ref-manual: Updates to deal with installing packages in initramfs

Fixes [YOCTO #4961]

Documented the user requirement to use PACKAGE_INSTALL to specify
packages for installation into an initramfs image.  Normally,
you use IMAGE_INSTALL.  To account for this user model, I updated
the PACKAGE_INSTALL and IMAGE_INSTALL variables.  I also added
a bit more information to the "Images" chapter item that
talks about the core-image-minimal-initramfs image.

(From yocto-docs rev: a1ad649cf310f281a7de584d5b9a1820ca99d4eb)

Signed-off-by: Scott Rifenbark <scott.m.rifenbark@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

1 files changed, 6 insertions, 2 deletions

diff --git a/documentation/ref-manual/ref-images.xml b/documentation/ref-manual/ref-images.xml
index 529decfc96..b12c49ac78 100644
--- a/documentation/ref-manual/ref-images.xml
+++ b/documentation/ref-manual/ref-images.xml
@@ -61,10 +61,14 @@
             The image includes headers and libraries you can use in a host development
             environment.
             </para></listitem>
-        <listitem><para><emphasis><filename>core-image-minimal-initramfs</filename>:</emphasis>
+        <listitem><para id='images-core-image-minimal-initramfs'><emphasis><filename>core-image-minimal-initramfs</filename>:</emphasis>
             A <filename>core-image-minimal</filename> image that has the Minimal RAM-based
-            Initial Root Filesystem (<filename>initramfs</filename>) as part of the kernel,
+            Initial Root Filesystem (initramfs) as part of the kernel,
             which allows the system to find the first “init” program more efficiently.
+            See the
+            <link linkend='var-PACKAGE_INSTALL'><filename>PACKAGE_INSTALL</filename></link>
+            variable for additional information helpful when working with
+            initramfs images.
             </para></listitem>
         <listitem><para><emphasis><filename>core-image-minimal-mtdutils</filename>:</emphasis>
             A <filename>core-image-minimal</filename> image that has support