kubeadm Configuration (v1beta2)

A list of changes since v1beta1:

“certificateKey” field is added to InitConfiguration and JoinConfiguration.
“ignorePreflightErrors” field is added to the NodeRegistrationOptions.
The JSON “omitempty” tag of the “taints” field (inside NodeRegistrationOptions) is removed.

See the Kubernetes 1.15 changelog for further details.

Migration from old kubeadm config versions

Please convert your v1beta1 configuration files to v1beta2 using the “kubeadm config migrate” command of kubeadm v1.15.x (conversion from older releases of kubeadm config files requires older release of kubeadm as well e.g.

kubeadm v1.11 should be used to migrate v1alpha1 to v1alpha2; kubeadm v1.12 should be used to translate v1alpha2 to v1alpha3;
kubeadm v1.13 or v1.14 should be used to translate v1alpha3 to v1beta1)

Nevertheless, kubeadm v1.15.x will support reading from v1beta1 version of the kubeadm config file format.

Basics

The preferred way to configure kubeadm is to pass an YAML configuration file with the --config option. Some of the configuration options defined in the kubeadm config file are also available as command line flags, but only the most common/simple use case are supported with this approach.

A kubeadm config file could contain multiple configuration types separated using three dashes (---).

kubeadm supports the following configuration types:

To print the defaults for “init” and “join” actions use the following commands:

kubeadm config print init-defaults
kubeadm config print join-defaults

The list of configuration types that must be included in a configuration file depends by the action you are performing (init or join) and by the configuration options you are going to use (defaults or advanced customization).

If some configuration types are not provided, or provided only partially, kubeadm will use default values; defaults provided by kubeadm includes also enforcing consistency of values across components when required (e.g. --cluster-cidr flag on controller manager and clusterCIDR on kube-proxy).

Users are always allowed to override default values, with the only exception of a small subset of setting with relevance for security (e.g. enforce authorization-mode Node and RBAC on API server)

If the user provides a configuration types that is not expected for the action you are performing, kubeadm will ignore those types and print a warning.

Kubeadm init configuration types

When executing kubeadm init with the --config option, the following configuration types could be used: InitConfiguration, ClusterConfiguration, KubeProxyConfiguration, KubeletConfiguration, but only one between InitConfiguration and ClusterConfiguration is mandatory.

The InitConfiguration type should be used to configure runtime settings, that in case of kubeadm init are the configuration of the bootstrap token and all the setting which are specific to the node where kubeadm is executed, including:

nodeRegistration, that holds fields that relate to registering the new node to the cluster; use it to customize the node name, the CRI socket to use or any other settings that should apply to this node only (e.g. the node ip).
apiServer, that represents the endpoint of the instance of the API server to be deployed on this node; use it e.g. to customize the API server advertise address.

apiVersion: kubeadm.k8s.io/v1beta2
kind: ClusterConfiguration
networking:
    ...
etcd:
    ...
apiServer:
  extraArgs:
    ...
  extraVolumes:
    ...
...

The ClusterConfiguration type should be used to configure cluster-wide settings, including settings for:

Networking, that holds configuration for the networking topology of the cluster; use it e.g. to customize pod subnet or services subnet.
Etcd configurations; use it e.g. to customize the local etcd or to configure the API server for using an external etcd cluster.
kube-apiserver, kube-scheduler, kube-controller-manager configurations; use it to customize control-plane components by adding customized setting or overriding kubeadm default settings.

The KubeProxyConfiguration type should be used to change the configuration passed to kube-proxy instances deployed in the cluster. If this object is not provided or provided only partially, kubeadm applies defaults.

See or https://pkg.go.dev/k8s.io/kube-proxy/config/v1alpha1#KubeProxyConfiguration for kube proxy official documentation.

apiVersion: kubelet.config.k8s.io/v1beta1
kind: KubeletConfiguration
  ...

The KubeletConfiguration type should be used to change the configurations that will be passed to all kubelet instances deployed in the cluster. If this object is not provided or provided only partially, kubeadm applies defaults.

See or https://pkg.go.dev/k8s.io/kubelet/config/v1beta1#KubeletConfiguration for kubelet official documentation.

Here is a fully populated example of a single YAML file containing multiple configuration types to be used during a kubeadm init run.

Kubeadm join configuration types

When executing kubeadm join with the --config option, the JoinConfiguration type should be provided.

apiVersion: kubeadm.k8s.io/v1beta2
kind: JoinConfiguration
  ...

The JoinConfiguration type should be used to configure runtime settings, that in case of kubeadm join are the discovery method used for accessing the cluster info and all the setting which are specific to the node where kubeadm is executed, including:

NodeRegistration, that holds fields that relate to registering the new node to the cluster; use it to customize the node name, the CRI socket to use or any other settings that should apply to this node only (e.g. the node IP).

`ClusterConfiguration`

ClusterConfiguration contains cluster-wide configuration for a kubeadm cluster

`ClusterStatus`

ClusterStatus contains the cluster status. The ClusterStatus will be stored in the kubeadm-config ConfigMap in the cluster, and then updated by kubeadm when additional control plane instance joins or leaves the cluster.

Field	Description
`apiVersion` string	`kubeadm.k8s.io/v1beta2`
`kind` string
`apiEndpoints` [Required]	`apiEndpoints` currently available in the cluster, one for each control plane/API server instance. The key of the map is the IP of the host’s default interface.

`InitConfiguration`

InitConfiguration contains a list of elements that is specific “kubeadm init”-only runtime information.

Field	Description
`apiVersion` string	`kubeadm.k8s.io/v1beta2`
`kind` string	`InitConfiguration`
`bootstrapTokens` [Required]	`bootstrapTokens` is respected at `kubeadm init` time and describes a set of bootstrap tokens to create. This information IS NOT uploaded to the kubeadm cluster ConfigMap, partly because of its sensitive nature.
`nodeRegistration` [Required] NodeRegistrationOptions	`nodeRegistration` holds fields that relate to registering the new control-plane node to the cluster.
`localAPIEndpoint` [Required]	`localAPIEndpoint` represents the endpoint of the API server instance that’s deployed on this control plane node. In HA setups, this differs from `ClusterConfiguration.controlPlaneEndpoint` in the sense that ControlPlaneEndpoint is the global endpoint for the cluster, which then load-balances the requests to each individual API server. This configuration object lets you customize what IP/DNS name and port the local API server advertises it’s accessible on. By default, kubeadm tries to auto-detect the IP of the default interface and use that, but in case that process fails you may set the desired value here.
`certificateKey` [Required] `string`

`JoinConfiguration`

JoinConfiguration contains elements describing a particular node.

Field	Description
`apiVersion` string	`kubeadm.k8s.io/v1beta2`
`kind` string	`JoinConfiguration`
`nodeRegistration` [Required]	`nodeRegistration` holds fields that relate to registering the new control-plane node to the cluster
`caCertPath` [Required] `string`	`caCertPath` is the path to the SSL certificate authority used to secure comunications between a node and the control-plane. Defaults to “/etc/kubernetes/pki/ca.crt”.
`discovery` [Required] Discovery	`discovery` specifies the options for the kubelet to use during the TLS bootstrap process.
`controlPlane` [Required]	`controlPlane` defines the additional control plane instance to be deployed on the joining node. If nil, no additional control plane instance will be deployed.

Appears in:

InitConfiguration

APIEndpoint struct contains elements of API server instance deployed on a node.

Field	Description
`advertiseAddress` [Required] `string`	`advertiseAddress` sets the IP address for the API server to advertise.
`bindPort` [Required] `int32`	`bindPort` sets the secure port for the API Server to bind to. Defaults to 6443.

`APIServer`

Appears in:

APIServer holds settings necessary for API server deployments in the cluster.

Field	Description
`ControlPlaneComponent` [Required] ControlPlaneComponent	(Members of `ControlPlaneComponent` are embedded into this type.) No description provided.
`certSANs` [Required] `[]string`	`certSANs` sets extra Subject Alternative Names (SANs) for the API Server signing certificate.
`timeoutForControlPlane` [Required]	`timeoutForControlPlane` controls the timeout that we wait for the API server to appear.

`BootstrapToken`

Appears in:

BootstrapToken describes one bootstrap token, stored as a Secret in the cluster

Field	Description
`token` [Required] BootstrapTokenString	`token` is used for establishing bidirectional trust between nodes and control-planes. Used for joining nodes in the cluster.
`description` [Required] `string`	`description` sets a human-friendly message why this token exists and what it’s used for, so other administrators can know its purpose.
`ttl` [Required]	`ttl` defines the time to live for this token. Defaults to ‘24h’. `expires` and `ttl` are mutually exclusive.
`expires` [Required] meta/v1.Time	`expires` specifies the timestamp when this token expires. Defaults to being set dynamically at runtime based on the `ttl`. `expires` and `ttl` are mutually exclusive.
`usages` [Required] `[]string`	`usages` describes the ways in which this token can be used. Can by default be used for establishing bidirectional trust, but that can be changed here.
`groups` [Required] `[]string`	`groups` specifies the extra groups that this token will authenticate as when/if used for authentication.

`BootstrapTokenDiscovery`

Appears in:

Discovery

BootstrapTokenDiscovery is used to set the options for bootstrap token based discovery

`BootstrapTokenString`

Appears in:

BootstrapToken

BootstrapTokenString is a token of the format abcdef.abcdef0123456789 that is used for both validation of the practically of the API server from a joining node’s point of view and as an authentication method for the node in the bootstrap phase of “kubeadm join”. This token is and should be short-lived

Field	Description
`-` [Required] `string`	No description provided.
`-` [Required] `string`	No description provided.

`ControlPlaneComponent`

Appears in:

ClusterConfiguration

ControlPlaneComponent holds settings common to control plane component of the cluster

Field	Description
`extraArgs` [Required] `map[string]string`	`extraArgs` is an extra set of flags to pass to a control plane component. A key in this map is the flag name as it appears on the command line except without leading dash(es).
`extraVolumes` [Required] []HostPathMount	`extraVolumes` is an extra set of host volumes mounted to the control plane component.

`DNS`

Appears in:

ClusterConfiguration

DNS defines the DNS addon that should be used in the cluster

Field	Description
`type` [Required]	`type` defines the DNS add-on to be used.
`ImageMeta` [Required] ImageMeta	(Members of `ImageMeta` are embedded into this type.) ImageMeta allows to customize the image used for the DNS component

`DNSAddOnType`

(Alias of string)

Appears in:

DNSAddOnType defines string identifying DNS add-on types.

`Discovery`

Appears in:

JoinConfiguration

Discovery specifies the options for the kubelet to use during the TLS Bootstrap process

Field	Description
`bootstrapToken` [Required]	`bootstrapToken` is used to set the options for bootstrap token based discovery. `bootstrapToken` and `file` are mutually exclusive.
`file` [Required] FileDiscovery	`file` is used to specify a file or URL to a kubeconfig file from which to load cluster information. and `file` are mutually exclusive.
`tlsBootstrapToken` [Required] `string`	`tlsBootstrapToken` is a token used for TLS bootstrapping. If `bootstrapToken` is set, this field is defaulted to `.bootstrapToken.token`, but can be overridden. If `file` is set, this field must be set in case the KubeConfigFile does not contain any other authentication information.
`timeout` [Required]

Appears in:

Etcd contains elements describing Etcd configuration.

Field	Description
`local` [Required] LocalEtcd	`local` provides configuration knobs for configuring the local etcd instance. `local` and `external` are mutually exclusive.
`external` [Required]	`external` describes how to connect to an external etcd cluster. `local` and `external` are mutually exclusive.

`ExternalEtcd`

Appears in:

ExternalEtcd describes an external etcd cluster. Kubeadm has no knowledge of where certificate files live and they must be supplied.

Field	Description
`endpoints` [Required] `[]string`	`endpoints` of etcd members.
`caFile` [Required] `string`	`caFile` is an SSL Certificate Authority (CA) file used to secure etcd communication. Required if using a TLS connection.
`certFile` [Required] `string`	`certFile` is an SSL certification file used to secure etcd communication. Required if using a TLS connection.
`keyFile` [Required] `string`	`keyFile` is an SSL key file used to secure etcd communication. Required if using a TLS connection.

`FileDiscovery`

Appears in:

FileDiscovery is used to specify a file or URL to a kubeconfig file from which to load cluster information

`HostPathMount`

Appears in:

HostPathMount contains elements describing volumes that are mounted from the host.

Field	Description
`name` [Required] `string`	`name` of the volume inside the Pod template.
`hostPath` [Required] `string`	`hostPath` is the path in the host that will be mounted inside the Pod.
`mountPath` [Required] `string`	`mountPath`is the path inside the Pod where hostPath volume will be mounted.
`readOnly` [Required] `bool`	`readOnly` controls write access to the volume.
`pathType` [Required] core/v1.HostPathType	`pathType` is the type of the HostPath.

`ImageMeta`

Appears in:

ImageMeta allows to customize the image used for components that are not originated from the Kubernetes/Kubernetes release process

Field	Description
`imageRepository` [Required] `string`	`imageRepository` sets the container registry to pull images from. If not set, the `imageRepository` defined in ClusterConfiguration will be used.
`imageTag` [Required] `string`	`imageTag` allows for specifying a tag for the image. In case this value is set, kubeadm does not change automatically the version of the above components during upgrades.

`JoinControlPlane`

Appears in:

JoinControlPlane contains elements describing an additional control plane instance to be deployed on the joining node.

Field	Description
`localAPIEndpoint` [Required] APIEndpoint	`localAPIEndpoint` represents the endpoint of the API server instance to be deployed on this node.
`certificateKey` [Required] `string`	`certificateKey` is the key that is used for decryption of certificates after they are downloaded from the secret upon joining a new control plane node. The corresponding encryption key is in the InitConfiguration.

`LocalEtcd`

Appears in:

Etcd

LocalEtcd describes that kubeadm should run an etcd cluster locally.

Field	Description
`ImageMeta` [Required]	(Members of `ImageMeta` are embedded into this type.) ImageMeta allows to customize the container used for etcd.
`dataDir` [Required] `string`	`dataDir` is the directory etcd will place its data. Defaults to “/var/lib/etcd”.
`extraArgs` [Required] `map[string]string`	`extraArgs` are extra arguments provided to the etcd binary when run inside a static pod. A key in this map is the flag name as it appears on the command line except without leading dash(es).
`serverCertSANs` [Required] `[]string`	`serverCertSANs` sets extra Subject Alternative Names (SANs) for the etcd server signing certificate.
`peerCertSANs` [Required] `[]string`	`peerCertSANs` sets extra Subject Alternative Names (SANs) for the etcd peer signing certificate.

`Networking`

Appears in:

Networking contains elements describing cluster’s networking configuration

Field	Description
`serviceSubnet` [Required] `string`	`serviceSubnet` is the subnet used by kubernetes Services. Defaults to “10.96.0.0/12”.
`podSubnet` [Required] `string`	`podSubnet` is the subnet used by Pods.
`dnsDomain` [Required] `string`	`dnsDomain` is the DNS domain used by kubernetes Services. Defaults to “cluster.local”.

`NodeRegistrationOptions`

Appears in:

JoinConfiguration

NodeRegistrationOptions holds fields that relate to registering a new control-plane or node to the cluster, either via “kubeadm init” or “kubeadm join”.

Field	Description
`name` [Required] `string`	`name` is the `.Metadata.Name` field of the Node API object that will be created in this `kubeadm init` or `kubeadm join` operation. This field is also used in the `CommonName` field of the kubelet’s client certificate to the API server. Defaults to the hostname of the node if not provided.
`criSocket` [Required] `string`	`criSocket` is used to retrieve container runtime information. This information will be annotated to the Node API object, for later re-use.
`taints` [Required]	`taints` specifies the taints the Node API object should be registered with. If this field is unset, i.e. nil, in the `kubeadm init` process it will be defaulted with a control-plane taint for control-plane nodes. If you don’t want to taint your control-plane node, set this field to an empty list, i.e. `taints: []`, in the YAML file. This field is solely used for Node registration.
`kubeletExtraArgs` [Required] `map[string]string`	`kubeletExtraArgs` passes through extra arguments to the kubelet. The arguments here are passed to the kubelet command line via the environment file kubeadm writes at runtime for the kubelet to source. This overrides the generic base-level configuration in the ‘kubelet-config-1.X’ ConfigMap. Flags have higher priority when parsing. These values are local and specific to the node kubeadm is executing on. A key in this map is the flag name as it appears on the command line except without leading dash(es).
`ignorePreflightErrors` [Required]