source: chapter08/introduction.xml@ a2434bd4

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<sect1 id="ch-system-introduction">
  <?dbhtml filename="introduction.html"?>

  <title>Introduction</title>

  <para>In this chapter, we start constructing the LFS system in earnest.
  </para>

  <para>The installation of this software is straightforward. Although in many
  cases the installation instructions could be made shorter and more generic,
  we have opted to provide the full instructions for every package to minimize
  the possibilities for mistakes.  The key to learning what makes a Linux system
  work is to know what each package is used for and why you (or the system)
  may need it.</para>

  <para>We do not recommend using customized optimizations.  They can make
  a program run slightly faster, but they may also cause compilation
  difficulties, and problems when running the program.  If a package refuses to
  compile with a customized optimization, try to compile it without
  optimization and see if that fixes the problem. Even if the package does compile when using a customized
  optimization, there is the risk it may have been compiled incorrectly because
  of the complex interactions between the code and the build tools.  Also note that
  the <option>-march</option> and <option>-mtune</option> options using values
  not specified in the book have not been tested. This may cause problems with
  the toolchain packages (Binutils, GCC and Glibc).  The small potential gains
  achieved by customizing compiler optimizations are often outweighed by the risks.
  First-time builders of LFS are encouraged to build without custom
  optimizations.</para>

  <para>On the other hand, we keep the optimizations enabled by the default
  configuration of the packages.  In addition, we sometimes explicitly enable an
  optimized configuration provided by a package but not enabled by
  default.  The package maintainers have already tested these configurations
  and consider them safe, so it's not likely they would break the build.
  Generally the default configuration already enables <option>-O2</option>
  or <option>-O3</option>, so the resulting system will still run very fast
  without any customized optimization, and be stable at the same time.</para>

  <para>Before the installation instructions, each installation page provides
  information about the package, including a concise description of what it
  contains, approximately how long it will take to build, and how much disk
  space is required during this building process. Following the installation
  instructions, there is a list of programs and libraries (along with brief
  descriptions) that the package installs.</para>

  <note><para>The SBU values and required disk space include test suite data
  for all applicable packages in <xref linkend="chapter-building-system"/>. SBU
  values have been calculated using a single CPU core (-j1) for all
  operations.</para></note>

  <sect2>
    <title>About Libraries</title>

    <para>In general, the LFS editors discourage building and installing static
    libraries.  Most static libraries have been made
    obsolete in a modern Linux system.  In addition, linking a static library
    into a program can be detrimental.  If an update to the library is needed
    to remove a security problem, every program that uses the static library will
    need to be relinked with the new library.  Since the use of static libraries
    is not always obvious, the relevant programs (and the procedures needed to
    do the linking) may not even be known.</para>

    <para>The procedures in this chapter remove or disable installation of
    most static libraries. Usually this is done by passing a
    <option>--disable-static</option> option to <command>configure</command>.
    In other cases, alternate means are needed. In a few cases, especially
    Glibc and GCC, the use of static libraries remains an essential feature of the
    package building process. </para>

    <para>For a more complete discussion of libraries, see
    <ulink url="&blfs-book;introduction/libraries.html">
    Libraries: Static or shared?</ulink> in the BLFS book.</para>

  </sect2>

</sect1>