Multibase

kustomize encourages defining multiple variants - e.g. dev, staging and prod, as overlays on a common base.

It’s possible to create an additional overlay to compose these variants together - just declare the overlays as the bases of a new kustomization.

This is also a means to apply a common label or annotation across the variants, if for some reason the base isn’t under your control. It also allows one to define a left-most namePrefix across the variants - something that cannot be done by modifying the common base.

The following demonstrates this using a base that is just a single pod.

Define a place to work:

DEMO_HOME = $(mktemp -d)

/base

Define a common base:

$ cd $DEMO_HOME
$ mkdir base
$ cd base

Create a Sample Pod File and Kustomize file in base

$ vim kustomization.yaml

# kustomization.yaml contents
resources:
- pod.yaml

# pod.yaml contents
apiVersion: v1
kind: Pod
metadata:
  name: myapp-pod
  labels:
    app: myapp
spec:
  containers:
  - name: nginx
    image: nginx:latest

/dev

Define a dev variant overlaying base:

$ cd $DEMO_HOME
$ mkdir dev
$ cd dev

Create a Kustomize file in dev

# kustomization.yaml contents
resources:
- ./../base
namePrefix: dev-

/staging

Define a staging variant overlaying base:

$ cd $DEMO_HOME
$ mkdir staging
$ cd staging

Create a Kustomize file in staging

# kustomization.yaml contents
resources:
- ./../base
namePrefix: stag-

/production

Define a production variant overlaying base:

$ cd $DEMO_HOME
$ mkdir production
$ cd production

Create a Kustomize file in production

# kustomization.yaml contents
resources:
- ./../base
namePrefix: prod-

kustomize @ root dir

Then define a Kustomization composing three variants together:

# kustomization.yaml contents
resources:
- ./dev
- ./staging
- ./production
namePrefix: cluster-a-

directory structure

.
├── kustomization.yaml
├── base
│   ├── kustomization.yaml
│   └── pod.yaml
├── dev
│   └── kustomization.yaml
├── production
│   └── kustomization.yaml
└── staging
    └── kustomization.yaml

Confirm that the kustomize build output contains three pod objects from dev, staging and production variants.

output

apiVersion: v1
kind: Pod
metadata:
  labels:
    app: myapp
  name: cluster-a-dev-myapp-pod
spec:
  containers:
  - image: nginx:latest
    name: nginx
---
apiVersion: v1
kind: Pod
metadata:
  labels:
    app: myapp
  name: cluster-a-prod-myapp-pod
spec:
  containers:
  - image: nginx:latest
    name: nginx
---
apiVersion: v1
kind: Pod
metadata:
  labels:
    app: myapp
  name: cluster-a-stag-myapp-pod
spec:
  containers:
  - image: nginx:latest
    name: nginx

Similarly to adding different namePrefix in different variants, one can also add different namespace and compose those variants in one kustomization. For more details, take a look at multi-namespaces.

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