3 files changed, 48 insertions, 2 deletions

diff --git a/documentation/poky-ref-manual/ref-structure.xml b/documentation/poky-ref-manual/ref-structure.xml
index c2644df374..166907ceef 100644
--- a/documentation/poky-ref-manual/ref-structure.xml
+++ b/documentation/poky-ref-manual/ref-structure.xml
@@ -247,11 +247,20 @@
         <title><filename>build/conf/bblayers.conf</filename></title>
 
         <para>
-            This file defines layers, which is a directory tree, traversed (or walked) by BitBake. 
+            This file defines layers, which are directory trees, traversed (or walked) by BitBake.
             If <filename>bblayers.conf</filename> 
             is not present, it is created from <filename>bblayers.conf.sample</filename> when 
             you <filename>source</filename> the environment setup script.
         </para>
+
+        <para>
+            The <filename>bblayers.conf</filename> file uses the
+            <link linkend='var-BBLAYERS'><filename>BBLAYERS</filename></link> variable to
+            list the layers BitBake tries to find.
+            The file uses the
+            <link linkend='var-BBLAYERS_NON_REMOVABLE'><filename>BBLAYERS_NON_REMOVABLE</filename></link>
+            variable to list layers that must not be removed.
+        </para>
     </section>
 
     <section id='structure-build-conf-sanity_info'>
diff --git a/documentation/poky-ref-manual/ref-variables.xml b/documentation/poky-ref-manual/ref-variables.xml
index 9ced42499e..0de6bfcf5c 100644
--- a/documentation/poky-ref-manual/ref-variables.xml
+++ b/documentation/poky-ref-manual/ref-variables.xml
@@ -422,6 +422,11 @@
        /home/scottrif/poky/meta-yocto-bsp \
        /home/scottrif/poky/meta-mykernel \
        "
+
+     BBLAYERS_NON_REMOVABLE ?= " \
+       /home/scottrif/poky/meta \
+       /home/scottrif/poky/meta-yocto \
+       "
                     </literallayout>
                     This example enables four layers, one of which is a custom, user-defined layer 
                     named <filename>meta-mykernel</filename>.
@@ -429,6 +434,34 @@
             </glossdef>
         </glossentry>
 
+        <glossentry id='var-BBLAYERS_NON_REMOVABLE'><glossterm>BBLAYERS_NON_REMOVABLE</glossterm>
+            <glossdef>
+Core layer for images cannot be removed
+                <para>Lists core layers that cannot be removed from the
+                    <filename>bblayers.conf</filename> file.
+                    In order for BitBake to build your image, your
+                    <filename>bblayers.conf</filename> file must include the
+                    <filename>meta</filename> and <filename>meta-yocto</filename>
+                    core layers.
+                    Here is an example that shows these two layers listed in
+                    the <filename>BBLAYERS_NON_REMOVABLE</filename> statement:
+                    <literallayout class='monospaced'>
+     BBLAYERS = " \
+       /home/scottrif/poky/meta \
+       /home/scottrif/poky/meta-yocto \
+       /home/scottrif/poky/meta-yocto-bsp \
+       /home/scottrif/poky/meta-mykernel \
+       "
+
+     BBLAYERS_NON_REMOVABLE ?= " \
+       /home/scottrif/poky/meta \
+       /home/scottrif/poky/meta-yocto \
+       "
+                    </literallayout>
+                </para>
+            </glossdef>
+        </glossentry>
+
         <glossentry id='var-BP'><glossterm>BP</glossterm>
             <glossdef>
                 <para>The base recipe name and version but without any special 
diff --git a/documentation/poky-ref-manual/technical-details.xml b/documentation/poky-ref-manual/technical-details.xml
index 654d9252a9..042a96ed87 100644
--- a/documentation/poky-ref-manual/technical-details.xml
+++ b/documentation/poky-ref-manual/technical-details.xml
@@ -662,7 +662,11 @@
         /home/nitin/prj/poky.git/meta-yocto \
         /home/nitin/prj/poky.git/meta-yocto-bsp \
         /home/nitin/prj/meta-x32.git \
-     "
+        "
+     BBLAYERS_NON_REMOVABLE ?= " \
+        /home/nitin/prj/poky.git/meta \
+        /home/nitin/prj/poky.git/meta-yocto \
+        "
                     </literallayout></para></listitem>
                 <listitem><para>Enable the x32 psABI tuning file for <filename>x86_64</filename>
                     machines by editing the <filename>conf/local.conf</filename> like this: