are adding Windows Server Virtual Machines as nodes to your Kubernetes environment, there is a compatibility issue with certain virtualization products. Specifically the Windows version of the kubelet.exe calls `GetPhysicallyInstalledSystemMemory` to get the physical memory installed on Windows machines and reports it as part of node metrics to heapster. This API call fails for VMware and VirtualBox virtualization environments. This issue is not present in bare metal Windows deployments, in Hyper-V,...

- The certificate signer no longer accepts ca.key passwords via the `CFSSL_CA_PK_PASSWORD` environment variable. This capability was not prompted by user request, never advertised, and recommended against in the security audit. ([#84677](https://github.com/kubernetes/kubernetes/pull/84677), [@mikedanese](https://github.com/mikedanese))

* `hack/local-up-cluster.sh` now enables the Node authorizer by default. Authorization modes can be overridden with the `AUTHORIZATION_MODE` environment variable, and the `ENABLE_RBAC` environment variable is no longer used. ([#49812](https://github.com/kubernetes/kubernetes/pull/49812), [@liggitt](https://github.com/liggitt))

   - Server-side feature gate: PortForwardWebsocket
   - Client-side (kubectl) feature gate: PORT_FORWARD_WEBSOCKETS environment variable

efficiently. kubeadm has promoted high availability (HA) capability to beta, allowing users to use the familiar `kubeadm init` and `kubeadm join` commands to [configure and deploy an HA control plane](https://kubernetes.io/docs/setup/production-environment/tools/kubeadm/high-availability/). An entire new test suite has been created specifically for ensuring these features will stay stable over time.

Certificate management has become more robust in 1.15, with kubeadm now seamlessly rotating...

- Kubeadm: make sure the extra environment variables written to a kubeadm managed PodSpec are sorted alpha-numerically by the environment variable name. ([#126743](https://github.com/kubernetes/kubernetes/pull/126743), [@neolit123](https://github.com/neolit123)) [SIG Cluster Lifecycle]

to "systemd" unless the user is explicit about it. This requires existing machine setups to configure the container runtime to use the "systemd" driver. Documentation on this topic can be found here: https://kubernetes.io/docs/setup/production-environment/container-runtimes/. When upgrading existing clusters / nodes using "kubeadm upgrade" the old cgroupDriver value is preserved, but in 1.22 this change will also apply to "upgrade". For more information on migrating to the "systemd" driver or remaining...

- Kubeadm: now sets the host `OS` environment variables when executing `crictl` during image pulls. This fixed a bug where `*PROXY` environment variables did not affect `crictl` internet connectivity. ([#110134](https://github.com/kubernetes/kubernetes/pull/110134), [@mk46](https://github.com/mk46))

- Added a alpha feature, behind the `RelaxedEnvironmentVariableValidation` feature gate.
  When that gate is enabled, Kubernetes allows almost all printable ASCII characters to be used in the names
  of environment variables for containers in Pods. ([#123385](https://github.com/kubernetes/kubernetes/pull/123385), [@HirazawaUi](https://github.com/HirazawaUi))

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          <name>prerequisites</name>
          <version>4.0.0+</version>
          <description>Describes the prerequisites in the build environment for this project.</description>
          <association>
            <type>Prerequisites</type>
          </association>
        </field>