Module: 19 Helm 3

Helm is a tool for managing Kubernetes packages called charts. It is maintained by the CNCF - in collaboration with Microsoft, Google, Bitnami and the Helm contributor community.
A chart is a collection of files that describe a related set of Kubernetes resources. With a single chart, you can run a basic application or something more complex, like a full web app inside the Kubernetes cluster. Helm charts help you define, install and upgrade even the most complex Kubernetes application.
What are the main differences between Helm 3 and the previous version?

One of the biggest differences between Helm 2 and Helm 3 is its architecture. Indeed, there is no more Tiller (the server-side component of Helm 2). Tiller was configured to have full access on all Kubernetes cluster. With this new architecture Helm 3 is more secure. Helm interacts directly with Kubernetes API server. The permissions are based on the Kubernetes config file. This means you can restrict user permissions

What is Helm and How to install Helm version 3?

Helm is a package manager for Kubernetes. Helm is the K8s equivalent of yum or apt. It accomplishes the same goals as Linux system package managers like APT or YUM: managing the installation of applications and dependencies behind the scenes and hiding the complexity from the user.

Why use Helm?

As the Kubernetes platform and ecosystem continued to expand, deploying one and only one Kubernetes configuration file (ie: a single YAML) was not the norm anymore. As number of K8S deployment files increased, how to manage those files? Helm solves that problem.

Helm Charts

Helm uses a packaging format called Charts. A Helm Chart is a collection of files that describe a set of Kubernetes resources. Helm Charts helps you define, install, and upgrade even the most complex Kubernetes application. Charts are easy to create, version, share, and publish.

Helm Kubernetes Integration

In helm 3 there is no tiller component. Helm client directly interacts with the Kubernetes API for the helm chart deployment.

Helm 3 can be installed many ways. We will install Helm 3 using scripts option.

Download scripts 

curl -fsSL -o get_helm.sh https://raw.githubusercontent.com/helm/helm/master/scripts/get-helm-3

provide permission
sudo chmod 700 get_helm.sh


Execute script to install
sudo ./get_helm.sh

 
Verify installation
helm version --client

Basic commands

To upload a chart to Kubernetes, you can use the following command:

let's do our custom application on the helm chart 

helm create [NAME] [CHART]


helm lint ./mychart/  #To check the file form 

helm install [NAME] [CHART]

If you want to upgrade your chart, use the following command and choose the release you want:


helm upgrade [RELEASE] [CHART]

Otherwise, you can do a rollback. If you do not specify the revision, it will rollback to the previous version.

helm rollback [RELEASE] [REVISION]

helm install --dry-run --debug ./mychart/ --generate-name

 helm install kelly-app mychart/
 kubectl get pods
 kubectl get svc
 helm ls
 kubectl get all
 cd mychart/
 ls
 vi Chart.yaml
 vi values.yaml
then cd templates 
vi deployment.yml and comment out livenessprobe and readinessprobe 

 cd ..
 helm ls
 helm upgrade kelly-app mychart/
 helm ls
 kubectl get all
 helm rollback kelly-app 1
 helm ls
 kubectl get pods

To retrieve a package from a package repository, and download it locally:

helm pull [CHART]

You have two commands to search:

helm search hub

This command search for charts in the Helm Hub.

helm search repo

These commands search repositories that you have added to your local helm client. This search is done over local data, and no public network connection is needed.

If you want to uninstall a release, here is the command:

helm uninstall [RELEASE]

Repository commands

You have a few commands to interact with chart repositories. A repository is a place where you can find and share charts.

You can add a chart repository:

helm repo add [NAME] [URL]

You can list chart repositories:

helm repo list | ls

You can remove a chart repository:

helm repo remove | rm [NAME]

And finally, you can get the latest information about charts from the respective chart repositories:

helm repo update

Monitoring commands

helm status [RELEASE]

This command shows you the status of your release. The status consists of:

• last deployment time
• kubernetes namespace in which the release lives
• state of the release (can be: unknown, deployed, uninstalled, superseded, failed, uninstalling, pending-install, pending-upgrade or pending-rollback)
• list of resources that this release consists of, sorted by kind
• details on last test suite run, if applicable
• additional notes provided by the chart

helm list | helm ls:

You can list all applications that have been installed in the cluster using helm.

helm history [RELEASE]

You can see with this command all the historical revisions for a given release.

Create your own chart

helm create [NAME]

helm package [CHART]

This command packages a chart into a versioned chart archive file.

helm lint [CHART]

This command takes a path to a chart and runs a series of tests to verify that the chart is well-formed.

With these commands, you are now able deploying your app on Kubernetes with Helm 3.