kustomize

What it does

How to write it

kustomize build DIR
kubectl apply -k DIR
kubectl kustomize DIR

Main parts

kustomization.yaml fields

resources

Files or folders to include (also remote Git URLs).

namespace

Put everything in this namespace.

images

Change image names and tags.

replicas

Change replica counts.

patches

Strategic-merge or JSON patches for any field.

labels / commonAnnotations

Add labels / annotations to all objects.

namePrefix / nameSuffix

Change object names.

configMapGenerator / secretGenerator

Make ConfigMaps/Secrets from files (with a hash suffix).

components

Re-usable optional parts.

Most used

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$ run as a normal user# run as root (or with sudo)

1. 1The folder layout

   $tree shop
   shop/
   ├── base/
   │   ├── deployment.yaml
   │   ├── service.yaml
   │   └── kustomization.yaml
   └── overlays/
       ├── dev/kustomization.yaml
       └── prod/kustomization.yaml

2. 2The base

   $cat shop/base/kustomization.yaml
   resources:
     - deployment.yaml
     - service.yaml
   labels:
     - pairs: { app: shop }

3. 3A prod overlay

   $cat shop/overlays/prod/kustomization.yaml
   resources: [../../base]
   namespace: shop-prod
   images:
     - name: ghcr.io/s0sta/shop
       newTag: 1.4.0
   replicas:
     - name: shop
       count: 3
   patches:
     - target: { kind: Deployment, name: shop }
       patch: |-
         - op: add
           path: /spec/template/spec/containers/0/resources
           value: { limits: { memory: 512Mi, cpu: 500m } }

4. 4See and apply the result

   $kustomize build shop/overlays/prod | less
   $kubectl diff -k shop/overlays/prod
   $kubectl apply -k shop/overlays/prod

5. 5Change the image tag in CI

   $cd shop/overlays/prod && kustomize edit set image ghcr.io/s0sta/shop=ghcr.io/s0sta/shop:1.5.0
   $git commit -am "shop 1.5.0 to prod" && git push

6. 6Make a ConfigMap from a file

   $cat shop/base/kustomization.yaml
   configMapGenerator:
     - name: shop-config
       files: [app.properties]

   The name gets a hash; pods restart by themselves when the file changes.

7. 7Scan the final YAML

   $kustomize build shop/overlays/prod > prod.yaml && trivy config prod.yaml

8. 8Use a remote base from Git

   $cat kustomization.yaml
   resources:
     - https://github.com/s0sta/platform//apps/shop/base?ref=v1.4.0

9. 9Add a label and a name prefix to everything

   $cat overlays/dev/kustomization.yaml
   resources: [../../base]
   namePrefix: dev-
   labels:
     - pairs: { env: dev }

10. 10Patch with a small YAML file

    $cat overlays/prod/probe.yaml
    apiVersion: apps/v1
    kind: Deployment
    metadata: { name: shop }
    spec:
      template:
        spec:
          containers:
            - name: shop
              readinessProbe: { httpGet: { path: /health, port: 8080 } }
    $kustomize edit add patch --path probe.yaml

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Files

kustomization.yaml

The file in every base and overlay folder.

Exit codes