Subcharts & dependencies

Compose charts; share values.

A chart can depend on other charts — subcharts — declared in Chart.yaml. Installing an app that needs Postgres and Redis can pull in their charts as dependencies rather than you re-templating a database. You list dependencies with a name, version, and repository, then helm dependency update fetches them into charts/. This is how big applications are assembled from reusable pieces.

dependencies:
  - name: postgresql
    version: "15.5.x"
    repository: https://charts.bitnami.com/bitnami
    condition: postgresql.enabled     # toggle the subchart on/off
  - name: redis
    version: "19.x.x"
    repository: https://charts.bitnami.com/bitnami
# helm dependency update  ->  fetches these into charts/

Passing values to subcharts

Parent values reach a subchart under a key matching the subchart name, so postgresql: { auth: { database: payments } } in the parent’s values configures the postgresql subchart. A condition (postgresql.enabled) lets consumers turn a dependency off — deploy with the bundled database in dev, disable it and point at a managed database in prod. global values are shared across all subcharts for things like a common image registry.

postgresql:
  enabled: true
  auth:
    database: payments
    existingSecret: pg-credentials     # subchart config, keyed by subchart name
global:
  imageRegistry: registry.internal      # shared with every subchart