Kubernetes v1.31: kubeadm v1beta4

As part of the Kubernetes v1.31 release, kubeadm is adopting a new (v1beta4) version of its configuration file format. Configuration in the previous v1beta3 format is now formally deprecated, which means it's supported but you should migrate to v1beta4 and stop using the deprecated format. Support for v1beta3 configuration will be removed after a minimum of 3 Kubernetes minor releases.

In this article, I'll walk you through key changes; I'll explain about the kubeadm v1beta4 configuration format, and how to migrate from v1beta3 to v1beta4.

You can read the reference for the v1beta4 configuration format:kubeadm Configuration (v1beta4).

A list of changes since v1beta3

This version improves on the v1beta3format by fixing some minor issues and adding a few new fields.

To put it simply,

Two new configuration elements: ResetConfiguration and UpgradeConfiguration
For InitConfiguration and JoinConfiguration, dryRun mode and nodeRegistration.imagePullSerial are supported
For ClusterConfiguration, there are new fields including certificateValidityPeriod,caCertificateValidityPeriod, encryptionAlgorithm, dns.disabled and proxy.disabled.
Support extraEnvs for all control plan components
extraArgs changed from a map to structured extra arguments for duplicates
Add a timeouts structure for init, join, upgrade and reset.

For details, you can see the official document below:

Support custom environment variables in control plane components under ClusterConfiguration. Use apiServer.extraEnvs, controllerManager.extraEnvs, scheduler.extraEnvs, etcd.local.extraEnvs.
The ResetConfiguration API type is now supported in v1beta4. Users are able to reset a node by passing a --config file to kubeadm reset.
dryRun mode is now configurable in InitConfiguration and JoinConfiguration.
Replace the existing string/string extra argument maps with structured extra arguments that support duplicates. The change applies to ClusterConfiguration - apiServer.extraArgs, controllerManager.extraArgs,scheduler.extraArgs, etcd.local.extraArgs. Also to nodeRegistrationOptions.kubeletExtraArgs.
Added ClusterConfiguration.encryptionAlgorithm that can be used to set the asymmetric encryption algorithm used for this cluster's keys and certificates. Can be one of "RSA-2048" (default), "RSA-3072", "RSA-4096" or "ECDSA-P256".
Added ClusterConfiguration.dns.disabled and ClusterConfiguration.proxy.disabled that can be used to disable the CoreDNS and kube-proxy addons during cluster initialization. Skipping the related addons phases, during cluster creation will set the same fields to true.
Added the nodeRegistration.imagePullSerial field in InitConfiguration and JoinConfiguration, which can be used to control if kubeadm pulls images serially or in parallel.
The UpgradeConfiguration kubeadm API is now supported in v1beta4 when passing --config tokubeadm upgrade subcommands. For upgrade subcommands, the usage of component configuration for kubelet and kube-proxy, as well as InitConfiguration and ClusterConfiguration, is now deprecated and will be ignored when passing --config.
Added a timeouts structure to InitConfiguration, JoinConfiguration, ResetConfiguration andUpgradeConfiguration that can be used to configure various timeouts. The ClusterConfiguration.timeoutForControlPlane field is replaced by timeouts.controlPlaneComponentHealthCheck. The JoinConfiguration.discovery.timeout is replaced by timeouts.discovery.
Added a certificateValidityPeriod and caCertificateValidityPeriod fields to ClusterConfiguration. These fields can be used to control the validity period of certificates generated by kubeadm during sub-commands such as init, join, upgrade and certs. Default values continue to be 1 year for non-CA certificates and 10 years for CA certificates. Also note that only non-CA certificates are renewable by kubeadm certs renew.

These changes simplify the configuration of tools that use kubeadm and improve the extensibility of kubeadm itself.

How to migrate v1beta3 configuration to v1beta4?

If your configuration is not using the latest version, it is recommended that you migrate using the kubeadm config migrate command.

This command reads an existing configuration file that uses the old format, and writes a new file that uses the current format.

Example

Using kubeadm v1.31, run kubeadm config migrate --old-config old-v1beta3.yaml --new-config new-v1beta4.yaml

How do I get involved?

Huge thanks to all the contributors who helped with the design, implementation, and review of this feature:

Lubomir I. Ivanov (neolit123)
Dave Chen(chendave)
Paco Xu (pacoxu)
Sata Qiu(sataqiu)
Baofa Fan(carlory)
Calvin Chen(calvin0327)
Ruquan Zhao(ruquanzhao)

For those interested in getting involved in future discussions on kubeadm configuration, you can reach out kubeadm or SIG-cluster-lifecycle by several means: