Chart templates and values.yaml in Kubernetes - Cheat Sheet & Quick Revision

Recall & Review

beginner

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

The values.yaml file stores default configuration values for the Helm chart. It allows users to customize the chart by overriding these values during installation.

beginner

How do templates in a Helm chart use values from values.yaml?

Templates use the Go templating syntax to access values from values.yaml using {{ .Values.key }}. This inserts the configured value into Kubernetes resource files.

intermediate

What happens if a value is not defined in values.yaml but is referenced in a template?

If a value is missing, Helm uses an empty string or default if specified in the template. This can cause errors or unexpected behavior if the template expects a value.

intermediate

Explain how you can override values in values.yaml when installing a Helm chart.

You can override values by using the --set flag with helm install or by providing a custom YAML file with the -f option. This changes the configuration without modifying the original values.yaml.

beginner

What is the role of the templates/ directory in a Helm chart?

The templates/ directory contains Kubernetes manifest templates. Helm processes these templates by injecting values from values.yaml to generate final resource files for deployment.

Which file in a Helm chart holds the default configuration values?

A values.yaml

B Chart.yaml

C templates/deployment.yaml

D README.md

The values.yaml file contains default configuration values for the Helm chart.

How do you reference a value named 'replicaCount' from values.yaml inside a template?

A {{ .Chart.replicaCount }}

B {{ .replicaCount }}

C {{ .Config.replicaCount }}

D {{ .Values.replicaCount }}

Values from values.yaml are accessed in templates using {{ .Values.key }} syntax.

What command option allows you to override values.yaml during Helm install?

A --override

B --config

C --set

D --values

The --set flag lets you override specific values when installing a Helm chart.

If a value is missing in values.yaml and not handled in the template, what is likely to happen?

A Helm automatically fills it with a default value

B Template renders with empty or default value

C Helm installation fails with an error

D The value is ignored silently

Missing values usually render as empty strings unless the template provides a default.

Where are Kubernetes resource templates stored in a Helm chart?

A templates/

B charts/

C config/

D resources/

The templates/ directory holds the Kubernetes manifest templates in a Helm chart.

Describe how Helm uses the values.yaml file and templates together to deploy Kubernetes resources.

Think about how configuration and templates combine to create Kubernetes files.

Explain how you can customize a Helm chart deployment without changing the original values.yaml file.

Consider command line options for Helm install.

Practice

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

easy

A. To store default configuration values for templates

B. To define Kubernetes resource limits

C. To write deployment scripts

D. To list all Kubernetes nodes

Solution

1. Step 1: Understand Helm chart structure

   Helm charts use templates with placeholders to create Kubernetes manifests dynamically.

2. Step 2: Role of values.yaml

   The values.yaml file provides default values for these placeholders, allowing customization without changing templates.

3. Final Answer:

   To store default configuration values for templates -> Option A

4. Quick Check:

   values.yaml = default settings [OK]

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

Common Mistakes:

• Confusing values.yaml with deployment scripts
• Thinking it defines resource limits directly
• Assuming it lists Kubernetes nodes

2. Which of the following is the correct syntax to reference a value named replicaCount from values.yaml inside a Helm template?

easy

A. {{ .Values.replicaCount }}

B. {{ .replicaCount }}

C. {{ values.replicaCount }}

D. {{ .Config.replicaCount }}

Solution

1. Step 1: Understand Helm template syntax

   Helm templates access values using the .Values object followed by the key name.

2. Step 2: Match syntax for replicaCount

   The correct way is {{ .Values.replicaCount }} to get the value from values.yaml.

3. Final Answer:

   {{ .Values.replicaCount }} -> Option A

4. Quick Check:

   Use .Values.key to access values [OK]

Hint: Use .Values.key to get values in templates [OK]

Common Mistakes:

• Omitting the .Values prefix
• Using lowercase 'values' instead of .Values
• Confusing .Config with .Values

3. Given this snippet in values.yaml:

replicaCount: 3
image:
  repository: nginx
  tag: stable

What will be the output of this Helm template snippet?

{{ .Values.replicaCount }} replicas of {{ .Values.image.repository }}:{{ .Values.image.tag }}

medium

A. replicaCount replicas of image.repository:image.tag

B. Error: undefined values

C. 3 replicas of nginx:latest

D. 3 replicas of nginx:stable

Solution

1. Step 1: Read values.yaml keys and values

   replicaCount is 3, image.repository is 'nginx', and image.tag is 'stable'.

2. Step 2: Substitute values in template

   The template outputs: '3 replicas of nginx:stable' by replacing placeholders with values.

3. Final Answer:

   3 replicas of nginx:stable -> Option D

4. Quick Check:

   Values replaced correctly = 3 replicas of nginx:stable [OK]

Hint: Match keys exactly to get correct output [OK]

Common Mistakes:

• Using wrong tags like 'latest' instead of 'stable'
• Not accessing nested keys properly
• Expecting literal placeholders in output

4. You have this template snippet:

{{ if .Values.enableFeature }}Feature is enabled{{ else }}Feature is disabled{{ end }}

But the output always shows "Feature is disabled" even when you set enableFeature: true in values.yaml. What is the likely cause?

medium

A. The template syntax is incorrect and missing a closing tag

B. enableFeature is set as a string "true" instead of boolean true

C. The values.yaml file is not saved properly

D. Helm does not support boolean values in values.yaml

Solution

1. Step 1: Check boolean handling in values.yaml

   YAML treats unquoted true as boolean, but quoted "true" is a string, which evaluates as true in some contexts but false in Helm conditionals.

2. Step 2: Understand Helm conditional evaluation

   Helm expects boolean true, so if enableFeature is a string, the condition fails and goes to else.

3. Final Answer:

   enableFeature is set as a string "true" instead of boolean true -> Option B

4. Quick Check:

   Boolean true must be unquoted in values.yaml [OK]

Hint: Use unquoted true/false for booleans in values.yaml [OK]

Common Mistakes:

• Quoting booleans as strings
• Assuming template syntax error without checking values
• Not saving values.yaml after changes

5. You want to create a Helm chart template that sets the container port only if service.port is defined in values.yaml. Which template snippet correctly implements this conditional logic?

hard

A. {{- if .Values.service.port }}
containerPort: "{{ .Values.service.port }}"
{{- else }}
containerPort: 80
{{- end }}

B. {{- if .service.port }}
containerPort: {{ .service.port }}
{{- end }}

C. {{- if .Values.service.port }}
containerPort: {{ .Values.service.port }}
{{- end }}

D. {{- if .Values.service.port != null }}
containerPort: {{ .Values.service.port }}
{{- end }}

Solution

1. Step 1: Identify correct value reference

   Use .Values.service.port to access the port value from values.yaml.

2. Step 2: Use proper conditional syntax

   Helm templates use {{- if .Values.service.port }} to check if the value exists and is non-empty.

3. Step 3: Evaluate options

   {{- if .Values.service.port }} containerPort: {{ .Values.service.port }} {{- end }} correctly uses the conditional and outputs the port only if defined. {{- if .service.port }} containerPort: {{ .service.port }} {{- end }} misses .Values. {{- if .Values.service.port }} containerPort: "{{ .Values.service.port }}" {{- else }} containerPort: 80 {{- end }} adds an else block which is not requested. {{- if .Values.service.port != null }} containerPort: {{ .Values.service.port }} {{- end }} uses invalid syntax (!= null is not valid in Helm templates).

4. Final Answer:

   {{- if .Values.service.port }} containerPort: {{ .Values.service.port }} {{- end }} -> Option C

5. Quick Check:

   Use if .Values.key for conditionals [OK]

Hint: Check existence with if .Values.key, no need for != null [OK]

Common Mistakes:

• Omitting .Values prefix
• Using invalid comparison operators
• Adding unnecessary else blocks