Plugins SDK: description of environment_config.yaml

Change-Id: I3255ba5887d6acae5111a54f869da23c96cba741

plugindocs/fuel-plugin-sdk-guide/reference/files/environment_config.rst

@@ -1,4 +1,42 @@
 .. _environment_config.yaml:
 
+=======================
 environment_config.yaml
 =======================
+
+Fuel uses the ``environment_config.yaml`` file for the additional attributes
+that will appear on the :guilabel:`Settings` tab of the Fuel web UI.
+
+When Fuel deploys the environment, these attributes pass to the task executor
+so that the data is available in the ``/etc/astute.yaml`` file on each target
+node and can be accessed from your bash or Puppet scripts.
+
+Example:
+
+.. code-block:: ini
+
+	attributes:
+		metadata:
+			group: 'other'
+			restrictions:
+				- "settings:common.libvirt_type.value == 'kvm'"
+		fuel_plugin_name_attr1:
+			value: 'Set default value'
+			label: 'Text field 1'
+			description: 'Description for text field 1'
+			weight: 25
+			type: 'text'
+		fuel_plugin_name_attr2:
+			value: 'Set default value'
+			label: 'Text field 2'
+			description: 'Description for text field 2'
+			weight: 25
+			type: 'text'
+
+The file should consist of the``attributes`` keywords, followed by ``metadata``
+and the list of atttributes. The ``metadata`` keyword may contain ``group``
+and ``restrictions``. 
+
+For descriptions of the fields, refer to `this section`_ in Fuel Developer Guide.
+
+.. _this section: http://docs.openstack.org/developer/fuel-docs/devdocs/develop/nailgun/customization/settings.html