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 installingkubectl
in the official documentation.You can test your connectivity with the following command:
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-fra1-helm3-example do-fra1-helm3-example do-fra1-helm3-example-adminIn this example the asterisk (
*
) indicates that we are connected to thedo-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
:
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:
You may be prompted for your password. Provide it and press ENTER
to continue.
The output will look like this:
Output
Downloading 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:
The output will be similar to this:
Output
NAME 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:
The output will look like this:
Output
NAME 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:
The output will look like the following:
Output
NAME 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:
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:
You’ll see the following output:
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 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:
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.
Helm releases can be deleted with the helm delete
command:
- helm delete dashboard-demo
The output will be:
Output
release "dashboard-demo" uninstalled
You can try listing Helm releases:
You’ll see that there are none:
Output
NAME 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.