Introduction to Helm charts

Category : Kubernetes | Sub Category : Kubernetes With Java | By Prasad Bonam Last updated: 2023-11-21 13:30:47 Viewed : 208

Helm is a package manager for Kubernetes that simplifies the deployment and management of applications. Helm uses a packaging format called charts, which are a collection of pre-configured Kubernetes resources. Helm charts allow you to define, install, and upgrade even the most complex Kubernetes applications.

Key Concepts:

1. Chart:

   • A Helm package is called a chart.
   • Charts are versioned, shareable packages that contain all the Kubernetes resources needed to run an application.

2. Release:

   • A specific instance of a chart is called a release.
   • Each release is a deployed version of a chart, with its own configuration, resources, and revision history.

3. Repository:

   • A collection of charts is stored in a Helm repository.
   • Helm charts can be hosted in public or private repositories for easy sharing and distribution.

Helm Chart Structure:

A Helm chart is organized in a directory structure containing the following key files and directories:

• Chart.yaml:

  • Metadata about the chart, including name, version, and description.

• values.yaml:

  • Default configuration values for the chart.
  • Users can override these values during installation.

• templates/:

  • Directory containing Kubernetes resource files written in YAML or Helm`s template language.
  • These files define the resources that will be deployed when the chart is installed.

• charts/:

  • Directory containing subcharts or dependencies that the main chart relies on.

Helm Commands:

1. Install a Chart:

   bashCopy code
   helm install <release-name> <chart-name>
   

   • <release-name> is the name you give to the release.
   • <chart-name> is the name or path of the chart.

2. Upgrade a Release:

   bashCopy code
   helm upgrade <release-name> <chart-name>
   

   • Upgrades an existing release with changes from a new chart.

3. List Releases:

   bashCopy code
   helm list
   

   • Lists all releases, their statuses, and revision numbers.

4. Uninstall a Release:

   bashCopy code
   helm uninstall <release-name>
   

   • Removes a release from the cluster.

5. Show Chart Information:

   bashCopy code
   helm show chart <chart-name>
   

   • Displays information about a chart, including its dependencies.

Example Helm Chart:

Here is a simple Helm chart structure for a basic NGINX deployment:

plaintextCopy code
my-nginx-chart/
|-- Chart.yaml
|-- values.yaml
|-- templates/
|   |-- deployment.yaml
|   |-- service.yaml

• Chart.yaml contains metadata about the chart.
• values.yaml contains default configuration values.
• templates/ contains Kubernetes resource files (e.g., deployment.yaml and service.yaml) written in Helm`s template language.

Helm Repository:

Helm charts can be stored in a repository for easy sharing and distribution. Helm provides commands to manage repositories:

• Add a Repository:

  bashCopy code
  helm repo add <repo-name> <repo-url>
  

  • Adds a Helm chart repository.

• Search for Charts:

  bashCopy code
  helm search repo <keyword>
  

  • Searches for charts in the specified repository.

• Fetch the Latest Charts:

  bashCopy code
  helm repo update
  

  • Updates the local repository cache with the latest available charts.

Helm makes it easy to package, deploy, and manage Kubernetes applications, making it a popular choice for application deployment in Kubernetes clusters.