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KubernetesResources.md

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Kubernetes Resources

1. In a Kubernetes definition file, how is the metadata field typically defined?

The metadata field provides information about the object, such as its name, labels, and namespace.

metadata:
  name: example-pod
  namespace: default
  labels:
    app: my-app

Scenario: Assign meaningful labels to identify and organize resources for easier selection and filtering.

2. How can you view the list of created deployments in Kubernetes?

Use the following command:

kubectl get deployments

Scenario: To check deployments in a specific namespace, use -n <namespace>.

3. How can you create a pod in Kubernetes using a YAML file named pod-definition.yml?

Run:

kubectl apply -f pod-definition.yml

Scenario: Automate pod creation in CI/CD pipelines by storing YAML files in version control.

4. By default, when a Docker container is deployed within a pod, how can users access the application?

Users access the application via the pod’s IP address or by exposing it through a service. Scenario: Use a ClusterIP or NodePort service to expose applications within or outside the cluster.

5. In which Kubernetes namespace are the resources created that should be made available to all users?

The default namespace. Scenario: For shared resources like config maps or secrets, use kube-system or custom namespaces for better isolation.

6. When scaling an application in Kubernetes to handle increased user load, how are additional instances typically created?

Scale deployments using:

kubectl scale deployment <deployment-name> --replicas=<number>

Scenario: Use Horizontal Pod Autoscaler (HPA) for automatic scaling based on resource utilization.

7. What is the smallest object that can be created in Kubernetes?

The Pod. Scenario: Deploy a single containerized application directly as a pod during initial testing.

8. How can you view the created ReplicaSet in Kubernetes?

Run:

kubectl get replicasets

Scenario: View ReplicaSet details to troubleshoot issues with scaling or pod creation.

9. In a Kubernetes definition file, the kind field is used to specify:

The type of resource being defined, such as Pod, Deployment, or Service.

10. What is the primary role of controllers in Kubernetes?

Controllers manage the desired state of objects, ensuring the cluster matches the configuration defined. Scenario: Use the Deployment controller to ensure specified replicas are always running.

11. How do you apply changes to a modified Kubernetes deployment object using a definition file called deployment-def.yml?

Run:

kubectl apply -f deployment-def.yml

12. What is the role of a ReplicaSet in Kubernetes?

ReplicaSets maintain the desired number of pod replicas and replace failed ones.

13. What is the correct API version to use in the replication controller definition file?

Use apiVersion: v1.

14. What command can you use to update the image of your application in a Kubernetes deployment without modifying the deployment definition file?

Run:

kubectl set image deployment/<deployment-name> <container-name>=<image>

Scenario: Update a backend service image to deploy the latest bug fixes.

15. Why does a ReplicaSet require a selector definition, even if the pod definition is provided in the template?

The selector ensures the ReplicaSet can identify and manage the correct pods.

16. What is the advantage of having multiple containers within the same pod in Kubernetes?

Containers in the same pod share resources and enable sidecar patterns for logging, caching, etc.

17. What is the recommended approach for expanding the physical capacity of a Kubernetes cluster when the current node lacks sufficient capacity?

Add a new node to the cluster. Scenario: Use cloud-based auto-scaling groups to provision nodes dynamically.

18. What is the purpose of a Deployment in Kubernetes?

To manage pod scaling, updates, and rollbacks.

19. Why is the use of a replication controller important in Kubernetes?

It ensures a specified number of pod replicas are always running.

20. You want to create a pod in the dev namespace instead of the default namespace using a YAML manifest file called pod-def.yml. Which command should you use to achieve this?

Run:

kubectl apply -f pod-def.yml -n dev

21. To list pods in the kube-system namespace, which command should you use?

Run:

kubectl get pods -n kube-system

22. How can you update the number of replicas in a replica set using the kubectl scale command?

Run:

kubectl scale replicaset <replica-set-name> --replicas=<number>

23. How can you view the history and revisions of a deployment rollout in Kubernetes?

Run:

kubectl rollout history deployment/<deployment-name>

Scenario: Use the command to identify and rollback to stable versions during deployment failures.

24. Why are deployment rollouts and revisions important in Kubernetes?

They allow tracking changes and reverting to a stable state when issues occur.

25. Regardless of the approach used to create an object in Kubernetes, what does Kubernetes use to store information about the object internally?

Kubernetes uses etcd, a distributed key-value store.

26. How can you update a replica set to scale from 3 replicas to 6 replicas?

Run:

kubectl scale rs <replica-set-name> --replicas=6

27. When using the kubectl apply command in Kubernetes, which of the following sources does it consider before deciding what changes to make?

It compares the local file with the cluster’s last applied configuration.

28. In Kubernetes, which namespace is automatically created by Kubernetes when the cluster is first set up?

The kube-system namespace.

29. Which API version would you typically use when creating a Pod object in a Kubernetes definition file?

Use apiVersion: v1.

30. How can you switch to a specific namespace permanently in Kubernetes, so that you don't have to specify the namespace option each time you run a command?

Set the namespace context:

kubectl config set-context --current --namespace=<namespace>

31. How can you create a new namespace in Kubernetes?

Run:

kubectl create namespace <namespace-name>

32. What parameter is used with the kubectl run command to specify the application image when deploying a Docker container as a pod?

Use the --image parameter to specify the application image.

kubectl run <pod-name> --image=<image-name>

Example:

kubectl run my-pod --image=nginx

33. Why is it beneficial to use labels in Kubernetes when deploying multiple pods?

Labels allow for:

  1. Organization: Grouping resources logically (e.g., all pods related to a specific app).
  2. Selection: Simplifies the use of selectors in services, ReplicaSets, and deployments.
  3. Management: Enables filtering and bulk operations on resources.

Example:

labels:
  app: web
  tier: frontend

34. How can you rollback a Kubernetes deployment to a previous revision?

Use the following command:

kubectl rollout undo deployment/<deployment-name>

To rollback to a specific revision:

kubectl rollout undo deployment/<deployment-name> --to-revision=<revision-number>

35. In a Kubernetes definition file, why is the "containers" property within the "spec" section defined as a list or an array?

The containers property supports multiple containers within a pod, enabling patterns like sidecar or ambassador.

Example:

spec:
  containers:
  - name: main-app
    image: nginx
  - name: sidecar
    image: busybox

36. Which of the following fields are required in a Kubernetes definition file?

Typically required fields are:

  1. apiVersion: Defines the Kubernetes API version.
  2. kind: Specifies the type of resource (e.g., Pod, Deployment).
  3. metadata: Includes name and labels.
  4. spec: Configuration details.

Example:

apiVersion: v1
kind: Pod
metadata:
  name: my-pod
spec:
  containers:
  - name: nginx
    image: nginx

37. Which approach is used to specify what actions should be performed in Kubernetes without specifying how they should be executed?

The declarative approach. Users describe the desired state of the system, and Kubernetes ensures this state.

38. To connect a web-app pod in the default namespace to a service named "db-service" in the "dev" namespace, what is the correct hostname format?

The hostname format is:

<service-name>.<namespace>.svc.cluster.local

For this example:

db-service.dev.svc.cluster.local

39. When using the kubectl apply command to create an object in Kubernetes, what happens to the YAML version of the local object config file?

The configuration is applied to the cluster and stored as the "last-applied-configuration" annotation.

40. When using a replication controller in Kubernetes, how can you specify the number of replicas (instances) of a pod that should be running?

Specify the replicas in the YAML file or use the --replicas flag:

spec:
  replicas: 3

Command:

kubectl scale rc <replication-controller-name> --replicas=3

41. When you create a deployment in Kubernetes, what additional objects are automatically created alongside the deployment?

A ReplicaSet is created to manage the pods.

42. How can you check the status of a deployment rollout in Kubernetes?

Use:

kubectl rollout status deployment/<deployment-name>

43. What is the default deployment strategy in Kubernetes where the application never goes down during the update?

The RollingUpdate strategy ensures zero downtime.

44. How does a ReplicaSet know which pods to monitor?

Through label selectors defined in its spec.selector field.

Example:

spec:
  selector:
    matchLabels:
      app: my-app

45. When a new deployment is created, what is the result of the rollout process?

The deployment creates a new ReplicaSet, which in turn creates the required pods.

46. What does the kubectl apply command do in the declarative approach of managing objects in Kubernetes?

It:

  1. Creates resources if they do not exist.
  2. Updates resources if they already exist, based on changes in the YAML file.

47. What is the purpose of assigning quotas to Kubernetes namespaces?

Quotas ensure resource limits, preventing one namespace from monopolizing cluster resources.

Example:

apiVersion: v1
kind: ResourceQuota
metadata:
  name: resource-limits
  namespace: dev
spec:
  hard:
    cpu: "4"
    memory: "16Gi"

48. What command would you use to view the list of created replication controllers in Kubernetes?

kubectl get rc

49. Why would you create separate namespaces for dev and production environments in Kubernetes?

  1. Isolation: Prevents interference between environments.
  2. Resource Quotas: Allocates resources specific to environments.
  3. Access Control: Facilitates RBAC policies.

50. Which namespace in Kubernetes is created at cluster startup and contains internal services required for networking and DNS?

The kube-system namespace.

51. How can you view pods in all namespaces in Kubernetes?

kubectl get pods --all-namespaces

52. What are the two strategies for making deployments in Kubernetes?

  1. Recreate: Terminates old pods before creating new ones.
  2. RollingUpdate: Gradually updates pods to avoid downtime.

53. To view all the objects created after a deployment, which command can you use?

kubectl get all

54. How can you view detailed information about a specific pod named "my-app-pod" in Kubernetes?

kubectl describe pod my-app-pod

55. How can you limit resources in a namespace in Kubernetes?

By creating a ResourceQuota object.

56. Why is the "last applied configuration" feature useful in Kubernetes?

It helps in auditing changes and reverting configurations during troubleshooting.

57. Why is the template section required in the replica set specification, even if there are existing pods with matching labels?

The template defines how new pods should be created, ensuring consistent configurations.