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Transformer Configurations

Kustomize creates new resources by applying a series of transformations to an original set of resources. Kustomize provides the following default transformers:

  • annotations
  • images
  • labels
  • name reference
  • namespace
  • prefix/suffix
  • variable reference

A fieldSpec list, in a transformer's configuration, determines which resource types and which fields within those types the transformer can modify.

FieldSpec

FieldSpec is a type that represents a path to a field in one kind of resource.

group: some-group
version: some-version
kind: some-kind
path: path/to/the/field
create: false

If create is set to true, the transformer creates the path to the field in the resource if the path is not already found. This is most useful for label and annotation transformers, where the path for labels or annotations may not be set before the transformation.

Images transformer

The default images transformer updates the specified image key values found in paths that include containers and initcontainers sub-paths. If found, the image key value is customized by the values set in the newName, newTag, and digest fields. The name field should match the image key value in a resource.

Example kustomization.yaml:

images:
  - name: postgres
    newName: my-registry/my-postgres
    newTag: v1
  - name: nginx
    newTag: 1.8.0
  - name: my-demo-app
    newName: my-app
  - name: alpine
    digest: sha256:25a0d4

Image transformer configurations can be customized by creating a list of images containing the path and kind fields. The images transformation tutorial shows how to specify the default images transformer and customize the images transformer configuration.

Prefix/suffix transformer

The prefix/suffix transformer adds a prefix/suffix to the metadata/name field for all resources. Here is the default prefix transformer configuration:

namePrefix:
- path: metadata/name

Example kustomization.yaml:

namePrefix:
  alices-

nameSuffix:
  -v2

Labels transformer

The labels transformer adds labels to the metadata/labels field for all resources. It also adds labels to the spec/selector field in all Service resources as well as the spec/selector/matchLabels field in all Deployment resources.

Example:

commonLabels:
- path: metadata/labels
  create: true

- path: spec/selector
  create: true
  version: v1
  kind: Service

- path: spec/selector/matchLabels
  create: true
  kind: Deployment

Example kustomization.yaml:

commonLabels:
  someName: someValue
  owner: alice
  app: bingo

Annotations transformer

The annotations transformer adds annotations to the metadata/annotations field for all resources. Annotations are also added to spec/template/metadata/annotations for Deployment, ReplicaSet, DaemonSet, StatefulSet, Job, and CronJob resources, and spec/jobTemplate/spec/template/metadata/annotations for CronJob resources.

Example kustomization.yaml

commonAnnotations:
  oncallPager: 800-555-1212

Name reference transformer

Name reference transformer's configuration is different from all other transformers. It contains a list of nameReferences, which represent all of the possible fields that a type could be used as a reference in other types of resources. A nameReference contains a type such as ConfigMap as well as a list of fieldSpecs where ConfigMap is referenced in other resources. Here is an example:

kind: ConfigMap
version: v1
fieldSpecs:
- kind: Pod
  version: v1
  path: spec/volumes/configMap/name
- kind: Deployment
  path: spec/template/spec/volumes/configMap/name
- kind: Job
  path: spec/template/spec/volumes/configMap/name

Name reference transformer's configuration contains a list of nameReferences for resources such as ConfigMap, Secret, Service, Role, and ServiceAccount. Here is an example configuration:

nameReference:
- kind: ConfigMap
  version: v1
  fieldSpecs:
  - path: spec/volumes/configMap/name
    version: v1
    kind: Pod
  - path: spec/containers/env/valueFrom/configMapKeyRef/name
    version: v1
    kind: Pod
  # ...
- kind: Secret
  version: v1
  fieldSpecs:
  - path: spec/volumes/secret/secretName
    version: v1
    kind: Pod
  - path: spec/containers/env/valueFrom/secretKeyRef/name
    version: v1
    kind: Pod

Customizing transformer configurations

In addition to the default transformers, you can create custom transformer configurations. Save the default transformer configurations to a local directory by calling kustomize config save -d, and modify and use these configurations. This tutorial shows how to create custom transformer configurations:

  • support a CRD type
  • add extra fields for variable substitution
  • add extra fields for name reference

Supporting escape characters in CRD path

metadata:
  annotations:
    foo.k8s.io/bar: baz

Kustomize supports escaping special characters in path, e.g metadata/annotations/foo.k8s.io\/bar