expressions</a>.
</p>


<h2 id="Variables">Variables</h2>

<p>
A variable is a storage location for holding a <i>value</i>.
The set of permissible values is determined by the
variable's <i><a href="#Types">type</a></i>.
</p>

<p>
A <a href="#Variable_declarations">variable declaration</a>
or, for function parameters and results, the signature

}

// EnvVar represents an environment variable present in a Container.
message EnvVar {
  // Name of the environment variable. Must be a C_IDENTIFIER.
  optional string name = 1;

  // Variable references $(VAR_NAME) are expanded
  // using the previously defined environment variables in the container and
  // any service environment variables. If a variable cannot be resolved,

OpenStack cloud provider can now be specified as environment variables. When we convert the OpenStack cloud provider to run in an external process, we can now use the kubernetes Secrets capability to inject the OS_* variables. This way we can specify the cloud configuration as a configmap, and specify secrets for the userid/password information. The configmap is mounted as a file, and the secrets are made available as environment variables. The external controller itself runs as a pod/daemonset. For...

- Added options for configuring `nf_conntrack_udp_timeout`, and `nf_conntrack_udp_timeout_stream` variables of netfilter conntrack subsystem. ([#120808](https://github.com/kubernetes/kubernetes/pull/120808), [@aroradaman](https://github.com/aroradaman))

### ConfigMap
* Volumes and environment variables populated from ConfigMap and Secret objects can now tolerate the named source object or specific keys being missing, by adding `optional: true` to the volume or environment variable source specifications. ([#39981](https://github.com/kubernetes/kubernetes/pull/39981), [@fraenkel](https://github.com/fraenkel))

- [`KT-56682`](https://youtrack.jetbrains.com/issue/KT-56682) K2: False-negative UNINITIALIZED_VARIABLE on access to delegated property
- [`KT-56678`](https://youtrack.jetbrains.com/issue/KT-56678) K2: False-negative UNINITIALIZED_VARIABLE if corresponding variable has initializer

- Kubeadm: fix an issue with the kube-proxy container env. variables ([#84888](https://github.com/kubernetes/kubernetes/pull/84888), [@neolit123](https://github.com/neolit123))

- 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))

- The `ServiceAccountIssuerDiscovery` feature gate is removed. It reached GA in Kubernetes 1.21. ([#103685](https://github.com/kubernetes/kubernetes/pull/103685), [@mengjiao-liu](https://github.com/mengjiao-liu))
- The `constants/variables` from k8s.io for STABLE metrics is now supported. ([#103654](https://github.com/kubernetes/kubernetes/pull/103654), [@coffeepac](https://github.com/coffeepac))

    * [prometheus-to-sd addon] Bump prometheus-to-sd to 0.3.1 to pick up security fixes, bug fixes and new features.
    * [event-exporter addon] Bump event-exporter to 0.2.3 to pick up security fixes.
* [GCP] Added env variables to control CPU requests of kube-controller-manager and kube-scheduler. ([#68823](https://github.com/kubernetes/kubernetes/pull/68823), [@loburm](https://github.com/loburm))