Chart values and customization in Kubernetes - Mini Project: Build & Apply

Chart values and customization

📖 Scenario: You are deploying a simple web application using Helm charts on Kubernetes. You want to customize the deployment by changing the number of replicas and the container image version using the chart's values.yaml file.

🎯 Goal: Learn how to set up a values.yaml file with specific values and customize a Helm chart deployment by overriding default values.

📋 What You'll Learn

Create a values.yaml file with specific values

Add a variable for the number of replicas

Use the variable in the deployment template

Print the final rendered Kubernetes deployment manifest

💡 Why This Matters

🌍 Real World

Helm charts are widely used to package and deploy applications on Kubernetes clusters. Customizing chart values allows teams to deploy the same application with different settings easily.

💼 Career

Understanding how to customize Helm charts is essential for Kubernetes administrators and DevOps engineers to manage scalable and configurable deployments.

1

Create the initial values.yaml file

Create a values.yaml file with the following exact content:
replicaCount: 2
image:
repository: nginx
tag: 1.19.0

Kubernetes

# Create a values.yaml file with replicaCount 2 and image repository nginx with tag 1.19.0
# Your code here

Hint

The values.yaml file defines default values for your Helm chart. Use proper indentation for nested keys.

2

Add a variable for replicas in the deployment template

In the deployment template file deployment.yaml, add the line replicas: {{ .Values.replicaCount }} under the spec: section to use the replicaCount value from values.yaml.

Kubernetes

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
spec:
  # Add replicas line here
  template:
    spec:
      containers:
      - name: nginx
        image: nginx:1.19.0
# Your code here

Hint

Use Helm template syntax {{ .Values.replicaCount }} to access the value from values.yaml.

3

Use image repository and tag variables in the container spec

Modify the container image line in deployment.yaml to use the repository and tag from values.yaml with this exact syntax:
image: {{ .Values.image.repository }}:{{ .Values.image.tag }}

Kubernetes

replicaCount: 2
image:
  repository: nginx
  tag: 1.19.0
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
spec:
  replicas: {{ .Values.replicaCount }}
  template:
    spec:
      containers:
      - name: nginx
        # Update image line here
# Your code here

Hint

Use Helm template variables to dynamically set the container image from values.yaml.

4

Render and print the final Kubernetes deployment manifest

Run the Helm template command to render the deployment manifest using the values.yaml file and print the output exactly as shown:
helm template my-nginx . -f values.yaml

Kubernetes

# Run the Helm template command below
# Your code here

Hint

Use the helm template command with the -f values.yaml option to apply your custom values and see the final manifest.

Practice

1. What is the main purpose of the values.yaml file in a Helm chart?

easy

A. To define Kubernetes cluster nodes

B. To store the application source code

C. To provide default configuration values for the chart

D. To list all installed Helm charts

Solution

1. Step 1: Understand the role of values.yaml

   The values.yaml file contains default settings that the Helm chart uses when installing an app.

2. Step 2: Compare other options

   Options B, C, and D describe unrelated tasks: source code, cluster nodes, and installed charts, which are not the purpose of values.yaml.

3. Final Answer:

   To provide default configuration values for the chart -> Option C

4. Quick Check:

   Default config = values.yaml [OK]

Hint: Remember: values.yaml holds default settings [OK]

Common Mistakes:

• Confusing values.yaml with application code
• Thinking values.yaml manages cluster nodes
• Assuming values.yaml lists installed charts

2. Which of the following is the correct way to override a Helm chart value from the command line?

easy

A. helm install myapp ./chart --set image.tag=1.2.3

B. helm install myapp ./chart -override image.tag=1.2.3

C. helm install myapp ./chart --config image.tag=1.2.3

D. helm install myapp ./chart --change image.tag=1.2.3

Solution

1. Step 1: Recall Helm syntax for setting values

   The correct flag to override values is --set, followed by the key=value pair.

2. Step 2: Check other options for correctness

   Options A, C, and D use invalid flags (-override, --config, --change) which Helm does not recognize.

3. Final Answer:

   helm install myapp ./chart --set image.tag=1.2.3 -> Option A

4. Quick Check:

   Override values with --set [OK]

Hint: Use --set key=value to override values [OK]

Common Mistakes:

• Using incorrect flags like --config or --change
• Forgetting to use --set for overrides
• Misplacing the key=value syntax

3. Given this snippet from values.yaml:

replicaCount: 2
image:
  repository: nginx
  tag: stable

What will be the replica count if you run:

helm install myapp ./chart --set replicaCount=5

medium

A. 2

B. 5

C. stable

D. nginx

Solution

1. Step 1: Understand default and override values

   The default replicaCount is 2 from values.yaml. The command line uses --set replicaCount=5 to override it.

2. Step 2: Determine final replica count

   Overrides from --set take priority, so replicaCount becomes 5.

3. Final Answer:

   5 -> Option B

4. Quick Check:

   Command line override changes replicaCount to 5 [OK]

Hint: Command line --set overrides values.yaml [OK]

Common Mistakes:

• Ignoring command line overrides
• Confusing image tag or repository with replicaCount
• Assuming default always applies

4. You tried to override a nested value with helm install myapp ./chart --set image.tag=1.0.0, but the deployment still uses the old tag. What is the most likely cause?

medium

A. The chart does not use the image.tag value in templates

B. You must use --set-string instead of --set

C. The values.yaml file is missing

D. You need to delete the release before installing

Solution

1. Step 1: Check if the chart templates use the overridden value

   If the chart templates do not reference image.tag, overriding it has no effect.

2. Step 2: Evaluate other options

   Using --set-string is only needed for forcing string types, not usually for tags. Missing values.yaml would cause defaults to fail, and deleting release is unrelated to value overrides.

3. Final Answer:

   The chart does not use the image.tag value in templates -> Option A

4. Quick Check:

   Override ignored if template doesn't use value [OK]

Hint: Ensure templates use the value you override [OK]

Common Mistakes:

• Assuming --set always works without template usage
• Confusing --set and --set-string flags
• Thinking release deletion is needed for overrides

5. You want to customize a Helm chart to deploy multiple instances of the same app with different configurations. Which approach best supports this?

hard

A. Install the chart once and manually edit Kubernetes resources

B. Edit the chart source code to hardcode different values

C. Use helm upgrade without changing values

D. Create separate values.yaml files for each instance and install with --values

Solution

1. Step 1: Understand multi-instance customization

   Using separate values.yaml files allows you to define different settings for each instance without changing the chart code.

2. Step 2: Evaluate other options

   Editing chart source is complex and error-prone. Using helm upgrade without changes won't customize. Manually editing resources breaks Helm management.

3. Final Answer:

   Create separate values.yaml files for each instance and install with --values -> Option D

4. Quick Check:

   Use multiple values files for multi-instance customization [OK]

Hint: Use different values files per instance with --values [OK]

Common Mistakes:

• Hardcoding values in chart source
• Ignoring Helm's value override features
• Manually editing deployed resources