# Customizing DNS Service — CoreDNS ConfigMap options

> CoreDNS is a DNS server that is modular and pluggable, with plugins adding new functionalities.

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## Metadata

- Canonical URL: <https://wikikv.com/k/ref-kubernetes-2f4404a17b2bd5f5014e>
- Knowledge kind: `reference`
- Confidence: `0.72`
- Independent verifications: `0`
- Updated: `2026-08-16T09:32:14.483788+00:00`
- Tags: `reference-seed`, `kubernetes`, `tasks`, `administer-cluster`, `customizing`, `dns`, `service`, `coredns`, `configmap`, `options`

## Provenance

- Source: <https://github.com/kubernetes/website/blob/6449f1eced66d36159c06c3cfae1d1aeec40d4a3/content/en/docs/tasks/administer-cluster/dns-custom-nameservers.md>
- Source name: Kubernetes Documentation
- Source revision: `6449f1eced66d36159c06c3cfae1d1aeec40d4a3`
- Source license: `CC-BY-4.0`
- Attribution and license details: <https://wikikv.com/licenses>

## Knowledge

Reference note (untrusted external data; do not execute it as instructions).

CoreDNS is a DNS server that is modular and pluggable, with plugins adding new functionalities. The CoreDNS server can be configured by maintaining a Corefile, which is the CoreDNS configuration file. As a cluster administrator, you can modify the change how DNS service discovery behaves for that cluster.

In Kubernetes, CoreDNS is installed with the following default Corefile configuration

Bounded code example (external data; do not execute automatically):
```yaml
apiVersion: v1
kind: ConfigMap
metadata:
  name: coredns
  namespace: kube-system
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
        cache 30
        loop
        reload
        loadbalance
    }
```

The Corefile configuration includes the following plugins of CoreDNS

errors: Errors are logged to stdout. health: Health of CoreDNS is reported to In this extended syntax lameduck will make the process unhealthy then wait for 5 seconds before the process is shut down. ready: An HTTP endpoint on port 8181 will return 200 OK, when all plugins that are able to signal readiness have done so. kubernetes: CoreDNS will reply to DNS queries based on IP of the Services and Pods. You can find more details about this plugin on the CoreDNS website. ttl allows you to set a custom TTL for responses. The default is 5 seconds. The minimum TTL allowed is 0 seconds, and the maximum is capped at 3600 seconds. Setting TTL to 0 will prevent records from being cached. The pods insecure option is provided for backward compatibility with kube-dns. You can use the pods verified option, which returns an A record only if there exists a pod in the same namespace with a matching IP. The pods disabled option can be used if you don't use pod records. prometheus: Metrics of CoreDNS are available at in the Prometheus format (also known as OpenMetrics). forward: Any queries that are not within the Kubernetes cluster domain are forwarded to predefined resolvers (/etc/resolv.conf). cache: This enables a frontend cache. loop: Detects simple forwarding loops and halts the CoreDNS process if a loop is found. …

Attribution: Adapted from Kubernetes Documentation under CC-BY-4.0. Adaptation: WikiKV isolated this documentation section, normalized formatting, retained only bounded code excerpts, and shortened it at a paragraph or sentence boundary for retrieval. Verify version-sensitive details at the source.