Hi, the statement means that there may be a case when the configMap is not defined. Referencing an undefined configMap prevents the pod from starting. If you have the configMap reference marked as optional, in the case of an undefined configMap the pod still starts. It is a failsafe option when referencing configMaps, ensuring that the pods run either way.
Hi, in the final course version, due to multiple document formats and final formatting the displayed yaml may not be indented correctly. However, if you download the resource files for labs, you will find yaml files where the containers with volume mounts and volumes are correctly indented.
Hi, the pod networking plugin solves the pod-to-pod communication requirement of the Kubernetes cluster.
The following links provide more details on the Kubernetes cluster networking, plugins, differences:
For the purpose of these labs, the Calico plugin is used because it is one of the many plugins providing networking and network policies support. This is installed by the k8sMaster.sh script.
The IP address 10.128.0.3 is displayed towards the end of the output on the Master node once the k8sMaster.sh script has completed initializing the Master node. This is the IP address that Minions will use to join the cluster.