Kubernetes Prow Robot
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## {{% heading "whatsnext" %}}
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## {{% heading "whatsnext" %}}
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* Learn about the [lifecycle of a Pod](/docs/concepts/workloads/pods/pod-lifecycle/).
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* Learn about the [lifecycle of a Pod](/docs/concepts/workloads/pods/pod-lifecycle/).
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* Learn about [PodPresets](/docs/concepts/workloads/pods/podpreset/).
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* Learn about [RuntimeClass](/docs/concepts/containers/runtime-class/) and how you can use it to
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* Learn about [RuntimeClass](/docs/concepts/containers/runtime-class/) and how you can use it to
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configure different Pods with different container runtime configurations.
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configure different Pods with different container runtime configurations.
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* Read about [Pod topology spread constraints](/docs/concepts/workloads/pods/pod-topology-spread-constraints/).
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* Read about [Pod topology spread constraints](/docs/concepts/workloads/pods/pod-topology-spread-constraints/).
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@@ -1,91 +0,0 @@
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---
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reviewers:
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- jessfraz
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title: Pod Presets
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content_type: concept
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weight: 50
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---
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<!-- overview -->
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{{< feature-state for_k8s_version="v1.6" state="alpha" >}}
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This page provides an overview of PodPresets, which are objects for injecting
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certain information into pods at creation time. The information can include
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secrets, volumes, volume mounts, and environment variables.
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<!-- body -->
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## Understanding Pod presets
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A PodPreset is an API resource for injecting additional runtime requirements
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into a Pod at creation time.
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You use [label selectors](/docs/concepts/overview/working-with-objects/labels/#label-selectors)
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to specify the Pods to which a given PodPreset applies.
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Using a PodPreset allows pod template authors to not have to explicitly provide
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all information for every pod. This way, authors of pod templates consuming a
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specific service do not need to know all the details about that service.
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## Enable PodPreset in your cluster {#enable-pod-preset}
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In order to use Pod presets in your cluster you must ensure the following:
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1. You have enabled the API type `settings.k8s.io/v1alpha1/podpreset`. For
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example, this can be done by including `settings.k8s.io/v1alpha1=true` in
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the `--runtime-config` option for the API server. In minikube add this flag
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`--extra-config=apiserver.runtime-config=settings.k8s.io/v1alpha1=true` while
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starting the cluster.
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1. You have enabled the admission controller named `PodPreset`. One way to doing this
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is to include `PodPreset` in the `--enable-admission-plugins` option value specified
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for the API server. For example, if you use Minikube, add this flag:
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```shell
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--extra-config=apiserver.enable-admission-plugins=NamespaceLifecycle,LimitRanger,ServiceAccount,DefaultStorageClass,DefaultTolerationSeconds,NodeRestriction,MutatingAdmissionWebhook,ValidatingAdmissionWebhook,ResourceQuota,PodPreset
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```
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while starting your cluster.
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## How it works
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Kubernetes provides an admission controller (`PodPreset`) which, when enabled,
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applies Pod Presets to incoming pod creation requests.
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When a pod creation request occurs, the system does the following:
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1. Retrieve all `PodPresets` available for use.
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1. Check if the label selectors of any `PodPreset` matches the labels on the
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pod being created.
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1. Attempt to merge the various resources defined by the `PodPreset` into the
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Pod being created.
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1. On error, throw an event documenting the merge error on the pod, and create
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the pod _without_ any injected resources from the `PodPreset`.
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1. Annotate the resulting modified Pod spec to indicate that it has been
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modified by a `PodPreset`. The annotation is of the form
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`podpreset.admission.kubernetes.io/podpreset-<pod-preset name>: "<resource version>"`.
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Each Pod can be matched by zero or more PodPresets; and each PodPreset can be
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applied to zero or more Pods. When a PodPreset is applied to one or more
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Pods, Kubernetes modifies the Pod Spec. For changes to `env`, `envFrom`, and
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`volumeMounts`, Kubernetes modifies the container spec for all containers in
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the Pod; for changes to `volumes`, Kubernetes modifies the Pod Spec.
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{{< note >}}
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A Pod Preset is capable of modifying the following fields in a Pod spec when appropriate:
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- The `.spec.containers` field
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- The `.spec.initContainers` field
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{{< /note >}}
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### Disable Pod Preset for a specific pod
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There may be instances where you wish for a Pod to not be altered by any Pod
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preset mutations. In these cases, you can add an annotation in the Pod's `.spec`
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of the form: `podpreset.admission.kubernetes.io/exclude: "true"`.
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## {{% heading "whatsnext" %}}
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See [Injecting data into a Pod using PodPreset](/docs/tasks/inject-data-application/podpreset/)
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For more information about the background, see the [design proposal for PodPreset](https://git.k8s.io/community/contributors/design-proposals/service-catalog/pod-preset.md).
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