Kustomize技术问题：如何设置待补丁资源metadata.name及从变量赋值

1. How to target a resource by metadata.name for patching #

When you need to apply a patch to a specific resource, Kustomize makes it straightforward to target by metadata.name using the target field in your kustomization.yaml. Here's exactly how to do it:

• Define your patch with a target block that specifies the resource's kind and metadata.name. This ensures the patch only applies to the exact resource you intend, avoiding accidental changes to similar resources.

Example: Patch a specific Deployment #

Suppose you want to bump the replica count of a Deployment named my-web-app:

# kustomization.yaml
patches:
- target:
    kind: Deployment
    name: my-web-app
  patch: |-
    apiVersion: apps/v1
    kind: Deployment
    metadata:
      name: my-web-app
    spec:
      replicas: 3

Using a separate patch file #

If you prefer keeping patches in individual files, reference the file while still targeting by name:

# kustomization.yaml
patches:
- target:
    kind: Deployment
    name: my-web-app
  path: ./deployment-replica-patch.yaml

The patch file itself just needs to include the resource's metadata.name to match, but the target block adds an extra layer of specificity that's helpful in complex kustomizations.

2. Dynamically setting metadata.name for base resources (like Namespaces) #

This is a common pain point when working with resources where the name isn't fixed upfront—think ephemeral test namespaces or environment-specific resources you can't hardcode. I've used two reliable methods to handle this:

Method 1: Command-line variable expansion (simple, direct input) #

If you want to pass the name straight from your terminal, use Kustomize's built-in variable expansion (requires Kustomize v4.1.0 or later):

1. In your base resource file (e.g., namespace.yaml), use a variable placeholder for the name:

apiVersion: v1
kind: Namespace
metadata:
  name: $(NAMESPACE_NAME)

2. In your base kustomization.yaml, declare the variable with an optional default value:

# base/kustomization.yaml
resources:
- namespace.yaml

# Apply common labels to all resources (including the dynamic namespace)
commonLabels:
  environment: $(ENV)

vars:
- name: NAMESPACE_NAME
  value: default-namespace # Fallback if no value is provided
- name: ENV
  value: dev

3. Build with your desired values passed via command line (don't forget the --enable-var-expansion flag—it's required):

kustomize build ./base --var="NAMESPACE_NAME=test-ns-456" --var="ENV=test" --enable-var-expansion

This replaces the placeholders with your input values, and still applies all Kustomize transforms like commonLabels to the final resource.

Method 2: Replacements (pull values from other resources) #

If you want to source the name from another resource (like a generated ConfigMap for environment configs), use Kustomize's replacements feature:

1. In your base, define a placeholder Namespace (we'll replace this name later):

# base/namespace.yaml
apiVersion: v1
kind: Namespace
metadata:
  name: placeholder-namespace

2. In your overlay (or base), generate a ConfigMap with the dynamic namespace name, then define the replacement:

# overlay/kustomization.yaml
bases:
- ../base

# Apply common labels to all resources
commonLabels:
  app: my-app

# Generate a ConfigMap with your desired namespace name
configMapGenerator:
- name: namespace-config
  literals:
  - namespace=prod-ns-2024

# Replace the placeholder namespace name with the value from the ConfigMap
replacements:
- source:
    kind: ConfigMap
    name: namespace-config
    apiVersion: v1
    fieldpath: data.namespace
  targets:
  - select:
      kind: Namespace
      name: placeholder-namespace
    fieldpaths:
    - metadata.name

When you build the overlay, Kustomize will swap the placeholder name with the value from the ConfigMap, while retaining all your commonLabels and other transforms.

内容的提问来源于stack exchange，提问作者DevLounge