Helm is a package manager for Kubernetes. Similar to Debian’s Apt and Python’s pip, Helm provides a way to find, share, and manage Kubernetes applications.
Helm charts helps you define, install, and upgrade Kubernetes applications without having to directly manage a Kubernetes manifest. They are easy to create, version, share, and publish.
Helm packages are charts that are preconfigured in Kubernetes and ready to be deployed. Charts consist of configuration files (mostly in YAML), which include metadata that describes the application, the infrastructure needed to operate it in terms of the standard Kubernetes manifest, and custom configuration files.
To follow along with this tutorial, you’ll need:
The Helm client is a command line interface (CLI) that enables you to develop charts; manage repositories, releases, and charts on a cluster; and interface with Kubernetes API server.
We’ll use Helm3 for this tutorial.
To install Helm, execute the following commands.
$ curl https://raw.githubusercontent.com/kubernetes/helm/master/scripts/get-helm-3 > get_helm.sh $ chmod 700 get_helm.sh $ ./get_helm.sh
You can test the installation by executing the following.
$ helm version
Once Helm is installed, you can add chart repositories, which is required to install Kubernetes applications available on the charts.
To add the official Helm stable chart, execute the following.
helm repo add stable https://kubernetes-charts.storage.googleapis.com/
You can list charts on a repository using:
helm search repo stable
This lists all the charts available in the
stable repo that can be installed to the cluster.
You can also discover awesome Helm charts that represent Kubernetes applications on Helm Hub.
Click on any chart to see instructions on how to use it and other details.
You can install any existing chart from public charts. For this exercise, we’ll install a WordPress application using the Bitnami Helm Chart repository. This also packages the Bitnami MariaDB chart, which is required to bootstrap a MariaDB deployment for the database requirements of the WordPress application.
First, add the repository by executing:
helm repo add bitnami https://charts.bitnami.com/bitnami
Next, install the WordPress application with a release name of choice. We’ll call our project
myblog and pass custom values for the WordPress username and password.
helm install myblog bitnami/wordpress --version 8.1.4 --set wordpressUsername=admin,wordpressPassword=password
The above command also sets the WordPress administrator account username and password to
password, respectively. Note that this is in the form of
-wordpress. You can read more about the Bitnami WordPress chart and its configuration parameters on HelmHub.
To get the running pods of the Kubernetes application, execute the following.
kubectl get pods
Run the following to get the IP address of the Kubernetes application.
kubectl get service myblog-wordpress
To get a list of all Kubernetes objects created when you installed the chart, execute:
kubectl get all
Remember, we installed the chart with the release name
myblog. This is a running instance of the chart. It can be installed multiple times with different release names.
helm ls to get a list of all releases installed.
Head to the official docs for more Helm commands.
Helm also allows you to delete, upgrade, or roll back a chart release.
To uninstall an application and delete all Kubernetes objects tied to it, execute the following.
helm delete myblog
Helm enables you to scaffold the creation of a chart, which creates the basic files required for a chart.
To create a chart, run the following command.
helm create samplechart
Helm chart files are structured in the following format.
samplechart/ Chart.yaml values.yaml charts/ templates/ deployment.yaml ingress.yaml serviceaccount.yaml _helpers.tpl NOTES.txt service.yaml tests/ test-connection.yaml
Chart.yaml contains a detailed description of the chart. It can be accessed within templates.
charts/ contains other charts, called subcharts.
values.yaml contains the default values for a chart. You can override these values during
helm install or
helm upgrade by passing a custom values file or using the
templates/ directory contains template files. Helm sends all the files in the
templates/ directory through the template rendering engine. It then collects the results of those templates and sends them to Kubernetes as manifests.
Other files in the
templates/ directory include:
NOTES.txt— The “help text” for your chart. This will be displayed to your users when they run helm install.
deployment.yaml— A basic manifest for creating a Kubernetes deployment
service.yaml— A basic manifest for creating a service endpoint for your deployment
_helpers.tpl— A place to put template helpers that you can re-use throughout the chart
The docs outline some best practices for creating your own Helm chart.
Install the local chart as-is by executing:
helm install sample-app ./samplechart
If you follow the information that displays after you install the chart, you’ll see a default Nginx page when you visit the running forwarded pod.
Helm is a useful tool for your Kubernetes workflow because it helps you avoid having to directly write or modify Kubernetes manifests. It also abstracts a lot of complexity and helps you deploy and manage applications more efficiently.
For a deeper dive deeper into Helm, check out the following resources.
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