What’s New in Kubernetes 1.21? 51 Features from CronJobs to Dual‑Stack

Release Overview

Kubernetes 1.21, the first release of 2021, contains 51 enhancements: 13 promoted to stable , 16 to beta , 20 to alpha , and 2 features are deprecated.

Key Features

CronJobs graduate to stable

The CronJob API, beta since v1.8, is now stable. It enables reliable scheduled tasks such as backups and report generation.

Immutable Secrets and ConfigMaps

Both Secret and ConfigMap objects gain an immutable field. When set to true, any update to the object is rejected. To change the data you must create a new, uniquely‑named resource and redeploy the consuming pods, which also reduces controller watch load.

IPv4/IPv6 Dual‑Stack Support

Dual‑stack networking is promoted to beta and enabled by default. Pods, services, and nodes can receive both an IPv4 and an IPv6 address, improving scalability and allowing clusters to operate in environments where IPv4 addresses are scarce.

Graceful Node Shutdown

The feature moves to beta. The kubelet detects an imminent system shutdown via systemd, notifies running pods, and gives them a configurable termination grace period instead of being killed abruptly.

PersistentVolume Health Monitor (alpha)

An alpha feature adds health monitoring for PersistentVolumes. Controllers can observe the volumeHealth condition and avoid reads/writes from unhealthy volumes.

Simplified Golang‑based Build Toolchain

The release consolidates multiple historic build systems into a single Golang‑based toolchain, lowering the entry barrier for new contributors and reducing maintenance complexity.

Major Changes

PodSecurityPolicy Deprecation

PodSecurityPolicy is deprecated in 1.21 and slated for removal in 1.25. A replacement mechanism (tentatively “PSP replacement policy”) is under development to cover core use‑cases.

TopologyKeys Deprecation

The topologyKeys field is deprecated. It is replaced by the alpha feature “topology‑aware hints”, which provides a more flexible way to influence pod placement.

Other Graduated Features

EndpointSlice

Sysctl support

PodDisruptionBudgets

Notable Feature Updates

External client‑go credential providers – promoted to beta

Structured logging – slated for beta in 1.22

TTL after Jobs and Pods cleanup – promoted to beta

Installation Guidance

The release binaries are available at:

https://github.com/kubernetes/kubernetes/releases/tag/v1.21.0

For a quick local cluster you can use kind with Docker:

kind create cluster --image kindest/node:v1.21.1

For a from‑scratch installation see the “Kubernetes the Hard Way” guide.

Release Notes

Full release notes are published at:

https://kubernetes.io/blog/2021/04/08/kubernetes-1-21-release-announcement/

Version Identity