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
Why is Helm called the ‘package manager for Kubernetes’?
Helm works like a package manager because it can discover, install, upgrade and uninstall software on a Kubernetes cluster.
In this way, it can be thought of like apt for Ubuntu, or yum for Fedora, which are all capable of discovering, downloading and installing software onto a system.
However there is an important distinction. A Helm chart repository does not usually contain the Docker images that will be pulled onto the Kubernetes. Instead, each Helm chart usually references images by pointing to their location in a public or private Docker registry.
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 installcommand, you are creating a new release of that chart on your Kubernetes cluster.
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
helm search will search either Artifact Hub (
hub option) or all repositories configured on your system (
$ 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
$ 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
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
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):
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 get manifest <release-name>
You’ll need to know the release name you’re looking for (you can list all releases using
Print the status message of a release
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
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 .