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Helm Tutorials: What is Helm & How it works?

June 26, 2023 comments off

What is Package Manager?

Package Manager contains many software package which is easy to install – remove and update. example of package manager includes yum, apt, nuget, chcoclate, play store, apple store.

What is Helm?

  • Package Manager for installing kubernetes package
  • kubernetes helm package is being called “CHART”

Helm is the best way to find, share, and use software built for Kubernetes.

Helm helps you manage Kubernetes applications — Helm Charts help you define, install, and upgrade even the most complex Kubernetes application.

Charts are easy to create, version, share, and publish — so start using Helm and stop the copy-and-paste.

Helm is a graduated project in the CNCF and is maintained by the Helm community.

With and Without Helm

Feature of Helm?

What is kubernetes helm package?

kubernetes helm package is collection of kubernetes API resources yaml file which can be stored with certain structure for easy one click install-update-remove.

Helm Architecture

Helm Workflow

How Does Helm Work?

Helm Chart Anatomy

Helm Terminogy

  1. Chart: A Helm chart is a collection of files that describes a set of Kubernetes resources. It includes templates, values files, and other metadata required to deploy an application to a Kubernetes cluster.
  2. Release: A release is an instance of a chart deployed to a Kubernetes cluster. It represents a specific version of an application running in the cluster.
  3. Repository: A repository is a location where Helm charts are stored. It can be a local directory or a remote server accessible via HTTP(S), Git, or Amazon S3.
  4. Values: Values are parameters that can be customized when installing a Helm chart. They allow you to configure the deployment by providing specific values for variables defined in the chart.
  5. Template: Templates are files written in Go template language that define Kubernetes resource manifests. They allow you to dynamically generate YAML or JSON files based on the provided values.
  6. Release Namespace: A release namespace is the Kubernetes namespace in which a release is deployed. By default, Helm deploys releases to the same namespace as the Tiller (Helm’s server-side component) installation.
  7. Tiller: Tiller is the server-side component of Helm that interacts with the Kubernetes API server to manage releases. It has been deprecated in Helm 3, and Helm 3 no longer requires Tiller.
  8. Dependency: A Helm dependency is a chart that another chart depends on. It allows you to manage complex deployments by specifying and resolving dependencies between charts.
  9. Upgrade: Upgrading a release refers to updating the deployed version of a chart in a Kubernetes cluster. Helm provides commands to upgrade releases with new versions of charts or modify configuration values.
  10. Rollback: Rollback allows you to revert a release to a previous version. It is useful in case a new release version causes i

How to install helm?

- helm client must be installed in kubectl workstation
- Download your desired version
- Unpack it (tar -zxvf helm-v3.0.0-linux-amd64.tar.gz)
- Find the helm binary in the unpacked directory, and move it to its desired destination (mv linux-amd64/helm /usr/local/bin/helm)
https://helm.sh/docs/intro/install/

Commands in Linux?

$ wget https://get.helm.sh/helm-v3.6.2-linux-amd64.tar.gz
$ tar -zxvf helm-v3.6.2-linux-amd64.tar.gz
$ cd linux-amd64
$ echo $PATH
$ mv helm /usr/local/bin
$ helm
$ helm version

How to use helm for Install – updating – removing a helm package called “CHART”?

Step 1 - Visit a helm.sh --> https://artifacthub.io/

Step 2 - Search & Identify a desire chart which you want to install in k8 cluster?

Step 3 - Add helm repo e.g tomcat chat
$ helm repo add bitnami https://charts.bitnami.com/bitnami

Step 4 - Install chart eg. tomcat
$ helm install my-release bitnami/tomcat

Step 5 - Verify 
$ helm list

Step 6 - Remove 
$ helm uninstall my-release

How to create custom helm chart?

$ helm create scmgalaxy

How to install Local chart?
$ helm install scmgalaxy ./scmgalaxy

Helm Help info

  [root@rajesh k8]# helm
The Kubernetes package manager

Common actions for Helm:

- helm search:    search for charts
- helm pull:      download a chart to your local directory to view
- helm install:   upload the chart to Kubernetes
- helm list:      list releases of charts

Environment variables:

| Name                               | Description                                                                       |
|------------------------------------|-----------------------------------------------------------------------------------|
| $HELM_CACHE_HOME                   | set an alternative location for storing cached files.                             |
| $HELM_CONFIG_HOME                  | set an alternative location for storing Helm configuration.                       |
| $HELM_DATA_HOME                    | set an alternative location for storing Helm data.                                |
| $HELM_DEBUG                        | indicate whether or not Helm is running in Debug mode                             |
| $HELM_DRIVER                       | set the backend storage driver. Values are: configmap, secret, memory, postgres   |
| $HELM_DRIVER_SQL_CONNECTION_STRING | set the connection string the SQL storage driver should use.                      |
| $HELM_MAX_HISTORY                  | set the maximum number of helm release history.                                   |
| $HELM_NAMESPACE                    | set the namespace used for the helm operations.                                   |
| $HELM_NO_PLUGINS                   | disable plugins. Set HELM_NO_PLUGINS=1 to disable plugins.                        |
| $HELM_PLUGINS                      | set the path to the plugins directory                                             |
| $HELM_REGISTRY_CONFIG              | set the path to the registry config file.                                         |
| $HELM_REPOSITORY_CACHE             | set the path to the repository cache directory                                    |
| $HELM_REPOSITORY_CONFIG            | set the path to the repositories file.                                            |
| $KUBECONFIG                        | set an alternative Kubernetes configuration file (default "~/.kube/config")       |
| $HELM_KUBEAPISERVER                | set the Kubernetes API Server Endpoint for authentication                         |
| $HELM_KUBECAFILE                   | set the Kubernetes certificate authority file.                                    |
| $HELM_KUBEASGROUPS                 | set the Groups to use for impersonation using a comma-separated list.             |
| $HELM_KUBEASUSER                   | set the Username to impersonate for the operation.                                |
| $HELM_KUBECONTEXT                  | set the name of the kubeconfig context.                                           |
| $HELM_KUBETOKEN                    | set the Bearer KubeToken used for authentication.                                 |

Helm stores cache, configuration, and data based on the following configuration order:

- If a HELM_*_HOME environment variable is set, it will be used
- Otherwise, on systems supporting the XDG base directory specification, the XDG variables will be used
- When no other location is set a default location will be used based on the operating system

By default, the default directories depend on the Operating System. The defaults are listed below:

| Operating System | Cache Path                | Configuration Path             | Data Path               |
|------------------|---------------------------|--------------------------------|-------------------------|
| Linux            | $HOME/.cache/helm         | $HOME/.config/helm             | $HOME/.local/share/helm |
| macOS            | $HOME/Library/Caches/helm | $HOME/Library/Preferences/helm | $HOME/Library/helm      |
| Windows          | %TEMP%\helm               | %APPDATA%\helm                 | %APPDATA%\helm          |

Usage:
  helm [command]

Available Commands:
  completion  generate autocompletion scripts for the specified shell
  create      create a new chart with the given name
  dependency  manage a chart's dependencies
  env         helm client environment information
  get         download extended information of a named release
  help        Help about any command
  history     fetch release history
  install     install a chart
  lint        examine a chart for possible issues
  list        list releases
  package     package a chart directory into a chart archive
  plugin      install, list, or uninstall Helm plugins
  pull        download a chart from a repository and (optionally) unpack it in local directory
  repo        add, list, remove, update, and index chart repositories
  rollback    roll back a release to a previous revision
  search      search for a keyword in charts
  show        show information of a chart
  status      display the status of the named release
  template    locally render templates
  test        run tests for a release
  uninstall   uninstall a release
  upgrade     upgrade a release
  verify      verify that a chart at the given path has been signed and is valid
  version     print the client version information

Flags:
      --debug                       enable verbose output
  -h, --help                        help for helm
      --kube-apiserver string       the address and the port for the Kubernetes API server
      --kube-as-group stringArray   group to impersonate for the operation, this flag can be repeated to specify multiple groups.
      --kube-as-user string         username to impersonate for the operation
      --kube-ca-file string         the certificate authority file for the Kubernetes API server connection
      --kube-context string         name of the kubeconfig context to use
      --kube-token string           bearer token used for authentication
      --kubeconfig string           path to the kubeconfig file
  -n, --namespace string            namespace scope for this request
      --registry-config string      path to the registry config file (default "/root/.config/helm/registry.json")
      --repository-cache string     path to the file containing cached repository indexes (default "/root/.cache/helm/repository")
      --repository-config string    path to the file containing repository names and URLs (default "/root/.config/helm/repositories.yaml")

Use "helm [command] --help" for more information about a command.
Rajesh Kumar
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