kustomize Kubernetes SIGs
winget install --id=Kubernetes.kustomize -e kustomize lets you customize raw, template-free YAML files for multiple purposes, leaving the original YAML untouched and usable as is. kustomize targets kubernetes; it understands and can patch kubernetes style API objects. It's like make, in that what it does is declared in a file, and it's like sed, in that it emits edited text.
Kustomize is a YAML customization tool designed to modify Kubernetes-style API objects without altering the original files. It enables users to create customized YAML configurations by applying patches or overlays, while leaving the source files intact.
Key Features:
- Kubernetes API Compatibility: Works seamlessly with Kubernetes-style resources and API objects.
- Declarative Customization: Define customizations in a declarative file (kustomization.yaml), similar to makefiles.
- Patch-Based Editing: Applies patches or overlays to modify configurations without changing the original YAML files.
- Multi-Purpose Use Cases: Supports various use cases, from development environments to production deployments.
Audience & Benefit: Ideal for Kubernetes users who need to manage multiple configuration variants (e.g., development, staging, production) while maintaining consistency across environments. Kustomize ensures that customizations are applied without modifying the original YAML files, making it easier to update configurations and collaborate with upstream resources. It can be installed via winget for quick setup.
README
kustomize
kustomize lets you customize raw, template-free YAML
files for multiple purposes, leaving the original YAML
untouched and usable as is.
kustomize targets kubernetes; it understands and can
patch kubernetes style API objects. It's like
make, in that what it does is declared in a file,
and it's like sed, in that it emits edited text.
This tool is sponsored by sig-cli (KEP).
kubectl integration
To find the kustomize version embedded in recent versions of kubectl, run kubectl version:
> kubectl version --client
Client Version: v1.31.0
Kustomize Version: v5.4.2
The kustomize build flow at v2.0.3 was added to kubectl v1.14. The kustomize flow in kubectl remained frozen at v2.0.3 until kubectl v1.21, which updated it to v4.0.5. It will be updated on a regular basis going forward, and such updates will be reflected in the Kubernetes release notes.
| Kubectl version | Kustomize version |
|---|---|
| < v1.14 | n/a |
| v1.14-v1.20 | v2.0.3 |
| v1.21 | v4.0.5 |
| v1.22 | v4.2.0 |
| v1.23 | v4.4.1 |
| v1.24 | v4.5.4 |
| v1.25 | v4.5.7 |
| v1.26 | v4.5.7 |
| v1.27 | v5.0.1 |
For examples and guides for using the kubectl integration please see the kubernetes documentation.
Usage
1) Make a kustomization file
In some directory containing your YAML resource files (deployments, services, configmaps, etc.), create a kustomization file.
This file should declare those resources, and any customization to apply to them, e.g. add a common label.
base: kustomization + resources
kustomization.yaml deployment.yaml service.yaml
+---------------------------------------------+ +-------------------------------------------------------+ +-----------------------------------+
| apiVersion: kustomize.config.k8s.io/v1beta1 | | apiVersion: apps/v1 | | apiVersion: v1 |
| kind: Kustomization | | kind: Deployment | | kind: Service |
| labels: | | metadata: | | metadata: |
| - includeSelectors: true | | name: myapp | | name: myapp |
| pairs: | | spec: | | spec: |
| app: myapp | | selector: | | selector: |
| resources: | | matchLabels: | | app: myapp |
| - deployment.yaml | | app: myapp | | ports: |
| - service.yaml | | template: | | - port: 6060 |
| configMapGenerator: | | metadata: | | targetPort: 6060 |
| - name: myapp-map | | labels: | +-----------------------------------+
| literals: | | app: myapp |
| - KEY=value | | spec: |
+---------------------------------------------+ | containers: |
| - name: myapp |
| image: myapp |
| resources: |
| limits: |
| memory: "128Mi" |
| cpu: "500m" |
| ports: |
| - containerPort: 6060 |
+-------------------------------------------------------+
File structure:
> > ~/someApp > ├── deployment.yaml > ├── kustomization.yaml > └── service.yaml >
The resources in this directory could be a fork of someone else's configuration. If so, you can easily rebase from the source material to capture improvements, because you don't modify the resources directly.
Generate customized YAML with:
kustomize build ~/someApp
The YAML can be directly applied to a cluster:
> > kustomize build ~/someApp | kubectl apply -f - >
2) Create variants using overlays
Manage traditional variants of a configuration - like development, staging and production - using overlays that modify a common base.
overlay: kustomization + patches
kustomization.yaml replica_count.yaml cpu_count.yaml
+-----------------------------------------------+ +-------------------------------+ +------------------------------------------+
| apiVersion: kustomize.config.k8s.io/v1beta1 | | apiVersion: apps/v1 | | apiVersion: apps/v1 |
| kind: Kustomization | | kind: Deployment | | kind: Deployment |
| labels: | | metadata: | | metadata: |
| - includeSelectors: true | | name: myapp | | name: myapp |
| pairs: | | spec: | | spec: |
| variant: prod | | replicas: 80 | | template: |
| resources: | +-------------------------------+ | spec: |
| - ../../base | | containers: |
| patches: | | - name: myapp |
| - path: replica_count.yaml | | resources: |
| - path: cpu_count.yaml | | limits: |
+-----------------------------------------------+ | memory: "128Mi" |
| cpu: "7000m" |
+------------------------------------------+
File structure:
> > ~/someApp > ├── base > │ ├── deployment.yaml > │ ├── kustomization.yaml > │ └── service.yaml > └── overlays > ├── development > │ ├── cpu_count.yaml > │ ├── kustomization.yaml > │ └── replica_count.yaml > └── production > ├── cpu_count.yaml > ├── kustomization.yaml > └── replica_count.yaml >
Take the work from step (1) above, move it into a
someApp subdirectory called base, then
place overlays in a sibling directory.
An overlay is just another kustomization, referring to the base, and referring to patches to apply to that base.
This arrangement makes it easy to manage your
configuration with git. The base could have files
from an upstream repository managed by someone else.
The overlays could be in a repository you own.
Arranging the repo clones as siblings on disk avoids
the need for git submodules (though that works fine, if
you are a submodule fan).
Generate YAML with
kustomize build ~/someApp/overlays/production
The YAML can be directly applied to a cluster:
> sh > kustomize build ~/someApp/overlays/production | kubectl apply -f - >
Community
Code of conduct
Participation in the Kubernetes community is governed by the Kubernetes Code of Conduct.