CoreDNS — Flexible DNS Server Written in Go

What it is

CoreDNS is a DNS server written in Go that uses a plugin architecture for all its functionality. Every feature, from caching to logging to Kubernetes service discovery, is a plugin that can be enabled or disabled. CoreDNS is a CNCF-graduated project and has been the default in-cluster DNS provider for Kubernetes since version 1.13.

Cluster administrators, DevOps engineers, and anyone running Kubernetes benefit from understanding CoreDNS since it handles all internal DNS resolution in their clusters. It also serves as a general-purpose DNS server for non-Kubernetes use cases.

How it saves time or tokens

CoreDNS replaces complex DNS configurations with a declarative Corefile format. Instead of managing BIND zone files or dnsmasq configurations, you declare your DNS behavior in a simple, readable format. The plugin architecture means you add only the features you need, keeping the server lightweight and its configuration minimal.

How to use

1. Download the CoreDNS binary or use it as the default DNS in your Kubernetes cluster
2. Write a Corefile specifying zones and plugins
3. Start CoreDNS with coredns -conf Corefile

Example

# Corefile example
.:53 {
    forward . 8.8.8.8 8.8.4.4
    cache 30
    log
    errors
}

example.com:53 {
    file db.example.com
    log
}

# Download and run
curl -LO https://github.com/coredns/coredns/releases/latest/download/coredns_linux_amd64.tgz
tar xzf coredns_linux_amd64.tgz
./coredns -conf Corefile

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Common pitfalls

• Plugin order in the Corefile matters; some plugins must come before others for correct behavior
• Kubernetes CoreDNS ConfigMap changes require a pod restart to take effect; not all changes are picked up automatically
• Misconfigured forward plugins can create DNS loops; always use upstream resolvers, not the server itself