Top 25 Helm Interview Questions & Answers

1. Introduction

Preparing for a technical interview can be a daunting task, especially when it comes to modern cloud-native technologies. This article aims to guide you through some of the most pertinent helm interview questions you might encounter. Whether you’re a seasoned DevOps professional or a Kubernetes enthusiast, understanding Helm’s role and functionality will be crucial in showcasing your expertise.

2. Helm’s Role in Kubernetes Orchestration

Within the Kubernetes ecosystem, Helm is akin to a package manager, streamlining the deployment and management of applications. Its importance lies in its ability to package Kubernetes resources into reusable units called charts, which simplifies complex application deployment processes. Helm charts empower developers and operators to define, install, and upgrade even the most complex Kubernetes applications. This not only enhances productivity but also ensures consistency across different deployment environments. By using Helm, teams can focus on the application’s specifics without getting bogged down by the nuances of Kubernetes resource management.

3. Helm Interview Questions

Q1. Can you explain what Helm is and why it is important in Kubernetes environments? (Kubernetes & Helm Basics)

Helm is a package manager for Kubernetes that simplifies the process of defining, installing, and upgrading even the most complex Kubernetes applications. It can be thought of as the equivalent of apt or yum for Kubernetes. Helm uses a packaging format called charts, which are collections of files that describe a related set of Kubernetes resources.

Why Helm is important:

• Managing Complexity: Applications often require a multitude of Kubernetes resources such as Deployments, Services, and ConfigMaps. Helm charts encapsulate all these resources into a single package, making deployment and management more straightforward.
• Version Control for Deployments: Helm charts are versioned, allowing for controlled releases and rollbacks to previous configurations, which is crucial for maintaining application stability.
• Customization: Helm charts can be easily customized for different environments through values that override chart defaults, making it simple to set up development, staging, and production configurations.
• Sharing and Reusability: Helm charts can be shared through chart repositories, making it easy to reuse and distribute applications.
• Release Management: Helm provides release management which helps in tracking the installation, upgrading, and deletion of Kubernetes applications.

Q2. How do Helm Charts work and what are their key components? (Helm Charts Understanding)

Helm Charts are the fundamental unit of Helm and work as a collection of files that describe a related set of Kubernetes resources. The key components of a Helm chart are:

• Chart.yaml: The main chart description file, which contains metadata about the chart such as the version, name, and description.
• values.yaml: This file provides the default values for the chart’s templates, which can be overridden during installation or upgrade.
• templates/: This directory contains template files that generate Kubernetes manifest files when combined with values. These templates use the Go templating language.
• charts/: A directory containing any charts upon which this chart depends.
• README.md: An optional but recommended file that provides information about the chart usage, configuration, installation, etc.

Q3. Describe the process of installing a Helm chart in a Kubernetes cluster. (Helm Chart Installation)

The process of installing a Helm chart involves several steps:

1. First, ensure that Helm is installed on your local machine and that you have Kubernetes cluster access with the correct context set in your kubeconfig file.
2. Find the chart you want to install. You can search for charts in public repositories or use charts from your local file system.
3. Once you have identified the chart, use the helm install command to deploy it. You can specify a release name or let Helm generate one for you.
4. If needed, you can override the default values in the values.yaml file by providing your own values file or using --set to override specific keys at the command line.

Here’s a basic example of installing a Helm chart:

helm install my-release my-chart/ --values my-values.yaml

This will create a new release named "my-release" using the chart located in the my-chart/ directory and the configurations specified in my-values.yaml.

Q4. What are Helm Releases, and how do you manage them? (Helm Release Management)

A Helm Release is an instance of a Helm chart running in a Kubernetes cluster. Each time a chart is installed, a new release is created. Managing Helm releases involves several tasks, such as listing, upgrading, rolling back, and deleting releases.

Here are common Helm commands to manage releases:

• helm list: List all the releases in a cluster.
• helm upgrade [RELEASE] [CHART]: Upgrade a release with a newer version of the chart or values.
• helm rollback [RELEASE] [REVISION]: Roll back a release to a previous revision.
• helm uninstall [RELEASE]: Remove a release from the cluster.

Q5. How can you update an application using Helm? (Application Update & Rollout)

To update an application using Helm, you would typically perform a Helm upgrade. This involves making changes to your Helm chart or updating the values and then applying those changes with the helm upgrade command. Here are the steps:

1. Update your Helm chart or the values.yaml file with the new application configuration or image versions.
2. Use the helm upgrade command to apply the changes to the existing release. You can also use the --install flag to combine upgrade and install.
3. Monitor the rollout status to ensure the upgrade was successful.

Example:

helm upgrade my-release my-chart/ --values my-values.yaml

This command will update the "my-release" with the changes specified in my-chart/ and my-values.yaml. The upgrade process will handle the deployment strategy defined in the chart, such as rolling updates for Deployments.

Q6. What is a Helm Repository and how do you add one? (Helm Repository Management)

A Helm Repository is a place where packaged charts can be stored and shared. It is a server that houses an index.yaml file and the packaged charts, which can be accessed by the Helm CLI to install and manage applications on a Kubernetes cluster.

To add a Helm repository, you can use the helm repo add command followed by a repository name and the URL where the repository is located. Here is an example:

helm repo add stable https://charts.helm.sh/stable

After adding a repository, you can then list the repositories you have added with helm repo list, and update your local list of charts with helm repo update.

Q7. How do you create and package your own Helm Chart? (Helm Chart Creation & Packaging)

Creating and packaging a Helm chart involves several steps:

1. Create a chart: Use the helm create <chart-name> command to create a new chart directory structure with the necessary files and directories in it.

   helm create my-chart
   

2. Customize the chart: Modify the chart files according to your application’s configuration and resource definitions. The key files are:

   • Chart.yaml – The main file that contains the description of your chart.
   • values.yaml – The file that contains the default configuration values for your chart.
   • templates/ – A directory that contains template files that will generate valid Kubernetes manifest files when combined with values.

3. Package the chart: After customization, package the chart into a chart archive (a tarball) using the helm package command.

   helm package my-chart
   

4. (Optional) Host your chart: If you want to share your chart, you can host it on a Helm repository. This involves placing the packaged chart on a web server or using a cloud storage service, and adding an index.yaml file that contains information about the chart.

Q8. Can you discuss Helm’s security mechanisms and how you would secure a Helm deployment? (Security & Compliance)

How to Answer:
Discuss the security practices and tools Helm provides or integrates with, and how you would apply them to secure Helm deployments.

My Answer:
Helm has several security mechanisms to help secure deployments:

• Role-based access control (RBAC): Helm leverages Kubernetes’ RBAC to control who can install and manage charts. Charts can define RBAC rules, and users can deploy charts with only the necessary permissions.
• Helm Secrets: Helm integrates with tools like helm-secrets for managing and storing secrets safely. It uses encryption to keep secrets secure during the deployment process.
• Chart provenance and integrity: Helm supports signing charts with PGP keys to ensure their integrity and authenticity. You can create and verify signed packages with the helm package and helm verify commands.
• Tiller removal: In Helm 3, the Tiller server component was removed, which eliminates the security concerns around Tiller’s management of cluster state and permissions.
• Namespace scoping: Helm 3 allows you to specify the namespace for a release, limiting the impact and access scope of a chart.

To secure a Helm deployment, one would:

• Implement RBAC: Create service accounts, roles, and role bindings in Kubernetes for fine-grained access control.
• Use namespaces: Deploy applications in specific namespaces to isolate resources and manage permissions more effectively.
• Encrypt secrets: Use helm-secrets or integrate with external secret management systems like HashiCorp Vault.
• Sign and verify charts: Sign your Helm charts and verify them upon deployment to ensure they haven’t been tampered with.

Q9. What is Tiller, and how does it interact with Helm? (Note: As of Helm 3, Tiller is no longer used. The question is to check historical understanding.) (Helm Architecture)

Tiller was the server-side component of Helm in versions 1 and 2. It interacted with the Kubernetes API server to install, manage, and orchestrate Helm chart releases. Tiller was responsible for:

• Keeping track of releases
• Performing upgrades or rollbacks
• Managing release configurations

The Helm client would interact with Tiller to execute Helm commands. However, due to concerns regarding the security and operational complexity, Tiller was removed in Helm 3. Now, Helm directly interacts with the Kubernetes API, improving security and simplifying the architecture.

Q10. How can you rollback a Helm release to a previous version? (Helm Rollback Procedure)

To rollback a Helm release to a previous version, you use the helm rollback command followed by the release name and the revision number you want to roll back to. Here is the syntax:

helm rollback [RELEASE] [REVISION]

For example, to rollback the release named my-app to revision 2, you would run:

helm rollback my-app 2

Before rolling back, you can check the revision history of the release with helm history [RELEASE] to identify the revision number to which you want to return. Here’s an example of how you might use this command and what the output could look like:

helm history my-app

REVISION	UPDATED	STATUS	CHART	APP VERSION	DESCRIPTION
1	Thu Nov 10 09:32:12 2022	SUPERSEDED	my-app-0.1.0	1.16.0	Install complete
2	Thu Nov 11 10:15:42 2022	SUPERSEDED	my-app-0.1.1	1.16.1	Upgrade complete
3	Thu Nov 12 11:48:37 2022	DEPLOYED	my-app-0.1.2	1.16.2	Upgrade complete

The rollback command will revert the release to the state it was in at the specified revision, including all Kubernetes resources and configuration.

Q11. What are Helm hooks and what can they be used for? (Advanced Helm Features)

Helm hooks are a powerful feature that allow chart developers to control the lifecycle of a Helm chart by running custom workloads or tasks at specific points in the chart’s lifecycle. They can be used for a variety of purposes, such as:

• Database migrations: Before the application starts, a hook might perform necessary database migrations.
• Backup and restore: A pre-delete hook could be used to back up state before the chart is removed from the cluster.
• Testing: Post-install hooks might run integration or smoke tests against the deployed application.
• Registering with external systems: A post-install hook could register the deployed service with a service discovery system.

Hooks are defined by adding annotations to Kubernetes manifest files within your Helm chart. Here is an example:

apiVersion: batch/v1
kind: Job
metadata:
  name: "{{ .Release.Name }}-hook"
  annotations:
    "helm.sh/hook": post-install,post-upgrade
    "helm.sh/hook-weight": "5"
    "helm.sh/hook-delete-policy": hook-succeeded
spec:
  template:
    # ... Job spec goes here ...

The above manifest defines a Job that runs after installation (post-install) and upgrade (post-upgrade) of the chart.

Q12. How would you troubleshoot a failed Helm deployment? (Troubleshooting & Debugging)

When troubleshooting a failed Helm deployment, here are the steps you can take:

1. Use helm status: This command provides the current status of the release and might include error messages explaining why the release failed.
2. Check release history: The helm history command provides a list of revisions for a release, which can help identify what changes were made and potentially what caused the failure.
3. Review Kubernetes events: Using kubectl get events can provide insights into what is happening in the cluster, which can point out issues with the deployed resources.
4. Inspect logs of pods and containers: The command kubectl logs <pod-name> can be used to review the logs of the failed pods. Look for error messages or stack traces.
5. Run helm lint on the chart: This checks the chart for possible issues that could cause a deployment to fail.
6. Run the chart with --dry-run --debug options: This simulates a deployment and provides verbose output without actually performing any changes. It can help identify configuration problems.

Q13. What is the difference between a Helm linter and what does it do? (Code Quality & Best Practices)

Firstly, to clarify the question, it might be asking about the difference between Helm linter and other linting tools, or the role of a Helm linter. I will answer focusing on the role of Helm linter:

The Helm linter, invoked with helm lint, is a tool that analyzes Helm charts to ensure they follow best practices and that their manifests are well-formed and free from common errors. It checks for things like:

• Missing required fields
• Incorrectly formatted data
• Best practice violations in chart metadata
• Deprecated API usage

Using the Helm linter helps maintain code quality and can prevent runtime issues due to misconfiguration or deprecated practices.

Q14. Can you explain how to use Helm to manage dependencies in your charts? (Dependency Management)

To manage dependencies in Helm charts, you can specify the dependencies in a Chart.yaml file or manage them with a requirements.yaml file for Helm 2. Here is how you can handle dependencies using Helm:

1. Define dependencies: In the Chart.yaml file (Helm 3) or the requirements.yaml file (Helm 2), list the dependencies along with their version and repository.

   Example Chart.yaml snippet for Helm 3:

   dependencies:
     - name: mysql
       version: "1.3.2"
       repository: "https://charts.bitnami.com/bitnami"
   

2. Add repositories: If the dependencies come from a repository not already known to your Helm client, add the repository using helm repo add.

3. Download dependencies: Run helm dependency update <chart> to download the specified dependencies into the charts/ directory of your chart.

4. Inspect dependencies: Use helm dependency list <chart> to see the status of the dependencies.

5. Package chart with dependencies: When packaging your chart with helm package, the dependencies will be included.

Q15. How do you configure Helm for a highly available Kubernetes cluster? (High Availability & Scalability)

Configuring Helm for a highly available Kubernetes cluster involves setting up Helm’s server component, Tiller (for Helm 2), in a resilient and scalable fashion. Since Helm 3 removed Tiller, the following instructions mainly apply to Helm 2:

• Tiller with High Availability: Deploy Tiller in a highly available configuration, ensuring that it can be scheduled on multiple nodes. Use a Deployment with more than one replica and a PodDisruptionBudget.
• Persistent Storage: Use a persistent volume for Tiller’s storage backend to ensure that state is preserved across pod rescheduling and restarts.
• Resource Limits: Define resource limits and requests for Tiller to ensure it receives the necessary CPU and memory resources.
• Readiness and Liveness Probes: Implement readiness and liveness probes for Tiller to facilitate proper health checking and recovery.
• RBAC Configuration: Set up Role-Based Access Control (RBAC) policies that allow Tiller to manage resources without compromising the security of the cluster.
• Secure Communication: Ensure that Tiller is configured to use TLS for secure communication between the Helm client and Tiller server.

For Helm 3 users, focusing on managing Helm’s configuration and repository setup for high concurrency and operation under load is key. You should also consider a backup and recovery strategy for the Helm release information stored in the cluster’s secrets or configmaps.

Q16. In what scenarios would you use Helm over kubectl or other Kubernetes tools? (Tooling & Ecosystem)

Helm is a package manager for Kubernetes that facilitates the deployment and management of applications. Here are scenarios where Helm has advantages over kubectl or other Kubernetes tools:

• Complex Application Management: Helm is useful when deploying complex applications with many dependent components, as it can package these together as a single unit called a chart.
• Release Management: Helm tracks a release of a chart and can roll back changes easily, making it suitable for managing application releases.
• Shared Applications: When you need to share applications between different teams or businesses, Helm charts can be easily distributed and installed.
• Configuration Consistency: Helm charts can encapsulate configuration best practices, ensuring consistent application configuration across environments.
• Templating: Helm has powerful templating capabilities that can generate Kubernetes manifest files from templates with a set of values, reducing duplication and errors.
• Scaling Operations: Helm is useful in automating the deployment process, which is particularly important in large-scale systems where manual deployment would be error-prone and inefficient.

Q17. What are the best practices for versioning Helm charts? (Version Control & Release Management)

For versioning Helm charts, it’s important to follow a set of best practices to ensure a smooth and predictable release process:

• Semantic Versioning: Use Semantic Versioning (SemVer) to manage your chart versions. This means incrementing the MAJOR version when you make incompatible API changes, the MINOR version when you add functionality in a backward-compatible manner, and the PATCH version for backward-compatible bug fixes.
• Chart Revisions: In addition to versioning, Helm also stores revisions for each release. Keep track of these revisions for rollback purposes.
• Immutability: Once a chart version is released, it should be immutable. Any change should result in a new version.
• README and CHANGELOG: Maintain a README file with clear instructions and a CHANGELOG to document changes between chart versions.

Here is a markdown table illustrating an example changelog snippet:

Version	Changes	Date
1.0.1	Fix typo in deployment template	2023-01-10
1.1.0	Add new feature X	2023-02-15
2.0.0	Breaking change in API Y	2023-03-22

Q18. How do you customize the installation of a Helm chart using values files? (Configuration & Customization)

To customize the installation of a Helm chart using values files, follow these steps:

• Create a values.yaml file with your configuration parameters. For example:

replicaCount: 3
service:
  type: LoadBalancer
  port: 80
image:
  repository: myrepo/myapp
  tag: v1.2.3

• Pass the values.yaml file to Helm during the installation process using the -f or --values flag:

helm install my-release -f values.yaml ./my-chart

• Helm merges these values with the default values provided by the chart and applies the configuration to the Kubernetes manifest templates.

Q19. Explain how Helm helps with the application upgrade process and how it ensures zero downtime. (Zero Downtime Deployment & Upgrades)

Helm helps with the application upgrade process by managing releases and performing a series of orchestrated updates to Kubernetes resources. Here’s how it ensures zero downtime:

• Rolling Updates: Helm manages Kubernetes deployments that can be configured to perform rolling updates. New pods are brought up before old ones are terminated, ensuring service availability.
• Revisions Management: Helm keeps track of the revisions of a release, allowing for easy rollbacks if needed. In case of an issue with the upgrade, you can quickly revert to a previous working version.
• Configurable Strategy: You can configure the upgrade strategy in your Helm charts (e.g., Recreate or RollingUpdate) to fit your zero downtime requirements.
• Hooks: Helm provides hooks that can be used to run jobs before, during, and after an upgrade to ensure service continuity.

Q20. How can you use Helm to template Kubernetes manifests? (Templating & Automation)

Helm uses a templating engine to render Kubernetes manifests from templates and a set of values. Here’s an example of how to use Helm for templating:

• Create a template file for a Kubernetes resource, for instance, a deployment.yaml template:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: {{ .Values.app.name }}
spec:
  replicas: {{ .Values.replicaCount }}
  template:
    ...

• Define your values in a values.yaml file:

app:
  name: my-app
replicaCount: 3

• Run the helm template command to generate the Kubernetes manifests:

helm template my-release ./my-chart -f values.yaml

• Helm will process the templates with the provided values and print the resulting Kubernetes manifests, ready to be applied to your cluster using kubectl or directly deployed with Helm.

Q21. What are some of the limitations of Helm, and how do you overcome them? (Limitations & Workarounds)

Limitations of Helm:

• Complexity for New Users: Helm charts can be daunting for beginners due to their complexity and the Helm templating language.
• Tiller Security Issues: Before Helm 3, Tiller (the server-side component) often required extensive permissions, posing a security risk.
• Release Management: Helm manages releases in a namespace scope, which may not be suitable for cluster-wide resources or multi-tenant clusters.
• Limited Validation Capability: Helm does not perform extensive validation on the Kubernetes resources it creates, potentially leading to runtime errors.
• Upgrades and Rollbacks: Helm’s upgrade and rollback mechanisms can sometimes be tricky, especially when dealing with custom resource definitions (CRDs) or stateful applications.

Workarounds:

• Complexity for New Users: Offer comprehensive documentation, examples, and best practices to help new users get up to speed.
• Tiller Security Issues: Eliminated in Helm 3 by removing Tiller, making Helm more secure by default.
• Release Management: Use additional tools or plugins like Helmfile to manage Helm releases at a higher level and support multi-tenant clusters.
• Limited Validation Capability: Integrate additional validation tools such as kubeval or kube-score in your deployment pipeline to catch potential issues early.
• Upgrades and Rollbacks: Be cautious with Helm’s upgrade and rollback functionality by thoroughly testing Helm charts and implementing proper backup strategies for stateful components.

Q22. Describe how Helm chart dependencies are updated. (Dependency Updates & Chart Management)

To update Helm chart dependencies, you would typically follow these steps:

1. Specify Dependencies: In your Helm chart, dependencies are defined in the Chart.yaml file under the dependencies field, where you specify the name, version, and repository of each dependency.

2. Lock Dependencies: Use the helm dependency update <chart> command to update the Chart.lock file, which locks the dependencies to a specific version based on the constraints set in Chart.yaml.

3. Update Dependencies: To actually update the dependencies to their latest versions that satisfy the version constraints, you would run the helm dependency update <chart> command. This will fetch the updated dependencies and place them in the charts/ directory of your Helm chart.

4. Verify Updates: After updating the dependencies, you should verify the updates by reviewing changes and testing your Helm chart to ensure the updated dependencies don’t break your application.

Q23. How would you integrate Helm with a continuous deployment pipeline? (CI/CD Integration)

To integrate Helm into a continuous deployment pipeline, the following steps can be taken:

1. Version Control: Store your Helm charts in a version control system.
2. Chart Linting and Validation: Include steps in your pipeline to lint and validate the Helm chart using helm lint and other validation tools.
3. Automated Testing: Implement automated tests that deploy the Helm chart to a test environment and run integration/end-to-end tests.
4. Image Building and Tagging: If the pipeline also builds Docker images, integrate steps to build the image, tag it with a unique identifier, and push it to a Docker registry.
5. Helm Chart Versioning: Automatically bump the Helm chart version using semantic versioning principles.
6. Chart Packaging and Repository Upload: Package the Helm chart with helm package and upload it to a Helm chart repository using helm push or a similar command.
7. Deployment: Deploy the Helm chart to the target environment using helm upgrade --install, ensuring that the correct values file or parameters are applied for the environment.
8. Rollback and Monitoring: In case of deployment issues, automate rollback procedures using helm rollback. Implement monitoring to verify deployment success.

Q24. Can you list some common alternative tools to Helm and why would you choose Helm over them? (Tool Comparison & Choice Rationale)

Common Alternative Tools to Helm:

• Kustomize
• Terraform
• Ansible
• Jsonnet/Tanka
• Skaffold

Reasons to Choose Helm:

• Popularity and Community Support: Helm is widely adopted in the Kubernetes ecosystem, meaning a large community and a plethora of existing charts.
• Release Management: Helm excels at managing releases and their lifecycle, including upgrades and rollbacks.
• Chart Repository: The concept of chart repositories with versioning enables easy sharing and re-use of application definitions.
• Template Engine: Helm’s template engine allows for dynamic generation of Kubernetes manifests with conditional logic and parameterization.

Q25. What is your experience with Helm chart repositories, and have you ever set one up? (Experience & Practical Knowledge)

My Experience:

I have substantial experience with Helm chart repositories, both using public repositories like Helm Hub (now Artifact Hub) and setting up private repositories for organizational use. Here’s my practical experience:

• Chart Development: I’ve developed custom Helm charts for various applications and services, ensuring best practices for maintainability and security.
• Repository Setup: I’ve set up Helm chart repositories using both cloud-based solutions like AWS S3 with the Helm S3 plugin and on-premises solutions like ChartMuseum or Harbor.
• Automation: Automated the process of packaging charts and pushing them to the Helm repository as part of a CI/CD pipeline.
• Access Control: Managed user permissions and access control to ensure that only authorized users can push or pull charts from the repository.

How to set up a private Helm chart repository (example with ChartMuseum):

1. Install and start ChartMuseum server.
2. Configure storage options (local, Amazon S3, Google Cloud Storage, etc.).
3. Configure authentication/authorization if needed.
4. Use the Helm CLI to add your ChartMuseum installation as a Helm repository.
5. Package your Helm charts with helm package.
6. Upload packaged charts to the repository with curl or helm push plugin.
7. Users can then add your repository to their Helm and install charts from it.

4. Tips for Preparation

Start by immersing yourself in the Helm documentation; it’s the bedrock for understanding Helm’s functionalities and best practices. Build a foundational knowledge of Kubernetes, as Helm is a package manager specifically for Kubernetes. This will help you articulate how Helm streamlines the deployment process.

Next, get hands-on experience. Set up your own Kubernetes cluster, even if it’s a minikube on your local machine, and start deploying applications using Helm charts. Practice creating, updating, and troubleshooting deployments. This will not only give you practical experience but also confidence in discussing real-world scenarios.

Lastly, refresh your soft skills. Clear communication, problem-solving, and adaptability are crucial in tech interviews. Practice explaining complex concepts in simple terms and think of examples where you’ve demonstrated leadership or teamwork, as these anecdotes can be particularly persuasive.

5. During & After the Interview

During the interview, be clear and concise in your responses. Showcase your technical competence by linking your answers to real-world applications and experiences. Interviewers seek candidates who can not only perform tasks but also understand their impact on the larger ecosystem.

Avoid common pitfalls such as getting bogged down in technical jargon without explaining the context, or failing to admit when you don’t know an answer. It’s better to demonstrate how you’d find a solution than to bluff your way through a question.

Prepare intelligent questions for the interviewer about the company’s technology stack, culture, or the challenges they face with Kubernetes and Helm. This shows engagement and a genuine interest in the role.

After the interview, send a thank-you email to express your appreciation for the opportunity and to reiterate your enthusiasm for the position. Typically, companies may take a week or two to respond with feedback or next steps, but it’s acceptable to follow up if you haven’t heard back within that timeframe.