1. What is Helm, and why is it used in Kubernetes?

   • Helm is a package manager for Kubernetes that simplifies the deployment and management of Kubernetes applications. It uses charts, which are packages of pre-configured Kubernetes resources, to define and install applications. Helm makes it easier to version, share, and manage complex application deployments on Kubernetes.

2. How do you install Helm and initialize a Helm chart repository?

   • To install Helm, you can typically use a package manager like apt or brew, or download the binary from the Helm GitHub releases page. Once Helm is installed, initialize a chart repository using the following command:

         helm repo add <repository-name> <repository-url>
     

3. What is a Helm chart?

   • A Helm chart is a package of pre-configured Kubernetes resources. It contains templates, values, and optional files to define how an application should be deployed on a Kubernetes cluster. Charts make it easy to share and deploy applications consistently.

4. How do you create a new Helm chart?

   • To create a new Helm chart, you can use the helm create command. For example:

         helm create mychart
     

     This command generates the basic directory structure and files for a Helm chart.

5. What is the difference between a Helm release and a Helm chart?

   • A Helm chart is a package containing Kubernetes resource definitions, templates, and configuration. A Helm release is an instance of a Helm chart deployed on a Kubernetes cluster. You can have multiple releases of the same chart with different configurations.

6. How do you deploy a Helm chart to a Kubernetes cluster?

   • To deploy a Helm chart, use the helm install command. For example:

         helm install my-release mychart
     

     This command deploys the chart named mychart as a release named my-release to the cluster.

7. What are Helm values and how are they used?

   • Helm values are configuration parameters that can be customized when deploying a Helm chart. Values are defined in values.yaml file or provided using the --set flag during installation. They allow users to tailor the chart's behavior to their specific requirements.

8. What is a Helm template, and how does it work?

   • A Helm template is a Kubernetes manifest generated from a Helm chart's templates and values. Helm uses the Go templating engine to interpolate values into the templates, producing valid Kubernetes YAML files that are ready for deployment.

9. How do you upgrade a Helm release to a new version of a chart?

   • To upgrade a Helm release, use the helm upgrade command. For example:

         helm upgrade my-release mychart
     

     Helm will apply the changes from the new version of the chart to the existing release.

10. What is a Helm hook, and when might you use one?

    • A Helm hook is a way to perform actions at specific points in the Helm lifecycle, such as before or after a release is installed, upgraded, or deleted. Hooks are useful for tasks like database migrations or certificate issuance.

11. Explain the difference between Helm 2 and Helm 3.

    • Helm 2 used a server-side component called Tiller, which was removed in Helm 3 to improve security and simplicity. Helm 3 introduced several improvements, including better support for security, a restructured chart directory, and improved chart dependencies management.

12. What are Helm repositories, and how do you add or remove them?

    • Helm repositories are locations where Helm charts are stored and can be fetched from. You can add a repository helm repo add and remove it using helm repo remove.

13. How do you roll back a Helm release to a previous version?

    • To roll back a Helm release, use the helm rollback command. For example:

          helm rollback my-release 2
      

      This command rolls back the release named my-release to revision 2.

14. What is Tiller, and why was it removed in Helm 3?

    • Tiller was the server-side component in Helm 2 that managed releases. It was removed in Helm 3 to improve security because Tiller had access to the Kubernetes API with extensive permissions, which posed a security risk.

15. How can you secure Helm deployments in a Kubernetes cluster?

    • To secure Helm deployments, you can:

      • Use RBAC (Role-Based Access Control) to limit permissions.

      • Ensure that Helm and Kubernetes API are secured with appropriate authentication and authorization mechanisms.

      • Sign and verify Helm charts to ensure their integrity.

16. How do you manage dependencies in Helm charts?

    • Use the requirements.yaml file to specify chart dependencies. Helm will fetch and install these dependencies when deploying the parent chart.

17. What is the purpose of Helm plugins, and can you name a few useful Helm plugins?

    • Helm plugins extend Helm's functionality. Some useful Helm plugins include helm-diff for showing differences between releases, helm-secrets for managing secrets, and helmfile for managing multiple Helm releases.

18. How do you perform linting and testing of Helm charts?

    • Use helm lint to check chart validity. To test Helm charts, you can create test pods or use tools helm test to run tests defined in the chart.

Kubernetes Interview Questions on CustomResources

1. What are Custom Resources in Kubernetes?

   • Custom Resources (CRs) are an extension mechanism in Kubernetes that allows you to define and use custom objects in addition to the built-in resources like Pods, Services, and Deployments. They provide a way to extend the Kubernetes API to suit your application's specific needs.

2. Why would you use Custom Resources in Kubernetes?

   • Custom Resources are useful when you need to represent and manage application-specific resources that are not natively supported by Kubernetes. They enable you to define, create, and manage these resources using the Kubernetes API and tooling.

3. What is the difference between Custom Resources and Custom Resource Definitions (CRDs)?

   • Custom Resources are instances of custom objects, while Custom Resource Definitions (CRDs) define the schema or structure for these custom objects. CRDs specify the kind of custom resources that can be created and their validation rules.

4. How do you create a Custom Resource in Kubernetes?

   • To create a Custom Resource, you first need to define a Custom Resource Definition (CRD) that specifies the resource's schema. Once the CRD is created, you can create instances of the custom resource by applying YAML manifests that conform to the CRD's schema.

5. Explain the structure of a Custom Resource Definition (CRD).

   • A CRD typically includes the following fields:

     • apiVersion: The API version of the CRD.

     • kind: The kind of resource, which is typically "CustomResourceDefinition."

     • metadata: Metadata for the CRD.

     • spec: Defines the structure and validation rules for the custom resource, including its fields and their types.

6. What is a Controller in the context of Custom Resources?

   • Controllers are Kubernetes components or custom operators that watch for changes to Custom Resources and take action based on those changes. They help automate the management of custom resources by reconciling the desired state specified in the CR with the actual state of the resource.

7. Can you explain the reconciliation loop in a Custom Resource Controller?

   • The reconciliation loop is a core concept in a Custom Resource Controller. It continuously watches for changes in Custom Resources, compares the current state of the resource with the desired state specified in the CR, and takes actions to align them. This loop ensures that the custom resources are maintained as per their specifications.

8. What are some common use cases for Custom Resources in Kubernetes?

   • Common use cases include managing application-specific configurations, deploying and scaling custom applications, managing external resources or services, and automating complex workflows.

9. What tools or libraries can you use to build Custom Resource Controllers?

   • Popular choices include Kubernetes client libraries (e.g., client-go), Operator SDK, and Kubebuilder. These tools help simplify the development of Custom Resource Controllers.

10. How do you validate a Custom Resource to ensure it adheres to its CRD's schema?

    • You can define validation rules within the spec field of the CRD. Kubernetes will automatically validate any Custom Resources created against these rules. Additionally, you can implement custom validation logic in your Custom Resource Controller.