configMapGenerator

Generate ConfigMap resources.

Each entry in this list results in the creation of one ConfigMap resource (it’s a generator of n maps).

The example below creates four ConfigMaps:

  • first, with the names and contents of the given files
  • second, with key/value as data using key/value pairs from files
  • third, also with key/value as data, directly specified using literals
  • and a fourth, which sets an annotation and label via options for that single ConfigMap

Each configMapGenerator item accepts a parameter of behavior: [create|replace|merge]. This allows an overlay to modify or replace an existing configMap from the parent.

Also, each entry has an options field, that has the same subfields as the kustomization file’s generatorOptions field.

This options field allows one to add labels and/or annotations to the generated instance, or to individually disable the name suffix hash for that instance. Labels and annotations added here will not be overwritten by the global options associated with the kustomization file generatorOptions field. However, due to how booleans behave, if the global generatorOptions field specifies disableNameSuffixHash: true, this will trump any attempt to locally override it.

apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization

# These labels are added to all configmaps and secrets.
generatorOptions:
  labels:
    fruit: apple

configMapGenerator:
- name: my-java-server-props
  behavior: merge
  files:
  - application.properties
  - more.properties
- name: my-java-server-env-file-vars
  envs:
  - my-server-env.properties
  - more-server-props.env
- name: my-java-server-env-vars
  literals:
  - JAVA_HOME=/opt/java/jdk
  - JAVA_TOOL_OPTIONS=-agentlib:hprof
  options:
    disableNameSuffixHash: true
    labels:
      pet: dog
- name: dashboards
  files:
  - mydashboard.json
  options:
    annotations:
      dashboard: "1"
    labels:
      app.kubernetes.io/name: "app1"

It is also possible to define a key to set a name different than the filename.

The example below creates a ConfigMap with the name of file as myFileName.ini while the actual filename from which the configmap is created is whatever.ini.

apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization

configMapGenerator:
- name: app-whatever
  files:
  - myFileName.ini=whatever.ini

ConfigMap from File

ConfigMap Resources may be generated from files - such as a java .properties file. To generate a ConfigMap Resource for a file, add an entry to configMapGenerator with the filename.

Example: Generate a ConfigMap with a data item containing the contents of a file.

The ConfigMaps will have data values populated from the file contents. The contents of each file will appear as a single data item in the ConfigMap keyed by the filename.

The example illustrates how you can create ConfigMaps from File using Generators.

File Input

# kustomization.yaml
apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
configMapGenerator:
- name: my-application-properties
  files:
  - application.properties

# application.properties
FOO=Bar

Build Output

apiVersion: v1
data:
  application.properties: |-
        FOO=Bar
kind: ConfigMap
metadata:
  name: my-application-properties-f7mm6mhf59

ConfigMap from Literals

ConfigMap Resources may be generated from literal key-value pairs - such as JAVA_HOME=/opt/java/jdk. To generate a ConfigMap Resource from literal key-value pairs, add an entry to configMapGenerator with a list of literals.

Example: Create a ConfigMap with 2 data items generated from literals.

The example illustrates how you can create ConfigMaps from Literals using Generators.

File Input

# kustomization.yaml
apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
configMapGenerator:
- name: my-java-server-env-vars
  literals:
  - JAVA_HOME=/opt/java/jdk
  - JAVA_TOOL_OPTIONS=-agentlib:hprof

Build Output

apiVersion: v1
data:
  JAVA_HOME: /opt/java/jdk
  JAVA_TOOL_OPTIONS: -agentlib:hprof
kind: ConfigMap
metadata:
  name: my-java-server-env-vars-44k658k8gk

ConfigMap from env file

ConfigMap Resources may be generated from key-value pairs much the same as using the literals option but taking the key-value pairs from an environment file. These generally end in .env. To generate a ConfigMap Resource from an environment file, add an entry to configMapGenerator with a single env entry, e.g. env: config.env.

Example: Create a ConfigMap with 3 data items generated from an environment file.

File Input

# kustomization.yaml
apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
configMapGenerator:
- name: tracing-options
  env: tracing.env
# tracing.env
ENABLE_TRACING=true
SAMPLER_TYPE=probabilistic
SAMPLER_PARAMETERS=0.1

Build Output

apiVersion: v1
kind: ConfigMap
metadata:
  # The name has had a suffix applied
  name: tracing-options-6bh8gkdf7k
# The data has been populated from each literal pair
data:
  ENABLE_TRACING: "true"
  SAMPLER_TYPE: "probabilistic"
  SAMPLER_PARAMETERS: "0.1"

Propagating the Name Suffix

Letting ConfigMap or Secret know the name of the generated Resource name suffix

Workloads that reference the ConfigMap or Secret will need to know the name of the generated Resource including the suffix, however Apply takes care of this automatically for users. Apply will identify references to generated ConfigMaps and Secrets, and update them.

The generated ConfigMap name will be my-java-server-env-vars with a suffix unique to its contents. Changes to the contents will change the name suffix, resulting in the creation of a new ConfigMap, and transform Workloads to point to this one.

The PodTemplate volume references the ConfigMap by the name specified in the generator (excluding the suffix). Apply will update the name to include the suffix applied to the ConfigMap name.

Input: The kustomization.yaml and deployment.yaml files

# kustomization.yaml
apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
configMapGenerator:
- name: my-java-server-env-vars
  literals:
  - JAVA_HOME=/opt/java/jdk
  - JAVA_TOOL_OPTIONS=-agentlib:hprof
resources:
- deployment.yaml
# deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: test-deployment
  labels:
    app: test
spec:
  selector:
    matchLabels:
      app: test
  template:
    metadata:
      labels:
        app: test
    spec:
      containers:
      - name: container
        image: k8s.gcr.io/busybox
        command: [ "/bin/sh", "-c", "ls /etc/config/" ]
        volumeMounts:
        - name: config-volume
          mountPath: /etc/config
      volumes:
      - name: config-volume
        configMap:
          name: my-java-server-env-vars

Applied: The Resources that are Applied to the cluster.

apiVersion: v1
kind: ConfigMap
metadata:
  # The name has been updated to include the suffix
  name: my-java-server-env-vars-k44mhd6h5f
data:
  JAVA_HOME: /opt/java/jdk
  JAVA_TOOL_OPTIONS: -agentlib:hprof
---
apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: test
  name: test-deployment
spec:
  selector:
    matchLabels:
      app: test
  template:
    metadata:
      labels:
        app: test
    spec:
      containers:
      - command:
        - /bin/sh
        - -c
        - ls /etc/config/
        image: k8s.gcr.io/busybox
        name: container
        volumeMounts:
        - mountPath: /etc/config
          name: config-volume
      volumes:
      - configMap:
          # The name has been updated to include the
          # suffix matching the ConfigMap
          name: my-java-server-env-vars-k44mhd6h5f
        name: config-volume


Last modified February 4, 2021: Provide kustomization file overview. (8e1ef9f)