--- title: "Generating ConfigMaps" linkTitle: "Generating ConfigMaps" weight: 1 date: 2023-10-20 description: > Working with the ConfigMap Generator --- ConfigMap objects can be generated by adding a [`configMapGenerator`] entry to the `kustomization.yaml` file. ## Create ConfigMap from a 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. 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 following example generates a ConfigMap with a data item containing the contents of a file. 1. Create a Kustomization file. ```yaml # kustomization.yaml apiVersion: kustomize.config.k8s.io/v1beta1 kind: Kustomization configMapGenerator: - name: my-application-properties files: - application.properties ``` 2. Create a `.properties` file. ```yaml # application.properties FOO=Bar ``` 3. Create the ConfigMap using `kustomize build`. ```bash kustomize build . ``` The output is similar to: ```yaml apiVersion: v1 data: application.properties: |- FOO=Bar kind: ConfigMap metadata: name: my-application-properties-f7mm6mhf59 ``` It is also possible to [define a key](https://kubernetes.io/docs/tasks/configure-pod-container/configure-pod-configmap/#define-the-key-to-use-when-creating-a-configmap-from-a-file) 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`. ```yaml apiVersion: kustomize.config.k8s.io/v1beta1 kind: Kustomization configMapGenerator: - name: app-whatever files: - myFileName.ini=whatever.ini ``` ## Create 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`. {{< alert color="success" title="Literal Syntax" >}} - The key/value are separated by a `=` sign (left side is the key). - The value of each literal will appear as a data item in the ConfigMap keyed by its key. {{< /alert >}} The following example generates a ConfigMap with two data items generated from literals. 1. Create a Kustomization file. ```yaml # 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 ``` 2. Create the ConfigMap using `kustomize build`. ```bash kustomize build . ``` The output is similar to: ```yaml apiVersion: v1 data: JAVA_HOME: /opt/java/jdk JAVA_TOOL_OPTIONS: -agentlib:hprof kind: ConfigMap metadata: name: my-java-server-env-vars-44k658k8gk ``` ## Create 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 `envs` entry, e.g. `envs: [ 'config.env' ]`. {{< alert color="success" title="Environment File Syntax" >}} - The key/value pairs inside of the environment file are separated by a `=` sign (left side is the key). - The value of each line will appear as a data item in the ConfigMap keyed by its key. - Pairs may span a single line only. {{< /alert >}} The following example generates a ConfigMap with three data items generated from an environment file. 1. Create a Kustomization file. ```yaml # kustomization.yaml apiVersion: kustomize.config.k8s.io/v1beta1 kind: Kustomization configMapGenerator: - name: tracing-options envs: - tracing.env ``` 2. Create an environment file. ```bash # tracing.env ENABLE_TRACING=true SAMPLER_TYPE=probabilistic SAMPLER_PARAMETERS=0.1 ``` 3. Create the ConfigMap using `kustomize build`. ```bash kustomize build . ``` The output is similar to: ```yaml 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" ``` ## Create ConfigMap with options The labels and annotations of a generated ConfigMap can be set with the `options` field. The name suffix hash can also be disabled. Labels and annotations added with `options` will not be overwritten by values defind in the `generatorOptions` field. Note that `disableNameSuffixHash: true` defined in `globalOptions` will override the locally defined `options`. This is a result of boolean behavior. The following example generates a ConfigMap with labels, annotations and does not add a suffix hash to the name. 1. Create a Kustomization file. ```yaml # kustomization.yaml apiVersion: kustomize.config.k8s.io/v1beta1 kind: Kustomization generatorOptions: labels: fruit: apple configMapGenerator: - name: my-java-server-env-vars literals: - JAVA_HOME=/opt/java/jdk - JAVA_TOOL_OPTIONS=-agentlib:hprof options: disableNameSuffixHash: true labels: pet: dog annotations: dashboard: "1" ``` 2. Create the ConfigMap using `kustomize build`. ```bash kustomize build . ``` The ConfigMap manifest is created with labels and annotations. ```yaml apiVersion: v1 kind: ConfigMap metadata: name: my-java-server-env-vars labels: fruit: apple pet: dog annotations: dashboard: "1" data: JAVA_HOME: /opt/java/jdk JAVA_TOOL_OPTIONS: -agentlib:hprof ``` ## Override base ConfigMap values ConfigMap values from bases may be overridden by adding another generator for the ConfigMap in the overlay and specifying the `behavior` field. `behavior` may be one of: * `create` (default value): used to create a new ConfigMap. A name conflict error will be thrown if a ConfigMap with the same name and namespace already exists. * `replace`: replace an existing ConfigMap from the base. * `merge`: add or update the values in an existing ConfigMap from the base. When updating an existing ConfigMap with the `merge` or `replace` strategies, you must ensure that both the name and namespace match the ConfigMap you are targeting. For example, if the namespace is unspecified in the base, you should not specify it in the overlay. Conversely, if it is specified in the base, you must specify it in the overlay as well. This is true even if the overlay Kustomization includes a namespace, because `configMapGenerator` runs before the namespace transformer. ```yaml apiVersion: kustomize.config.k8s.io/v1beta1 kind: Kustomization namespace: my-new-namespace resources: - ../base configMapGenerator: - name: existing-name namespace: existing-ns # needs to match target ConfigMap from base behavior: replace literals: - ENV=dev ``` {{< alert color="warning" title="Name suffixing with overlay configMapGenerator" >}} When using `configMapGenerator` to override values of an existing ConfigMap, the overlay `configMapGenerator` does not cause suffixing of the existing ConfigMap's name to occur. To take advantage of name suffixing, use `configMapGenerator` in the base, and the overlay generator will correctly update the suffix based on the new content. {{< /alert >}} ## Propagate ConfigMap Name Suffix Workloads that reference the ConfigMap or Secret will need to know the name of the generated Resource, including the suffix. Kustomize takes care of this automatically by identifying references to generated ConfigMaps and Secrets, and updating them. In the following example, 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, which Kustomize will transform Workloads to point to. The PodTemplate volume references the ConfigMap by the name specified in the generator (excluding the suffix). Kustomize will update the name to include the suffix applied to the ConfigMap name. The following example generates a ConfigMap and propagates the ConfigMap name, including the suffix, to a Deployment that mounts the ConfigMap. 1. Create a Kustomization file. ```yaml # 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 ``` 2. Create a Deployment manifest. ```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: registry.k8s.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 ``` 3. Create the ConfigMap using `kustomize build`. ```bash kustomize build . ``` The output is similar to: ```yaml 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: registry.k8s.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 ``` [`configMapGenerator`]: /docs/reference/api/kustomization-file/configmapgenerator/