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.
If you’re looking for a managed Kubernetes hosting service, check out our simple, managed Kubernetes service built for growth.
Note: This tutorial covers the workflow for installing software on Kubernetes clusters with version 2 of the Helm package manager, which requires Tiller. If you’re working with version 3 of Helm follow our tutorial How To Install Software on Kubernetes Clusters with the Helm 3 Package Manager.
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
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.
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.
Note: We will bind this serviceaccount to the cluster-admin cluster role. This will give the tiller service superuser access to the cluster and allow it to install all resource types in all namespaces. This is fine for exploring Helm, but you may want a more locked-down configuration for a production Kubernetes cluster.
Please refer to the official Helm RBAC documentation for more information on setting up different RBAC scenarios for Tiller.
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
. . .
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
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
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
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
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
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.
Note: At this point you may want to actually load the Kubernetes Dashboard in your browser and check it out. To do so, first run the following command:
kubectl proxy
This creates a proxy that lets you access remote cluster resources from your local computer. Based on the previous instructions your dashboard service is named kubernetes-dashboard and it’s running in the default namespace. You may now access the dashboard at the following url:
http://localhost:8001/api/v1/namespaces/default/services/https:dashboard:/proxy/
If necessary, substitute your own service name and namespace for the highlighted portions. Instructions for actually using the dashboard are out of scope for this tutorial, but you can read the official Kubernetes Dashboard docs for more information.
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
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:
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
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
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.
