svn commit: r40602 - head/en_US.ISO8859-1/books/faq

[Eitan Adler]

Author: eadler
Date: Sun Jan 13 06:11:30 2013
New Revision: 40602
URL: http://svnweb.freebsd.org/changeset/doc/40602

Log:
  Update and expand on the why-kernel-big question in the handbook.
  
  PR:		docs/174244
  Submitted by:	Bas Smeelen <b.smeelen at ose.nl>
  Approved by:	bcr (mentor)

Modified:
  head/en_US.ISO8859-1/books/faq/book.xml

Modified: head/en_US.ISO8859-1/books/faq/book.xml
==============================================================================
--- head/en_US.ISO8859-1/books/faq/book.xml	Sun Jan 13 06:09:00 2013	(r40601)
+++ head/en_US.ISO8859-1/books/faq/book.xml	Sun Jan 13 06:11:30 2013	(r40602)
@@ -3297,17 +3297,27 @@ kern.timecounter.hardware: TSC -> i82
 	</question>
 
 	<answer>
-	  <para>Chances are, you compiled your kernel in <emphasis>debug
-	    mode</emphasis>.  Kernels built in debug mode contain many
-	    symbols that are used for debugging, thus greatly increasing
-	    the size of the kernel.  Note that there will be little or
-	    no performance decrease from running a debug kernel, and it
-	    is useful to keep one around in case of a system
-	    panic.</para>
-
-	  <para>However, if you are running low on disk space, or you
-	    simply do not want to run a debug kernel, make sure that
-	    both of the following are true:</para>
+	  <para>GENERIC kernels shipped with &os; and later are compiled
+	    in <emphasis>debug mode</emphasis>. Kernels built in debug mode
+	    contain many symbols in separate files that are used for
+	    debugging, thus greatly increasing the size of
+	    <filename class="directory">/boot/kernel/</filename>
+	    Note that there will be little or no performance loss
+	    from running a debug kernel, and it is useful to keep one around
+	    in case of a system panic.</para>
+
+	  <para>However, if you are running low on disk space, there are
+	    different options to reduce the size of /boot/kernel/.</para>
+
+	  <para>If you do not want the symbol files to be installed,
+	    make sure you have the following line present in /etc/src.conf:
+
+	    <programlisting>WITHOUT_KERNEL_SYMBOLS=yes</programlisting>
+
+	    For more information see &man.src.conf.5</para>
+
+	  <para>If you do not want to build a debug kernel, make
+	    sure that both of the following are true:</para>
 
 	  <itemizedlist>
 	    <listitem>
@@ -3325,9 +3335,32 @@ kern.timecounter.hardware: TSC -> i82
 
 	  <para>Either of the above settings will cause your kernel to
 	    be built in debug mode.  As long as you make sure you follow
-	    the steps above, you can build your kernel normally, and you
-	    should notice a fairly large size decrease; most kernels
-	    tend to be around 1.5 MB to 2 MB.</para>
+	    the steps above, you can build your kernel normally</para>
+
+	  <para>If you want only the modules you use to be built
+	    and installed, make sure you have a line like below in
+	    /etc/make.conf:</para>
+
+	  <programlisting>MODULES_OVERRIDE= <replaceable>accf_http ipfw</replaceable></programlisting>
+
+	  <para>Replace <emphasis>accf_httpd ipfw</emphasis> with a list
+	    of modules you need. Only these modules will be built. This
+	    does not only reduce the size of the kernel directory but
+	    also decreases the amount of time needed to build your kernel.
+	    For more information see
+	    <filename>/usr/share/examples/etc/make.conf</filename>
+	    </para>
+
+	  <para>You can also remove unneeded devices from your kernel
+	    to further reduce the size. See
+	    <xref linkend="make-kernel"/> for more information.</para>
+
+	  <para>To put any of these options into effect you will have
+	    to <ulink url="&url.books.handbook;/kernelconfig-building.html">build and install</ulink>
+	    your new kernel.</para>
+
+	  <para>Most kernels (/boot/kernel/kernel)
+	    tend to be around 12 MB to 16 MB.</para>
 	</answer>
       </qandaentry>