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Installing applications

There are two ways to add applications to your cluster: using your own manifests or via Helm charts. Manifests are suitable for your own applications, whilst Helm is suitable for ready-made software packages with a wide range of configuration options.

Prerequisites​

Installation via manifest​

You describe your own applications in YAML files and apply them as follows:

# Einzelne Datei
kubectl apply -f deployment.yaml

# Alle Dateien eines Verzeichnisses
kubectl apply -f ./manifeste/

You can find a complete example under Deploying the first image.

Installation via Helm​

Helm is the package manager for Kubernetes. A chart bundles all of an application’s manifests; you can customise the installation using configuration values without having to edit the manifests themselves.

Installing the helmet​

curl -fsSL https://raw.githubusercontent.com/helm/helm/main/scripts/get-helm-3 | bash
helm version

Add a repository​

helm repo add bitnami https://charts.bitnami.com/bitnami
helm repo update

Browse available charts:

helm search repo wordpress

Install the chart​

helm install meine-app bitnami/wordpress \
  --namespace web \
  --create-namespace

meine-app is the name you can choose for the installation (Release). You will manage the application under this name later on.

Customise the installation​

You can list the configurable values for a chart using:

helm show values bitnami/wordpress

You can set individual values directly:

helm install meine-app bitnami/wordpress \
  --namespace web \
  --create-namespace \
  --set service.type=ClusterIP \
  --set persistence.enabled=false

For more extensive adjustments, create a separate values file:

# werte.yaml
service:
  type: ClusterIP

persistence:
  enabled: false

resources:
  requests:
    cpu: 200m
    memory: 512Mi
  limits:
    cpu: 1000m
    memory: 1Gi
helm install meine-app bitnami/wordpress \
  --namespace web \
  --create-namespace \
  --values werte.yaml
Tipp

Keep your values file under version control. This ensures that it is clear which configuration was used to install an application – and that the installation can be reproduced.

Manage installations​

# Installationen auflisten
helm list --all-namespaces

# Verwendete Werte einer Installation anzeigen
helm get values meine-app -n web

# Status einer Installation
helm status meine-app -n web

Refresh​

helm repo update
helm upgrade meine-app bitnami/wordpress \
  --namespace web \
  --values werte.yaml
Warnung

helm upgrade (without --values) resets previously set values to the chart’s default values. Specify your value file again with every upgrade – or use --reuse-values.

Rewind​

# Verlauf der Installation
helm history meine-app -n web

# Auf die vorherige Version zurückrollen
helm rollback meine-app -n web

# Auf eine bestimmte Revision zurückrollen
helm rollback meine-app 3 -n web

Remove​

helm uninstall meine-app -n web
Hinweis

Data stored by an application outside the cluster – for example, in S3 Object Storage or on a database VM – remains in place when the installation is removed and must be cleaned up separately.

Check before installation​

With --dry-run, you can view the manifests that have been generated without making any changes to the cluster:

helm install meine-app bitnami/wordpress \
  --namespace web \
  --values werte.yaml \
  --dry-run --debug

Guidelines for production use​

  • Set resources: Set requests and limits to ensure that an application does not fully utilise a node.
  • Check persistence: Many charts request a persistent volume by default. This works in the cluster – just check that the storage class and the requested size match your needs.
  • Consider the service type: Charts often set service.type=LoadBalancer by default. A service of this type does not receive an external address; switch to NodePort or ClusterIP with Ingress.
  • Separate namespaces: Install applications in their own namespaces to clearly demarcate permissions and resources.
  • Specify the chart version: Use --version to pin the chart version and avoid unintended version jumps.
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