Creating custom Helm charts in Kubernetes - Step-by-Step CLI Walkthrough

Introduction

When you want to deploy applications on Kubernetes repeatedly and consistently, creating a custom Helm chart helps package all the app's settings and files together. This makes deploying and updating your app easier and less error-prone.

When you want to deploy your own application on Kubernetes with custom settings.

When you need to share your app deployment setup with your team or others.

When you want to manage app versions and upgrades smoothly on Kubernetes.

When you want to avoid typing long kubectl commands repeatedly for your app.

When you want to customize app configurations like ports, replicas, or environment variables easily.

Config File - Chart.yaml

Chart.yaml

apiVersion: v2
name: my-app
description: A Helm chart for deploying my custom app
version: 0.1.0
appVersion: "1.0"

apiVersion: Specifies Helm chart version format.

name: The chart's name.

description: A short explanation of what the chart does.

version: The chart's version for tracking changes.

appVersion: The version of the app the chart deploys.

Commands

This command creates a new Helm chart folder named 'my-app' with default files and folders to start customizing your app deployment.

Terminal

helm create my-app

Expected Output

Creating my-app

This command installs your custom Helm chart named 'my-app' into your Kubernetes cluster, deploying your app with the default settings.

Terminal

helm install my-app ./my-app

Expected Output

NAME: my-app

LAST DEPLOYED: Fri Apr 26 12:00:00 2024

NAMESPACE: default

STATUS: deployed

REVISION: 1

TEST SUITE: None

This command lists all Helm releases installed in your Kubernetes cluster to verify your app is deployed.

Terminal

helm list

Expected Output

NAME    NAMESPACE   REVISION    UPDATED                     STATUS      CHART         APP VERSION

my-app  default     1           2024-04-26 12:00:00.000000  deployed    my-app-0.1.0  1.0

This command removes the 'my-app' release from your Kubernetes cluster, cleaning up all deployed resources.

Terminal

helm uninstall my-app

Expected Output

release "my-app" uninstalled

Key Concept

If you remember nothing else from this pattern, remember: a Helm chart packages all your app's Kubernetes files and settings so you can deploy and manage your app easily with simple commands.

Common Mistakes

Trying to install a Helm chart without creating it first.

Helm needs the chart files and structure to deploy; without creating the chart, the install command fails.

Always run 'helm create my-app' to generate the chart files before installing.

Not updating the Chart.yaml or templates before installing, leading to deploying default or wrong settings.

The default chart files may not match your app's needs, causing deployment errors or misconfiguration.

Edit Chart.yaml and template files to match your app's requirements before running 'helm install'.

Forgetting to uninstall old releases before reinstalling, causing conflicts.

Helm will not install a release with the same name twice without uninstalling or upgrading, leading to errors.

Use 'helm uninstall my-app' to remove old releases before fresh installs or use 'helm upgrade' to update.

Summary

Use 'helm create my-app' to generate a new Helm chart with default files.

Customize the Chart.yaml and templates to fit your app's deployment needs.

Deploy your app with 'helm install my-app ./my-app' and verify with 'helm list'.

Remove your app deployment cleanly with 'helm uninstall my-app' when needed.

Practice

1. What is the primary purpose of a Helm chart in Kubernetes?

easy

A. To package and deploy Kubernetes applications easily

B. To monitor Kubernetes cluster health

C. To replace kubectl commands

D. To create virtual machines in Kubernetes

Solution

1. Step 1: Understand Helm chart role

   A Helm chart bundles Kubernetes resources and configurations for an app.

2. Step 2: Identify main use

   It simplifies sharing and deploying apps by packaging them.

3. Final Answer:

   To package and deploy Kubernetes applications easily -> Option A

4. Quick Check:

   Helm charts = package & deploy apps [OK]

Hint: Helm charts bundle apps for easy deployment [OK]

Common Mistakes:

• Confusing Helm with monitoring tools
• Thinking Helm replaces kubectl commands
• Assuming Helm creates virtual machines

2. Which command initializes a new Helm chart with default files?

easy

A. helm init

B. helm start

C. helm create

D. helm new

Solution

1. Step 1: Recall Helm commands

   The command to create a new chart with default files is helm create.

2. Step 2: Eliminate incorrect options

   helm init is deprecated, helm start and helm new do not exist.

3. Final Answer:

   helm create -> Option C

4. Quick Check:

   New chart command = helm create [OK]

Hint: Use 'helm create' to start a new chart fast [OK]

Common Mistakes:

• Using 'helm init' which is deprecated
• Trying 'helm start' or 'helm new' which are invalid
• Confusing 'helm create' with 'helm install'

3. Given this snippet in a Helm template file:

{{ .Values.replicaCount }}

If values.yaml sets replicaCount: 3, what will this render in the deployed manifest?

medium

A. {{ .Values.replicaCount }}

B. 3

C. replicaCount

D. null

Solution

1. Step 1: Understand Helm template variables

   {{ .Values.replicaCount }} inserts the value of replicaCount from values.yaml.

2. Step 2: Check the value in values.yaml

   Since replicaCount is set to 3, the template renders the number 3.

3. Final Answer:

   3 -> Option B

4. Quick Check:

   Template variable renders value = 3 [OK]

Hint: Template {{ .Values.key }} outputs the key's value [OK]

Common Mistakes:

• Thinking the template syntax prints literally
• Confusing key name with value
• Assuming missing values render as null

4. You created a Helm chart but get an error: template: deployment.yaml:10: unexpected EOF. What is the most likely cause?

medium

A. Cluster is not reachable

B. Incorrect image name in values.yaml

C. Helm version is outdated

D. Missing closing bracket in template syntax

Solution

1. Step 1: Analyze error message

   "unexpected EOF" means the template ended unexpectedly, often due to missing closing brackets.

2. Step 2: Identify common template syntax errors

   Missing a closing }} or {% causes this error.

3. Final Answer:

   Missing closing bracket in template syntax -> Option D

4. Quick Check:

   Unexpected EOF = missing closing bracket [OK]

Hint: Check all {{ }} pairs are closed properly [OK]

Common Mistakes:

• Blaming image name for syntax errors
• Assuming cluster issues cause template parse errors
• Ignoring template syntax mistakes

5. You want to create a Helm chart that allows users to set a custom container port via values.yaml. Which snippet correctly uses this value in the deployment.yaml template?

hard

A. ports:
- containerPort: {{ .Values.containerPort }}

B. ports:
- containerPort: $containerPort

C. ports:
- containerPort: {{ containerPort }}

D. ports:
- containerPort: .Values.containerPort

Solution

1. Step 1: Recall Helm template syntax for values

   Use {{ .Values.key }} to insert values from values.yaml.

2. Step 2: Check each option

   ports: - containerPort: {{ .Values.containerPort }} uses correct Helm syntax. The other options use invalid or incomplete syntax.

3. Final Answer:

   ports: - containerPort: {{ .Values.containerPort }} -> Option A

4. Quick Check:

   Use {{ .Values.key }} for values in templates [OK]

Hint: Use {{ .Values.key }} to access values.yaml keys [OK]

Common Mistakes:

• Using shell variable syntax like $containerPort
• Omitting the dot before Values
• Not using handlebars {{ }} for templating