>

        <para>This package contains compression and decompression routines
        used by some programs.</para>
      </listitem>

      <listitem>
        <para>Zstd</para>

        <para>This package supplies compression and decompression routines
        used by some programs. It provides high compression ratios and a very
        wide range of compression / speed trade-offs.</para>
      </listitem>

    </itemizedlist>

</sect1>