How To Install Software on Kubernetes Clusters with the Helm 2 Package Manager

Introduction

Helm is a package manager for Kubernetes that allows developers and operators to more easily configure and deploy applications on Kubernetes clusters.

In this tutorial we will set up Helm and use it to install, reconfigure, rollback, then delete an instance of the Kubernetes Dashboard application. The dashboard is an official web-based Kubernetes GUI.

For a conceptual overview of Helm and its packaging ecosystem, please read our article An Introduction to Helm.

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Prerequisites

For this tutorial you will need:

• A Kubernetes 1.8+ cluster with role-based access control (RBAC) enabled.

• The kubectl command-line tool installed on your local machine, configured to connect to your cluster. You can read more about installing kubectl in the official documentation.

  You can test your connectivity with the following command:

  kubectl cluster-info
  
  

  If you see no errors, you’re connected to the cluster. If you access multiple clusters with kubectl, be sure to verify that you’ve selected the correct cluster context:

  kubectl config get-contexts
  
  

  Output
  CURRENT   NAME                    CLUSTER                      AUTHINFO                      NAMESPACE
  *         do-nyc1-k8s-example     do-nyc1-k8s-example          do-nyc1-k8s-example-admin
            docker-for-desktop      docker-for-desktop-cluster   docker-for-desktop
  

  In this example the asterisk (*) indicates that we are connected to the do-nyc1-k8s-example cluster. To switch clusters run:

  kubectl config use-context context-name
  
  

When you are connected to the correct cluster, continue to Step 1 to begin installing Helm.

Step 1 — Installing Helm

First we’ll install the helm command-line utility on our local machine. Helm provides a script that handles the installation process on MacOS, Windows, or Linux.

Change to a writable directory and download the script from Helm’s GitHub repository:

cd /tmp
curl https://raw.githubusercontent.com/kubernetes/helm/master/scripts/get > install-helm.sh

Make the script executable with chmod:

chmod u+x install-helm.sh

At this point you can use your favorite text editor to open the script and inspect it to make sure it’s safe. When you are satisfied, run it:

./install-helm.sh

You may be prompted for your password. Provide it and press ENTER.

Output
helm installed into /usr/local/bin/helm
Run 'helm init' to configure helm.

Next we will finish the installation by installing some Helm components on our cluster.

Step 2 — Installing Tiller

Tiller is a companion to the helm command that runs on your cluster, receiving commands from helm and communicating directly with the Kubernetes API to do the actual work of creating and deleting resources. To give Tiller the permissions it needs to run on the cluster, we are going to make a Kubernetes serviceaccount resource.

Create the tiller serviceaccount:

kubectl -n kube-system create serviceaccount tiller

Next, bind the tiller serviceaccount to the cluster-admin role:

kubectl create clusterrolebinding tiller --clusterrole cluster-admin --serviceaccount=kube-system:tiller

Now we can run helm init, which installs Tiller on our cluster, along with some local housekeeping tasks such as downloading the stable repo details:

helm init --service-account tiller

Output
. . .

Tiller (the Helm server-side component) has been installed into your Kubernetes Cluster.

Please note: by default, Tiller is deployed with an insecure 'allow unauthenticated users' policy.
For more information on securing your installation see: https://docs.helm.sh/using_helm/#securing-your-helm-installation
Happy Helming!

To verify that Tiller is running, list the pods in thekube-system namespace:

kubectl get pods --namespace kube-system

Output
NAME                                    READY     STATUS    RESTARTS   AGE
. . .
kube-dns-64f766c69c-rm9tz               3/3       Running   0          22m
kube-proxy-worker-5884                  1/1       Running   1          21m
kube-proxy-worker-5885                  1/1       Running   1          21m
kubernetes-dashboard-7dd4fc69c8-c4gwk   1/1       Running   0          22m
tiller-deploy-5c688d5f9b-lccsk          1/1       Running   0          40s

The Tiller pod name begins with the prefix tiller-deploy-.

Now that we’ve installed both Helm components, we’re ready to use helm to install our first application.

Step 3 — Installing a Helm Chart

Helm software packages are called charts. Helm comes preconfigured with a curated chart repository called stable. You can browse the available charts in their GitHub repo. We are going to install the Kubernetes Dashboard as an example.

Use helm to install the kubernetes-dashboard package from the stable repo:

helm install stable/kubernetes-dashboard --name dashboard-demo

Output
NAME:   dashboard-demo
LAST DEPLOYED: Wed Aug  8 20:11:07 2018
NAMESPACE: default
STATUS: DEPLOYED

. . .

Notice the NAME line, highlighted in the above example output. In this case we specified the name dashboard-demo. This is the name of our release. A Helm release is a single deployment of one chart with a specific configuration. You can deploy multiple releases of the same chart with, each with its own configuration.

If you don’t specify your own release name using --name, Helm will create a random name for you.

We can ask Helm for a list of releases on this cluster:

helm list

Output
NAME           	REVISION	UPDATED                 	STATUS  	CHART                     	NAMESPACE
dashboard-demo	1       	Wed Aug  8 20:11:11 2018	DEPLOYED	kubernetes-dashboard-0.7.1	default

We can now use kubectl to verify that a new service has been deployed on the cluster:

kubectl get services

Output
NAME                                   TYPE        CLUSTER-IP     EXTERNAL-IP   PORT(S)   AGE
dashboard-demo-kubernetes-dashboard   ClusterIP   10.32.104.73   <none>        443/TCP   51s
kubernetes                             ClusterIP   10.32.0.1      <none>        443/TCP   34m

Notice that by default the service name corresponding to our release is a combination of the Helm release name and the chart name.

Now that we’ve deployed the application, let’s use Helm to change its configuration and update the deployment.

Step 4 — Updating a Release

The helm upgrade command can be used to upgrade a release with a new or updated chart, or update the it’s configuration options.

We’re going to make a simple change to our dashboard-demo release to demonstrate the update and rollback process: we’ll update the name of the dashboard service to just dashboard, instead of dashboard-demo-kubernetes-dashboard.

The kubernetes-dashboard chart provides a fullnameOverride configuration option to control the service name. Let’s run helm upgrade with this option set:

helm upgrade dashboard-demo stable/kubernetes-dashboard --set fullnameOverride="dashboard"

You’ll see output similar to the initial helm install step.

Check if your Kubernetes services reflect the updated values:

kubectl get services

Output
NAME                   TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)   AGE
kubernetes             ClusterIP   10.32.0.1       <none>        443/TCP   36m
dashboard              ClusterIP   10.32.198.148   <none>        443/TCP   40s

Our service name has been updated to the new value.

kubectl proxy

http://localhost:8001/api/v1/namespaces/default/services/https:dashboard:/proxy/

Next we’ll look at Helm’s ability to roll back releases.

Step 5 — Rolling Back a Release

When we updated our dashboard-demo release in the previous step, we created a second revision of the release. Helm retains all the details of previous releases in case you need to roll back to a prior configuration or chart.

Use helm list to inspect the release again:

helm list

Output
NAME           	REVISION	UPDATED                 	STATUS  	CHART                     	NAMESPACE
dashboard-demo	2       	Wed Aug  8 20:13:15 2018	DEPLOYED	kubernetes-dashboard-0.7.1	default

The REVISION column tells us that this is now the second revision.

Use helm rollback to roll back to the first revision:

helm rollback dashboard-demo 1

You should see the following output, indicating that the rollback succeeded:

Output
Rollback was a success! Happy Helming!

At this point, if you run kubectl get services again, you will notice that the service name has changed back to its previous value. Helm has re-deployed the application with revision 1’s configuration.

Next we’ll look into deleting releases with Helm.

Step 6 — Deleting a Release

Helm releases can be deleted with the helm delete command:

helm delete dashboard-demo

Output
release "dashboard-demo" deleted

Though the release has been deleted and the dashboard application is no longer running, Helm saves all the revision information in case you want to re-deploy the release. If you tried to helm install a new dashboard-demo release right now, you’d get an error:

Error: a release named dashboard-demo already exists.

If you use the --deleted flag to list your deleted releases, you’ll see that the release is still around:

helm list --deleted

Output
NAME           	REVISION	UPDATED                 	STATUS 	CHART                     	NAMESPACE
dashboard-demo	3       	Wed Aug  8 20:15:21 2018	DELETED	kubernetes-dashboard-0.7.1	default

To really delete the release and purge all old revisions, use the --purge flag with the helm delete command:

helm delete dashboard-demo --purge

Now the release has been truly deleted, and you can reuse the release name.

Conclusion

In this tutorial we installed the helm command-line tool and its tiller companion service. We also explored installing, upgrading, rolling back, and deleting Helm charts and releases.

For more information about Helm and Helm charts, please see the official Helm documentation.