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Setting up ExternalDNS for CoreDNS with minikube

This tutorial describes how to setup ExternalDNS for usage within a minikube cluster that makes use of CoreDNS and nginx ingress controller.
You need to:

  • install CoreDNS with etcd enabled
  • install external-dns with coredns as a provider
  • enable ingress controller for the minikube cluster

Creating a cluster

minikube start

Installing CoreDNS with etcd enabled

Helm chart is used to install etcd and CoreDNS.

Initializing helm chart

helm init

Installing etcd

etcd operator is used to manage etcd clusters.

helm install stable/etcd-operator --name my-etcd-op

etcd cluster is installed with example yaml from etcd operator website.

kubectl  apply -f https://raw.githubusercontent.com/coreos/etcd-operator/master/example/example-etcd-cluster.yaml

Installing CoreDNS

In order to make CoreDNS work with etcd backend, values.yaml of the chart should be changed with corresponding configurations.

wget https://raw.githubusercontent.com/helm/charts/master/stable/coredns/values.yaml

You need to edit/patch the file with below diff

diff --git a/values.yaml b/values.yaml
index 964e72b..e2fa934 100644
--- a/values.yaml
+++ b/values.yaml
@@ -27,12 +27,12 @@ service:

 rbac:
   # If true, create & use RBAC resources
-  create: false
+  create: true
   # Ignored if rbac.create is true
   serviceAccountName: default

 # isClusterService specifies whether chart should be deployed as cluster-service or normal k8s app.
-isClusterService: true
+isClusterService: false

 servers:
 - zones:
@@ -51,6 +51,12 @@ servers:
     parameters: 0.0.0.0:9153
   - name: proxy
     parameters: . /etc/resolv.conf
+  - name: etcd
+    parameters: example.org
+    configBlock: |-
+      stubzones
+      path /skydns
+      endpoint http://10.105.68.165:2379

 # Complete example with all the options:
 # - zones:                 # the `zones` block can be left out entirely, defaults to "."

Note:

  • IP address of etcd's endpoint should be get from etcd client service. It should be "example-etcd-cluster-client" in this example. This IP address is used through this document for etcd endpoint configuration.
$ kubectl get svc example-etcd-cluster-client
NAME                          TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)    AGE
example-etcd-cluster-client   ClusterIP   10.105.68.165   <none>        2379/TCP   16m
  • Parameters should configure your own domain. "example.org" is used in this example.

After configuration done in values.yaml, you can install coredns chart.

helm install --name my-coredns --values values.yaml stable/coredns

Installing ExternalDNS

Install external ExternalDNS

ETCD_URLS is configured to etcd client service address.

Manifest (for clusters without RBAC enabled)

apiVersion: apps/v1
kind: Deployment
metadata:
  name: external-dns
  namespace: kube-system
spec:
  strategy:
    type: Recreate
  selector:
    matchLabels:
      app: external-dns
  template:
    metadata:
      labels:
        app: external-dns
    spec:
      containers:
      - name: external-dns
        image: registry.opensource.zalan.do/teapot/external-dns:latest
        args:
        - --source=ingress
        - --provider=coredns
        - --log-level=debug # debug only
        env:
        - name: ETCD_URLS
          value: http://10.105.68.165:2379

Manifest (for clusters with RBAC enabled)

---
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: ClusterRole
metadata:
  name: external-dns
rules:
- apiGroups: [""]
  resources: ["services"]
  verbs: ["get","watch","list"]
- apiGroups: [""]
  resources: ["pods"]
  verbs: ["get","watch","list"]
- apiGroups: ["extensions"]
  resources: ["ingresses"]
  verbs: ["get","watch","list"]
- apiGroups: [""]
  resources: ["nodes"]
  verbs: ["list"]
---
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: ClusterRoleBinding
metadata:
  name: external-dns-viewer
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: external-dns
subjects:
- kind: ServiceAccount
  name: external-dns
  namespace: kube-system
---
apiVersion: v1
kind: ServiceAccount
metadata:
  name: external-dns
  namespace: kube-system
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: external-dns
  namespace: kube-system
spec:
  strategy:
    type: Recreate
  selector:
    matchLabels:
      app: external-dns
  template:
    metadata:
      labels:
        app: external-dns
    spec:
      serviceAccountName: external-dns
      containers:
      - name: external-dns
        image: registry.opensource.zalan.do/teapot/external-dns:latest
        args:
        - --source=ingress
        - --provider=coredns
        - --log-level=debug # debug only
        env:
        - name: ETCD_URLS
          value: http://10.105.68.165:2379

Enable the ingress controller

You can use the ingress controller in minikube cluster. It needs to enable ingress addon in the cluster.

minikube addons enable ingress

Testing ingress example

$ cat ingress.yaml      
kind: Ingress
metadata:
  name: nginx
  annotations:
    kubernetes.io/ingress.class: "nginx"
spec:
  rules:
  - host: nginx.example.org
    http:
      paths:
      - backend:
          serviceName: nginx
          servicePort: 80

$ kubectl apply -f ingress.yaml
ingress.extensions "nginx" created

Wait a moment until DNS has the ingress IP. The DNS service IP is from CoreDNS service. It is "my-coredns-coredns" in this example.

$ kubectl get svc my-coredns-coredns
NAME                 TYPE        CLUSTER-IP     EXTERNAL-IP   PORT(S)   AGE
my-coredns-coredns   ClusterIP   10.100.4.143   <none>        53/UDP    12m

$ kubectl get ingress
NAME      HOSTS               ADDRESS     PORTS     AGE
nginx     nginx.example.org   10.0.2.15   80        2m

$ kubectl run -it --rm --restart=Never --image=infoblox/dnstools:latest dnstools
If you don't see a command prompt, try pressing enter.
dnstools# dig @10.100.4.143 nginx.example.org +short
dnstools# dig @10.100.4.143 nginx.example.org +short
10.0.2.15
dnstools#