source: clfs-embedded/BOOK/prologue/common/audience.xml@ a0038b3

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<sect1 id="pre-audience">
  <?dbhtml filename="audience.html"?>

  <title>Audience</title>

  <para>There are many reasons why somebody would want to read this book.
  The principal reason is to install a Linux system from the  source code.
  A question many people raise is, <quote>why go through all the hassle of
  manually building a Linux system from scratch when you can just download
  and install an existing one?</quote> That is a good question and is the
  impetus for this section of the book.</para>

  <para>One important reason for the existence of CLFS is to help people
  understand how a Linux system works.  Building an CLFS system helps
  demonstrate what makes Linux tick, and how things work together and
  depend on each other. One of the best things this learning experience
  provides is the ability to customize Linux to your own
  tastes and needs.</para>

  <para>A key benefit of CLFS is that it allows users to have more control
  over their system without any reliance on a Linux implementation designed
  by someone else.  With CLFS, <emphasis>you</emphasis> are in the driver's
  seat and dictate every aspect of the system, such as the directory layout
  and bootscript setup. You also dictate where, why, and how programs are
  installed.</para>

  <para>Another benefit of CLFS is the ability to create a very compact
  Linux system. When installing a regular distribution, one is often forced
  to include several programs which are probably never used. These programs
  waste disk space or CPU cycles.  It is not difficult to build an CLFS
  system of less than 100 megabytes (MB), which is substantially smaller
  than the majority of existing installations.  Does this still sound like a
  lot of space? A few of us have been working on creating a very small
  embedded CLFS system. We successfully built a system that was specialized
  to run the Apache web server with approximately 8MB of disk space used.
  Further stripping could bring this down to 5 MB or less. Try that with a
  regular distribution! This is only one of the many benefits of designing
  your own Linux implementation.</para>

  <para>We could compare Linux distributions to a hamburger purchased at
  a fast-food restaurant&mdash;you have no idea what might be in what you
  are eating. CLFS, on the other hand, does not give you a hamburger.
  Rather, CLFS provides the recipe to make the exact hamburger desired.
  This allows users to review the recipe, omit unwanted ingredients, and
  add your own ingredients to enhance the flavor of the burger. When you
  are satisfied with the recipe, move on to preparing it. It can be made
  to exact specifications&mdash;broil it, bake it, deep-fry it, or
  barbecue it.</para>

  <para>Another analogy that we can use is that of comparing CLFS with a
  finished house. CLFS provides the skeletal plan of a house, but it is up
  to you to build it. CLFS maintains the freedom to adjust plans throughout
  the process, customizing it to the needs and preferences of the user.</para>

  <para>Security is an additional advantage of a custom built Linux system.
  By compiling the entire system from source code, you are empowered to
  audit everything and apply all the security patches desired. It is no
  longer necessary to wait for somebody else to compile binary packages
  that fix a security hole. Unless you examine the patch and implement it
  yourself, you have no guarantee that the new binary package was built
  correctly and adequately fixes the problem.</para>

  <para>The goal of Cross Linux From Scratch is to build a complete and
  usable foundation-level system. Readers who do not wish to build their
  own Linux system from scratch may not benefit from the information in this
  book. If you only want to know what happens while the computer boots,
  we recommend the <quote>From Power Up To Bash Prompt</quote> HOWTO
  located at <ulink url="http://axiom.anu.edu.au/~okeefe/p2b/"/> or on
  The Linux Documentation Project's (TLDP) website at <ulink
  url="http://www.tldp.org/HOWTO/From-PowerUp-To-Bash-Prompt-HOWTO.html"/>.
  The HOWTO builds a system which is similar to that of this book, but it
  focuses strictly on creating a system capable of booting to a BASH prompt.
  Consider your objective. If you wish to build a Linux system and learn
  along the way, this book is your best choice.</para>

  <para>There are too many good reasons to build your own CLFS system to
  list them all here. This section is only the tip of the iceberg. As
  you continue in your CLFS experience, you will find the power that
  information and knowledge truly bring.</para>

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