[upstream] Update DevStack slides

Change-Id: I72e7b9fe4baf778ebf5d74ebeeb64f87dfbc7640

doc/upstream-training/source/slides/code-devstack.rst

@@ -6,24 +6,44 @@ Demo environment
    :class: fill
    :width: 100%
 
-devstack.org
-============
+DevStack
+========
 
-.. image:: ./_assets/11-01-devstack.png
-   :width: 100%
+- A bunch of scripts to build a full OpenStack environment
+- Used as
+
+  - Demo environment
+  - Part of the OpenStack project's functional testing
+
+- Single and multi node setup
+- Installs services from source
+
+  - from git master by default
+  - from stable branches by configuration, e.g. stable/newton
+
+- Documentation: http://docs.openstack.org/developer/devstack/
 
 http://localhost/
 =================
 
-.. image:: ./_assets/11-03-http-localhost.png
+.. image:: ./_assets/devstack-http-localhost.png
   :width: 100%
 
-http://localhost/
+Service terminals
 =================
 
-.. image:: ./_assets/11-04-git.png
+- Using Linux 'screen'
+- Access the terminals the installed services are running in
+- Use command 'screen -x' to see the running services
+- For further commands see the
+  `User's Manual <https://www.gnu.org/software/screen/manual/screen.html>`_
+
+.. image:: ./_assets/devstack-screen.png
+  :width: 90%
+  :align: center
 
 Exercise
 ========
 
-Get the code for the targeted contribution
+- Ensure you have the DevStack repository cloned to the VM you would like to
+  use it