add notes on labels setup for nginx/pihole sautomation

projects/Pihole/index.md

@@ -14,11 +14,37 @@ without installing any client-side software. Useful for blocking ad services at
 a DNS level. It uses a list of known ad services stored on github, can add your
 own. It can also operate as a internal dns router and dhcp server.
 
+## Automation (Docker Labels)
+
+To automate adding Custom DNS entries to Pi-hole when creating new Docker containers, I use the `docker-pihole-dns-shim` sidecar. This prevents the need to manually update Pi-hole's DNS records every time a new service is deployed.
+
+### Docker Compose Example (The Shim)
+The shim runs alongside your other management containers and watches the Docker socket. **Note:** Use the direct IP address of your Pi-hole (e.g., `10.0.0.11`) to ensure the container can reach the API.
+
+```yaml
+{{% include "/srv/configs/docker_compose/pihole-external-dns/docker-compose.yaml" %}}
+```
+
+### How to Auto-Configure a Service
+To create a DNS record in Pi-hole for a new container, add the following label to its `docker-compose.yaml`. The shim will automatically detect this and call the Pi-hole API.
+
+```yaml
+services:
+  my-app:
+    image: my-app:latest
+    labels:
+      # Format: [["domain", "IP_Address"]]
+      - "pihole.custom-record=[[\"myapp.wompmacho.com\", \"10.0.0.190\"]]" 
+```
+
+> [!important] Reverse Proxies
+> When using a reverse proxy like Nginx Proxy Manager, you should point the Pi-hole DNS record to the **IP of the Docker host/Proxy** (e.g., `10.0.0.190`), *not* the internal Docker IP of the individual container.
+
 ## Pihole Setup
 
 If you have a raspberry-pi or another device, its super easy to get things
 going.
-
+...
 - [pihole setup](https://github.com/pi-hole/pi-hole/?tab=readme-ov-file#one-step-automated-install).
 
 Any debian based system should be able to get things going quickly. Then all you