Helm¶

Resources¶

Outcomes¶

Understand what Helm is and its role in Kubernetes.
Learn how to install and configure Helm in a Kubernetes environment.
Understand how to use Helm charts to deploy applications.
Learn how to create and manage custom Helm charts.
Understand how to use Helm for application upgrades and rollbacks.

What is Helm?¶

Helm is a package manager for Kubernetes that simplifies the process of deploying, managing, and upgrading Kubernetes applications. Helm uses charts, which are pre-configured Kubernetes resource templates, to define the configuration and deployment of an application or service.

Key Benefits of Helm:¶

Simplified deployments: Helm automates the deployment of Kubernetes applications by using pre-configured templates.
Version control: Helm allows versioning of charts and rollback capabilities in case of failures.
Reuse: Helm charts can be reused across different environments such as development, staging, and production.
Customization: Charts can be customized using values, allowing flexibility without modifying the core chart.

How to Install Helm¶

To use Helm in your Kubernetes cluster, you first need to install Helm on your local machine and configure it to interact with your Kubernetes cluster.

Step 1: Install Helm CLI¶

The Helm client can be installed using the following commands depending on your operating system:

macOS:
```
brew install helm
```

Linux:

curl https://raw.githubusercontent.com/helm/helm/master/scripts/get-helm-3 | bash

Windows: Download the latest release from the Helm GitHub releases page.

Step 2: Configure Helm¶

Once Helm is installed, configure it to use your Kubernetes cluster by ensuring that kubectl is configured and connected to your cluster. Helm interacts with the Kubernetes API server using kubectl.

Step 3: Adding a Helm Repository¶

Helm uses repositories to store and distribute charts. To add the official Helm stable repository, use the following command:

helm repo add stable https://charts.helm.sh/stable

To list all available repositories:

helm repo list

Using Helm Charts to Deploy Applications¶

Helm charts define the structure of a Kubernetes application. A chart contains templates for Kubernetes resources, including deployments, services, and config maps.

Step 1: Searching for a Chart¶

Helm allows you to search for charts in a repository. For example, to search for nginx charts in the stable repository:

helm search repo nginx

Step 2: Installing a Helm Chart¶

To deploy an application using Helm, you can use the helm install command. For example, to install an nginx server:

helm install my-nginx stable/nginx

This command will deploy the nginx chart, and Helm will create the necessary Kubernetes resources based on the chart's configuration.

Step 3: Viewing the Deployed Application¶

You can view the status of the deployed application using the helm status command:

helm status my-nginx

To see all installed Helm releases:

helm list

Customizing Helm Charts¶

Helm allows you to customize the deployment of applications by passing a values.yaml file or using the --set flag during installation.

Example: Customizing a Deployment¶

You can pass custom values when installing a chart using the --set option. For example, to customize the replicaCount value for an nginx deployment:

helm install my-nginx stable/nginx --set replicaCount=3

Alternatively, you can create a values.yaml file with your custom values:

replicaCount: 3

Then, install the chart with the values file:

helm install my-nginx stable/nginx -f values.yaml

Creating Custom Helm Charts¶

In addition to using pre-existing charts, Helm allows you to create custom charts for your own applications.

Step 1: Create a New Helm Chart¶

You can create a new Helm chart using the following command:

helm create my-chart

This command generates a directory structure for your new chart, which includes: - templates/: Contains the Kubernetes manifest templates. - values.yaml: Default configuration values. - Chart.yaml: Metadata about the chart (name, version, etc.).

Step 2: Editing the Chart¶

You can modify the default chart to fit your application. For example, you can edit the deployment template in the templates/deployment.yaml file.

apiVersion: apps/v1
kind: Deployment
metadata:
  name: {{ include "my-chart.fullname" . }}
spec:
  replicas: {{ .Values.replicaCount }}
  template:
    metadata:
      labels:
        app: {{ include "my-chart.name" . }}
    spec:
      containers:
      - name: {{ .Chart.Name }}
        image: {{ .Values.image.repository }}:{{ .Values.image.tag }}
        ports:
        - containerPort: 80

Step 3: Deploying the Custom Chart¶

Once your custom chart is ready, you can deploy it using Helm:

helm install my-app ./my-chart

Helm will render the templates with the provided values and create the Kubernetes resources.

Helm Chart Upgrades and Rollbacks¶

Helm simplifies application management by allowing seamless upgrades and rollbacks.

Step 1: Upgrading a Helm Release¶

To upgrade an existing Helm release with new values or a newer version of the chart:

helm upgrade my-nginx stable/nginx --set replicaCount=5

Helm will apply the changes to the Kubernetes resources without downtime.

Step 2: Rolling Back a Helm Release¶

If something goes wrong after an upgrade, Helm allows you to roll back to a previous version:

helm rollback my-nginx 1

This command will roll back the release my-nginx to revision 1.

Best Practices for Using Helm¶

Version your charts: Always version your custom charts to track changes over time.
Test charts locally: Use the helm template command to render templates locally and check for errors before deploying.
Use values.yaml for configuration: Store custom values in a values.yaml file instead of using the --set flag to keep deployments consistent.
Automate with CI/CD: Use Helm in your CI/CD pipeline to automate deployments and manage upgrades in a consistent and repeatable way.
Secure Helm: Helm 3 removed Tiller, improving security, but ensure your Helm charts and deployments follow best security practices, such as least privilege and encryption for sensitive data.

Summary¶

Helm simplifies Kubernetes application management by packaging, deploying, and upgrading applications using charts. With Helm, you can easily deploy complex applications, manage configuration through values.yaml files, and handle versioning and rollbacks. By using Helm, Kubernetes users can streamline their deployment processes, improve application scalability, and automate infrastructure management. ```