Kubernetes (CKA) - Container Orchestration & Pod Architecture Flashcards

Question 1

What is Kubernetes?

Accepted Answer

Kubernetes is an open-source container orchestration platform designed to automate the deployment, scaling, and management of containerized applications. It groups containers into logical units for easy management and discovery.

Question 2

What is a Kubernetes Pod?

Accepted Answer

A Pod is the smallest deployable unit in Kubernetes. It represents a single instance of a running process in your cluster. A Pod typically encapsulates one or more containers (e.g., Docker containers), storage resources, a unique network IP, and options that govern how the containers should run.

Question 3

Describe the typical architecture of a Kubernetes Pod.

Accepted Answer

A Pod usually contains one primary application container. It can also include "sidecar" containers that augment the primary application, such as logging agents, monitoring agents, or data synchronization services. All containers within a Pod share the same network namespace, IP address, and IPC namespace, and can share storage volumes.

Question 4

List the main Pod lifecycle states.

Accepted Answer

The main Pod lifecycle states are:
*   `Pending`: The Pod has been accepted by the Kubernetes system, but one or more of the container images has not been created or configured.
*   `Running`: The Pod has been bound to a node, and all of the containers have been created. At least one container is still running, or is in the process of starting or restarting.
*   `Succeeded`: All containers in the Pod have terminated successfully, and will not restart.
*   `Failed`: All containers in the Pod have terminated, and at least one container has terminated in failure (i.e., it exited with a non-zero exit code).
*   `Unknown`: For some reason, the state of the Pod could not be obtained. This is typically due to an error in communicating with the node where the Pod should be running.

Question 5

Provide a basic YAML manifest example for a single-container Pod.

Accepted Answer

```yaml
apiVersion: v1
kind: Pod
metadata:
  name: my-nginx-pod
  labels:
    app: nginx
spec:
  containers:
  - name: nginx
    image: nginx:latest
    ports:
    - containerPort: 80
```

Question 6

What `kubectl` command is used to create resources from a YAML file?

Accepted Answer

The `kubectl apply -f <filename.yaml>` command is used to create or update Kubernetes resources defined in a YAML or JSON file.

Question 7

How do you list all Pods in the current namespace using `kubectl`?

Accepted Answer

Use the command `kubectl get pods`. To see more details, including the node they are running on, use `kubectl get pods -o wide`.

Question 8

How do you view the logs of a specific container within a Pod using `kubectl`?

Accepted Answer

Use `kubectl logs [-c ]`. If there's only one container in the Pod, `-c` is optional. For continuous logging, use `kubectl logs -f `.

Question 9

What `kubectl` command provides detailed information about a specific Pod, including events?

Accepted Answer

The `kubectl describe pod <pod-name>` command provides a comprehensive overview of a Pod's state, including its current status, events, resource limits, and container details.

Question 10

List the main components of the Kubernetes Control Plane.

Accepted Answer

The Kubernetes Control Plane (or Master Node components) consists of:
*   `kube-apiserver`
*   `etcd`
*   `kube-scheduler`
*   `kube-controller-manager`
*   `cloud-controller-manager` (optional, for cloud integrations)

Question 11

What is the role of the `kube-apiserver` in a Kubernetes cluster?

Accepted Answer

The `kube-apiserver` is the front end of the Kubernetes Control Plane. It exposes the Kubernetes API, which is used by all other Control Plane components and external clients (`kubectl`). It validates and configures data for API objects like Pods, Services, etc.

Question 12

What is the function of `etcd` in Kubernetes?

Accepted Answer

`etcd` is a consistent and highly available key-value store used as Kubernetes' backing store for all cluster data. It stores the entire state of the Kubernetes cluster, including configurations, status information, and metadata.

Question 13

Explain the role of the `kube-scheduler`.

Accepted Answer

The `kube-scheduler` watches for newly created Pods with no assigned node and selects a node for them to run on. It considers various factors like resource requirements, hardware/software/policy constraints, affinity/anti-affinity specifications, and data locality.

Question 14

What does the `kube-controller-manager` do?

Accepted Answer

The `kube-controller-manager` runs controller processes. Each controller is a control loop that watches the shared state of the cluster through the API server and makes changes attempting to move the current state towards the desired state. Examples include the Node Controller, Replication Controller, Endpoints Controller, and Service Account & Token Controllers.

Question 15

What is the purpose of the `cloud-controller-manager`?

Accepted Answer

The `cloud-controller-manager` embeds cloud-specific control logic. It allows you to link your cluster into your cloud provider's API, separating cloud-dependent components from cloud-independent components. This includes controllers for nodes, routes, services, and volumes.

Question 16

List the main components found on a Kubernetes Worker Node.

Accepted Answer

A Kubernetes Worker Node (or Minion Node) typically runs:
*   `kubelet`
*   `kube-proxy`
*   Container Runtime (e.g., containerd, CRI-O, Docker Engine)

Question 17

What is the `kubelet` and its primary function?

Accepted Answer

The `kubelet` is an agent that runs on each node in the cluster. It ensures that containers are running in a Pod. It takes a set of PodSpecs (provided via the API server) and ensures that the described containers are healthy and running.

Question 18

Explain the role of `kube-proxy` on a Worker Node.

Accepted Answer

`kube-proxy` is a network proxy that runs on each node. It maintains network rules on nodes, allowing network communication to your Pods from inside or outside of your cluster. It handles Service abstraction by forwarding traffic to the correct Pods.

Question 19

What is a Kubernetes Deployment?

Accepted Answer

A Deployment is a higher-level abstraction that manages a set of identical Pods. It provides declarative updates for Pods and ReplicaSets. You describe a desired state in a Deployment, and the Deployment Controller changes the actual state to the desired state at a controlled rate. It's ideal for stateless applications.

Question 20

What is a Kubernetes Service?

Accepted Answer

A Kubernetes Service is an abstract way to expose an application running on a set of Pods as a network service. Services enable loose coupling between dependent Pods. They provide a stable IP address and DNS name for a group of Pods, even if the underlying Pods change or restart.

Question 21

Name and briefly describe the four main types of Kubernetes Services.

Accepted Answer

The four main types of Kubernetes Services are: * `ClusterIP`: Exposes the Service on an internal IP in the cluster. Only reachable from within the cluster. Default type. * `NodePort`: Exposes the Service on a static port on each Node's IP. Makes the Service accessible from outside the cluster using `:`. * `LoadBalancer`: Exposes the Service externally using a cloud provider's load balancer. Only available with cloud providers that support it. * `ExternalName`: Maps the Service to the contents of the `externalName` field (e.g., `foo.bar.example.com`) by returning a `CNAME` record. No proxying is involved.

Question 22

What is a Kubernetes Ingress and why is it used?

Accepted Answer

An Ingress is an API object that manages external access to services in a cluster, typically HTTP/S. It provides HTTP and HTTPS routing to services based on hostnames or URL paths. An Ingress controller (e.g., NGINX Ingress Controller) must be deployed in the cluster to fulfill the Ingress rules.

Question 23

Differentiate between a Persistent Volume (PV) and a Persistent Volume Claim (PVC).

Accepted Answer

*   **Persistent Volume (PV):** A piece of storage in the cluster that has been provisioned by an administrator or dynamically provisioned using Storage Classes. It's a cluster resource, independent of Pod lifecycles.
*   **Persistent Volume Claim (PVC):** A request for storage by a user. It's a request for a PV resource, specifying size, access modes (e.g., ReadWriteOnce, ReadOnlyMany), and storage class. Pods consume PVCs.

Question 24

What is Role-Based Access Control (RBAC) in Kubernetes?

Accepted Answer

RBAC is a method of regulating access to computer or network resources based on the roles of individual users within an enterprise. In Kubernetes, RBAC allows you to define who can do what in your cluster by granting specific permissions to users or service accounts.

Question 25

List the key resources used to configure RBAC in Kubernetes.

Accepted Answer

The key RBAC resources are:
*   `Role`: Defines a set of permissions within a specific namespace.
*   `ClusterRole`: Defines a set of permissions across the entire cluster (non-namespaced).
*   `RoleBinding`: Grants the permissions defined in a `Role` to a user, group, or service account within a specific namespace.
*   `ClusterRoleBinding`: Grants the permissions defined in a `ClusterRole` to a user, group, or service account across the entire cluster.

Kubernetes (CKA) - Container Orchestration & Pod Architecture

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