1 files changed, 72 insertions, 0 deletions
diff --git a/bitbake/doc/bitbake-user-manual/bitbake-user-manual-metadata.xml b/bitbake/doc/bitbake-user-manual/bitbake-user-manual-metadata.xml
index 199ab23095..a125ad332e 100644
--- a/bitbake/doc/bitbake-user-manual/bitbake-user-manual-metadata.xml
+++ b/bitbake/doc/bitbake-user-manual/bitbake-user-manual-metadata.xml
@@ -61,6 +61,78 @@
            </para>
        </section>
+        <section id='modifying-existing-variables'>
+            <title>Modifying Existing Variables</title>
+            <para>
+                Sometimes you need to modify existing variables.
+                Following are some cases where you might find you want to
+                modify an existing variable:
+                <itemizedlist>
+                    <listitem><para>
+                        Customize a recipe that uses the variable.
+                        </para></listitem>
+                    <listitem><para>
+                        Change a variable's default value used in a
+                        <filename>*.bbclass</filename> file.
+                        </para></listitem>
+                    <listitem><para>
+                        Change the variable in a <filename>*.bbappend</filename>
+                        file to override the variable in the original recipe.
+                        </para></listitem>
+                    <listitem><para>
+                        Change the variable in a configuration file so that the
+                        value overrides an existing configuration.
+                        </para></listitem>
+                </itemizedlist>
+            </para>
+            <para>
+                Changing a variable value can sometimes depend on how the
+                value was originally assigned and also on the desired
+                intent of the change.
+                In particular, when you append a value to a variable that
+                has a default value, the resulting value might not be what
+                you expect.
+                In this case, the value you provide might replace the value
+                rather than append to the default value.
+            </para>
+            <para>
+                If after you have changed a variable's value and something
+                unexplained occurs, you can use BitBake to check the actual
+                value of the suspect variable.
+                You can make these checks for both configuration and recipe
+                level changes:
+                <itemizedlist>
+                    <listitem><para>
+                        For configuration changes, use the following:
+                        <literallayout class='monospaced'>
+     $ bitbake -e
+                        </literallayout>
+                        This command displays variable values after the
+                        configuration files (i.e. <filename>local.conf</filename>,
+                        <filename>bblayers.conf</filename>,
+                        <filename>bitbake.conf</filename> and so forth) have
+                        been parsed.
+                        <note>
+                            Variables that are exported to the environment are
+                            preceded by the string "export" in the command's
+                            output.
+                        </note>
+                        </para></listitem>
+                    <listitem><para>
+                        For recipe changes, use the following:
+                        <literallayout class='monospaced'>
+     $ bitbake <replaceable>recipe</replaceable> -e | grep VARIABLE="
+                        </literallayout>
+                        This command checks to see if the variable actually
+                        makes it into a specific recipe.
+                        </para></listitem>
+                </itemizedlist>
+            </para>
+        </section>
        <section id='line-joining'>
            <title>Line Joining</title>

diff --git a/bitbake/doc/bitbake-user-manual/bitbake-user-manual-metadata.xml b/bitbake/doc/bitbake-user-manual/bitbake-user-manual-metadata.xml index 199ab23095..a125ad332e 100644 --- a/bitbake/doc/bitbake-user-manual/bitbake-user-manual-metadata.xml +++ b/bitbake/doc/bitbake-user-manual/bitbake-user-manual-metadata.xml
@@ -61,6 +61,78 @@
61	</para>	61	</para>
62	</section>	62	</section>
63		63
		64	<section id='modifying-existing-variables'>
		65	<title>Modifying Existing Variables</title>
		66
		67	<para>
		68	Sometimes you need to modify existing variables.
		69	Following are some cases where you might find you want to
		70	modify an existing variable:
		71	<itemizedlist>
		72	<listitem><para>
		73	Customize a recipe that uses the variable.
		74	</para></listitem>
		75	<listitem><para>
		76	Change a variable's default value used in a
		77	<filename>*.bbclass</filename> file.
		78	</para></listitem>
		79	<listitem><para>
		80	Change the variable in a <filename>*.bbappend</filename>
		81	file to override the variable in the original recipe.
		82	</para></listitem>
		83	<listitem><para>
		84	Change the variable in a configuration file so that the
		85	value overrides an existing configuration.
		86	</para></listitem>
		87	</itemizedlist>
		88	</para>
		89
		90	<para>
		91	Changing a variable value can sometimes depend on how the
		92	value was originally assigned and also on the desired
		93	intent of the change.
		94	In particular, when you append a value to a variable that
		95	has a default value, the resulting value might not be what
		96	you expect.
		97	In this case, the value you provide might replace the value
		98	rather than append to the default value.
		99	</para>
		100
		101	<para>
		102	If after you have changed a variable's value and something
		103	unexplained occurs, you can use BitBake to check the actual
		104	value of the suspect variable.
		105	You can make these checks for both configuration and recipe
		106	level changes:
		107	<itemizedlist>
		108	<listitem><para>
		109	For configuration changes, use the following:
		110	<literallayout class='monospaced'>
		111	$ bitbake -e
		112	</literallayout>
		113	This command displays variable values after the
		114	configuration files (i.e. <filename>local.conf</filename>,
		115	<filename>bblayers.conf</filename>,
		116	<filename>bitbake.conf</filename> and so forth) have
		117	been parsed.
		118	<note>
		119	Variables that are exported to the environment are
		120	preceded by the string "export" in the command's
		121	output.
		122	</note>
		123	</para></listitem>
		124	<listitem><para>
		125	For recipe changes, use the following:
		126	<literallayout class='monospaced'>
		127	$ bitbake <replaceable>recipe</replaceable> -e \| grep VARIABLE="
		128	</literallayout>
		129	This command checks to see if the variable actually
		130	makes it into a specific recipe.
		131	</para></listitem>
		132	</itemizedlist>
		133	</para>
		134	</section>
		135
64	<section id='line-joining'>	136	<section id='line-joining'>
65	<title>Line Joining</title>	137	<title>Line Joining</title>
66		138