CoreDNS ConfigMap中data字段内.server项的命名规则及作用咨询

Hey there! Let's unpack your CoreDNS questions about that test.server file and how these custom configs work.

What do we call these .server files? #

These are custom server blocks (or sometimes referred to as custom zone configurations) stored in the coredns-custom ConfigMap. They're CoreDNS's built-in way to let you extend or override its default DNS handling without editing the main Corefile directly.

What's the point of test.server specifically? #

The test part is just a custom prefix you can name anything you want—CoreDNS only cares about the .server suffix. Here's what it does:

• It's an organizational label to help you keep custom configs tidy. If you later add rules for another domain (like example.com), you could create example.server instead of cramming everything into one file, making maintenance way easier.
• In your setup, this file defines a dedicated rule set for mydomain.com requests: forwarding them to external DNS servers, caching responses for 30 seconds, and logging errors.

Correct naming rules for these files #

Follow these simple rules and you're good to go:

• Mandatory suffix: The file must end with .server—this is how CoreDNS detects and loads these custom blocks into its main configuration. You already nailed this key part!
• Flexible prefix: The part before .server can be any valid ConfigMap key name: letters, numbers, -, _, and . are all allowed. Avoid spaces or special characters like !@#$%^&* though.
• Pro tip: Use a prefix that matches your domain (e.g., mydomain.server instead of test.server)—it makes it instantly clear what the config does when you come back to it later.

Quick breakdown of your config #

Your test.server defines a server block that tells CoreDNS:

For any DNS requests targeting mydomain.com (and all its subdomains like foo.mydomain.com, bar.mydomain.com), do three things:

1. Log any errors that occur during processing
2. Cache responses for 30 seconds to speed up repeated requests
3. Forward the request to the external DNS servers 10.0.0.3 and 10.0.0.4

内容的提问来源于stack exchange，提问作者InsOp