Update page on managing nodes (backport #6313)

source/Tutorials/Demos/Managed-Nodes.rst

@@ -3,8 +3,52 @@
     Managed-Nodes
     Tutorials/Managed-Nodes
 
-Managing nodes with managed lifecycles
-======================================
+Managing node lifecycles - example
+==================================
 
-This page lives now directly side-by-side with the `code <https://github.com/ros2/demos/blob/{REPOS_FILE_BRANCH}/lifecycle/README.rst>`__.
-For more information about the ``lifecycle`` package, refer to `rosindex <https://index.ros.org/p/lifecycle/>`__.
+Managed lifecycles for nodes allow greater control over the state of the ROS system.
+This example uses a simple talker/listener pair of managed nodes to show how a managed lifecycle can be implemented and used.
+You can use the example to understand and experiment with managing nodes in this way.
+
+**Area: ROS-framework | Content-type: example | Experience: expert**
+
+.. contents:: Contents
+   :depth: 2
+   :local:
+
+Summary
+-------
+
+ROS 2 introduces the concept of managed nodes, also called lifecycle nodes.
+These nodes can be used to ensure that resources are correctly initialised, activated, deactivated, and cleaned up as the node moves between lifecycle states.
+A common use case is nodes that control hardware, where devices such as cameras, lidars, motor drivers, and other sensors and actuators must be started, configured, and shut down in a controlled order.
+
+Using lifecycle nodes helps ensure hardware is only initialised when it is ready, and is safely released during shutdown or error recovery.
+The following packages enable you to implement these managed nodes: `rclcpp_lifecycle <https://index.ros.org/p/rclcpp_lifecycle/>`__ (implementation library) and `lifecycle_msgs <https://index.ros.org/p/lifecycle_msgs/>`__ (interface definitions).
+
+Prerequisites
+-------------
+
+See the :doc:`installation instructions <../../Installation>` for details on installing ROS 2.
+
+Example
+-------
+
+Access the example
+^^^^^^^^^^^^^^^^^^
+
+Information on how to run the example is here: `lifecycle_demo_launch.py <https://github.com/ros2/demos/blob/{REPOS_FILE_BRANCH}/lifecycle_py/launch/lifecycle_demo_launch.py>`__
+
+Commentary
+^^^^^^^^^^
+
+For more information about how to run it and what's happening, see: `lifecycle README <https://github.com/ros2/demos/blob/{REPOS_FILE_BRANCH}/lifecycle/README.rst>`__
+
+Related content
+---------------
+
+Packages/reference:
+
+* `rclcpp_lifecycle <https://index.ros.org/p/rclcpp_lifecycle/>`_ (implementation library): Package containing a prototype for lifecycle implementation.
+* `lifecycle_msgs <https://index.ros.org/p/lifecycle_msgs/>`_ (interface definitions): Package containing some lifecycle related message and service definitions.
+* `lifecycle <https://docs.ros.org/en/{DISTRO}/p/lifecycle/>`_: Package containing demos for lifecycle implementation.