dev-manual, ref-manual: Noting TMPDIR cannot be on NFS

Fixes [YOCTO #5442]

Updated the TMPDIR variable to call out the scenario where a user
might want to separtely set TMPDIR to a local drive and thus be
able to have the Build Directory on NFS.

Updated the "Build Directory" term with a note indicating that by
default, TMPDIR is inside the Build Directory and thus cannot be
on NFS.  However, the user is able to by-pass that per setting
TMPDIR separately outside of the Build Directory.

(From yocto-docs rev: a5a308c512a3f4285bce16f17974dbf6b67432b2)

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

1 files changed, 20 insertions, 4 deletions

diff --git a/documentation/dev-manual/dev-manual-newbie.xml b/documentation/dev-manual/dev-manual-newbie.xml
index 1245345cc4..3d4a9b225f 100644
--- a/documentation/dev-manual/dev-manual-newbie.xml
+++ b/documentation/dev-manual/dev-manual-newbie.xml
@@ -520,9 +520,10 @@
                 </para></listitem>
             <listitem>
                 <para id='build-directory'><emphasis>Build Directory:</emphasis>
-                This term refers to the area used by the OpenEmbedded build system for builds.
-                The area is created when you <filename>source</filename> the setup
-                environment script that is found in the Source Directory
+                This term refers to the area used by the OpenEmbedded build
+                system for builds.
+                The area is created when you <filename>source</filename> the
+                setup environment script that is found in the Source Directory
                 (i.e. <ulink url='&YOCTO_DOCS_REF_URL;#structure-core-script'><filename>&OE_INIT_FILE;</filename></ulink>
                 or
                 <ulink url='&YOCTO_DOCS_REF_URL;#structure-memres-core-script'><filename>oe-init-build-env-memres</filename></ulink>).
@@ -566,7 +567,22 @@
      $ source $HOME/poky/&OE_INIT_FILE; $HOME/mybuilds/YP-&POKYVERSION;
                             </literallayout></para></listitem>
                     </itemizedlist>
-                </para></listitem>
+                    <note>
+                        By default, the Build Directory contains
+                        <ulink url='&YOCTO_DOCS_REF_URL;#var-TMPDIR'><filename>TMPDIR</filename></ulink>,
+                        which is a temporary directory the build system uses for
+                        its work.
+                        <filename>TMPDIR</filename> cannot be under NFS.
+                        Thus, by default, the Build Directory cannot be under NFS.
+                        However, if you need the Build Directory to be under NFS,
+                        you can set this up by setting <filename>TMPDIR</filename>
+                        in your <filename>local.conf</filename> file
+                        to use a local drive.
+                        Doing so effectively separates <filename>TMPDIR</filename>
+                        from <filename>TOPDIR</filename>, which is the Build
+                        Directory.
+                    </note>
+                    </para></listitem>
             <listitem><para id='build-system-term'><emphasis>Build System:</emphasis>
                 In the context of the Yocto Project,
                 this term refers to the OpenEmbedded build system used by the project.