How To Install Software on Kubernetes Clusters with the Helm 3 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, you will set up Helm 3 and use it to install, reconfigure, rollback, and 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.

Prerequisites

For this tutorial you will need:

A Kubernetes cluster with role-based access control (RBAC) enabled. Helm 3.1 supports clusters from versions 1.14 to 1.17. For further information check the Helm releases page.
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
```
```
OutputCURRENT   NAME                    CLUSTER                 AUTHINFO                      NAMESPACE
*         do-fra1-helm3-example   do-fra1-helm3-example   do-fra1-helm3-example-admin
```
In this example the asterisk (*) indicates that we are connected to the do-fra1-helm3-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, you’ll install the helm command-line utility on your 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 -fsSL -o get_helm.sh https://raw.githubusercontent.com/helm/helm/master/scripts/get-helm-3

Make the script executable with chmod:

chmod u+x get_helm.sh

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:

./get_helm.sh

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

The output will look like this:

OutputDownloading https://get.helm.sh/helm-v3.1.2-linux-amd64.tar.gz
Preparing to install helm into /usr/local/bin
helm installed into /usr/local/bin/helm

Now that you’ve got Helm installed, you’re ready to use Helm to install your first chart.

Step 2 — Installing a Helm Chart

Helm software packages are called charts. There is a curated chart repository called stable, mostly consisting of common charts, which you can see in their GitHub repo. Helm does not come preconfigured for it, so you’ll need to manually add it. Then, as an example, you are going to install the Kubernetes Dashboard.

Add the stable repo by running:

helm repo add stable https://kubernetes-charts.storage.googleapis.com

The output will be:

Output"stable" has been added to your repositories

Then, use helm to install the kubernetes-dashboard package from the stable repo:

helm install dashboard-demo stable/kubernetes-dashboard --set rbac.clusterAdminRole=true

The --set parameter lets you to customize chart variables, which the chart exposes to allow you to customize its configuration. Here, you set the rbac.clusterAdminRole variable to true to grant the Kubernetes Dashboard access to your whole cluster.

The output will look like:

Output
NAME: dashboard-demo
LAST DEPLOYED: Tue Mar 31 15:04:19 2020
NAMESPACE: default
STATUS: deployed
REVISION: 1
TEST SUITE: None
NOTES:
...

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

You can list all the releases in the cluster:

helm list

The output will be similar to this:

OutputNAME            NAMESPACE       REVISION        UPDATED                                 STATUS          CHART                           APP VERSION
dashboard-demo  default         1               2020-03-31 15:04:19.324774799 +0000 UTC deployed        kubernetes-dashboard-1.10.1     1.10.1

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

kubectl get services

The output will look like this:

OutputNAME                                  TYPE        CLUSTER-IP       EXTERNAL-IP   PORT(S)   AGE
dashboard-demo-kubernetes-dashboard   ClusterIP   10.245.115.214   <none>        443/TCP   4m44s
kubernetes                            ClusterIP   10.245.0.1       <none>        443/TCP   19m

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

Now that you’ve deployed the application, you’ll use Helm to change its configuration and update the deployment.

Step 3 — Updating a Release

The helm upgrade command can be used to upgrade a release with a new or updated chart, or update its configuration options (variables).

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

The kubernetes-dashboard chart provides a fullnameOverride configuration option to control the service name. To rename the release, run helm upgrade with this option set:

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

By passing in the --reuse-values argument, you make sure that chart variables you’ve previously set do not get reset by the upgrade process.

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

Check if your Kubernetes services reflect the updated values:

kubectl get services

The output will look like the following:

OutputNAME                   TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)   AGE
kubernetes             ClusterIP   10.245.0.1      <none>        443/TCP   38m
kubernetes-dashboard   ClusterIP   10.245.49.157   <none>        443/TCP   8s

Notice that the 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:kubernetes-dashboard:https/proxy/

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, you’ll have a look at Helm’s ability to roll back and delete releases.

Step 4 — Rolling Back and Deleting a Release

When you updated the dashboard-demo release in the previous step, you 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

You’ll see the following output:

OutputNAME            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 you 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:

OutputRollback 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.

Helm releases can be deleted with the helm delete command:

helm delete dashboard-demo

The output will be:

Outputrelease "dashboard-demo" uninstalled

You can try listing Helm releases:

helm list

You’ll see that there are none:

OutputNAME    NAMESPACE       REVISION        UPDATED STATUS  CHART   APP VERSION

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

Conclusion

In this tutorial, you installed the helm command-line tool and explored installing, upgrading, rolling back, and deleting Helm charts and releases by managing the kubernetes-dashboard chart.

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

Originally posted on DigitalOcean Community Tutorials
Author: DigitalOcean