Helm: A cheat sheet

Kubernetes

Helm is such a powerful tool and one to check out when you’re learning Kubernetes. In this article we’ll take a look at what it is, some of the main concepts, and some useful commands for Helm.

What is Helm?

Helm is called the package manager for Kubernetes. It makes it easier to package and deploy software on a Kubernetes cluster using app definitions called charts.

A chart is a package that can be shared and reused, which contains an application’s Kubernetes resource definitions (YAML files) and some templating logic.

Helm keeps track of the charts it installs on your Kubernetes cluster by adding labels to the objects created. These labels look like app.kubernetes.io/managed-by=Helm and app.kubernetes.io/instance: myapp.

Helm concepts

  • Chart is a package in Helm. It has a name, and contains a set of Kubernetes resource definitions that are used to deploy your application.

  • Repository is an online collection of charts. It has a URL. You can search, download and install charts from a repository.

  • Release is an instance or a deployment of a chart. When you perform a helm install command, you are creating a new release of that chart on your Kubernetes cluster.

Helm commands

So now let’s get into the most common Helm commands. Here’s your cheatsheet for using Helm!

Finding and viewing charts

Add a remote chart repository

This adds a collection of charts called a repository. Repositories often contain many charts, and can be found on an open source repository server like Chartmuseum, or a public chart repository like ArtifactHub:

helm repo add [name] [url]

Example - using the Bitnami chart repository:

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

List all your repositories

You can see all of the repositories (the remote locations for downloading charts) that you have added to your helm installation:

$ helm repo list
NAME         	URL                                              
kedacore     	https://kedacore.github.io/charts                
stable       	https://kubernetes-charts.storage.googleapis.com/
openfaas     	https://openfaas.github.io/faas-netes/           
jenkins      	https://charts.jenkins.io                        
bitnami      	https://charts.bitnami.com/bitnami               
concourse    	https://concourse-charts.storage.googleapis.com/

Search for a chart

Using helm search will search either Artifact Hub (hub option) or all repositories configured on your system (repo option):

$ helm search hub prometheus
URL                                               	CHART VERSION 	APP VERSION	DESCRIPTION                                       
https://hub.helm.sh/charts/prometheus-community...	12.0.1        	2.21.0     	Prometheus is a monitoring system and time seri...
...

$ helm search repo prometheus
NAME                                 	CHART VERSION	APP VERSION	DESCRIPTION                                       
bitnami/kube-prometheus              	3.1.1        	0.43.2     	kube-prometheus collects Kubernetes manifests t...
bitnami/prometheus-operator          	0.31.1       	0.41.0     	DEPRECATED The Prometheus Operator for Kubernet...
stable/prometheus                    	11.9.1       	2.19.0     	Prometheus is a monitoring system and time seri...

View information about a chart

To get information about a chart, or its values, use helm show, with chart or values:

$ helm repo add concourse https://concourse-charts.storage.googleapis.com/
$ helm show chart concourse/concourse
$ helm show values concourse/concourse

Installing and managing charts

The most common way people make use of Helm is to find and install charts onto a Kubernetes cluster. Here are the main commands you might use when installing charts.

Install a chart’s dependencies

If you have mentioned a dependency in your Chart.yaml, and you need to download it:

helm dependency update

Simulate an install (dry-run)

To simulate installing a chart without actually installing it, do a dry run:

helm install --dry-run ...

NB: this does actually seem to interact with the Kubernetes API, to check if objects already exist in the cluster, etc. For a fully local rendering of a template, use helm template ... (see further below).

Install a chart by reference from a repository

This will install a chart from a repository, so you should ensure that you’ve set up the repository first.

helm install myapp-instance sourcerepo/myapp

Install a chart by reference with an explicit URL

This allows you to specify the URL to the repository when you install:

helm install --repo http://charts.example.com my-app-instance myapp

Install a chart from a packaged file

helm install myapp-instance ./path/to/myappchart.tgz

Install a chart from an unpacked chart directory

This is especially useful when you are developing a chart locally, or you have not published it to a chart repository.

helm install myapp-instance ./path/to/chart

Install a template with a values override file

If you want to override the default values in the template with another values file, use -f:

helm install -f ./my-extra-values.yml ./mychart

Note that this will override default values where they are given, otherwise use the default values.

Install a template with specific values

When you want to install a Helm chart, and override its values explicitly at the command line:

helm install --set key1=val1,key2=val2 [name] [chart]

Example, installing chart sourcerepo/myapp and overriding the property foo.bar:

helm install --set foo.bar=hello myapp-instance sourcerepo/myapp

Getting information about deployed charts

List all releases (deployed charts)

When you want to see all the charts that have been deployed on your cluster (releases):

helm list

See all objects created by a release

When you want to get the YAML of all of the objects that comprise a release, or see all of the objects that were created when you did a helm install:

helm get manifest <release-name>

You’ll need to know the release name you’re looking for (you can list all releases using helm list).

When a chart is deployed (a release is created), a status message is shown. To print this message again:

helm status <release-name>

Uninstalling a release

To uninstall a chart release from your cluster:

helm uninstall <release-name>

Developing your own charts

Packaging your own software for use with Helm is known as creating a chart. You can create a chart yourself from scratch, or you can use the helm create chart which will initialise a chart for you.

Creating a new chart

If you want to create your own chart:

helm create [path]
helm create mychart

This will create a new skeleton or boilerplate chart at ./mychart, which is ready for you to edit and customise.

Locally render a chart template

Use helm template if you want Helm to show the output YAML from your Helm chart, if you were to helm install it. This is useful when debugging your chart:

helm template [NAME] [CHART]
helm template my-app-instance sourcerepo/my-app
helm template my-app-instance .