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Setting up ExternalDNS for RancherDNS(RDNS) with kubernetes

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

  • install RDNS with etcd enabled
  • install external-dns with rdns as a provider

Installing RDNS with etcdv3 backend

Clone RDNS

git clone https://github.com/rancher/rdns-server.git

Installing ETCD

cd rdns-server
docker-compose -f deploy/etcdv3/etcd-compose.yaml up -d

ETCD was successfully deployed on http://172.31.35.77:2379

Installing RDNS

export ETCD_ENDPOINTS="http://172.31.35.77:2379"
export DOMAIN="lb.rancher.cloud"
./scripts/start etcdv3

RDNS was successfully deployed on 172.31.35.77

Installing ExternalDNS

Install external ExternalDNS

ETCD_URLS is configured to etcd client service address. RDNS_ROOT_DOMAIN is configured to the same with RDNS DOMAIN environment. e.g. lb.rancher.cloud.

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:
      serviceAccountName: external-dns
      containers:
      - name: external-dns
        image: registry.k8s.io/external-dns/external-dns:v0.14.2
        args:
        - --source=ingress
        - --provider=rdns
        - --log-level=debug # debug only
        env:
        - name: ETCD_URLS
          value: http://172.31.35.77:2379
        - name: RDNS_ROOT_DOMAIN
          value: lb.rancher.cloud

Manifest (for clusters with RBAC enabled)

---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  name: external-dns
rules:
- apiGroups: [""]
  resources: ["services","endpoints","pods"]
  verbs: ["get","watch","list"]
- apiGroups: ["extensions","networking.k8s.io"]
  resources: ["ingresses"]
  verbs: ["get","watch","list"]
- apiGroups: [""]
  resources: ["nodes"]
  verbs: ["list"]
---
apiVersion: rbac.authorization.k8s.io/v1
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.k8s.io/external-dns/external-dns:v0.14.2
        args:
        - --source=ingress
        - --provider=rdns
        - --log-level=debug # debug only
        env:
        - name: ETCD_URLS
          value: http://172.31.35.77:2379
        - name: RDNS_ROOT_DOMAIN
          value: lb.rancher.cloud

Testing ingress example

$ cat ingress.yaml
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: nginx
spec:
  ingressClassName: nginx
  rules:
  - host: nginx.lb.rancher.cloud
    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 RDNS IP in this example is "172.31.35.77".

$ kubectl get ingress
NAME      HOSTS                    ADDRESS         PORTS     AGE
nginx     nginx.lb.rancher.cloud   172.31.42.211   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 @172.31.35.77 nginx.lb.rancher.cloud +short
172.31.42.211
dnstools#