helm-charts

# Helm Charts Package and deploy Kubernetes applications using Helm, the package manager for Kubernetes. ## When to Use This Skill Use this skill when: - Creating reusable Kubernetes application packages - Deploying applications with configurable values - Managing Helm releases and upgrades - Using third-party Helm charts - Implementing chart versioning and repositories ## Prerequisites - Helm 3.x installed - kubectl configured with cluster access - Basic Kubernetes knowledge ## Chart Structure ``` mychart/ ├── Chart.yaml # Chart metadata ├── values.yaml # Default configuration values ├── charts/ # Chart dependencies ├── templates/ # Kubernetes manifest templates │ ├── deployment.yaml │ ├── service.yaml │ ├── ingress.yaml │ ├── configmap.yaml │ ├── secret.yaml │ ├── _helpers.tpl # Template helpers │ ├── NOTES.txt # Post-install notes │ └── tests/ │ └── test-connection.yaml └── .helmignore # Files to ignore ``` ## Chart.yaml ```yaml apiVersion: v2 name: myapp description: A Helm chart for MyApp type: application version: 1.0.0 appVersion: "2.0.0" keywords: - myapp - web maintainers: - name: DevOps Team email: devops@example.com dependencies: - name: postgresql version: "12.x.x" repository: "https://charts.bitnami.com/bitnami" condition: postgresql.enabled ``` ## values.yaml ```yaml replicaCount: 2 image: repository: myapp tag: "" # Defaults to appVersion pullPolicy: IfNotPresent service: type: ClusterIP port: 80 ingress: enabled: false className: nginx hosts: - host: myapp.example.com paths: - path: / pathType: Prefix tls: [] resources: limits: cpu: 500m memory: 256Mi requests: cpu: 100m memory: 128Mi postgresql: enabled: true auth: database: myapp ``` ## Templates ### Deployment Template ```yaml # templates/deployment.yaml apiVersion: apps/v1 kind: Deployment metadata: name: {{ include "myapp.fullname" . }} labels: {{- include "myapp.labels" . | nindent 4 }} spec: replicas: {{ .Values.replicaCount }} selector: matchLabels: {{- include "myapp.selectorLabels" . | nindent 6 }} template: metadata: labels: {{- include "myapp.selectorLabels" . | nindent 8 }} spec: containers: - name: {{ .Chart.Name }} image: "{{ .Values.image.repository }}:{{ .Values.image.tag | default .Chart.AppVersion }}" imagePullPolicy: {{ .Values.image.pullPolicy }} ports: - name: http containerPort: 8080 {{- with .Values.resources }} resources: {{- toYaml . | nindent 12 }} {{- end }} env: - name: DATABASE_URL valueFrom: secretKeyRef: name: {{ include "myapp.fullname" . }}-secrets key: database-url ``` ### Helper Functions ```yaml # templates/_helpers.tpl {{/* Expand the name of the chart. */}} {{- define "myapp.name" -}} {{- default .Chart.Name .Values.nameOverride | trunc 63 | trimSuffix "-" }} {{- end }} {{/* Create a default fully qualified app name. */}} {{- define "myapp.fullname" -}} {{- if .Values.fullnameOverride }} {{- .Values.fullnameOverride | trunc 63 | trimSuffix "-" }} {{- else }} {{- $name := default .Chart.Name .Values.nameOverride }} {{- printf "%s-%s" .Release.Name $name | trunc 63 | trimSuffix "-" }} {{- end }} {{- end }} {{/* Common labels */}} {{- define "myapp.labels" -}} helm.sh/chart: {{ .Chart.Name }}-{{ .Chart.Version }} {{ include "myapp.selectorLabels" . }} app.kubernetes.io/version: {{ .Chart.AppVersion | quote }} app.kubernetes.io/managed-by: {{ .Release.Service }} {{- end }} {{/* Selector labels */}} {{- define "myapp.selectorLabels" -}} app.kubernetes.io/name: {{ include "myapp.name" . }} app.kubernetes.io/instance: {{ .Release.Name }} {{- end }} ``` ### Conditional Resources ```yaml # templates/ingress.yaml {{- if .Values.ingress.enabled -}} apiVersion: networking.k8s.io/v1 kind: Ingress metadata: name: {{ include "myapp.fullname" . }} labels: {{- include "myapp.labels" . | nindent 4 }} {{- with .Values.ingress.annotations }} annotations: {{- toYaml . | nindent 4 }} {{- end }} spec: ingressClassName: {{ .Values.ingress.className }} {{- if .Values.ingress.tls }} tls: {{- range .Values.ingress.tls }} - hosts: {{- range .hosts }} - {{ . | quote }} {{- end }} secretName: {{ .secretName }} {{- end }} {{- end }} rules: {{- range .Values.ingress.hosts }} - host: {{ .host | quote }} http: paths: {{- range .paths }} - path: {{ .path }} pathType: {{ .pathType }} backend: service: name: {{ include "myapp.fullname" $ }} port: number: {{ $.Values.service.port }} {{- end }} {{- end }} {{- end }} ``` ## Helm Commands ### Installing Charts ```bash # Install from local chart helm install myapp ./mychart # Install with custom values helm install myapp ./mychart -f custom-values.yaml # Install with value overrides helm install myapp ./mychart \ --set replicaCount=3 \ --set image.tag=2.0.0 # Install in specific namespace helm install myapp ./mychart -n production --create-namespace # Dry run to preview helm install myapp ./mychart --dry-run --debug ``` ### Managing Releases ```bash # List releases helm list helm list -A # All namespaces # Upgrade release helm upgrade myapp ./mychart helm upgrade myapp ./mychart -f new-values.yaml # Rollback helm rollback myapp 1 helm history myapp # Uninstall helm uninstall myapp ``` ### Chart Development ```bash # Create new chart helm create mychart # Lint chart helm lint ./mychart # Template locally (debug) helm template myapp ./mychart # Package chart helm package ./mychart # Update dependencies helm dependency update ./mychart ``` ## Repositories ```bash # Add repository helm repo add bitnami https://charts.bitnami.com/bitnami # Update repositories helm repo update # Search charts helm search repo postgresql helm search hub prometheus # Install from repo helm install postgres bitnami/postgresql # Show chart info helm show values bitnami/postgresql ``` ## Advanced Features ### Hooks ```yaml # templates/pre-install-job.yaml apiVersion: batch/v1 kind: Job metadata: name: {{ include "myapp.fullname" . }}-migration annotations: "helm.sh/hook": pre-install,pre-upgrade "helm.sh/hook-weight": "-5" "helm.sh/hook-delete-policy": hook-succeeded spec: template: spec: containers: - name: migrate image: "{{ .Values.image.repository }}:{{ .Values.image.tag }}" command: ["./migrate.sh"] restartPolicy: Never ``` ### Tests ```yaml # templates/tests/test-connection.yaml apiVersion: v1 kind: Pod metadata: name: "{{ include "myapp.fullname" . }}-test-connection" annotations: "helm.sh/hook": test spec: containers: - name: wget image: busybox command: ['wget'] args: ['{{ include "myapp.fullname" . }}:{{ .Values.service.port }}'] restartPolicy: Never ``` ```bash # Run tests helm test myapp ``` ### Library Charts ```yaml # Chart.yaml apiVersion: v2 name: mylib type: library version: 1.0.0 ``` ```yaml # Using library chart dependencies: - name: mylib version: "1.x.x" repository: "file://../mylib" ``` ## OCI Registry Support ```bash # Login to registry helm registry login registry.example.com # Push chart to OCI registry helm push mychart-1.0.0.tgz oci://registry.example.com/charts # Pull from OCI registry helm pull oci://registry.example.com/charts/mychart --version 1.0.0 # Install from OCI helm install myapp oci://registry.example.com/charts/mychart ``` ## Common Issues ### Issue: YAML Indentation Errors **Problem**: Template renders with wrong indentation **Solution**: Use `nindent` helper function ```yaml {{- toYaml .Values.resources | nindent 12 }} ``` ### Issue: Values Not Applying **Problem**: Custom values not reflected **Solution**: Check value paths, use `--debug` flag ```bash helm template myapp ./mychart --debug ``` ### Issue: Dependency Errors **Problem**: Chart dependencies not found **Solution**: Run `helm dependency update` ### Issue: Release Already Exists **Problem**: Cannot install, release exists **Solution**: Use `helm upgrade --install` ```bash helm upgrade --install myapp ./mychart ``` ## Best Practices - Use semantic versioning for charts - Provide comprehensive default values - Document all values in values.yaml with comments - Use helper templates for repeated patterns - Implement chart tests - Use .helmignore to exclude unnecessary files - Pin dependency versions - Use `helm lint` in CI pipelines ## Related Skills - kubernetes-ops (`kubernetes-ops`) - K8s fundamentals - argocd-gitops (`argocd-gitops`) - GitOps with Helm - kustomize (`kustomize`) - Alternative templating ## Limitations - Guidance executes against real environments: confirm target, blast radius, and rollback plan before applying anything. - Never deploy to production without explicit approval. Docs-only import: upstream scripts and templates not bundled. ### Example ```bash git status && git diff --stat kubectl diff -f manifest.yaml ``` > Adapted from [BagelHole/DevOps-Security-Agent-Skills](https://github.com/BagelHole/DevOps-Security-Agent-Skills) (MIT); frontmatter, When to Use/Limitations, and safety boundaries added for upstream compliance. Docs-only import: helper scripts and templates not bundled.