docs(talos): add README for image customization

Created `_packer/schematic.yaml` for defining image customization and `_packer/README.md` to guide on adding extensions to Talos images using the image factory.

Signed-off-by: Marcel Richter <[email protected]>

_packer/.gitignore

@@ -0,0 +1 @@
+hcloud.auto.pkrvars.hcl

_packer/README.md

@@ -0,0 +1,26 @@
+# Add Extension to tho Talos Image
+
+You can use the image factory to achieve this. The image factory is a tool that allows you to create custom Talos
+images. You can find the documentation [here](https://www.talos.dev/v1.6/learn-more/image-factory/).
+
+You can also use the endpoint to generate images. To achieve this, you need to adjust the `schematic.yaml` file to
+include the extension you want to add to the image and then run the following command:
+
+```shell
+curl -X POST --data-binary @schematic.yaml https://factory.talos.dev/schematics
+```
+
+Then you can use the ID and the current Talos Version to get the image URLs with extensions:
+
+- `https://factory.talos.dev/image/<ID>/<VERSION>/hcloud-amd64.raw.xz`.
+- `https://factory.talos.dev/image/<ID>/<VERSION>/hcloud-arm64.raw.xz`.
+
+Use these URLs in the `talos-hcloud.pkr.hcl` and replace `image_arm` and `image_x86` to create the snapshots with the
+extensions.
+
+You can create a file `hcloud.auto.pkrvars.hcl` to overwrite the default values. The file should look like this:
+```hcl
+talos_version = "v1.6.7"
+image_url_arm = "https://factory.talos.dev/image/376567988ad370138ad8b2698212367b8edcb69b5fd68c80be1f2ec7d603b4ba/v1.6.7/hcloud-arm64.raw.xz"
+image_url_x86 = "https://factory.talos.dev/image/376567988ad370138ad8b2698212367b8edcb69b5fd68c80be1f2ec7d603b4ba/v1.6.7/hcloud-amd64.raw.xz"
+```

_packer/create.sh

@@ -11,4 +11,4 @@ if [[ -z "${HCLOUD_TOKEN:-}" ]]; then
     export HCLOUD_TOKEN=$hcloud_token
 fi
 echo "Running packer build for talos-hcloud.pkr.hcl"
-packer init talos-hcloud.pkr.hcl && packer build talos-hcloud.pkr.hcl
+packer init . && packer build .

_packer/schematic.yaml

@@ -0,0 +1,7 @@
+# This file is used to define the schematic configuration for image factory.
+# The following extensions are required for longhorn for example.
+customization:
+  systemExtensions:
+    officialExtensions:
+      - siderolabs/iscsi-tools
+      - siderolabs/util-linux-tools

_packer/talos-hcloud.pkr.hcl

@@ -13,14 +13,24 @@ variable "talos_version" {
   default = "v1.6.7"
 }
 
+variable "image_url_arm" {
+  type    = string
+  default = null
+}
+
+variable "image_url_x86" {
+  type    = string
+  default = null
+}
+
 variable "server_location" {
   type    = string
   default = "fsn1"
 }
 
 locals {
-  image_arm = "https://github.com/siderolabs/talos/releases/download/${var.talos_version}/hcloud-arm64.raw.xz"
-  image_x86 = "https://github.com/siderolabs/talos/releases/download/${var.talos_version}/hcloud-amd64.raw.xz"
+  image_arm = var.image_url_arm != null ? var.image_url_arm : "https://github.com/siderolabs/talos/releases/download/${var.talos_version}/hcloud-arm64.raw.xz"
+  image_x86 = var.image_url_x86 != null ? var.image_url_x86 : "https://github.com/siderolabs/talos/releases/download/${var.talos_version}/hcloud-amd64.raw.xz"
 
   # Add local variables for inline shell commands
   download_image = "wget --timeout=5 --waitretry=5 --tries=5 --retry-connrefused --inet4-only -O /tmp/talos.raw.xz "