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Description of Keys in config and cluster.spec

This list is not complete but aims to document any keys that are less than self-explanatory. Our godoc reference provides a more detailed list of API values. ClusterSpec, defined as kind: Cluster in YAML, and InstanceGroup, defined as kind: InstanceGroup in YAML, are the two top-level API values used to describe a cluster.

spec

api

This object configures how we expose the API:

  • dns will allow direct access to master instances, and configure DNS to point directly to the master nodes.
  • loadBalancer will configure a load balancer (ELB) in front of the master nodes, and configure DNS to point to the ELB.

DNS example:

spec:
  api:
    dns: {}

When configuring a LoadBalancer, you can also choose to have a public ELB or an internal (VPC only) ELB. The type field should be Public or Internal.

Additionally, you can increase idle timeout of the load balancer by setting its idleTimeoutSeconds. The default idle timeout is 5 minutes, with a maximum of 3600 seconds (60 minutes) being allowed by AWS. For more information see configuring idle timeouts.

spec:
  api:
    loadBalancer:
      type: Public
      idleTimeoutSeconds: 300

etcdClusters v3 & tls

Although kops doesn't presently default to etcd3, it is possible to turn on both v3 and TLS authentication for communication amongst cluster members. These options may be enabled via the cluster spec (manifests only i.e. no command line options as yet). An upfront warning; at present no upgrade path exists for migrating from v2 to v3 so DO NOT try to enable this on a v2 running cluster as it must be done on cluster creation. The below example snippet assumes a HA cluster of three masters.

etcdClusters:
- etcdMembers:
  - instanceGroup: master0-az0
    name: a-1
  - instanceGroup: master1-az0
    name: a-2
  - instanceGroup: master0-az1
    name: b-1
  enableEtcdTLS: true
  name: main
  version: 3.0.17
- etcdMembers:
  - instanceGroup: master0-az0
    name: a-1
  - instanceGroup: master1-az0
    name: a-2
  - instanceGroup: master0-az1
    name: b-1
  enableEtcdTLS: true
  name: events
  version: 3.0.17

sshAccess

This array configures the CIDRs that are able to ssh into nodes. On AWS this is manifested as inbound security group rules on the nodes and master security groups.

Use this key to restrict cluster access to an office ip address range, for example.

spec:
  sshAccess:
    - 12.34.56.78/32

kubernetesApiAccess

This array configures the CIDRs that are able to access the kubernetes API. On AWS this is manifested as inbound security group rules on the ELB or master security groups.

Use this key to restrict cluster access to an office ip address range, for example.

spec:
  kubernetesApiAccess:
    - 12.34.56.78/32

cluster.spec Subnet Keys

id

ID of a subnet to share in an existing VPC.

egress

The resource identifier (ID) of something in your existing VPC that you would like to use as "egress" to the outside world.

This feature was originally envisioned to allow re-use of NAT Gateways. In this case, the usage is as follows. Although NAT gateways are "public"-facing resources, in the Cluster spec, you must specify them in the private subnet section. One way to think about this is that you are specifying "egress", which is the default route out from this private subnet.

spec:
  subnets:
  - cidr: 10.20.64.0/21
    name: us-east-1a
    egress: nat-987654321
    type: Private
    zone: us-east-1a
  - cidr: 10.20.32.0/21
    name: utility-us-east-1a
    id: subnet-12345
    type: Utility
    zone: us-east-1a

kubeAPIServer

This block contains configuration for the kube-apiserver.

oidc flags for Open ID Connect Tokens

Read more about this here: https://kubernetes.io/docs/admin/authentication/#openid-connect-tokens

spec:
  kubeAPIServer:
    oidcIssuerURL: https://your-oidc-provider.svc.cluster.local
    oidcClientID: kubernetes
    oidcUsernameClaim: sub
    oidcGroupsClaim: user_roles
    oidcCAFile: /etc/kubernetes/ssl/kc-ca.pem

audit logging

Read more about this here: https://kubernetes.io/docs/admin/audit

spec:
  kubeAPIServer:
    auditLogPath: /var/log/kube-apiserver-audit.log
    auditLogMaxAge: 10
    auditLogMaxBackups: 1
    auditLogMaxSize: 100
    auditPolicyFile: /srv/kubernetes/audit.conf

Note: you could use the fileAssets feature to push an advanced audit policy file on the master nodes.

runtimeConfig

Keys and values here are translated into --runtime-config values for kube-apiserver, separated by commas.

Use this to enable alpha features, for example:

spec:
  kubeAPIServer:
    runtimeConfig:
      batch/v2alpha1: "true"
      apps/v1alpha1: "true"

serviceNodePortRange

This value is passed as --service-node-port-range for kube-apiserver.

spec:
  kubeAPIServer:
    serviceNodePortRange: 30000-33000

Will result in the flag --runtime-config=batch/v2alpha1=true,apps/v1alpha1=true. Note that kube-apiserver accepts true as a value for switch-like flags.

externalDns

This block contains configuration options for your external-DNS provider. The current external-DNS provider is the kops dns-controller, which can set up DNS records for Kubernetes resources. dns-controller is scheduled to be phased out and replaced with external-dns.

spec:
  watchIngress: true

Default kops behavior is false. watchIngress: true uses the default dns-controller behavior which is to watch the ingress controller for changes. Set this option at risk of interrupting Service updates in some cases.

kubelet

This block contains configurations for kubelet. See https://kubernetes.io/docs/admin/kubelet/

NOTE: Where the corresponding configuration value can be empty, fields can be set to empty in the spec, and an empty string will be passed as the configuration value.

spec:
  kubelet:
    resolvConf: ""

Will result in the flag --resolv-conf= being built.

Enable Custom metrics support

To use custom metrics in kubernetes as per custom metrics doc we have to set the flag --enable-custom-metrics to true on all the kubelets. We can specify that in the kubelet spec in our cluster.yml.

spec:
  kubelet:
    enableCustomMetrics: true

kubeScheduler

This block contains configurations for kube-scheduler. See https://kubernetes.io/docs/admin/kube-scheduler/

spec:
  kubeScheduler:
    usePolicyConfigMap: true

Will make kube-scheduler use the scheduler policy from configmap "scheduler-policy" in namespace kube-system.

Note that as of Kubernetes 1.8.0 kube-scheduler does not reload its configuration from configmap automatically. You will need to ssh into the master instance and restart the Docker container manually.

kubeControllerManager

This block contains configurations for the controller-manager.

spec:
  kubeControllerManager:
    horizontalPodAutoscalerSyncPeriod: 15s

For more details on horizontalPodAutoscalerSyncPeriod see the HPA docs

Feature Gates

spec:
  kubelet:
    featureGates:
      Accelerators: "true"
      AllowExtTrafficLocalEndpoints: "false"

Will result in the flag --feature-gates=Accelerators=true,AllowExtTrafficLocalEndpoints=false

NOTE: Feature gate ExperimentalCriticalPodAnnotation is enabled by default because some critical components like kube-proxy depend on its presence.

Compute Resources Reservation

spec:
  kubelet:
    kubeReserved:
        cpu: "100m"
        memory: "100Mi"
        storage: "1Gi"
    kubeReservedCgroup: "/kube-reserved"
    systemReserved:
        cpu: "100m"
        memory: "100Mi"
        storage: "1Gi"
    systemReservedCgroup: "/system-reserved"
    enforceNodeAllocatable: "pods,system-reserved,kube-reserved"

Will result in the flag --kube-reserved=cpu=100m,memory=100Mi,storage=1Gi --kube-reserved-cgroup=/kube-reserved --system-reserved=cpu=100mi,memory=100Mi,storage=1Gi --system-reserved-cgroup=/system-reserved --enforce-node-allocatable=pods,system-reserved,kube-reserved

Learn more about reserving compute resources.

networkID

On AWS, this is the id of the VPC the cluster is created in. If creating a cluster from scratch, this field does not need to be specified at create time; kops will create a VPC for you.

spec:
  networkID: vpc-abcdefg1

More information about running in an existing VPC is here.

hooks

Hooks allow for the execution of an action before the installation of Kubernetes on every node in a cluster. For instance you can install Nvidia drivers for using GPUs. This hooks can be in the form of Docker images or manifest files (systemd units). Hooks can be placed in either the cluster spec, meaning they will be globally deployed, or they can be placed into the instanceGroup specification. Note: service names on the instanceGroup which overlap with the cluster spec take precedence and ignore the cluster spec definition, i.e. if you have a unit file 'myunit.service' in cluster and then one in the instanceGroup, only the instanceGroup is applied.

spec:
  # many sections removed
  hooks:
  - before:
    - some_service.service
    requires:
    - docker.service
      execContainer:
      image: kopeio/nvidia-bootstrap:1.6
      # these are added as -e to the docker environment
      environment:
        AWS_REGION: eu-west-1
        SOME_VAR: SOME_VALUE

  # or a raw systemd unit
  hooks:
  - name: iptable-restore.service
    roles:
    - Node
    - Master
    before:
    - kubelet.service
    manifest: |
      [Service]
      EnvironmentFile=/etc/environment
      # do some stuff

  # or disable a systemd unit
  hooks:
  - name: update-engine.service
    disabled: true

  # or you could wrap this into a full unit
  hooks:
  - name: disable-update-engine.service
    before:
    - update-engine.service
    manifest: |
      Type=oneshot
      ExecStart=/usr/bin/systemctl stop update-engine.service

Install Ceph

spec:
  # many sections removed
  hooks:
  - execContainer:
      command:
      - sh
      - -c
      - chroot /rootfs apt-get update && chroot /rootfs apt-get install -y ceph-common
      image: busybox

fileAssets

FileAssets is an alpha feature which permits you to place inline file content into the cluster and instanceGroup specification. It's desiginated as alpha as you can probably do this via kubernetes daemonsets as an alternative.

spec:
  fileAssets:
  - name: iptable-restore
    # Note if not path is specificied the default path it /srv/kubernetes/assets/<name>
    path: /var/lib/iptables/rules-save
    roles: [Master,Node,Bastion] # a list of roles to apply the asset to, zero defaults to all
    content: |
      some file content

cloudConfig

If you are using aws as cloudProvider, you can disable authorization of ELB security group to Kubernetes Nodes security group. In other words, it will not add security group rule. This can be usefull to avoid AWS limit: 50 rules per security group.

spec:
  cloudConfig:
    disableSecurityGroupIngress: true

registryMirrors

If you have a bunch of Docker instances (physicsal or vm) running, each time one of them pulls an image that is not present on the host, it will fetch it from the internet (DockerHub). By caching these images, you can keep the traffic within your local network and avoid egress bandwidth usage. This setting benefits not only cluster provisioning but also image pulling.

@see Cache-Mirror Dockerhub For Speed @see Configure the Docker daemon.

spec:
  docker:
    registryMirrors:
    - https://registry.example.com

WARNING: this works only for Kubernetes version above 1.7.0.

For avoid to create security group per each elb, you can specify security group id, that will be assigned to your LoadBalancer. It must be security group id, not name. Also, security group must be empty, because Kubernetes will add rules per ports that are specified in service file. This can be usefull to avoid AWS limits: 500 security groups per region and 50 rules per security group.

spec:
  cloudConfig:
    elbSecurityGroup: sg-123445678

sshKeyName

In some cases, it may be desirable to use an existing AWS SSH key instead of allowing kops to create a new one. Providing the name of a key already in AWS is an alternative to --ssh-public-key.

spec:
  sshKeyName: myexistingkey