source: introduction/welcome/conventions.xml

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<sect1 id="conventions">
  <?dbhtml filename="conventions.html"?>


  <title>Conventions Used in this Book</title>

  <sect2>
  <title>Typographical Conventions</title>
  <para>To make things easy to follow, a number of conventions are used
  throughout the book.  Here are some examples:</para>

<screen><userinput>./configure --prefix=/usr</userinput></screen>

  <blockquote>
    <para>This form of text should be typed exactly as shown unless
    otherwise noted in the surrounding text. It is also used to identify
    references to specific commands.</para>
  </blockquote>

<screen><computeroutput>install-info: unknown option
`--dir-file=/mnt/lfs/usr/info/dir'</computeroutput></screen>

  <blockquote>
    <para>This form of text (fixed width font) shows screen
    output, probably the result of issuing a command. It is also used to
    show filenames such as <filename>/boot/grub/grub.conf</filename></para>
  </blockquote>

  <note>
    <para>Please configure your browser to display fixed-width text with
    a good monospaced font, with which you can distinguish the glyphs of
    <literal>Il1</literal> or <literal>O0</literal> clearly.</para>
  </note>

  <para><emphasis>Emphasis</emphasis></para>

  <blockquote>
    <para>This form of text is used for several purposes,
    but mainly to emphasize important points, or to give examples of
    what to type.</para>
  </blockquote>

  <para><ulink url="https://www.&lfs-domainname;/"/></para>

  <blockquote>
    <para>This form of text is used for hypertext links external to
    the book, such as HowTos, download locations, websites, etc.</para>
  </blockquote>

  <para><xref linkend="seamonkey"/></para>

  <blockquote>
    <para>This form of text is used for links internal to
    the book, such as another section describing a different package.</para>
  </blockquote>

<screen><userinput>cat &gt; $LFS/etc/group &lt;&lt; "EOF"
<literal>root:x:0:
bin:x:1:
......</literal>
EOF</userinput></screen>

  <blockquote>
    <para>This style is mainly used when creating configuration
    files.  The first command (in bold) tells the system to create
    the file <filename>$LFS/etc/group</filename> from whatever is typed on the
    following lines, until the sequence EOF is encountered.
    Therefore, this whole section is usually typed exactly as shown.
    Remember, copy and paste is your friend!</para>
  </blockquote>

  <para><replaceable>&lt;REPLACED TEXT&gt;</replaceable></para>

  <blockquote>
    <para>This form of text is used to encapsulate text that should be
    modified, and is not to be typed as shown, or copied and pasted.
    The angle brackets are not part of the literal text; they are part of the
    substitution.</para>
  </blockquote>

  <para><systemitem class='username'>root</systemitem></para>

  <blockquote>
    <para>This form of text is used to show a specific system user or group
    reference in the instructions.</para>
  </blockquote>

  <para>&nbsp;</para> <!-- add extra white space to improve readability -->
  </sect2>

  <sect2>
  <title>Conventions Used for Package Dependencies</title>

    <para>When new packages are created, the software's authors depend on prior work.  In
    order to build a package in BLFS, these dependencies must be built before
    the desired package can be compiled.  For each package, prerequisites are listed
    in one or more separate sections:  Required, Recommended, and Optional.</para>

    <bridgehead renderas="sect3">Required Dependencies</bridgehead>

    <para>These dependencies are the bare minimum needed to
    build the package.  Packages in LFS, and the required
    dependencies of these required packages, are omitted from this list.
    Always remember to check for nested dependencies. If a dependency is
    said to be <quote>runtime</quote>, then it is not needed for building
    the package, but only to use it after installation.</para>

    <bridgehead renderas="sect3">Recommended Dependencies</bridgehead>

    <para>These are dependencies the BLFS editors have determined
    are important to give the package reasonable capabilities.  If a
    recommended dependency is not said to be <quote>runtime</quote>, package
    installation instructions assume it is installed.  If it
    is not installed, the instructions may require modification, to
    accommodate the missing package. A recommended <quote>runtime</quote>
    dependency does not need to be installed before building the package, but
    must be built afterwards for running the package with reasonable
    capabilities.</para>

    <bridgehead renderas="sect3">Optional Dependencies</bridgehead>

    <para>These are dependencies the package <emphasis>may</emphasis> use.  Integration
    of optional dependencies may be automatic by the package, or
    additional steps not presented by BLFS may be necessary.  Optional dependencies are
    sometimes listed without explicit BLFS instructions.  In this case you must
    determine how to perform the installation yourself.</para>

    <para>&nbsp;</para> <!-- add extra white space to improve readability -->
  </sect2>

  <sect2>
  <title>Conventions Used for Kernel Configuration Options</title>

    <para>Some packages require specific kernel configuration options.
    The general layout for these looks like this:</para>

    <xi:include xmlns:xi="http://www.w3.org/2001/XInclude"
      href="conventions-kernel.xml"/>

    <para>[...] on the right gives the symbolic name of the option, so you
    can easily check whether it is set in your <filename>.config</filename>
    file. Note that the <filename>.config</filename> file contains a
    <literal>CONFIG_</literal> prefix before all symbolic names.  The
    meaning of the various entries is:

    <blockquote>
    <informaltable frame='none'><tgroup cols="2">
      <colspec align="left"/><colspec align="left"/><tbody>
      <row>
        <entry><emphasis role="bold">Master section</emphasis></entry>
        <entry>top level menu item</entry>
      </row>
      <row>
        <entry><emphasis role="bold">Subsection</emphasis></entry>
        <entry>submenu item</entry>
      </row>
      <row>
        <entry>
          <emphasis role="bold">Required parameter</emphasis></entry>
        <entry>
          the option can either be built-in, or not selected: it must be
          selected
        </entry>
      </row>
      <row>
        <entry>
          <emphasis role="bold">Required parameter (not as
          module)</emphasis>
        </entry>
        <entry>
          the option can be built-in, a module, or not selected (tri-state):
          it must be selected as built-in
        </entry>
      </row>
      <row>
        <entry>
          <emphasis role="bold">Required parameter (could be
          a module)</emphasis>
        </entry>
        <entry>
          the option can be built-in, a module, or not selected:
          it must be selected, either as built-in or as a module
        </entry>
      </row>
      <row>
        <entry>
          <emphasis role="bold">Required parameter (as
          a module)</emphasis>
        </entry>
        <entry>
          the option can be built-in, a module, or not selected:
          it must be selected as a module; selecting it as built-in
          may cause unwanted effects
        </entry>
      </row>
      <row>
        <entry>
          <emphasis role="bold">Optional parameter</emphasis>
        </entry>
        <entry>
          the option can be built-in, a module, or not
          selected: it may be selected as a module or built-in if you
          need it for driving the hardware or optional kernel features
        </entry>
      </row>
      <row>
        <entry>
          <emphasis role="bold">Optional parameter (as a module
          if enabled)</emphasis>
        </entry>
        <entry>
          the option can be built-in, a module, or not
          selected: it may be selected as a module if you need it
          for driving the hardware or optional kernel features, but
          selecting it as built-in may cause unwanted effects
        </entry>
      </row>
      <row>
        <entry>
          <emphasis role="bold">Incompatible parameter</emphasis>
        </entry>
        <entry>
          the option can either be built-in or not selected: it must
          <emphasis>not</emphasis> be selected
        </entry>
      </row>
      <row>
        <entry>
          <emphasis role="bold">Incompatible parameter (even as module)</emphasis>
        </entry>
        <entry>
          the option can be built-in, a module, or not selected:
          it must <emphasis>not</emphasis> be selected
        </entry>
      </row>
    </tbody></tgroup></informaltable>
    </blockquote>
    </para>

    <para>Note that, depending on other selections, the angle brackets
    (&lt;&gt;) in the configuration menu may appear as braces ({}) if the option cannot be unselected,
    or even as dashes (-*- or -M-), when the choice is imposed.
    The help text describing the option specifies the other selections on which this
    option relies, and how those other selections are set.</para>

    <para>
      The letter in <emphasis role='blue'>blue</emphasis> is the hotkey
      for this option.  If you are running
      <command>make menuconfig</command>, you can press a key to quickly
      traverse all the options with this key as the hotkey on the screen.
    </para>

    <para>&nbsp;</para> <!-- add extra white space to improve readability -->
  </sect2>

  <sect2>
  <title>SBU values in BLFS</title>

    <para>As in LFS, each package in BLFS has a build time listed in Standard
    Build Units (SBUs).   These times are relative to the time it took to build
    binutils in LFS, and are intended to provide some insight into how long it
    will take to build a package. Most times listed are for a single processor
    or core to build the package. In some cases, large, long running builds
    tested on multi-core systems have SBU times listed with comments such
    as '(parallelism=4)'.  These values indicate testing was done using
    multiple cores.  Note that while this speeds up the build on systems with
    the appropriate hardware, the speedup is not linear and to some extent
    depends on the individual package and the specific hardware used.  </para>

    <para>For packages which use ninja (i.e., anything using meson) or rust, by
    default all cores are used; similar comments will be seen on such packages
    even when the build time is minimal.</para>

    <para>Where even a parallel build takes more than 15 SBU, on certain
    machines the time may be considerably greater even when the build does not
    use swap. In particular, different micro-architectures will build some
    files at different relative speeds, and this can introduce delays when
    certain make targets wait for another file to be created. Where a large
    build uses a lot of C++ files, processors with Simultaneous Multi Threading
    will share the Floating Point Unit and can take 45% longer than when using
    four 'prime' cores (measured on an intel i7 using taskset and keeping the
    other cores idle).</para>

    <para>Some packages do not support parallel builds; for these, the
    make command must specify -j1.  Packages that are known to impose such limits are
    so marked in the text.</para>

  </sect2>

</sect1>