Certified Kubernetes Administrator (CKA) Practice Test

The primary function of a ReplicaSet in Kubernetes is to maintain a stable set of Pods running at all times. This means that if any of the Pods managed by the ReplicaSet fail or are terminated, the ReplicaSet automatically creates new Pods to replace them, ensuring that the desired number of replicas is always maintained. The ReplicaSet uses a label selector to identify the Pods it should manage and can also be used to scale the number of running Pods up or down as needed. This provides high availability for applications by ensuring that there are always a specified number of identical Pods running to serve user requests or perform tasks.

The other choices refer to different Kubernetes concepts. For instance, persistent storage is handled by Persistent Volumes and Persistent Volume Claims, not by a ReplicaSet. Access control to the cluster is managed through Role-Based Access Control (RBAC) policies, not by ReplicaSets. Network policies, which govern the communication between Pods, are a separate function that does not relate to the role of maintaining Pod replicas. Therefore, the function of a ReplicaSet is distinct and essential specifically for ensuring consistent availability of the applications it manages.