10 Helm Chart Interview Questions and Answers

Helm Charts have become an essential tool for managing Kubernetes applications, providing a streamlined way to define, install, and upgrade even the most complex Kubernetes applications. By packaging Kubernetes resources into a single, reusable unit, Helm Charts simplify the deployment process and enhance maintainability. This makes them a critical skill for anyone working with container orchestration and cloud-native applications.

This article offers a curated selection of Helm Chart interview questions designed to test and expand your understanding of this powerful tool. By working through these questions, you will gain deeper insights into Helm Charts, preparing you to confidently discuss and demonstrate your expertise in any technical interview setting.

Helm Chart Interview Questions and Answers

1. What is a Helm Chart and what are its primary components?

A Helm Chart is a package manager for Kubernetes that simplifies the deployment process by managing resources through a single package. It is particularly useful for deploying complex applications requiring multiple resources.

The primary components of a Helm Chart are:

• Chart.yaml: Contains metadata about the chart, such as its name, version, and description.
• values.yaml: Contains default configuration values for the chart, which users can override during installation.
• templates/: Contains Kubernetes resource templates written in Go templating language.
• charts/: Can contain other charts that the current chart depends on, allowing for dependencies.
• README.md: Provides documentation about the chart, including usage instructions and configuration options.
• requirements.yaml: Specifies the dependencies for the chart.

2. Describe how values.yaml file is used in Helm Charts.

The values.yaml file defines default values for the chart’s templates, allowing users to customize their Kubernetes applications. Users can override these defaults by specifying their own values in a separate YAML file or via the command line.

Example:

# values.yaml
replicaCount: 3
image:
  repository: nginx
  tag: stable
  pullPolicy: IfNotPresent
service:
  type: ClusterIP
  port: 80

The corresponding deployment template might look like this:

# templates/deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: {{ .Release.Name }}
spec:
  replicas: {{ .Values.replicaCount }}
  selector:
    matchLabels:
      app: {{ .Release.Name }}
  template:
    metadata:
      labels:
        app: {{ .Release.Name }}
    spec:
      containers:
      - name: {{ .Release.Name }}
        image: "{{ .Values.image.repository }}:{{ .Values.image.tag }}"
        imagePullPolicy: {{ .Values.image.pullPolicy }}
        ports:
        - containerPort: {{ .Values.service.port }}

Users can override these values by providing their own in a separate YAML file or via the command line:

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

3. Write a Helm template snippet to create a Kubernetes Deployment resource.

A Helm template snippet to create a Kubernetes Deployment resource can be written as follows:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: {{ .Release.Name }}-deployment
  labels:
    app: {{ .Release.Name }}
spec:
  replicas: {{ .Values.replicas }}
  selector:
    matchLabels:
      app: {{ .Release.Name }}
  template:
    metadata:
      labels:
        app: {{ .Release.Name }}
    spec:
      containers:
      - name: {{ .Chart.Name }}
        image: "{{ .Values.image.repository }}:{{ .Values.image.tag }}"
        ports:
        - containerPort: {{ .Values.service.port }}

In this snippet:

• The apiVersion, kind, and metadata fields define the basic structure of the Deployment resource.
• The spec field contains the specification for the Deployment, including the number of replicas and the selector for matching labels.
• The template field defines the Pod template, including metadata and the specification for the containers.
• The {{ .Release.Name }}, {{ .Values.replicas }}, {{ .Values.image.repository }}, {{ .Values.image.tag }}, and {{ .Values.service.port }} placeholders are used to dynamically insert values from the Helm chart’s values file.

4. How can you override default values in a Helm Chart during installation?

In Helm, default values for a chart are defined in a values.yaml file. These values can be overridden during installation or upgrade using the --set flag or by providing a custom values.yaml file.

To override values using the --set flag, specify the key-value pairs directly in the command line. This method is useful for quick changes without creating a new file.

Example:

helm install my-release my-chart --set image.tag=2.0.0

Alternatively, create a custom values.yaml file with the desired overrides and pass it to the Helm command using the -f or --values flag. This method is more suitable for complex configurations or when multiple values need to be overridden.

Example:

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

5. What are Helm hooks and how are they used? Provide an example.

Helm hooks are special annotations that allow you to execute tasks at specific points in the release lifecycle, such as database migrations or backups. They are defined in the metadata section of Kubernetes manifests using the “helm.sh/hook” annotation.

Example:

apiVersion: batch/v1
kind: Job
metadata:
  name: pre-install-job
  annotations:
    "helm.sh/hook": pre-install
spec:
  template:
    spec:
      containers:
      - name: pre-install-job
        image: busybox
        command: ['sh', '-c', 'echo Pre-install job running']
      restartPolicy: Never

In this example, a Kubernetes Job is defined with the “helm.sh/hook” annotation set to “pre-install”. This job will run before the Helm chart is installed.

6. How do you manage secrets in Helm Charts?

Managing secrets in Helm Charts involves securely handling sensitive information such as passwords, API keys, and certificates. There are several methods to manage secrets:

• Kubernetes Secrets: Helm can leverage Kubernetes Secrets to store sensitive data. You can create a Kubernetes Secret and reference it in your Helm templates.
• Helm Secrets Plugin: This plugin allows you to encrypt your secrets using tools like SOPS (Secrets OPerationS) or Mozilla’s sops.
• External Secret Management Tools: Tools like HashiCorp Vault, AWS Secrets Manager, and Azure Key Vault can be used to manage secrets externally.

Example of using Kubernetes Secrets in a Helm Chart:

# templates/deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: {{ .Release.Name }}
spec:
  template:
    spec:
      containers:
        - name: myapp
          image: myapp:{{ .Values.image.tag }}
          env:
            - name: DATABASE_PASSWORD
              valueFrom:
                secretKeyRef:
                  name: myapp-secret
                  key: password

In this example, the DATABASE_PASSWORD environment variable is populated from a Kubernetes Secret named myapp-secret.

7. Write a Helm template function to conditionally include a resource based on a value in values.yaml.

In Helm, you can conditionally include resources in your templates based on values specified in the values.yaml file. This is useful for enabling or disabling certain features or components of your application.

To achieve this, use the if statement in your Helm templates. The if statement checks the value from the values.yaml file and includes the resource only if the condition is met.

Example:

# values.yaml
enableService: true

# templates/service.yaml
{{- if .Values.enableService }}
apiVersion: v1
kind: Service
metadata:
  name: my-service
spec:
  selector:
    app: my-app
  ports:
    <ul>
      <li>protocol: TCP</li>
      <li>port: 80</li>
      <li>targetPort: 9376</li>
    </ul>
{{- end }}

In this example, the Service resource will only be included in the rendered output if the enableService value in the values.yaml file is set to true.

8. Discuss the security implications of using Helm and how to mitigate potential risks.

Helm charts simplify the deployment of applications on Kubernetes, but they also introduce several security implications. One concern is the risk of deploying untrusted or malicious charts. To mitigate this risk, use charts from trusted repositories and review the chart contents before deployment.

Another concern is the management of sensitive data. Helm charts often require configuration values, which may include sensitive information such as passwords, API keys, and certificates. Storing these values in plain text within the chart or values files can lead to exposure. To address this, use Kubernetes secrets to manage sensitive information and employ tools like Helm Secrets to encrypt sensitive values.

Access control is also important. By default, Helm uses a service account with cluster-wide permissions, which can be a security risk if not properly managed. Implementing Role-Based Access Control (RBAC) policies to limit the permissions of Helm’s service account can help mitigate this risk. Additionally, using tools like Tillerless Helm or Helm 3, which do not require a server-side component with elevated permissions, can enhance security.

9. Describe some advanced templating functions in Helm and their use cases.

Helm uses templating to manage Kubernetes manifests. Advanced templating functions in Helm can enhance the flexibility and reusability of charts. Some of these functions include:

• include: Allows you to include the content of another template and pass it through the template engine.
• required: Ensures that a value is provided. If the value is missing, Helm will throw an error.
• tpl: Allows you to render a string as a template.
• lookup: Enables you to query Kubernetes resources from within your templates.

Example:

# templates/configmap.yaml
apiVersion: v1
kind: ConfigMap
metadata:
  name: {{ include "mychart.fullname" . }}
data:
  myvalue: {{ required "A value for myvalue is required!" .Values.myvalue | quote }}
  dynamic: {{ tpl .Values.dynamicTemplate . }}

In this example, the include function is used to include the content of another template, required ensures that a value is provided for myvalue, and tpl renders a string as a template.

10. How do you test Helm Charts before deploying them to a production environment?

Testing Helm Charts before deploying them to a production environment ensures that the charts are correctly configured and will function as expected. There are several methods and tools available for testing Helm Charts:

• Linting with helm lint: This command checks the syntax and structure of the Helm Chart to ensure it adheres to best practices and is free of common errors.
• Template Rendering with helm template: This command renders the Helm Chart templates locally, allowing you to inspect the generated Kubernetes manifests without actually deploying them.
• Unit Testing with Helm Unit Test Frameworks (e.g., helm-unittest): These frameworks allow you to write unit tests for your Helm templates, ensuring that the templates render correctly under various conditions.
• Integration Testing with Tools like kubeval and kube-score: These tools validate the generated Kubernetes manifests against the Kubernetes API schema and best practices.
• Local Deployment with Minikube or Kind (Kubernetes in Docker): Deploying the Helm Chart to a local Kubernetes cluster allows you to test the chart in an environment that closely resembles production.
• Continuous Integration (CI) Pipelines: Integrating Helm Chart testing into your CI pipeline ensures that the charts are automatically tested whenever changes are made. Tools like Jenkins, GitLab CI, and GitHub Actions can be used to automate the testing process.