In a Kubernetes cluster, the components on the worker nodes - kubelet and kube-proxy - need to communicate with Kubernetes control plane components, specifically kube-apiserver. In order to ensure that communication is kept private, not interfered with, and ensure that each component of the cluster is talking to another trusted component, we strongly recommend using client TLS certificates on nodes. The normal process of bootstrapping these components, especially worker nodes that need certificates so they can communicate safely with kube-apiserver, can be a challenging process as it is often outside of the scope of Kubernetes and requires significant additional work.

This page provides an overview of admission controllers. An admission controller is a piece of code that intercepts requests to the Kubernetes API server prior to persistence of the resource, but after the request is authenticated and authorized. Several important features of Kubernetes require an admission controller to be enabled in order to properly support the feature. As a result, a Kubernetes API server that is not properly configured with the right set of admission controllers is an incomplete server that will not support all the features you expect.

The tables below enumerate the configuration parameters on PodSecurityPolicy objects, whether the field mutates and/or validates pods, and how the configuration values map to the Pod Security Standards. For each applicable parameter, the allowed values for the Baseline and Restricted profiles are listed. Anything outside the allowed values for those profiles would fall under the Privileged profile. "No opinion" means all values are allowed under all Pod Security Standards.

FEATURE STATE: Kubernetes v1.30 [stable] This page provides an overview of Validating Admission Policy. What is Validating Admission Policy? Validating admission policies offer a declarative, in-process alternative to validating admission webhooks. Validating admission policies use the Common Expression Language (CEL) to declare the validation rules of a policy. Validation admission policies are highly configurable, enabling policy authors to define policies that can be parameterized and scoped to resources as needed by cluster administrators.

Role-based access control (RBAC) is a method of regulating access to computer or network resources based on the roles of individual users within your organization. RBAC authorization uses the rbac.authorization.k8s.io API group to drive authorization decisions, allowing you to dynamically configure policies through the Kubernetes API. To enable RBAC, start the API server with the --authorization-config flag set to a file that includes the RBAC authorizer; for example: apiVersion: apiserver.

FEATURE STATE: Kubernetes v1.18 [stable] Bootstrap tokens are a simple bearer token that is meant to be used when creating new clusters or joining new nodes to an existing cluster. It was built to support kubeadm, but can be used in other contexts for users that wish to start clusters without kubeadm. It is also built to work, via RBAC policy, with the kubelet TLS Bootstrapping system. Bootstrap Tokens Overview Bootstrap Tokens are defined with a specific type (bootstrap.

A WebHook is an HTTP callback: an HTTP POST that occurs when something happens; a simple event-notification via HTTP POST. A web application implementing WebHooks will POST a message to a URL when certain things happen. When specified, mode Webhook causes Kubernetes to query an outside REST service when determining user privileges. Configuration File Format Mode Webhook requires a file for HTTP configuration, specify by the --authorization-webhook-config-file=SOME_FILENAME flag. The configuration file uses the kubeconfig file format.

Seccomp stands for secure computing mode and has been a feature of the Linux kernel since version 2.6.12. It can be used to sandbox the privileges of a process, restricting the calls it is able to make from userspace into the kernel. Kubernetes lets you automatically apply seccomp profiles loaded onto a node to your Pods and containers. Seccomp fields FEATURE STATE: Kubernetes v1.19 [stable] There are four ways to specify a seccomp profile for a pod:

Performs a best effort revert of changes made by kubeadm init or kubeadm join. Synopsis Performs a best effort revert of changes made to this host by 'kubeadm init' or 'kubeadm join' The "reset" command executes the following phases: preflight Run reset pre-flight checks remove-etcd-member Remove a local etcd member. cleanup-node Run cleanup node. kubeadm reset [flags] Options --cert-dir string     Default: "/etc/kubernetes/pki" The path to the directory where the certificates are stored.

During kubeadm init, kubeadm uploads the ClusterConfiguration object to your cluster in a ConfigMap called kubeadm-config in the kube-system namespace. This configuration is then read during kubeadm join, kubeadm reset and kubeadm upgrade. You can use kubeadm config print to print the default static configuration that kubeadm uses for kubeadm init and kubeadm join. Note:The output of the command is meant to serve as an example. You must manually edit the output of this command to adapt to your setup.