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.