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Configuration options

Using a configuration file

k0s can be installed without a config file. In that case the default configuration will be used. You can, though, create and run your own non-default configuration (used by the k0s controller nodes).

k0s supports providing only partial configurations. In case of partial configuration is provided, k0s will use the defaults for any missing values.

  1. Generate a yaml config file that uses the default settings.

    mkdir -p /etc/k0s
k0s config create > /etc/k0s/k0s.yaml

  2. Modify the new yaml config file according to your needs, refer to Configuration file reference below. You can remove the default values if wanted as k0s supports partial configs too.

  3. Install k0s with your new config file.

    sudo k0s install controller -c /etc/k0s/k0s.yaml

  4. If you need to modify your existing configuration later on, you can change your config file also when k0s is running, but remember to restart k0s to apply your configuration changes.

    sudo k0s stop
sudo k0s start

Configuration file reference

CAUTION: As many of the available options affect items deep in the stack, you should fully understand the correlation between the configuration file components and your specific environment before making any changes.

A YAML config file follows, with defaults as generated by the k0s config create command:

apiVersion: k0s.k0sproject.io/v1beta1
kind: ClusterConfig
metadata:
  name: k0s
spec:
  api:
    address: 192.168.68.104
    externalAddress: my-lb-address.example.com
    k0sApiPort: 9443
    port: 6443
    sans:
    - 192.168.68.104
    tunneledNetworkingMode: false
  controllerManager: {}
  extensions:
    helm:
      charts: null
      repositories: null
    storage:
      create_default_storage_class: false
      type: external_storage
  images:
    default_pull_policy: IfNotPresent
    calico:
      cni:
        image: docker.io/calico/cni
        version: v3.24.5
      kubecontrollers:
        image: docker.io/calico/kube-controllers
        version: v3.24.5
      node:
        image: docker.io/calico/node
        version: v3.24.5
    coredns:
      image: docker.io/coredns/coredns
      version: 1.10.0
    konnectivity:
      image: quay.io/k0sproject/apiserver-network-proxy-agent
      version: 0.0.33-k0s
    kubeproxy:
      image: registry.k8s.io/kube-proxy
      version: v1.26.0
    kuberouter:
      cni:
        image: docker.io/cloudnativelabs/kube-router
        version: v1.5.1
      cniInstaller:
        image: quay.io/k0sproject/cni-node
        version: 1.1.1-k0s.0
    metricsserver:
      image: registry.k8s.io/metrics-server/metrics-server
      version: v0.6.2
    pushgateway:
      image: quay.io/k0sproject/pushgateway-ttl
      version: edge@sha256:7031f6bf6c957e2fdb496161fe3bea0a5bde3de800deeba7b2155187196ecbd9
  installConfig:
    users:
      etcdUser: etcd
      kineUser: kube-apiserver
      konnectivityUser: konnectivity-server
      kubeAPIserverUser: kube-apiserver
      kubeSchedulerUser: kube-scheduler
  konnectivity:
    adminPort: 8133
    agentPort: 8132
  network:
    calico: null
    clusterDomain: cluster.local
    dualStack: {}
    kubeProxy:
      metricsBindAddress: 0.0.0.0:10249
      mode: iptables
    kuberouter:
      autoMTU: true
      hairpin: Enabled
      ipMasq: false
      metricsPort: 8080
      mtu: 0
      peerRouterASNs: ""
      peerRouterIPs: ""
    nodeLocalLoadBalancing:
      enabled: false
      envoyProxy:
        apiServerBindPort: 7443
        image:
          image: docker.io/envoyproxy/envoy-distroless
          version: v1.24.1
        konnectivityServerBindPort: 7132
      type: EnvoyProxy
    podCIDR: 10.244.0.0/16
    provider: kuberouter
    serviceCIDR: 10.96.0.0/12
  scheduler: {}
  storage:
    etcd:
      externalCluster: null
      peerAddress: 192.168.68.104
    type: etcd
  telemetry:
    enabled: true

spec Key Detail

spec.api

Element Description
externalAddress The loadbalancer address (for k0s controllers running behind a loadbalancer). Configures all cluster components to connect to this address and also configures this address for use when joining new nodes to the cluster.
address Local address on which to bind an API. Also serves as one of the addresses pushed on the k0s create service certificate on the API. Defaults to first non-local address found on the node.
sans List of additional addresses to push to API servers serving the certificate.
extraArgs Map of key-values (strings) for any extra arguments to pass down to Kubernetes api-server process.
port¹ Custom port for kube-api server to listen on (default: 6443)
k0sApiPort¹ Custom port for k0s-api server to listen on (default: 9443)
tunneledNetworkingMode Whether to tunnel Kubernetes access from worker nodes via local port forwarding. (default: false)

¹ If port and k0sApiPort are used with the externalAddress element, the loadbalancer serving at externalAddress must listen on the same ports.

spec.storage

Element Description
type Type of the data store (valid values:etcd or kine). Note: Type etcd will cause k0s to create and manage an elastic etcd cluster within the controller nodes.
etcd.peerAddress Node address used for etcd cluster peering.
etcd.extraArgs Map of key-values (strings) for any extra arguments to pass down to etcd process.
kine.dataSource kine datasource URL.

spec.network

Element Description
provider Network provider (valid values: calico, kuberouter, or custom). For custom, you can push any network provider (default: kuberouter). Be aware that it is your responsibility to configure all of the CNI-related setups, including the CNI provider itself and all necessary host levels setups (for example, CNI binaries). Note: Once you initialize the cluster with a network provider the only way to change providers is through a full cluster redeployment.
podCIDR Pod network CIDR to use in the cluster.
serviceCIDR Network CIDR to use for cluster VIP services.
clusterDomain Cluster Domain to be passed to the kubelet and the coredns configuration.

spec.network.calico

Element Description
mode vxlan (default), ipip or bird
overlay Overlay mode: Always (default), CrossSubnet or Never (requires mode=vxlan to disable calico overlay-network).
vxlanPort The UDP port for VXLAN (default: 4789).
vxlanVNI The virtual network ID for VXLAN (default: 4096).
mtu MTU for overlay network (default: 0, which causes Calico to detect optimal MTU during bootstrap).
wireguard Enable wireguard-based encryption (default: false). Your host system must be wireguard ready (refer to the Calico documentation for details).
flexVolumeDriverPath The host path for Calicos flex-volume-driver(default: /usr/libexec/k0s/kubelet-plugins/volume/exec/nodeagent~uds). Change this path only if the default path is unwriteable (refer to Project Calico Issue #2712 for details). Ideally, you will pair this option with a custom volumePluginDir in the profile you use for your worker nodes.
ipAutodetectionMethod Use to force Calico to pick up the interface for pod network inter-node routing (default: "", meaning not set, so that Calico will instead use its defaults). For more information, refer to the Calico documentation.
envVars Map of key-values (strings) for any calico-node environment variable.

spec.network.calico.envVars

Environment variable's value must be string, e.g.:

spec:
  network:
    provider: calico
    calico:
      envVars:
        TEST_BOOL_VAR: "true"
        TEST_INT_VAR: "42"
        TEST_STRING_VAR: test

K0s runs Calico with some predefined vars, which can be overwritten by setting new value in spec.network.calico.envVars:

CALICO_IPV4POOL_CIDR: "{{ spec.network.podCIDR }}"
CALICO_DISABLE_FILE_LOGGING: "true"
FELIX_DEFAULTENDPOINTTOHOSTACTION: "ACCEPT"
FELIX_LOGSEVERITYSCREEN: "info"
FELIX_HEALTHENABLED: "true"
FELIX_PROMETHEUSMETRICSENABLED: "true"

In SingleStack mode there are additional vars:

FELIX_IPV6SUPPORT: "false"

In DualStack mode there are additional vars:

CALICO_IPV6POOL_NAT_OUTGOING: "true"
FELIX_IPV6SUPPORT: "true"
IP6: "autodetect"
CALICO_IPV6POOL_CIDR: "{{ spec.network.dualStack.IPv6podCIDR }}"

spec.network.kuberouter

Element Description
autoMTU Autodetection of used MTU (default: true).
mtu Override MTU setting, if autoMTU must be set to false).
metricsPort Kube-router metrics server port. Set to 0 to disable metrics (default: 8080).
peerRouterIPs Comma-separated list of global peer addresses.
peerRouterASNs Comma-separated list of global peer ASNs.
hairpin Hairpin mode, supported modes Enabled: enabled cluster wide, Allowed: must be allowed per service using annotations, Disabled: doesn't work at all (default: Enabled)
hairpinMode Deprecated Use hairpin instead. If both hairpin and hairpinMode are defined, this is ignored. If only hairpinMode is configured explicitly activates hairpinMode (https://github.com/cloudnativelabs/kube-router/blob/master/docs/user-guide.md#hairpin-mode).
ipMasq IP masquerade for traffic originating from the pod network, and destined outside of it (default: false)

Note: Kube-router allows many networking aspects to be configured per node, service, and pod (for more information, refer to the Kube-router user guide).

spec.network.kubeProxy

Element Description
disabled Disable kube-proxy altogether (default: false).
mode Kube proxy operating mode, supported modes iptables, ipvs, userspace (default: iptables)
iptables Kube proxy iptables settings
ipvs Kube proxy ipvs settings

Default kube-proxy iptables settings:

iptables:
  masqueradeAll: false
  masqueradeBit: null
  minSyncPeriod: 0s
  syncPeriod: 0s

Default kube-proxy ipvs settings:

ipvs:
  excludeCIDRs: null
  minSyncPeriod: 0s
  scheduler: ""
  strictARP: false
  syncPeriod: 0s
  tcpFinTimeout: 0s
  tcpTimeout: 0s
  udpTimeout: 0s

spec.network.nodeLocalLoadBalancing

Configuration options related to k0s's node-local load balancing feature.

Note: This feature is experimental! Expect instabilities and/or breaking changes.

Element Description
enabled Indicates if node-local load balancing should be used to access Kubernetes API servers from worker nodes. Default: false.
type The type of the node-local load balancer to deploy on worker nodes. Default: EnvoyProxy. (This is the only option for now.)
envoyProxy Configuration options related to the "EnvoyProxy" type of load balancing.
spec.network.nodeLocalLoadBalancing.envoyProxy

Configuration options required for using Envoy as the backing implementation for node-local load balancing.

Note: This type of load balancing is not supported on ARMv7 workers.

Element Description
image The OCI image that's being used for the Envoy Pod.
imagePullPolicy The pull policy being used used for the Envoy Pod. Defaults to spec.images.default_pull_policy if omitted.
apiServerBindPort Port number on which to bind the Envoy load balancer for the Kubernetes API server to on a worker's loopback interface. Default: 7443.
konnectivityServerBindPort Port number on which to bind the Envoy load balancer for the konnectivity server to on a worker's loopback interface. Default: 7132.

spec.controllerManager

Element Description
extraArgs Map of key-values (strings) for any extra arguments you want to pass down to the Kubernetes controller manager process.

spec.scheduler

Element Description
extraArgs Map of key-values (strings) for any extra arguments you want to pass down to Kubernetes scheduler process.

spec.workerProfiles

Worker profiles are used to manage worker-specific configuration in a centralized manner. A ConfigMap is generated for each worker profile. Based on the --profile argument given to the k0s worker, the configuration in the corresponding ConfigMap is is picked up during startup.

The worker profiles are defined as an array. Each element has following properties:

Property Description
name String; name to use as profile selector for the worker process
values Object; Kubelet configuration overrides, see below for details

spec.workerProfiles[].values (Kubelet configuration overrides)

The Kubelet configuration overrides of a profile override the defaults defined by k0s.

Note that there are several fields that cannot be overridden:

  • clusterDNS
  • clusterDomain
  • apiVersion
  • kind
  • staticPodURL

Examples

Feature Gates

The below is an example of a worker profile with feature gates enabled:

spec:
  workerProfiles:
    - name: custom-feature-gate      # name of the worker profile
      values:
         featureGates:        # feature gates mapping
            DevicePlugins: true
            Accelerators: true
            AllowExtTrafficLocalEndpoints: false
Custom volumePluginDir
spec:
  workerProfiles:
    - name: custom-pluginDir
      values:
         volumePluginDir: /var/libexec/k0s/kubelet-plugins/volume/exec
Eviction Policy
spec:
  workerProfiles:
    - name: custom-eviction
      values:
        evictionHard:
          memory.available: "500Mi"
          nodefs.available: "1Gi"
          imagefs.available: "100Gi"
        evictionMinimumReclaim:
          memory.available: "0Mi"
          nodefs.available: "500Mi"
          imagefs.available: "2Gi"
Unsafe Sysctls
spec:
  workerProfiles:
    - name: custom-eviction
      values:
        allowedUnsafeSysctls:
          - fs.inotify.max_user_instances

spec.images

Nodes under the images key all have the same basic structure:

spec:
  images:
    coredns:
      image: quay.io/coredns/coredns
      version: v1.7.0

Available keys

  • spec.images.konnectivity
  • spec.images.metricsserver
  • spec.images.kubeproxy
  • spec.images.coredns
  • spec.images.calico.cni
  • spec.images.calico.flexvolume
  • spec.images.calico.node
  • spec.images.calico.kubecontrollers
  • spec.images.kuberouter.cni
  • spec.images.kuberouter.cniInstaller
  • spec.images.repository¹

¹ If spec.images.repository is set and not empty, every image will be pulled from images.repository

If spec.images.default_pull_policy is set and not empty, it will be used as a pull policy for each bundled image.

Example

images:
  repository: "my.own.repo"
  konnectivity:
    image: calico/kube-controllers
    version: v3.16.2
  metricsserver:
    image: registry.k8s.io/metrics-server/metrics-server
    version: v0.6.2

In the runtime the image names are calculated as my.own.repo/calico/kube-controllers:v3.16.2 and my.own.repo/metrics-server/metrics-server:v0.6.2. This only affects the the imgages pull location, and thus omitting an image specification here will not disable component deployment.

spec.extensions.helm

spec.extensions.helm is the config file key in which you configure the list of Helm repositories and charts to deploy during cluster bootstrap (for more information, refer to Helm Charts).

spec.extensions.storage

spec.extensions.storage controls bundled storage provider. The default value external makes no storage deployed.

To enable embedded host-local storage provider use the following configuration:

spec:
  extensions:
    storage:
      type: openebs_local_storage

spec.konnectivity

The spec.konnectivity key is the config file key in which you configure Konnectivity-related settings.

  • agentPort agent port to listen on (default 8132)
  • adminPort admin port to listen on (default 8133)

spec.telemetry

To improve the end-user experience k0s is configured by defaul to collect telemetry data from clusters and send it to the k0s development team. To disable the telemetry function, change the enabled setting to false.

The telemetry interval is ten minutes.

spec:
  telemetry:
    enabled: true

Disabling controller components

k0s allows to completely disable some of the system components. This allows users to build a minimal Kubernetes control plane and use what ever components they need to fulfill their need for the control plane. Disabling the system components happens through a command line flag for the controller process:

--disable-components strings                     disable components (valid items: api-config,autopilot,control-api,coredns,csr-approver,endpoint-reconciler,helm,konnectivity-server,kube-controller-manager,kube-proxy,kube-scheduler,metrics-server,network-provider,node-role,system-rbac,worker-config)

Note: As of k0s 1.26, the kubelet-config component has been replaced by the worker-config component. k0s will issue a warning when the old component name is being used. It is scheduled for removal in k0s 1.27. Please update to the new component name.

If you use k0sctl, just add the flag when installing the cluster for the first controller at spec.hosts.installFlags in the config file like e.g.:

spec:
  hosts:
  - role: controller
    installFlags:
    - --disable-components=metrics-server

As seen from the component list, the only always-on component is the Kubernetes api-server, without that k0s serves no purpose.