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Reference

Kubernetes v1.13 documentation is no longer actively maintained. The version you are currently viewing is a static snapshot. For up-to-date documentation, see the latest version.

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kubectl Usage Conventions

Recommended usage conventions for kubectl.

Using kubectl in Reusable Scripts
Best Practices

Using `kubectl` in Reusable Scripts

For a stable output in a script:

Request one of the machine-oriented output forms, such as -o name, -o json, -o yaml, -o go-template, or -o jsonpath.
Fully-qualify the version. For example, jobs.v1.batch/myjob. This will ensure that kubectl does not use its default version that can change over time.
Specify the --generator flag to pin to a specific behavior when you use generator-based commands such as kubectl run or kubectl expose.
Don’t rely on context, preferences, or other implicit states.

Best Practices

`kubectl run`

For kubectl run to satisfy infrastructure as code:

Tag the image with a version-specific tag and don’t move that tag to a new version. For example, use :v1234, v1.2.3, r03062016-1-4, rather than :latest (For more information, see Best Practices for Configuration).
Capture the parameters in a checked-in script, or at least use --record to annotate the created objects with the command line for an image that is lightly parameterized.
Check in the script for an image that is heavily parameterized.
Switch to configuration files checked into source control for features that are needed, but not expressible via kubectl run flags.
Pin to a specific generator version, such as kubectl run --generator=deployment/v1beta1.

Generators

You can create the following resources using kubectl run with the --generator flag:

Resource	kubectl command
Pod	`kubectl run --generator=run-pod/v1`
Replication controller	`kubectl run --generator=run/v1`
Deployment	`kubectl run --generator=extensions/v1beta1`
-for an endpoint (default)	`kubectl run --generator=deployment/v1beta1`
Deployment	`kubectl run --generator=apps/v1beta1`
-for an endpoint (recommended)	`kubectl run --generator=deployment/apps.v1beta1`
Job	`kubectl run --generator=job/v1`
CronJob	`kubectl run --generator=batch/v1beta1`
-for an endpoint (default)	`kubectl run --generator=cronjob/v1beta1`
CronJob	`kubectl run --generator=batch/v2alpha1`
-for an endpoint (deprecated)	`kubectl run --generator=cronjob/v2alpha1`

If you do not specify a generator flag, other flags prompt you to use a specific generator. The following table lists the flags that force you to use specific generators, depending on the version of the cluster:

Generated Resource	Cluster v1.4 and later	Cluster v1.3	Cluster v1.2	Cluster v1.1 and earlier
Pod	`--restart=Never`	`--restart=Never`	`--generator=run-pod/v1`	`--restart=OnFailure` OR `--restart=Never`
Replication Controller	`--generator=run/v1`	`--generator=run/v1`	`--generator=run/v1`	`--restart=Always`
Deployment	`--restart=Always`	`--restart=Always`	`--restart=Always`	N/A
Job	`--restart=OnFailure`	`--restart=OnFailure`	`--restart=OnFailure` OR `--restart=Never`	N/A
Cron Job	`--schedule=<cron>`	N/A	N/A	N/A

Note: These flags use a default generator only when you have not specified any flag. This means that when you combine --generator with other flags the generator that you specified later does not change. For example, in a cluster v1.4, if you initially specify --restart=Always, a Deployment is created; if you later specify --restart=Always and --generator=run/v1, a Replication Controller is created. This enables you to pin to a specific behavior with the generator, even when the default generator is changed later.

The flags set the generator in the following order: first the --schedule flag, then the --restart policy flag, and finally the --generator flag.

To check the final resource that was created, use the --dry-run flag, which provides the object to be submitted to the cluster.

`kubectl apply`

You can use kubectl apply to create or update resources. However, to update a resource you should have created the resource by using kubectl apply or kubectl create --save-config. For more information about using kubectl apply to update resources, see Managing Resources.

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