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Exercise 2: Working with Helm charts

Now that you have Helm installed, it's time to install our first release and do some basic operations on it.

A release is an installed instance of a Helm chart.

The Kube Apps hub provides a list of official charts. While the source code of these charts is hosted on the Kubernetes project.

Installing a Chart

  1. We will install tomcat from the stable official repository. You can install your favourite chart though. To install a release, we will use the install command:
# install a release named 'tomcat' of the tomcat chart from the stable repository.
helm install --name=tomcat stable/tomcat --tiller-namespace <your-namespace>
  1. Congratulations! You have installed your first release! Follow the instructions you got on the terminal after executing the install command to expose and access the app in your browser.

Inspecting a Chart

Let's inspect what happened in the cluster:

# to list all releases deployed in the your namespace 
helm list --tiller-namespace <your-namespace>

# to get the status of the release
helm status tomcat --tiller-namespace <your-namespace>

# to get the k8s manifest(s) for a release
helm get tomcat --tiller-namespace <your-namespace>

# to view pods, services and ingresses in the default namespace
kubectl get pods,svc -n <your-namespace>

Upgrading a Release

We installed the tomcat release with default values, now let's upgrade our release with some custom config values (e.g the image tag):

helm upgrade --set image.tomcat.tag=8.5 tomcat stable/tomcat --tiller-namespace <your-namespace>

The command above will create a new pod. Watch for the new pod:

kubectl get pods -n <your-namespace> -w

You can check all the values you could configure for the tomcat chart here.

Tip: you can also create a custom values.yaml file with your customized values and use it to override the defaults: helm install --name tomcat -f my_custom_values.yaml stable/tomcat --tiller-namespace

Rolling back a Release

Let's rollback our tomcat release to the first version:

# get the history of a release
helm history tomcat --tiller-namespace <your-namespace>

# rollback revision (version) number 1 of 'tomcat'
helm rollback tomcat 1 --tiller-namespace <your-namespace>

# now check the status again
helm status tomcat --tiller-namespace <your-namespace>

Delete a Release

Let's delete our tomcat release:

helm delete tomcat --tiller-namespace <your-namespace>

Although the delete command removes all k8s resources created but it does not delete the release history maintained by Helm.

# list deleted releases
helm list --deleted --tiller-namespace <your-namespace>

# purge delete 'tomcat' i.e. delete its k8s resource and/or history
helm delete --purge tomcat --tiller-namespace <your-namespace>