Concepts

2 minutes read

What is Helm ? 🔗

Helm is a Package Manager for Kubernetes, it allows defining, installing, upgrading and deleting applications.
A Helm Chart is an application packaged with Helm, it has a script file/folder structure and uses a templating language.
The Helm Client is a binary used to manipulate application packaged with Helm.

The complete documentation can be found at https://helm.sh

ArtifactHub 🔗

The ArtifactHub is the place where many applications are distributed and ready to be deployed in a Kubernetes cluster.

Installing a chart 🔗

An application installed from a Chart is called a release.

Installing a chart from a helm repository

# Adding a repository
helm repo add grafana https://grafana.github.io/helm-charts

# Installing a chart (= creating a release from this chart)
helm install my-grafana grafana/grafana --version 7.3.8

Installing a chart from an OCI registry

helm install my-redis oci://registry-1.docker.io/bitnamicharts/redis

Base commands 🔗

Creating / upgrading a release

helm install my-release CHART_URL -f values.test.yaml
or
helm upgrade --install my-release CHART_URL -f values.test.yaml

Getting information about a given release

helm get all/hooks/manifest/notes/values my-release

Listing existing releases

helm list

Removing a release

helm delete my-release

Creating a chart to package an application 🔗

The following command creates a sample Chart containing resources to deploy a NGinx server:

helm create my-app

The folder structure created is as follows:

$ tree my-app
my-app
├── Chart.yaml
├── charts
├── templates
│   ├── NOTES.txt
│   ├── _helpers.tpl
│   ├── deployment.yaml
│   ├── ingress.yaml
│   ├── service.yaml
│   ├── serviceaccount.yaml
│   └── tests
│       └── test-connection.yaml
└── values.yaml

Chart.yaml contains the application metadata and the dependencies list
charts is a folder used to store the dependent charts
NOTES.txt provides the post install instructions to the user
_helpers.tpl contains functions and variables to simplify the templating
the YAML files in the templates’ folder contain specifications with templating code
values.yaml defines the configuration values for the application

Packaging the VotingApp with Helm 🔗

In the exercises we created many resources and put them all in a single folder. We will now use Helm to package the VotingApp to ease the distribution and deployment of this application.