How to use the command `kubectl replace` (with examples)

kubectl replace is a command-line tool used in Kubernetes to replace a resource by file or stdin. It allows users to update the desired state of a resource with the definition provided.

Use case 1: Replace the resource using the resource definition file

Code:

kubectl replace -f path/to/file.yml

Motivation: This use case allows users to replace a resource in Kubernetes by providing a resource definition file. It is particularly useful when there have been changes made to the resource’s YAML file and you want to apply those changes to an existing resource in the cluster.

Explanation:

• kubectl replace is the command itself.
• -f path/to/file.yml is the flag to specify the path to the resource definition file.

Example output:

deployment.apps/my-deployment replaced

Use case 2: Replace the resource using the input passed into stdin

Code:

kubectl replace -f -

Motivation: This use case allows users to replace a Kubernetes resource by passing the resource definition through stdin. It can be useful when the resource definition is generated dynamically or when piping the output of another command.

Explanation:

• kubectl replace is the command.
• -f - is the flag to indicate that the resource definition will be passed through stdin.

Example output:

deployment.apps/my-deployment replaced

Use case 3: Force replace, delete and then re-create the resource

Code:

kubectl replace --force -f path/to/file.yml

Motivation: This use case is helpful when we want to forcefully replace a resource by deleting and then re-creating it. It can be used when updating a resource that has strict dependency requirements or when we want to ensure that the resource gets recreated with the updated state.

Explanation:

• kubectl replace is the command.
• --force flag forces the replace operation, deleting and re-creating the resource.
• -f path/to/file.yml is the flag to specify the path to the resource definition file.

Example output:

deployment.apps/my-deployment replaced with --force

Conclusion:

The kubectl replace command is a powerful tool for updating and replacing resources in Kubernetes. Whether you want to apply changes from a file or stdin, or forcibly recreate a resource, kubectl replace provides the flexibility and control needed to manage Kubernetes resources effectively.