You are viewing documentation for Kubernetes version: v1.21

Kubernetes v1.21 documentation is no longer actively maintained. The version you are currently viewing is a static snapshot. For up-to-date documentation, see the latest version.

kubeadm Configuration (v1beta2)

Package v1beta2 defines the v1beta2 version of the kubeadm configuration file format. This version improves on the v1beta1 format by fixing some minor issues and adding a few new fields.

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 is used in a more places where appropriate.
  • 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:

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

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

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

apiVersion: kubeproxy.config.k8s.io/v1alpha1
kind: KubeProxyConfiguration

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

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.

apiVersion: kubeadm.k8s.io/v1beta2
kind: InitConfiguration
bootstrapTokens:
    ...
nodeRegistration:
    ...

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).

  • LocalAPIEndpoint, 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.

    apiVersion: kubeproxy.config.k8s.io/v1alpha1
    kind: KubeProxyConfiguration
       ...
    

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 https://kubernetes.io/docs/reference/command-line-tools-reference/kube-proxy/ or https://godoc.org/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 https://kubernetes.io/docs/reference/command-line-tools-reference/kubelet/ or https://godoc.org/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.

apiVersion: kubeadm.k8s.io/v1beta2
kind: InitConfiguration
bootstrapTokens:
  - token: "9a08jv.c0izixklcxtmnze7"
    description: "kubeadm bootstrap token"
    ttl: "24h"
  - token: "783bde.3f89s0fje9f38fhf"
    description: "another bootstrap token"
    usages:
      - authentication
      - signing
    groups:
      - system:bootstrappers:kubeadm:default-node-token
nodeRegistration:
  name: "ec2-10-100-0-1"
  criSocket: "/var/run/dockershim.sock"
  taints:
    - key: "kubeadmNode"
      value: "master"
      effect: "NoSchedule"
  kubeletExtraArgs:
    cgroup-driver: "cgroupfs"
  ignorePreflightErrors:
    - IsPrivilegedUser
localAPIEndpoint:
  advertiseAddress: "10.100.0.1"
  bindPort: 6443
certificateKey: "e6a2eb8581237ab72a4f494f30285ec12a9694d750b9785706a83bfcbbbd2204"
---
apiVersion: kubeadm.k8s.io/v1beta2
kind: ClusterConfiguration
etcd:
  # one of local or external
  local:
    imageRepository: "k8s.gcr.io"
    imageTag: "3.2.24"
    dataDir: "/var/lib/etcd"
    extraArgs:
      listen-client-urls: "http://10.100.0.1:2379"
    serverCertSANs:
      - "ec2-10-100-0-1.compute-1.amazonaws.com"
    peerCertSANs:
      - "10.100.0.1"
  # external:
    # endpoints:
    # - "10.100.0.1:2379"
    # - "10.100.0.2:2379"
    # caFile: "/etcd/kubernetes/pki/etcd/etcd-ca.crt"
    # certFile: "/etcd/kubernetes/pki/etcd/etcd.crt"
    # keyFile: "/etcd/kubernetes/pki/etcd/etcd.key"
 networking:
   serviceSubnet: "10.96.0.0/12"
   podSubnet: "10.100.0.1/24"
   dnsDomain: "cluster.local"
 kubernetesVersion: "v1.12.0"
 controlPlaneEndpoint: "10.100.0.1:6443"
 apiServer:
   extraArgs:
     authorization-mode: "Node,RBAC"
   extraVolumes:
     - name: "some-volume"
       hostPath: "/etc/some-path"
       mountPath: "/etc/some-pod-path"
       readOnly: false
       pathType: File
   certSANs:
     - "10.100.1.1"
     - "ec2-10-100-0-1.compute-1.amazonaws.com"
   timeoutForControlPlane: 4m0s
 controllerManager:
   extraArgs:
     "node-cidr-mask-size": "20"
   extraVolumes:
     - name: "some-volume"
       hostPath: "/etc/some-path"
       mountPath: "/etc/some-pod-path"
       readOnly: false
       pathType: File
 scheduler:
   extraArgs:
     address: "10.100.0.1"
   extraVolumes:
     - name: "some-volume"
       hostPath: "/etc/some-path"
       mountPath: "/etc/some-pod-path"
       readOnly: false
       pathType: File
certificatesDir: "/etc/kubernetes/pki"
imageRepository: "k8s.gcr.io"
useHyperKubeImage: false
clusterName: "example-cluster"
---
apiVersion: kubelet.config.k8s.io/v1beta1
kind: KubeletConfiguration
# kubelet specific options here
---
apiVersion: kubeproxy.config.k8s.io/v1alpha1
kind: KubeProxyConfiguration
# kube-proxy specific options here

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).

  • APIEndpoint, that represents the endpoint of the instance of the API server to be eventually deployed on this node.

Resource Types

ClusterConfiguration

ClusterConfiguration contains cluster-wide configuration for a kubeadm cluster

FieldDescription
apiVersion
string
kubeadm.k8s.io/v1beta2
kind
string
ClusterConfiguration
etcd [Required]
Etcd
`etcd` holds configuration for etcd.
networking [Required]
Networking
`networking` holds configuration for the networking topology of the cluster.
kubernetesVersion [Required]
string
`kubernetesVersion` is the target version of the control plane.
controlPlaneEndpoint [Required]
string
`controlPlaneEndpoint` sets a stable IP address or DNS name for the control plane; it can be a valid IP address or a RFC-1123 DNS subdomain, both with optional TCP port. In case the ControlPlaneEndpoint is not specified, the AdvertiseAddress + BindPort are used; in case the ControlPlaneEndpoint is specified but without a TCP port, the BindPort is used. Possible usages are:
  • In a cluster with more than one control plane instances, this field should be assigned the address of the external load balancer in front of the control plane instances.
  • In environments with enforced node recycling, the ControlPlaneEndpoint could be used for assigning a stable DNS to the control plane.
apiServer [Required]
APIServer
`apiServer` contains extra settings for the API server.
controllerManager [Required]
ControlPlaneComponent
`controllerManager` contains extra settings for the controller manager.
scheduler [Required]
ControlPlaneComponent
`scheduler` contains extra settings for the scheduler.
dns [Required]
DNS
`dns` defines the options for the DNS add-on.
certificatesDir [Required]
string
`certificatesDir` specifies where to store or look for all required certificates.
imageRepository [Required]
string
`imageRepository` sets the container registry to pull images from. If empty, `k8s.gcr.io` will be used by default; in case of kubernetes version is a CI build (kubernetes version starts with `ci/` or `ci-cross/`) `gcr.io/k8s-staging-ci-images` will be used as a default for control plane components and for kube-proxy, while `k8s.gcr.io` will be used for all the other images.
useHyperKubeImage [Required]
bool
`useHyperKubeImage` controls if hyperkube should be used for Kubernetes components instead of their respective separate images DEPRECATED: As hyperkube is itself deprecated, this fields is too. It will be removed in future kubeadm config versions, kubeadm will print multiple warnings when this is set to true, and at some point it may become ignored.
featureGates [Required]
map[string]bool
Feature gates enabled by the user.
clusterName [Required]
string
The cluster name

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.

FieldDescription
apiVersion
string
kubeadm.k8s.io/v1beta2
kind
string
ClusterStatus
apiEndpoints [Required]
map[string]github.com/tengqm/kubeconfig/config/kubeadm/v1beta2.APIEndpoint
`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.

FieldDescription
apiVersion
string
kubeadm.k8s.io/v1beta2
kind
string
InitConfiguration
bootstrapTokens [Required]
[]BootstrapToken
`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]
APIEndpoint
`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 loadbalances 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
`certificateKey` sets the key with which certificates and keys are encrypted prior to being uploaded in a Secret in the cluster during the "uploadcerts" init phase.

JoinConfiguration

JoinConfiguration contains elements describing a particular node.

FieldDescription
apiVersion
string
kubeadm.k8s.io/v1beta2
kind
string
JoinConfiguration
nodeRegistration [Required]
NodeRegistrationOptions
`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 node and 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]
JoinControlPlane
`controlPlane` defines the additional control plane instance to be deployed on the joining node. If nil, no additional control plane instance will be deployed.

APIEndpoint

Appears in:

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

FieldDescription
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

FieldDescription
ControlPlaneComponent [Required]
ControlPlaneComponent
(Members of ControlPlaneComponent are embedded into this type.) No description provided.
certSANs [Required]
[]string
`certSANs` sets extra Subject Alternative Names for the API Server signing cert.
timeoutForControlPlane [Required]
meta/v1.Duration
`timeoutForControlPlane` controls the timeout that we use for API server to appear

BootstrapToken

Appears in:

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

FieldDescription
token [Required]
BootstrapTokenString
`token` 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]
meta/v1.Duration
`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:

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

FieldDescription
token [Required]
string
`token` is a token used to validate cluster information fetched from the control-plane.
apiServerEndpoint [Required]
string
`apiServerEndpoint` is an IP or domain name to the API server from which information will be fetched.
caCertHashes [Required]
[]string
discovery is used. The root CA found during discovery must match one of these values. Specifying an empty set disables root CA pinning, which can be unsafe. Each hash is specified as `:`, where the only currently supported type is "sha256". This is a hex-encoded SHA-256 hash of the Subject Public Key Info (SPKI) object in DER-encoded ASN.1. These hashes can be calculated using, for example, OpenSSL.
unsafeSkipCAVerification [Required]
bool
`unsafeSkipCAVerification` allows token-based discovery without CA verification via `caCertHashes`. This can weaken the security of kubeadm since other nodes can impersonate the control-plane.

BootstrapTokenString

Appears in:

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

FieldDescription
- [Required]
string
No description provided.
- [Required]
string
No description provided.

ControlPlaneComponent

Appears in:

ControlPlaneComponent holds settings common to control plane component of the cluster

FieldDescription
extraArgs [Required]
map[string]string
`extraArgs` is an extra set of flags to pass to the control plane component.
extraVolumes [Required]
[]HostPathMount
`extraVolumes` is an extra set of host volumes, mounted to the control plane component.

DNS

Appears in:

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

FieldDescription
type [Required]
DNSAddOnType
`type` defines the DNS add-on to use.
ImageMeta [Required]
ImageMeta
(Members of ImageMeta are embedded into this type.) `imageMeta` allows to customize the image used for the DNS.

DNSAddOnType

(Alias of string)

Appears in:

DNSAddOnType defines string identifying DNS add-on types

Discovery

Appears in:

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

FieldDescription
bootstrapToken [Required]
BootstrapTokenDiscovery
`bootstrapToken` is used to set the options for bootstrap token based discovery. `bootstrapToken` and `file` are mutually exclusive.
file [Required]
FileDiscovery
`file` specifies a file or URL to a kubeconfig file from which to load cluster information. `bootstrapToken` 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]
meta/v1.Duration
`timeout` modifies the discovery timeout.

Etcd

Appears in:

Etcd contains elements describing Etcd configuration.

FieldDescription
local [Required]
LocalEtcd
`local` provides configuration knobs for configuring the local etcd instance. `local` and `external` are mutually exclusive.
external [Required]
ExternalEtcd
`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.

FieldDescription
endpoints [Required]
[]string
`endpoints` are endpoints of etcd members. This field is required.
caFile [Required]
string
`caFile` is an SSL Certificate Authority 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

FieldDescription
kubeConfigPath [Required]
string
`kubeConfigPath` specifies the actual file path or URL to the kubeconfig file from which to load cluster information

HostPathMount

Appears in:

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

FieldDescription
name [Required]
string
`name` is the volume name 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 the `hostPath` volume is mounted.
readOnly [Required]
bool
`readOnly` controls write access to the volume.
pathType [Required]
core/v1.HostPathType
`pathType` is the type of the `hostPath` volume.

ImageMeta

Appears in:

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

FieldDescription
imageRepository [Required]
string
`imageRepository` sets the container registry to pull images from. If not set, the ImageRepository defined in ClusterConfiguration will be used instead.
imageTag [Required]
string
`imageTag` allows to specify 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.

FieldDescription
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:

LocalEtcd describes that kubeadm should run an etcd cluster locally

FieldDescription
ImageMeta [Required]
ImageMeta
(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.
serverCertSANs [Required]
[]string
`serverCertSANs` sets extra Subject Alternative Names for the etcd server signing cert.
peerCertSANs [Required]
[]string
`peerCertSANs` sets extra Subject Alternative Names for the etcd peer signing cert.

Networking

Appears in:

Networking contains elements describing cluster's networking configuration

FieldDescription
serviceSubnet [Required]
string
`serviceSubnet` is the subnet used by k8s 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 k8s services. Defaults to "cluster.local".

NodeRegistrationOptions

Appears in:

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

FieldDescription
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 info. This information will be annotated to the Node API object, for later re-use.
taints [Required]
[]core/v1.Taint
`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 to `['"node-role.kubernetes.io/master"=""']`. 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.
ignorePreflightErrors [Required]
[]string
`ignorePreflightErrors` provides a slice of pre-flight errors to be ignored when the current node is registered.
Last modified July 23, 2021 at 12:01 PM PST : Fix kubeadm config reference (8bd5598f3)