helm

Helm - the package manager for Kubernetes

• Helm is the Kubernetes package manager and is used to streamline installing and managing Kubernetes applications.
• Helm consists of the helm tool, which needs to be installed, and a chart.
• A chart is a Helm package, which contains the following:
  • A description of the package
  • One or more templates containing Kubernetes manifest files

• Charts can be stored locally, or accessed from remote Helm repositories.

• To use Helm, a few steps need to be performed:

  • Optional: add repositories
  • Find charts to install
  • Install charts
  • Manage the installed application

• Helm doesn't come with a default repository.

• The main site for finding Helm charts, is through https://artifacthub.io

• Search for specific software here, and run the commands to install it; for instance, to run the Kubernetes Dashboard:

  • helm repo add kubernetes-dashboard https://kubernetes.github.io/dashboard/
  • helm install kubernetes-dashboard kubernetes-dashboard/kubernetes-dashboard
  • The last command creates the local application name "kubernetes-dashboard" by installing the application "kubernetes-dashboard" from the repo "kubernetes-dashboard".

• After adding repositories, use helm repo update to ensure access to the most up-to-date information.

• Use helm install to install the chart with default parameters.

  • Notice that a chart may be installed multiple times, which is why it's important to assign the right name.

• After installation, use helm list to list currently installed charts.

• Optionally, use helm delete to remove currently installed charts.

# you can install with snap
sudo snap install helm --classic
# Fetch the binary from https://github.com/helm/helm/releases; check for the latest release!
tar xvf helm-xxxx.tar.gz
sudo mv linux-amd64/helm /usr/local/bin
helm version

helm search <keyword>

# Add the Kubernetes Dashboard repo, then install it
helm repo add kubernetes-dashboard https://kubernetes.github.io/dashboard/
helm install kubernetes-dashboard kubernetes-dashboard/kubernetes-dashboard

# Add the Bitnami repo and search its charts
helm repo add bitnami https://charts.bitnami.com/bitnami
helm repo list
helm search repo bitnami
helm search repo file
helm search repo nginx --versions

# Install a chart with a generated name, then inspect and manage it
helm install bitnami/mysql --generate-name
kubectl get all
helm show chart bitnami/mysql
helm show all bitnami/mysql
helm list [--all-namespaces]
helm status mysql-xxxx

Creating a template from a Helm Chart

• The helm template command can be used to write the configuration in a Helm chart to a YAML file without deploying the resources in the cluster.
• This allows you to generate a YAML file, allowing you to install the application using kubectl apply while still having the benefit of using the Helm chart parameters.

# Add the Argo repo, then render Argo CD to a YAML template without deploying
helm repo add argo https://argoproj.github.io/argo-helm
helm repo update
helm search repo argo/argo-cd
helm template my-argo-cd argo/argo-cd --version 7.7.14 > argo-cd-template.yaml

# Export default values, customize them, then render and apply
helm show values argo/argo-cd > values.yaml
# search for server.service.type: ClusterIP (line 2120) and change to NodePort
vim values.yaml
helm template my-argocd argo/argo-cd -f values.yaml > argo-cd-template.yaml
kubectl apply -f argo-cd-template.yaml
kubectl get all
kubectl delete -f argo-cd-template.yaml

Managing application with helm

Customizing Helm Applications

• A Helm chart consists of templates to which specific values are applied.
• The values are stored in the values.yaml file, within the Helm chart.
• Use helm show values to list current values (a lot!).
• Read documentation on artifacthub.io for a list of all values.
• Create a custom values.yaml which will be merged with the generic values.yaml file: helm install ... --values values.yaml
• When upgrading an application, you'll have to use --values values.yaml as well.

Overriding Values

• The default values.yaml file which is a part of the Helm chart contains default values which are defined as a key-value pair.
• To get information about useful values, check the documentation of the Helm chart: artifacthub.io is a good place to do so.
• While installing the chart, you can use a custom values.yaml file, provided with --values values.yaml as an argument to helm install to overwrite the default values.
• Alternatively, use helm install ... --set key=value to set individual values.
• Best practice: use a values.yaml file and only use --set when absolutely necessary.

# Add the repo, inspect specific values, customize them, then install and verify
helm repo add bitnami https://charts.bitnami.com/bitnami
helm show values bitnami/nginx
helm show values bitnami/nginx | grep commonLabels
helm show values bitnami/nginx | grep replicaCount
# Edit values.yaml and set:
#   commonLabels: "type: helmapp"
#   replicaCount: 3
vim values.yaml
helm install bitnami/nginx --generate-name --values values.yaml
helm list
helm get values nginx-xxxx
helm get values --all nginx-xxxx

Helm Upgrades

• A Helm chart is the package you install from the Helm repository.
• A Helm installation is an installed instance of that package.
• A Helm release is a combination between a chart and an installation.
• You can upgrade either of these.
• For instance, to first run a nginx installation without exposing it, use helm install bitginx bitnami/nginx --set ingress.enabled=false
• Next, to make the application accessible, use helm update bitginx bitnami/nginx --set ingress.enabled=true
• Use helm repo update to fetch the latest version of charts from the repository.
• Use helm upgrade bitginx bitnami/nginx to upgrade to the latest version of the application.

# Install nginx without ingress, then enable ingress to expose it
helm install bitginx bitnami/nginx --set ingress.enabled=false
helm update bitginx bitnami/nginx --set ingress.enabled=true
# Refresh repo metadata, then upgrade the release to the latest chart version
helm repo update
helm upgrade bitginx bitnami/nginx

Understanding Kustomize

• kustomize is a Kubernetes feature that uses a file with the name kustomization.yaml to apply changes to a set of resources.
• This is convenient for applying changes to input files that the user does not control himself, and which contents may change because of new versions appearing in Git.
• Use kubectl apply -k ./ in the directory with the kustomization.yaml and the files it refers to to apply changes.
• Use kubectl delete -k ./ in the same directory to delete all that was created by the Kustomization.

# sample kustomization.yaml
resources:
- deployment.yaml
- service.yaml
namePrefix: test-
namespace: testing
commonLabels:
  environment: testing

Using Kustomization Overlays

• Kustomization can be used to define a base configuration, as well as multiple deployment scenarios (overlays) as in dev, staging, and prod, for instance.
• In such a configuration, the main kustomization.yaml defines the structure:

- base
  - deployment.yaml
  - service.yaml
  - kustomization.yaml
- overlays
  - dev
    - kustomization.yaml
  - staging
    - kustomization.yaml
  - prod
    - kustomization.yaml

• In each of the overlays/{dev,staging,prod}/kustomization.yaml, users would reference the base configuration in the resources field, and specify changes for that specific environment:

# overlays/dev/kustomization.yaml
resources:
- ../../base
namePrefix: dev-
namespace: development
commonLabels:
  environment: development