docs: cover DNS Server and multi-module builds

Author: mirkobrombin

README.md

@@ -14,10 +14,15 @@ GoUP! is a minimal, tweakable web server written in Go. You can use it to serve
 - Support for SSL/TLS with custom certificates
 - Custom headers for HTTP responses
 - Support for multiple domains and virtual hosting
+- Native Authoritative DNS Server (A, AAAA, CNAME, TXT, MX, NS)
 - Logging to both console and files - JSON formatted (structured logs)
 - Optional TUI interface for real-time monitoring
 - HTTP/2 and HTTP/3 support (not configurable, HTTP/1.1 is used for unencrypted connections, HTTP/2 and HTTP/3 for encrypted connections)
 
+## Documentation
+
+- [DNS Server Guide](docs/dns.md) explanation of the DNS module configuration and usage.
+
 ## Future Plans
 
 - API for dynamic configuration changes
@@ -94,10 +99,24 @@ Go is required to build the software, ensure you have it installed on your syste
 
 2. **Build the software:**
 
+   Standard build (includes both Web and DNS modules):
    ```bash
    go build -o ~/.local/bin/goup cmd/goup/main.go
    ```
 
+   **Specialized Builds**:
+   You can build optimized binaries using build tags to exclude unused modules:
+
+   *Web Server Only*:
+   ```bash
+   go build -tags web_only -o goup-web cmd/goup/main.go
+   ```
+
+   *DNS Server Only*:
+   ```bash
+   go build -tags dns_only -o goup-dns cmd/goup/main.go
+   ```
+
 
 ## Usage
 

docs/dns.md

@@ -0,0 +1,80 @@
+# GoUp Native Authoritative DNS Server
+
+GoUp includes a built-in, lightweight authoritative DNS server written in Go. It runs alongside the web server (or standalone) and shares the same high-performance architecture.
+
+## Features
+
+- **Authoritative Only**: Designed to serve your zones, not to act as a recursive resolver.
+- **Record Types**: Supports `A`, `AAAA`, `CNAME`, `TXT`, `MX`, `NS`.
+- **Integrated Logging**: detailed query logging to `logs/system/`.
+- **Performance**: Runs on its own goroutine with low overhead.
+- **Failover**: Optional upstream resolvers for non-authoritative zones (limited forwarding).
+
+## Configuration
+
+The DNS server is configured in the global configuration file (`~/.config/goup/conf.global.json`).
+
+### Enabling DNS
+
+```json
+{
+  "dns": {
+    "enable": true,
+    "port": 53,
+    "upstream_resolvers": ["1.1.1.1", "8.8.8.8"],
+    "zones": {
+      "example.com": [
+        { "type": "A", "name": "@", "value": "192.168.1.10", "ttl": 300 },
+        { "type": "CNAME", "name": "www", "value": "@", "ttl": 300 },
+        { "type": "TXT", "name": "_test", "value": "hello world", "ttl": 3600 }
+      ]
+    }
+  }
+}
+```
+
+### Fields
+
+- **enable**: Set to `true` to start the DNS server.
+- **port**: UDP/TCP port to listen on (default: 53). *Note: Ports < 1024 require root/sudo.*
+- **upstream_resolvers**: List of DNS servers to forward queries to if no local zone matches (optional).
+- **zones**: Map of zone names to their records.
+
+### Record Structure
+
+- **type**: Record type (`A`, `AAAA`, `CNAME`, `TXT`, `MX`, `NS`).
+- **name**: Subdomain name. Use `@` for the zone apex (e.g. `example.com`), or just the name (e.g. `www`).
+- **value**: The IP address, target domain, or text content.
+- **ttl**: Time-To-Live in seconds.
+- **prio**: Priority (only for `MX` records).
+
+## Running the Server
+
+You can run the DNS server in different modes using the CLI:
+
+1.  **Full Stack (Web + DNS)** (Default)
+    ```bash
+    goup start
+    ```
+2.  **DNS Only**
+    ```bash
+    goup start-dns
+    ```
+3.  **Web Only**
+    ```bash
+    goup start-web
+    ```
+
+## Specialized Builds
+
+For deployment in constrained environments, you can compile GoUp with only the components you need to save binary size.
+
+- **Build DNS-Only Binary**:
+  ```bash
+  go build -tags dns_only -o goup-dns cmd/goup/main.go
+  ```
+
+- **Build Web-Only Binary**:
+  ```bash
+  go build -tags web_only -o goup-web cmd/goup/main.go
+  ```