Fix README quick start to use host networking.

Fixes: unboundedsystems#4
Also add some more detail on interacting
with Docker networking.

README.md

@@ -1,12 +1,13 @@
 <p align="center"><img src="https://github.com/unboundedsystems/k3s-dind/raw/master/k3s-dind.png" /></p>
 
 # k3s-dind
+
 Lightweight k3s Kubernetes inside a Docker-in-Docker container
 
 ## Quick Start
-```console
-docker network create k3s
-docker run -d --privileged --name k3s --hostname k3s --network k3s unboundedsystems/k3s-dind
+
+```bash
+docker run -d --privileged --name k3s --hostname k3s -p 8443:8443 unboundedsystems/k3s-dind
 docker exec k3s get-kubeconfig.sh > ./k3sconfig
 export KUBECONFIG=./k3sconfig
 
@@ -18,19 +19,66 @@ kubectl create ...
 
 ```
 
+
 ## What is k3s-dind?
+
 k3s-dind allows you to quickly create a [lightweight local Kubernetes cluster](https://k3s.io/),
 self-contained inside a single Docker-in-Docker (DinD) container.
 
 ## What would I use it for?
+
 k3s-dind is awesome for:
+
 * Quickly running automated unit tests in Kubernetes
 * Running your containerized app locally for easier debugging
 * Testing out automation or changes to a Kubernetes cluster
 * Ensuring you're starting with a fresh cluster every time
 * Doing all that stuff in only 512MB of RAM!
 
+## Exposing network services
+
+### Docker host networking
+
+The Quick Start example above uses Docker's [host networking](https://docs.docker.com/network/host/), using the `-p 8443:8443` option to `docker run` to expose the Kubernetes API port.
+To run Kubernetes [services](https://kubernetes.io/docs/concepts/services-networking/service/) and make them available outside the cluster, you would need to use additional `-p` options to `docker run`, because Docker doesn't support exposing additional host networking ports after the container has been started.
+
+For example, to allow your Docker host to connect to a [Kubernetes service running on port 8080](https://kubernetes.io/docs/tasks/access-application-cluster/service-access-application-cluster/), you'd need to start k3s-dind like this:
+
+```bash
+docker run -d --privileged --name k3s --hostname k3s -p 8443:8443 -p 8080:8080 unboundedsystems/k3s-dind
+```
+
+### Docker named networks
+
+For more dynamic environments, you can also use k3s-dind with named Docker networks, such as a [bridge network](https://docs.docker.com/network/bridge/).
+Then, any other containers on the same named network with k3s-dind can access any Kubernetes services exposed by the k3s-dind cluster.
+
+First, create a Docker network, then run k3s-dind attached to that network:
+
+```bash
+docker network create mynetwork
+docker run -d --privileged --name k3s --hostname k3s --network mynetwork unboundedsystems/k3s-dind
+
+# The second argument to get-kubeconfig.sh is the container name of k3s-dind
+docker exec k3s get-kubeconfig.sh -yaml k3s > ./k3sconfig
+```
+
+Now, any container on `mynetwork` can access any service exposed by the k3s-dind cluster:
+
+```bash
+# Run a container that's on mynetwork and mount the kubeconfig
+docker run --rm -it -v ${PWD}/k3sconfig:/k3sconfig --network mynetwork k3integrations/kubectl
+
+# Now we're inside the container we just ran
+export KUBECONFIG=/k3sconfig
+
+kubectl get all
+NAME             CLUSTER-IP   EXTERNAL-IP   PORT(S)   AGE
+svc/kubernetes   10.43.0.1    <none>        443/TCP   10m
+```
+
 ## You made Kubernetes that small??
+
 Nope! The awesome folks over at [Rancher Labs](https://rancher.com/) did all
 the hard work of creating [k3s](https://k3s.io/). We just packaged it into
 a Docker-in-Docker container.