Handle environment variables

Manage rabbitmq-env config file that overrides the
defaults built in to the RabbitMQ startup scripts.

Change-Id: I1524ef715600c7b350ad981b15de31d9583f8268
Closes-Bug: PROD-26132
diff --git a/README.rst b/README.rst
index 5cae8aa..ec00f5b 100644
--- a/README.rst
+++ b/README.rst
@@ -175,6 +175,26 @@
         ssl:
          port: 5671
 
+Manage environment variables
+----------------------------
+
+Create a config file with variable settings that override the defaults
+built in to the RabbitMQ startup scripts:
+
+.. code-block:: yaml
+
+   rabbitmq:
+      server:
+        enabled: true
+        ...
+        env_variables:
+          hostname: localhost
+          node_port: 5671
+          export:
+            home: /var/lib/rabbitmq
+            erl_inetrc: /etc/rabbitmq/inetrc
+
+
 Usage
 =====