Document DNS-based early cache hints

README.md

@@ -26,7 +26,7 @@ the AMI:
 ```nix
 {
   quixosEarlyBuildNixConfig = {
-    substituters = [ "http://[2600:...]/cache" ];
+    substituters = [ "http://nix-cache.internal.example.org/cache" ];
     trustedPublicKeys = [ "nix-cache.internal.example.org-1:..." ];
   };
 }
@@ -35,9 +35,9 @@ the AMI:
 The AMI runner evaluates this output after writing `/etc/nixos/flake.nix` and
 passes the substituters and trusted public keys through `NIX_CONFIG` only for
 the first `nixos-rebuild switch`. It does not mutate `/etc/hosts`; first-boot
-substituters that need private addressing should use a direct address URL. The
+substituter hostnames must already resolve through DNS. The target NixOS
-target NixOS configuration should still declare the normal hostname-based cache
+configuration should still declare the same cache in `nix.settings` for all
-in `nix.settings` and `networking.hosts` for all later rebuilds.
+later rebuilds.
 
 ## Publish