Managing Kubernetes Objects Using Imperative Commands [page]deterministic

taskscliapi

Kubernetes objects can quickly be created, updated, and deleted directly using imperative commands built into the `kubectl` command-line tool. This document explains how those commands are organized and how to use them to manage live objects.

Install [`kubectl`](/docs/tasks/tools/).

## Trade-offs

The `kubectl` tool supports three kinds of object management:

* Imperative commands * Imperative object configuration * Declarative object configuration

See [Kubernetes Object Management](/docs/concepts/overview/working-with-objects/object-management/) for a discussion of the advantages and disadvantage of each kind of object management.

## How to create objects

The `kubectl` tool supports verb-driven commands for creating some of the most common object types. The commands are named to be recognizable to users unfamiliar with the Kubernetes object types.

`run`: Create a new Pod to run a Container.
`expose`: Create a new Service object to load balance traffic across Pods.
`autoscale`: Create a new Autoscaler object to automatically horizontally scale a controller, such as a Deployment.

The `kubectl` tool also supports creation commands driven by object type. These commands support more object types and are more explicit about their intent, but require users to know the type of objects they intend to create.

`create <objecttype> [<subtype>] <instancename>`

Some objects types have subtypes that you can specify in the `create` command. For example, the Service object has several subtypes including ClusterIP, LoadBalancer, and NodePort. Here's an example that creates a Service with subtype NodePort:

```shell kubectl create service nodeport <myservicename> ```

In the preceding example, the `create service nodeport` command is called a subcommand of the `create service` command.

You can use the `-h` flag to find the arguments and flags supported by a subcommand:

```shell kubectl create service nodeport -h ```

## How to update objects

The `kubectl` command supports verb-driven commands for some common update operations. These commands are named to enable users unfamiliar with Kubernetes objects to perform updates without knowing the specific fields that must be set:

`scale`: Horizontally scale a controller to add or remove Pods by updating the replica count of the controller.
`annotate`: Add or remove an annotation from an object.
`label`: Add or remove a label from an object.

The `kubectl` command also supports update commands driven by an aspect of the object. Setting this aspect may set different fields for different object types:

`set` `<field>`: Set an aspect of an object.

> Note: In Kubernetes version 1.5, not every verb-driven command has an associated aspect-driven command.

The `kubectl` tool supports these additional ways to update a live object directly, however they require a better understanding of the Kubernetes object schema.

`edit`: Directly edit the raw configuration of a live object by opening its configuration in an editor.
`patch`: Directly modify specific fields of a live object by using a patch string. For more details on patch strings, see the patch section in [API Conventions](https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#patch-operations).

## How to delete objects

You can use the `delete` command to delete an object from a cluster:

`delete <type>/<name>`

> Note: You can use `kubectl delete` for both imperative commands and imperative object configuration. The difference is in the arguments passed to the command. To use `kubectl delete` as an imperative command, pass the object to be deleted as an argument. Here's an example that passes a Deployment object named nginx:

```shell kubectl delete deployment/nginx ```

## How to view an object

TODO(pwittrock): Uncomment this when implemented.

You can use `kubectl view` to print specific fields of an object.