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add tutorial on how to use external-dns with GKE (#92)
* docs(tutorials): add tutorial on how to use external-dns with GKE * docs(gke): document how to setup a zone with its parent
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Martin Linkhorst
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docs/tutorials/gke.md
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docs/tutorials/gke.md
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# Setting up external-dns on Google Container Engine
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This tutorial describes how to setup `external-dns` for usage within a GKE cluster.
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Setup your environment to work with Google Cloud Platform. Fill in your values as needed, e.g. target project.
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```console
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$ gcloud config set project "zalando-external-dns-test"
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$ gcloud config set compute/region "europe-west1"
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$ gcloud config set compute/zone "europe-west1-d"
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```
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Create a GKE cluster.
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```console
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$ gcloud container clusters create "external-dns" \
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--num-nodes 1 \
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--scopes "https://www.googleapis.com/auth/ndev.clouddns.readwrite"
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```
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Create a DNS zone which will contain the managed DNS records.
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```console
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$ gcloud dns managed-zones create "external-dns-test-gcp-zalan-do" \
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--dns-name "external-dns-test.gcp.zalan.do." \
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--description "Automatically managed zone by kubernetes.io/external-dns"
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```
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Make a note of the nameservers that were assigned to your new zone.
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```console
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$ gcloud dns record-sets list \
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--zone "external-dns-test-gcp-zalan-do" \
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--name "external-dns-test.gcp.zalan.do." \
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--type NS
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NAME TYPE TTL DATA
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external-dns-test.gcp.zalan.do. NS 21600 ns-cloud-e1.googledomains.com.,ns-cloud-e2.googledomains.com.,ns-cloud-e3.googledomains.com.,ns-cloud-e4.googledomains.com.
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```
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In this case it's `ns-cloud-{e1-e4}.googledomains.com.` but your's could slightly differ, e.g. `{a1-a4}`, `{b1-b4}` etc.
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Tell the parent zone where to find the DNS records for this zone by adding the corresponding NS records there. Assuming the parent zone is "gcp-zalan-do" and the domain is "gcp.zalan.do" and that it's also hosted at Google we would do the following.
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```console
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$ gcloud dns record-sets transaction start --zone "gcp-zalan-do"
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$ gcloud dns record-sets transaction add ns-cloud-e{1..4}.googledomains.com. \
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--name "external-dns-test.gcp.zalan.do." --ttl 300 --type NS --zone "gcp-zalan-do"
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$ gcloud dns record-sets transaction execute --zone "gcp-zalan-do"
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```
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Connect your `kubectl` client to the cluster you just created.
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```console
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gcloud container clusters get-credentials "external-dns"
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```
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Apply the following manifest file to deploy `external-dns`.
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```yaml
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apiVersion: extensions/v1beta1
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kind: Deployment
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metadata:
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name: external-dns
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spec:
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strategy:
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type: Recreate
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template:
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metadata:
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labels:
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app: external-dns
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spec:
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containers:
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- name: external-dns
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image: gcr.io/zalando-docker/external-dns:476c3efddff941ac1b168895c2ba1d5693adc8cc
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args:
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- --in-cluster
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- --zone=external-dns-test-gcp-zalan-do
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- --source=service
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- --source=ingress
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- --dns-provider=google
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- --google-project=zalando-external-dns-test
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- --dry-run=false
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```
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Create the following sample application to test that `external-dns` works.
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```yaml
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apiVersion: v1
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kind: Service
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metadata:
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name: nginx
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annotations:
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external-dns.alpha.kubernetes.io/hostname: nginx.external-dns-test.gcp.zalan.do.
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spec:
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type: LoadBalancer
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ports:
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- port: 80
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targetPort: 80
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selector:
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app: nginx
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---
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apiVersion: extensions/v1beta1
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kind: Deployment
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metadata:
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name: nginx
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spec:
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template:
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metadata:
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labels:
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app: nginx
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spec:
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containers:
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- image: nginx
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name: nginx
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ports:
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- containerPort: 80
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```
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After roughly two minutes check that a corresponding DNS record for your service was created.
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```console
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$ gcloud dns record-sets list \
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--zone "external-dns-test-gcp-zalan-do" \
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--name "nginx.external-dns-test.gcp.zalan.do." \
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--type A
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NAME TYPE TTL DATA
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nginx.external-dns-test.gcp.zalan.do. A 300 104.155.60.49
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```
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Let's check that we can resolve this DNS name. We'll ask the nameservers assigned to your zone first.
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```console
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$ dig +short @ns-cloud-e1.googledomains.com. nginx.external-dns-test.gcp.zalan.do.
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104.155.60.49
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```
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Given you hooked up your DNS zone with its parent zone you can use `curl` to access your site.
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```console
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$ curl nginx.external-dns-test.gcp.zalan.do
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<!DOCTYPE html>
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<html>
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<head>
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<title>Welcome to nginx!</title>
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...
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</head>
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<body>
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...
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</body>
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</html>
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```
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Let's check that Ingress works as well. Create the following Ingress.
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```yaml
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apiVersion: extensions/v1beta1
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kind: Ingress
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metadata:
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name: nginx
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spec:
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rules:
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- host: via-ingress.external-dns-test.gcp.zalan.do
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http:
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paths:
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- backend:
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serviceName: nginx
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servicePort: 80
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```
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Again, after roughly two minutes check that a corresponding DNS record for your Ingress was created.
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```console
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$ gcloud dns record-sets list \
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--zone "external-dns-test-gcp-zalan-do" \
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--name "via-ingress.external-dns-test.gcp.zalan.do." \
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--type A
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NAME TYPE TTL DATA
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via-ingress.external-dns-test.gcp.zalan.do. A 300 130.211.46.224
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```
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Let's check that we can resolve this DNS name as well.
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```console
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dig +short @ns-cloud-e1.googledomains.com. via-ingress.external-dns-test.gcp.zalan.do.
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130.211.46.224
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```
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Try with `curl` as well.
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```console
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$ curl via-ingress.external-dns-test.gcp.zalan.do
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<!DOCTYPE html>
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<html>
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<head>
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<title>Welcome to nginx!</title>
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...
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</head>
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<body>
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...
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</body>
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</html>
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```
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## Clean up
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Make sure to delete all Service and Ingress objects before terminating the cluster so all load balancers get cleaned up correctly.
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```console
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$ kubectl delete service nginx
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$ kubectl delete ingress nginx
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```
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Give `external-dns` some time to clean up the DNS records for you. Then delete the managed zone and cluster.
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```console
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$ gcloud dns managed-zones delete "external-dns-test-gcp-zalan-do"
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$ gcloud container clusters delete "external-dns"
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```
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Also delete the NS records for your removed zone from the parent zone.
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```console
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$ gcloud dns record-sets transaction start --zone "gcp-zalan-do"
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$ gcloud dns record-sets transaction remove ns-cloud-e{1..4}.googledomains.com. \
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--name "external-dns-test.gcp.zalan.do." --ttl 300 --type NS --zone "gcp-zalan-do"
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$ gcloud dns record-sets transaction execute --zone "gcp-zalan-do"
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```
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