systemd-custom: add a section discussing core dumps

git-svn-id: http://svn.linuxfromscratch.org/LFS/trunk/BOOK@11781 4aa44e1e-78dd-0310-a6d2-fbcd4c07a689

chapter07/systemd-custom.xml

@@ -209,6 +209,52 @@ EOF</userinput></screen>
 
   </sect2>
 
+  <sect2>
+    <title>Working with Core Dumps</title>
+
+    <para>Core dumps are useful to debug crashed programs, especially
+    when a daemon process crashes. On systemd booted systems the core
+    dumping is handled by <command>systemd-coredump</command>.  It will
+    log the core dump into the journal and store the core dump itself in
+    <filename class="directory">/var/lib/systemd/coredump</filename>.
+    To retrieve and process core dumps, <command>coredumpctl</command>
+    tool is provided.  Here are some examples of frequently used commands:
+    </para>
+
+    <itemizedlist>
+      <listitem>
+        <para><command>coredumpctl -r</command>: lists all core dumps in
+        reversed chronological order.</para>
+      </listitem>
+      <listitem>
+        <para><command>coredumpctl -1 info</command>: show the information
+        of the last core dump.</para>
+      </listitem>
+      <listitem>
+        <para><command>coredumpctl -1 debug</command>: load the last core
+        dump into <ulink url="&blfs-book;general/gdb.html">GDB</ulink>.
+        </para>
+      </listitem>
+    </itemizedlist>
+
+    <para>Core dumps may use a lot of disk space.  The maximum disk space
+    used by core dumps can be limited by creating a configuration file in
+    <filename class="directory">/etc/systemd/coredump.conf.d</filename>.
+    For example:</para>
+
+<screen role="nodump"><userinput>mkdir -pv /etc/systemd/coredump.conf.d
+
+cat &gt; /etc/systemd/coredump.conf.d/maxuse.conf &lt;&lt; EOF
+<literal>[Coredump]
+MaxUse=5G</literal>
+EOF</userinput></screen>
+
+    <para>See <filename>systemd-coredump(8)</filename>,
+    <filename>coredumpctl(1)</filename>, and
+    <filename>coredump.conf.d(5)</filename> manual pages for more
+    information.</para>
+  </sect2>
+
   <sect2>
     <title>Long Running Processes</title>