Mixed Deck — All CKA Topics Flashcards

What is a Pod in Kubernetes?

Answer: The smallest deployable unit that can contain one or more containers

A Pod is Kubernetes' atomic deployment unit, wrapping one or more containers that share storage, networking, and a specification for how to run.

Which Service type allows external access to a Kubernetes application through a specific port on each node in the cluster?

Answer: NodePort

The NodePort Service type exposes the Service on a static port on each node's IP address. This means that any traffic sent to that specific port on any node in the cluster will be routed to the Service and its backing Pods. It's a common way to make a service accessible from outside the cluster, especially in development or smaller environments where an external load balancer isn't readily available.

Which of the following is the default Kubernetes DNS Service?

Answer: CoreDNS

CoreDNS is the default DNS server in Kubernetes clusters since version 1.11. It provides DNS resolution for services and Pods within the cluster, allowing them to discover each other by name rather than IP address. This is a critical component for inter-service communication and application functionality.

Which Service type creates a DNS CNAME alias pointing to an external hostname?

Answer: ExternalName

ExternalName service maps a Kubernetes service to an external DNS name by returning a CNAME record for the configured hostname.

What does 'kubectl get pods' show?

Answer: A list of all Pods and their status in the current namespace

This command displays all Pods in the current namespace with their name, ready status, current state, restarts, and age.

Which component of a Kubernetes cluster stores the configuration data in a key-value store?

Answer: etcd

etcd is a distributed, reliable key-value store that Kubernetes uses to store all cluster data, including configuration, state, and metadata. It acts as the cluster's single source of truth, ensuring consistency and availability of the control plane's critical information. Without etcd, the Kubernetes API server would not be able to retrieve or persist the desired state of the cluster.

What is the purpose of 'kubectl drain' command?

Answer: To safely evict all Pods from a node for maintenance

kubectl drain safely evicts all Pods from a node, cordoning it to prevent new Pod scheduling, allowing maintenance work on the node.

What is a Persistent Volume (PV)?

Answer: A storage resource in the cluster provisioned independently of Pod lifecycle

PVs are storage resources that exist beyond Pod lifecycle, ensuring data persistence even when Pods are destroyed and recreated.

Which Kubernetes resource is used to securely store sensitive data like API keys and passwords?

Answer: Secret

Secrets are Kubernetes objects designed to store sensitive information, such as passwords, OAuth tokens, and SSH keys. They provide a more secure way to manage this data than putting it directly into Pod definitions or ConfigMaps. Secrets can be mounted as files into Pods or exposed as environment variables, allowing applications to access sensitive data without hardcoding it.

What is the maximum data size allowed in a single Kubernetes ConfigMap?

Answer: 1 MiB

Kubernetes enforces a 1 MiB (1,048,576 byte) limit on ConfigMap data to avoid overwhelming the etcd storage backend.

What is a ConfigMap?

Answer: An object storing non-confidential configuration data as key-value pairs

ConfigMaps store configuration data separately from application code, allowing configuration changes without rebuilding container images.

Which kubectl command creates a ConfigMap from all files in a directory named 'configs/'?

Answer: kubectl create configmap my-config --from-file=configs/

The --from-file flag accepts either a single file path or a directory path; when given a directory, it creates one key per file.

What is the purpose of a kube-scheduler in Kubernetes?

Answer: To allocate resources for Pods across the cluster.

The `kube-scheduler` is a control plane component responsible for watching newly created Pods that have no assigned node. It selects the best node for each Pod to run on, considering various factors like resource requirements, hardware constraints, policy constraints, and affinity/anti-affinity specifications. Its primary goal is to ensure efficient resource utilization and optimal placement of workloads across the cluster.

What is a ConfigMap?

Answer: An object storing non-confidential configuration data as key-value pairs

ConfigMaps store configuration data separately from application code, allowing configuration changes without rebuilding container images.

Where does Kubernetes store container log files on the node by default?

Answer: /var/log/containers/

Container logs are written to `/var/log/containers/` on the node, symlinked from `/var/log/pods/`.

How do you upgrade a Kubernetes cluster?

Answer: Upgrade control plane first, then worker nodes one at a time

Cluster upgrades follow a specific order: upgrade the control plane components first, then upgrade worker nodes one at a time (rolling upgrade) to maintain availability.

How does Kubernetes handle service discovery?

Answer: Through Services that provide stable DNS names and IP addresses for Pods

Kubernetes Services provide stable network endpoints with DNS names, automatically routing traffic to healthy Pods regardless of their changing IP addresses.

What is a Persistent Volume (PV)?

Answer: A storage resource in the cluster provisioned independently of Pod lifecycle

PVs are storage resources that exist beyond Pod lifecycle, ensuring data persistence even when Pods are destroyed and recreated.

What does 'kubectl get pods' show?

Answer: A list of all Pods and their status in the current namespace

This command displays all Pods in the current namespace with their name, ready status, current state, restarts, and age.

What happens when a Service's label selector matches no running pods?

Answer: The Endpoints object has no entries and traffic to the service is dropped

When no pods match the selector, the Endpoints/EndpointSlice contains no addresses and traffic sent to the service has no backend to reach.