Kustomize

Kustomize is a command-line utility tool used to customize Kubernetes resources. It allows users to create and manage Kubernetes manifests in a more modular and maintainable way. Kustomize makes it easy to manage multiple environments and configurations, as well as to apply changes to existing resources.

Example Usage:

1. To create a base configuration: kustomize create --resources=<directory>

2. To apply a configuration: kustomize build <directory> | kubectl apply -f -

3. To apply a patch: kustomize edit add patch <patch-file>

4. To add a new resource: kustomize edit add resource <resource-file>

5. To add a label to resources: kustomize edit add label <label-key>=<label-value>

6. To add an annotation to resources: kustomize edit add annotation <annotation-key>=<annotation-value>

7. To generate a YAML file: kustomize build <directory>

Overall, Kustomize is a useful tool for managing Kubernetes deployments and configurations. By allowing users to manage and customize Kubernetes resources in a modular and maintainable way, Kustomize can simplify the process of deploying and managing applications in Kubernetes.

Suppose you have a directory named my-app with the following structure:

my-app/
├── base/
│   ├── deployment.yaml
│   └── service.yaml
└── overlays/
    ├── dev/
    │   └── patch.yaml
    └── prod/
        ├── patch.yaml
        └── service.yaml

To build the dev overlay configuration, you can run:

cd my-app/overlays/dev
kustomize build

This will generate the Kubernetes YAML manifests for the dev environment by combining the base resources with the dev overlay patch file.

You can then apply these manifests to your Kubernetes cluster using kubectl apply:

kustomize build | kubectl apply -f -

This will apply the generated YAML manifests to your Kubernetes cluster.

Note that kustomize build can also be used to generate YAML manifests for other environments by changing the current directory to the corresponding overlay directory and running the kustomize build command.