lfs-book-zh_CN/prologue/audience.xml

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

<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 LFS's existence is to help people learn
how a Linux system works from the inside out. Building an LFS system
helps demonstrate what makes Linux tick, and how things work together
and depend on each other. One of the best things that this learning
experience provides is the ability to customize Linux to your own
tastes and needs.</para>

<para>A key benefit of LFS is that it allows users to have more
control over the system without relying on someone else's Linux
implementation.  With LFS, <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 LFS 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 worse, CPU cycles. It is
not difficult to build an LFS 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 LFS 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. LFS, on the other hand, does not give you a hamburger.
Rather, LFS 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 LFS with a
finished house. LFS provides the skeletal plan of a house, but it is up
to you to build it. LFS maintains the freedom to adjust plans
throughout the process, customizing it to the user's needs and
preferences.</para>

<para>An additional advantage of a custom built Linux system is
security. 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 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 while learning along the way, then this book is your best
choice.</para> 

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

</sect1>