add running outside of K8S

Author: gilesknap

docs/user/how-to/run_iocs.rst

@@ -1,4 +1,48 @@
 Run an IOC without Kubernetes
 =============================
 
-**TODO**
+When we run a containerized IOC we are selecting a generic IOC container image
+to launch and some configuration to pass to the IOC.  The configuration we
+pass is what makes the IOC a unique instance instead of a generic IOC.
+
+In the tutorials we are running the IOC in a Kubernetes cluster and we
+use a Kubernetes ConfigMap to pass the configuration to the IOC.
+
+However it is perfectly possible to do this without Kubernetes. To demonstrate
+this easily, first create the test beamline repo as described in
+`../tutorials/04_create_beamline`.
+
+Now if you cd into the test beamline repo and run the following command you
+will see the IOC running in a container:
+
+.. code-block:: bash
+
+    podman run -it -v $(pwd)/iocs/bl01t-ea-ioc-01/config:/repos/epics/ioc/config  ghcr.io/epics-containers/ioc-template-linux-runtime:23.3.3
+
+What you have done here is pull down the generic ``ioc-template-linux-runtime``
+container image from the GitHub Container Registry and run it.
+The -it means it is an interactive terminal session.
+
+The -v mounts the local directory ``iocs/bl01t-ea-ioc-01/config`` into the
+container at ``/repos/epics/ioc/config``.  This is where the IOC expects to
+find its configuration. The leading $(pwd) means the current working directory
+is appended to the path and that is required because the path for mounting
+into a container must be absolute.
+
+``iocs/bl01t-ea-ioc-01/config`` contains a simple iocShell boot script and the
+default behaviour is to pass that to the generic IOC binary.
+
+Using this approach you could manage your config folders and IOC launches
+yourself using whatever mechanism you prefer. Probably docker compose or
+docker swarm would be the most likely candidates.
+
+It may be worth noting that this ``ec`` command does exactly the same
+thing as the above podman command:
+
+.. code-block:: bash
+
+    ec ioc-launch iocs/bl01t-ea-ioc-01 --tag 23.3.3
+
+That is because ``ioc-launch`` is intended for locally testing an IOC instance
+that is destined for Kubernetes.
+