nixos-servers/docs/plans/completed/dns-automation.md

DNS Automation

Status: Completed (2026-02-04)

Goal: Automatically generate DNS entries from host configurations

Approach: Leverage Nix to generate zone file entries from flake host configurations

Since most hosts use static IPs defined in their NixOS configurations, we can extract this information and automatically generate A records. This keeps DNS in sync with the actual host configs.

Implementation

• Add optional CNAME field to host configurations
  • Added homelab.dns.cnames option in modules/homelab/dns.nix
  • Added homelab.dns.enable to allow opting out (defaults to true)
  • Documented in CLAUDE.md
• Create Nix function to extract DNS records from all hosts
  • Created lib/dns-zone.nix with extraction functions
  • Parses each host's networking.hostName and systemd.network.networks IP configuration
  • Collects CNAMEs from homelab.dns.cnames
  • Filters out VPN interfaces (wg*, tun*, tap*, vti*)
  • Generates complete zone file with A and CNAME records
• Integrate auto-generated records into zone files
  • External hosts separated to services/ns/external-hosts.nix
  • Zone includes comments showing which records are auto-generated vs external
• Update zone file serial number automatically
  • Uses self.sourceInfo.lastModified (git commit timestamp)
• Test zone file validity after generation
  • NSD validates zone at build time via nsd-checkzone
• Deploy process documented
  • Merge to master, run auto-upgrade on ns1/ns2

Files Created/Modified

File	Purpose
modules/homelab/dns.nix	Defines homelab.dns.* options
modules/homelab/default.nix	Module import hub
lib/dns-zone.nix	Zone generation functions
services/ns/external-hosts.nix	Non-flake host records
services/ns/master-authorative.nix	Uses generated zone
services/ns/secondary-authorative.nix	Uses generated zone

Usage

View generated zone:

nix eval .#nixosConfigurations.ns1.config.services.nsd.zones.'"home.2rjus.net"'.data --raw

Add CNAMEs to a host:

homelab.dns.cnames = [ "alias1" "alias2" ];

Exclude a host from DNS:

homelab.dns.enable = false;

Add non-flake hosts: Edit services/ns/external-hosts.nix