CoreDNS is a DNS server that chains plugins and provides DNS Services
$ helm repo add coredns https://coredns.github.io/helm
$ helm --namespace=kube-system install coredns coredns/corednsThis chart bootstraps a CoreDNS deployment on a Kubernetes cluster using the Helm package manager. This chart will provide DNS Services and can be deployed in multiple configuration to support various scenarios listed below:
- CoreDNS as a cluster dns service and a drop-in replacement for Kube/SkyDNS. This is the default mode and CoreDNS is deployed as cluster-service in kube-system namespace. This mode is chosen by setting
isClusterServiceto true. - CoreDNS as an external dns service. In this mode CoreDNS is deployed as any kubernetes app in user specified namespace. The CoreDNS service can be exposed outside the cluster by using using either the NodePort or LoadBalancer type of service. This mode is chosen by setting
isClusterServiceto false. - CoreDNS as an external dns provider for kubernetes federation. This is a sub case of 'external dns service' which uses etcd plugin for CoreDNS backend. This deployment mode as a dependency on
etcd-operatorchart, which needs to be pre-installed.
- Kubernetes 1.10 or later
The chart can be installed as follows:
$ helm repo add coredns https://coredns.github.io/helm
$ helm --namespace=kube-system install coredns coredns/corednsThe command deploys CoreDNS on the Kubernetes cluster in the default configuration. The configuration section lists various ways to override default configuration during deployment.
Tip: List all releases using
helm list --all-namespaces
To uninstall/delete the coredns deployment:
$ helm uninstall corednsThe command removes all the Kubernetes components associated with the chart and deletes the release.
| Parameter | Description | Default |
|---|---|---|
image.repository |
The image repository to pull from | coredns/coredns |
image.tag |
The image tag to pull from | 1.8.4 |
image.pullPolicy |
Image pull policy | IfNotPresent |
image.pullSecrets |
Specify container image pull secrets | [] |
replicaCount |
Number of replicas | 1 |
resources.limits.cpu |
Container maximum CPU | 100m |
resources.limits.memory |
Container maximum memory | 128Mi |
resources.requests.cpu |
Container requested CPU | 100m |
resources.requests.memory |
Container requested memory | 128Mi |
serviceType |
Kubernetes Service type | ClusterIP |
prometheus.service.enabled |
Set this to true to create Service for Prometheus metrics |
false |
prometheus.service.annotations |
Annotations to add to the metrics Service | {prometheus.io/scrape: "true", prometheus.io/port: "9153"} |
prometheus.monitor.enabled |
Set this to true to create ServiceMonitor for Prometheus operator |
false |
prometheus.monitor.additionalLabels |
Additional labels that can be used so ServiceMonitor will be discovered by Prometheus | {} |
prometheus.monitor.namespace |
Selector to select which namespaces the Endpoints objects are discovered from. | "" |
service.clusterIP |
IP address to assign to service | "" |
service.loadBalancerIP |
IP address to assign to load balancer (if supported) | "" |
service.externalIPs |
External IP addresses | [] |
service.externalTrafficPolicy |
Enable client source IP preservation | [] |
service.annotations |
Annotations to add to service | {} |
serviceAccount.create |
If true, create & use serviceAccount | false |
serviceAccount.name |
If not set & create is true, use template fullname | |
rbac.create |
If true, create & use RBAC resources | true |
rbac.pspEnable |
Specifies whether a PodSecurityPolicy should be created. | false |
isClusterService |
Specifies whether chart should be deployed as cluster-service or normal k8s app. | true |
priorityClassName |
Name of Priority Class to assign pods | "" |
servers |
Configuration for CoreDNS and plugins | See values.yml |
livenessProbe.enabled |
Enable/disable the Liveness probe | true |
livenessProbe.initialDelaySeconds |
Delay before liveness probe is initiated | 60 |
livenessProbe.periodSeconds |
How often to perform the probe | 10 |
livenessProbe.timeoutSeconds |
When the probe times out | 5 |
livenessProbe.failureThreshold |
Minimum consecutive failures for the probe to be considered failed after having succeeded. | 5 |
livenessProbe.successThreshold |
Minimum consecutive successes for the probe to be considered successful after having failed. | 1 |
readinessProbe.enabled |
Enable/disable the Readiness probe | true |
readinessProbe.initialDelaySeconds |
Delay before readiness probe is initiated | 30 |
readinessProbe.periodSeconds |
How often to perform the probe | 10 |
readinessProbe.timeoutSeconds |
When the probe times out | 5 |
readinessProbe.failureThreshold |
Minimum consecutive failures for the probe to be considered failed after having succeeded. | 5 |
readinessProbe.successThreshold |
Minimum consecutive successes for the probe to be considered successful after having failed. | 1 |
affinity |
Affinity settings for pod assignment | {} |
nodeSelector |
Node labels for pod assignment | {} |
tolerations |
Tolerations for pod assignment | [] |
zoneFiles |
Configure custom Zone files | [] |
extraVolumes |
Optional array of volumes to create | [] |
extraVolumeMounts |
Optional array of volumes to mount inside the CoreDNS container | [] |
extraSecrets |
Optional array of secrets to mount inside the CoreDNS container | [] |
customLabels |
Optional labels for Deployment(s), Pod, Service, ServiceMonitor objects | {} |
rollingUpdate.maxUnavailable |
Maximum number of unavailable replicas during rolling update | 1 |
rollingUpdate.maxSurge |
Maximum number of pods created above desired number of pods | 25% |
podDisruptionBudget |
Optional PodDisruptionBudget | {} |
podAnnotations |
Optional Pod only Annotations | {} |
terminationGracePeriodSeconds |
Optional duration in seconds the pod needs to terminate gracefully. | 30 |
preStopSleep |
Definition of Kubernetes preStop hook executed before Pod termination | {} |
hpa.enabled |
Enable Hpa autoscaler instead of proportional one | false |
hpa.minReplicas |
Hpa minimum number of CoreDNS replicas | 1 |
hpa.maxReplicas |
Hpa maximum number of CoreDNS replicas | 2 |
hpa.metrics |
Metrics definitions used by Hpa to scale up and down | {} |
autoscaler.enabled |
Optionally enabled a cluster-proportional-autoscaler for CoreDNS | false |
autoscaler.coresPerReplica |
Number of cores in the cluster per CoreDNS replica | 256 |
autoscaler.nodesPerReplica |
Number of nodes in the cluster per CoreDNS replica | 16 |
autoscaler.min |
Min size of replicaCount | 0 |
autoscaler.max |
Max size of replicaCount | 0 (aka no max) |
autoscaler.includeUnschedulableNodes |
Should the replicas scale based on the total number or only schedulable nodes | false |
autoscaler.preventSinglePointFailure |
If true does not allow single points of failure to form | true |
autoscaler.image.repository |
The image repository to pull autoscaler from | k8s.gcr.io/cluster-proportional-autoscaler-amd64 |
autoscaler.image.tag |
The image tag to pull autoscaler from | 1.8.1 |
autoscaler.image.pullPolicy |
Image pull policy for the autoscaler | IfNotPresent |
autoscaler.image.pullSecrets |
Specify container image pull secrets | [] |
autoscaler.priorityClassName |
Optional priority class for the autoscaler pod. priorityClassName used if not set. |
"" |
autoscaler.affinity |
Affinity settings for pod assignment for autoscaler | {} |
autoscaler.nodeSelector |
Node labels for pod assignment for autoscaler | {} |
autoscaler.tolerations |
Tolerations for pod assignment for autoscaler | [] |
autoscaler.resources.limits.cpu |
Container maximum CPU for cluster-proportional-autoscaler | 20m |
autoscaler.resources.limits.memory |
Container maximum memory for cluster-proportional-autoscaler | 10Mi |
autoscaler.resources.requests.cpu |
Container requested CPU for cluster-proportional-autoscaler | 20m |
autoscaler.resources.requests.memory |
Container requested memory for cluster-proportional-autoscaler | 10Mi |
autoscaler.configmap.annotations |
Annotations to add to autoscaler config map. For example to stop CI renaming them | {} |
autoscaler.livenessProbe.enabled |
Enable/disable the Liveness probe | true |
autoscaler.livenessProbe.initialDelaySeconds |
Delay before liveness probe is initiated | 10 |
autoscaler.livenessProbe.periodSeconds |
How often to perform the probe | 5 |
autoscaler.livenessProbe.timeoutSeconds |
When the probe times out | 5 |
autoscaler.livenessProbe.failureThreshold |
Minimum consecutive failures for the probe to be considered failed after having succeeded. | 3 |
autoscaler.livenessProbe.successThreshold |
Minimum consecutive successes for the probe to be considered successful after having failed. | 1 |
deployment.enabled |
Optionally disable the main deployment and its respective resources. | true |
deployment.name |
Name of the deployment if deployment.enabled is true. Otherwise the name of an existing deployment for the autoscaler or HPA to target. |
"" |
See values.yaml for configuration notes. Specify each parameter using the --set key=value[,key=value] argument to helm install. For example,
$ helm install coredns \
coredns/coredns \
--set rbac.create=falseThe above command disables automatic creation of RBAC rules.
Alternatively, a YAML file that specifies the values for the above parameters can be provided while installing the chart. For example,
$ helm install coredns coredns/coredns -f values.yamlTip: You can use the default values.yaml
The chart will automatically determine which protocols to listen on based on
the protocols you define in your zones. This means that you could potentially
use both "TCP" and "UDP" on a single port.
Some cloud environments like "GCE" or "Azure container service" cannot
create external loadbalancers with both "TCP" and "UDP" protocols. So
When deploying CoreDNS with serviceType="LoadBalancer" on such cloud
environments, make sure you do not attempt to use both protocols at the same
time.
By setting autoscaler.enabled = true a
cluster-proportional-autoscaler
will be deployed. This will default to a coredns replica for every 256 cores, or
16 nodes in the cluster. These can be changed with autoscaler.coresPerReplica
and autoscaler.nodesPerReplica. When cluster is using large nodes (with more
cores), coresPerReplica should dominate. If using small nodes,
nodesPerReplica should dominate.
This also creates a ServiceAccount, ClusterRole, and ClusterRoleBinding for the autoscaler deployment.
replicaCount is ignored if this is enabled.
By setting hpa.enabled = true a Horizontal Pod Autoscaler
is enabled for Coredns deployment. This can scale number of replicas based on meitrics
like CpuUtilization, MemoryUtilization or Custom ones.