How deeply does Kubernetes in Action, Second Edition cover CoreDNS?

Explains lookup names and resolver configuration, but stops short of CoreDNS implementation internals.

CoreDNS

As explained in Kubernetes in Action, Second Edition

CoreDNS is an extensible DNS server commonly deployed in Kubernetes clusters to provide service and pod name resolution.

CoreDNS commonly provides the internal DNS service in a Kubernetes cluster. Pods use it to resolve Service names into cluster IP addresses, so applications can connect without hard-coding those addresses. section 11.1.3

A Service can be resolved using progressively more specific DNS names:

<service-name> works when the Service is in the pod’s namespace. section 11.1.3
<service-name>.<namespace> works from any namespace; longer forms append .svc and the cluster domain. section 11.1.3
The default cluster domain is cluster.local, but the cluster can configure a different suffix. section 11.1.3

Connecting to a Service by name

A pod can call the quiz Service with curl http://quiz when both are in the same namespace, or curl http://quiz.kiada from another namespace. The pod’s /etc/resolv.conf points to the cluster DNS Service and supplies search domains that make short names work. section 11.1.3

/ # cat /etc/resolv.conf
search kiada.svc.cluster.local svc.cluster.local cluster.local localdomain
nameserver 10.96.0.10
options ndots:5

Inspect a pod’s resolver configuration to see its search domains and the cluster DNS nameserver. section 11.1.3

How Kubernetes in Action, Second Edition covers it

Cover of Kubernetes in Action, Second Edition

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Also explained in

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Acing the Certified Kubernetes Administrator Exam, Second EditionCoreDNS is a DNS server and plugin-based system that provides service discovery and name resolution for Kubernetes clusters.

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Related concepts

domain name systemuses · The Domain Name System is a distributed, hierarchical naming system that resolves domain names to IP addresses and other network resource records.
podkind of · A Kubernetes Pod is the smallest deployable unit in Kubernetes, grouping one or more co-located containers that share networking and other resources.
DNS serverimplements · A DNS server is a network service that answers domain-name queries by returning corresponding DNS records or obtaining them from other DNS servers.
configmapconfigured by · A ConfigMap is a Kubernetes API resource that stores non-confidential configuration data as key-value pairs for use by workloads and other cluster components.

This explainer was generated by Manning's knowledge graph from the text of Kubernetes in Action, Second Edition. The section links point to the parts of the book it draws on.