Using Helm Charts

Now that you have a solid understanding of what Helm charts are and how they are structured, it's time to put that knowledge into practice. In this lesson, we will explore how to use Helm charts to deploy applications to a Kubernetes cluster. You’ll learn how to find and download Helm charts from public repositories, install charts on your Kubernetes cluster, and manage Helm releases. By the end of this lesson, you’ll be equipped to deploy applications quickly and efficiently using Helm.

Finding and Downloading Helm Charts

The first step in using Helm charts is to find the chart that suits your needs. Helm charts are typically stored in repositories, which are collections of charts that can be publicly or privately hosted. There are many public Helm repositories available where you can find charts for a wide range of applications.

Popular Helm Repositories

Artifact Hub: A central hub for finding and sharing Kubernetes packages, including Helm charts. It aggregates charts from various repositories and is a great place to start your search.
Bitnami: A popular Helm repository known for its well-maintained and widely used charts for applications like Nginx, WordPress, and MySQL.
Stable Repository: Once the official Helm repository, now deprecated but still widely used through mirrors or forks.

Commands to interact with repositories:

Adding a Repository: Before you can use a chart, you need to add the repository to Helm.
```
helm repo add bitnami https://charts.bitnami.com/bitnami
```
Listing Repositories: You can list all added repositories to see what’s available.
```
helm repo list
```
Searching for Charts: Once the repository is added, you can search for specific charts.
```
helm search repo nginx
```

Downloading a Chart

While you can directly install charts from a repository, you might want to download a chart first to inspect or modify it.

Command to Download a Chart:

Download a Chart: This command fetches the chart files from the repository.
```
bashCopy codehelm pull bitnami/nginx --untar
```
The --untar flag extracts the chart into a directory, so you can explore its contents.

Installing a Helm Chart

Once you’ve identified the chart you want to use, installing it on your Kubernetes cluster is straightforward. Helm makes it easy to deploy an application with a single command.

Basic Installation

To install a chart, you use the helm install command. This command requires at least two arguments: a release name (a unique name for your deployment) and the chart to install.

Command to Install a Chart:

Installing a Chart:
```
helm install my-nginx bitnami/nginx
```
- my-nginx: This is the name of the release.
- bitnami/nginx: This specifies the chart from the Bitnami repository.

After running this command, Helm will:

Render the chart’s templates using the default or provided values.
Interact with the Kubernetes API to create the necessary resources.
Record the release in Helm’s history, allowing you to manage it later.

Customizing Installation with Values

One of the strengths of Helm is its ability to customize deployments using the values.yaml file. You can override these values at the time of installation using the --set flag or by providing a custom values file.

Customizing with --set Flag:

Command to Set a Custom Value:
```
helm install my-nginx bitnami/nginx --set service.type=NodePort
```
This command overrides the default service type, setting it to NodePort.

Customizing with a Custom Values File:

Using a Custom Values File:
```
helm install my-nginx bitnami/nginx -f custom-values.yaml
```
Here, custom-values.yaml contains your custom configuration.

Verifying the Installation

After installation, it’s essential to verify that everything was set up correctly.

Commands for Verifying Installation:

List Releases: Shows all the current releases in your cluster.
```
helm list
```
Get Release Status: Provides detailed information about a specific release.
```
helm status my-nginx
```
Check Kubernetes Resources: Use kubectl to see the created resources.
```
kubectl get all -l app.kubernetes.io/name=nginx
```

Managing Helm Releases

Helm doesn’t just stop at installing applications. It also provides powerful tools for managing your releases over time, including upgrading, rolling back, and uninstalling them.

Upgrading a Release

As your application evolves, you may need to upgrade your Helm release. This could involve updating to a new chart version or simply changing some configuration values.

Command to Upgrade a Release:

Upgrade Release:
```
helm upgrade my-nginx bitnami/nginx --set image.tag=1.17.0
```
This command upgrades the my-nginx release to use a different image tag.

Rolling Back a Release

If something goes wrong with an upgrade, Helm allows you to roll back to a previous release version.

Command to Roll Back a Release:

Rollback Release:
```
helm rollback my-nginx 1
```
This command rolls back the my-nginx release to version 1.

Uninstalling a Release

When you no longer need an application, you can uninstall the release. This command deletes all Kubernetes resources associated with the release.

Command to Uninstall a Release:

Uninstall Release:
```
helm uninstall my-nginx
```

Helm will clean up all the resources and remove the release from its history.

Hands-on Example: Deploying Nginx with Helm

To solidify your understanding, let’s walk through a hands-on example of deploying Nginx using a Helm chart.

Steps:

Add the Bitnami Repository:

helm repo add bitnami https://charts.bitnami.com/bitnami

Install the Nginx Chart:
```
helm install my-nginx bitnami/nginx
```

Verify the Installation:

helm list
helm status my-nginx
kubectl get all -l app.kubernetes.io/name=nginx

Upgrade the Nginx Release:

helm upgrade my-nginx bitnami/nginx --set image.tag=1.19.0

Rollback the Release if Needed:
```
helm rollback my-nginx 1
```
Uninstall the Release:
```
helm uninstall my-nginx
```

This example walks you through the complete lifecycle of a Helm release, from installation to uninstallation, giving you hands-on experience with the Helm CLI.

Summary

Using Helm charts to deploy applications on Kubernetes is a powerful and efficient way to manage your infrastructure. Helm simplifies the process of installing, upgrading, and managing applications, allowing you to focus on building and running your services rather than dealing with the complexities of Kubernetes resource management. By mastering the basics of using Helm charts, you’re well on your way to becoming proficient in Kubernetes application management.

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Last updated 1 year ago