We are going to be adding a host alias for example.com in this example by adding the following to the coredns configmap:
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hosts custom.hosts example.com {
1.2.3.4 example.com
fallthrough
} |
For multiple hosts
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hosts custom.hosts example.com test.com {
1.2.3.4 example.com
6.6.6.6 test.com
fallthrough
} |
Start by editing the coredns configmap:
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|---|---|---|---|---|
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kubectl -n kube-system edit configmap/coredns |
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apiVersion: v1
data:
Corefile: |
.:53 {
errors
health {
lameduck 5s
}
ready
kubernetes cluster.local in-addr.arpa ip6.arpa {
pods insecure
fallthrough in-addr.arpa ip6.arpa
ttl 30
}
prometheus :9153
forward . /etc/resolv.conf {
max_concurrent 1000
}
cache 30
loop
reload
loadbalance
hosts custom.hosts example.com test.com {
1.2.3.4 example.com
6.6.6.6 test.com
fallthrough
}
} |
Force CoreDNS to reload the ConfigMap by entering:
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|---|---|---|---|---|
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kubectl delete pod --namespace kube-system -l k8s-app=kube-dns |
Performing an nslookup from a pod should show the new IP address for example.com
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root@ssh-server-5bd5774cf7-fgvt4:/# nslookup example.com
Server: 10.96.0.10
Address: 10.96.0.10#53
Name: example.com
Address: 1.2.3.4 |
References
| Reference | URL |
|---|---|
| ** Add a Custom Host to Kubernetes | https://hjrocha.medium.com/add-a-custom-host-to-kubernetes-a06472cedccb |
| Coredns Host Plugin | https://coredns.io/plugins/hosts/ |
| Code Block |
|---|
apiVersion: v1
kind: ConfigMap
metadata:
name: coredns-custom
namespace: kube-system
data:
example.server: | # All custom server files must have a ".server" file extension.
# Change example.com to the domain you wish to forward.
example.com {
# Change 1.1.1.1 to your customer DNS resolver.
forward . 1.1.1.1
} |
Create the ConfigMap by entering:
kubectl apply -f <filename>.yaml
Verify the customizations have been applied by entering:
kubectl get configmaps --namespace=kube-system coredns-custom -o yaml
Force CoreDNS to reload the ConfigMap by entering:
kubectl delete pod --namespace kube-system -l k8s-app=kube-dns
References
| Reference | URL |
|---|---|
| Configuring DNS Servers for Kubernetes Clusters | https://docs.oracle.com/en-us/iaas/Content/ContEng/Tasks/contengconfiguringdnsserver.htm|
| Customizing DNS Service | https://kubernetes.io/docs/tasks/administer-cluster/dns-custom-nameservers/ |
| Debugging DNS Resolution | https://kubernetes.io/docs/tasks/administer-cluster/dns-debugging-resolution/ |
| Custom DNS Entries For Kubernetes | https://coredns.io/2017/05/08/custom-dns-entries-for-kubernetes/ |
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