DNS in Kubernetes (CoreDNS) - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is CoreDNS in Kubernetes?

CoreDNS is the default DNS server in Kubernetes. It helps services and pods find each other by translating service names into IP addresses.

beginner

How does CoreDNS help pods communicate in Kubernetes?

CoreDNS resolves service names to IP addresses, so pods can use simple names instead of IPs to connect to other services.

intermediate

Where is CoreDNS configured in a Kubernetes cluster?

CoreDNS runs as a Deployment in the kube-system namespace and is configured via a ConfigMap named 'coredns'.

intermediate

What file does CoreDNS use to define DNS rules and behavior?

CoreDNS uses a ConfigMap that contains a Corefile. The Corefile defines how DNS queries are handled.

beginner

What happens if CoreDNS is not running in a Kubernetes cluster?

Pods will not be able to resolve service names to IPs, causing communication failures between services.

What is the main role of CoreDNS in Kubernetes?

A Manage pod scheduling

B Translate service names to IP addresses

C Store container images

D Monitor cluster health

CoreDNS translates service names into IP addresses so pods can communicate easily.

Where does CoreDNS run inside a Kubernetes cluster?

A Inside each pod

B On the master node only

C As a DaemonSet on all nodes

D In the kube-system namespace as a Deployment

CoreDNS runs as a Deployment in the kube-system namespace.

What is the name of the file that configures CoreDNS behavior?

A Corefile

B Config.yaml

C DNS.conf

D Servicefile

CoreDNS uses a Corefile inside a ConfigMap to define DNS rules.

If CoreDNS stops working, what is the likely impact?

A Pods cannot resolve service names

B Pods will stop running

C Cluster nodes will reboot

D Storage volumes will be lost

Without CoreDNS, pods cannot resolve service names to IPs, breaking communication.

How can you check the CoreDNS pods status?

A kubectl get nodes

B kubectl get pods -n default

C kubectl get pods -n kube-system -l k8s-app=kube-dns

D kubectl describe service

CoreDNS pods are labeled 'k8s-app=kube-dns' in the kube-system namespace.

Explain how CoreDNS helps pods find each other in Kubernetes.

Think about how computers use DNS to find websites.

Describe what happens if CoreDNS is not functioning in a Kubernetes cluster.

Consider what happens if you can't look up phone numbers.