How to use the command 'kustomize' (with examples)

Kustomize is a command-line tool that allows you to customize Kubernetes resources before deploying them. It simplifies the process of creating and managing your deployments by providing a declarative approach to configuration.

Use case 1: Create a kustomization file with resources and namespace

Code:

kustomize create --resources deployment.yaml,service.yaml --namespace staging

Motivation: Creating a kustomization file with resources and namespace allows you to define the desired state of your resources and group them under a specific namespace. This helps to organize your deployments and manage them more efficiently.

Explanation:

• kustomize create: This command is used to create a new kustomization file.
• --resources deployment.yaml,service.yaml: Specifies the resources to be included in the kustomization file. In this example, it includes the ‘deployment.yaml’ and ‘service.yaml’ files.
• --namespace staging: Sets the namespace for the resources defined in the kustomization file. In this case, the namespace is set to ‘staging’.

Example output: A new kustomization file with the specified resources and namespace is created.

Use case 2: Build a kustomization file and deploy it with kubectl

Code:

kustomize build . | kubectl apply -f -

Motivation: Building a kustomization file and deploying it with kubectl allows you to apply the customizations defined in your kustomization file to your Kubernetes cluster.

Explanation:

• kustomize build .: This command builds the kustomization file in the current directory.
• |: The pipe symbol is used to pass the output of the kustomize build command to the next command.
• kubectl apply -f -: This command applies the generated output from the kustomize build command to the Kubernetes cluster. The -f - flag specifies that the Kubernetes resource definition should be read from standard input.

Example output: The resources defined in the kustomization file are deployed to the Kubernetes cluster.

Use case 3: Set an image in the kustomization file

Code:

kustomize edit set image busybox=alpine:3.6

Motivation: Setting an image in the kustomization file allows you to customize the container image used in your deployments. This is useful when you want to update the version of the container image or use a different image altogether.

Explanation:

• kustomize edit set image: This command is used to set an image in the kustomization file.
• busybox=alpine:3.6: Specifies the image to be set. In this example, it sets the image for the ‘busybox’ container to ‘alpine:3.6’.

Example output: The image for the specified container in the kustomization file is set to ‘alpine:3.6’.

Use case 4: Search for Kubernetes resources in the current directory to be added to the kustomization file

Code:

kustomize create --autodetect

Motivation: Searching for Kubernetes resources in the current directory helps to automatically identify and add the relevant resources to the kustomization file. This saves time and effort by eliminating the need to manually specify all the resources.

Explanation:

• kustomize create: This command creates a new kustomization file.
• --autodetect: This flag enables the automatic search for Kubernetes resources in the current directory to be added to the kustomization file.

Example output: The kustomization file is created with the automatically detected Kubernetes resources from the current directory.