CX overlayDevice reference added (#220)

Author: AtibQur

sites/cheerpx/src/content/docs/11-guides/File-System-support.md

@@ -185,11 +185,11 @@ await dataDevice.writeFile("/filename", "File content here");
 
 ## Block devices with ext2
 
-CheerpX supports ext2 filesystems, which can be configured as an overlay device. This allows for a flexible setup that can combine different storage types.
+CheerpX supports ext2 filesystems, which can be configured as an [`OverlayDevice`](/docs/reference/CheerpX.OverlayDevice). This allows for a flexible setup that can combine different storage types.
 
 ### Usage
 
-Create an ext2 filesystem by combining a [`HttpBytesDevice`](/docs/reference/httpBytesDevice) to acess disk blocks, an [`IDBDevice`](/docs/reference/CheerpX.IDBDevice) to cache and persist data and a `OverlayDevice` to combine the two.
+Create an ext2 filesystem by combining a [`HttpBytesDevice`](/docs/reference/httpBytesDevice) to acess disk blocks, an [`IDBDevice`](/docs/reference/CheerpX.IDBDevice) to cache and persist data and a [`OverlayDevice`](/docs/reference/CheerpX.OverlayDevice) to combine the two.
 
 ```javascript
 // Create an HttpBytesDevice for streaming disk blocks via HTTP
@@ -215,7 +215,7 @@ CheerpX supports various types of devices that can be used in the OverlayDevice
 
 1. [**HttpBytesDevice**](/docs/reference/httpBytesDevice): The default choice for loading filesystem images via HTTP. Suitable for most web-hosted files.
 2. **GitHubDevice**: Ideal for projects forked from the [WebVM](https://github.com/leaningtech/webvm/) repository. The Integrated GitHub Action will take care of preparing disk chunks for efficient access.
-3. **OverlayDevice**: `OverlayDevice` supports chaining, making it possible to efficiently "fork" disk images while only storing the changes from previous versions.
+3. [**OverlayDevice**](/docs/reference/CheerpX.OverlayDevice): `OverlayDevice` supports chaining, making it possible to efficiently _fork_ disk images while only storing the changes from previous versions.
 
 ## Best practices
 

sites/cheerpx/src/content/docs/12-reference/CheerpX.OverlayDevice/create.md

@@ -0,0 +1,51 @@
+---
+title: create
+description: Create a writable persistent overlay device on top of another block device.
+---
+
+```ts
+namespace CheerpX {
+	class OverlayDevice {
+		static async create(
+			baseDevice: Device,
+			overlayDevice: Device
+		): Promise<OverlayDevice>;
+	}
+}
+```
+
+## Parameters
+
+- **baseDevice (`Device`)** - The underlying device (e.g., [`HttpBytesDevice`](/docs/reference/httpBytesDevice), [`IDBDevice`](/docs/reference/CheerpX.IDBDevice)) that serves as the base layer for the filesystem.
+
+- **overlayDevice (`Device`)** - The writable layer that will overlay the base device, enabling persistent changes.
+
+## Returns
+
+`CheerpX.OverlayDevice.create` returns a [Promise] that resolves to an instance of the `OverlayDevice`. The `OverlayDevice` allows you to overlay a writable layer on top of the base device, enabling persistent changes while still accessing the base data.
+
+## Example
+
+Create an `OverlayDevice` instance to combine a [`HttpBytesDevice`](/docs/reference/httpBytesDevice) for streaming data from an HTTP source and an [`IDBDevice`](/docs/reference/CheerpX.IDBDevice) for caching and persistent local storage.
+
+```ts {8, 12}
+// Create a read-only HttpBytesDevice for streaming disk blocks via HTTP
+const httpDevice = await CheerpX.HttpBytesDevice.create("/cheerpXImage.ext2");
+
+// Create an IDBDevice for local persistent storage
+const idbDevice = await CheerpX.IDBDevice.create("block_idbDevice");
+
+// Create an OverlayDevice to combine the two devices
+const overlayDevice = await CheerpX.OverlayDevice.create(httpDevice, idbDevice);
+
+// Mount the overlay device in the CheerpX environment as an ext2 filesystem
+const cx = await CheerpX.Linux.create({
+	mounts: [{ type: "ext2", path: "/", dev: overlayDevice }],
+});
+```
+
+In this example, the `OverlayDevice` provides a writable layer on top of the [`HttpBytesDevice`](/docs/reference/httpBytesDevice) (which serves as a read-only block device for streaming), allowing changes to be stored locally via the [`IDBDevice`](/docs/reference/CheerpX.IDBDevice).
+
+For more information, please check out the [Files and File system guide](/docs/guides/File-System-support). This guide provides more details on how to work with files and directories in CheerpX.
+
+[Promise]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise