update docs

README.md

@@ -1,6 +1,12 @@
 # Terraform Docker Packer
 
-This Terraform module serves as an abstraction to builds machine images from Packer configurations through Docker.
+This Terraform module serves as an abstraction to builds machine images from Packer configurations through Docker.  
+A pre-existing Docker image with Packer installed is required.  
+The build runs in the background and outpout the image to the local directory.  
+To see the build progress, you need to show the Docker logs like this:
+```
+docker logs -f $(docker ps -q -f name=packer-builder-arm)
+```
 
 ## Requirements
 

examples/raspios/README.md

@@ -1,10 +1,21 @@
 # RaspiOS
 
-Build a new ARM64 device image based on RaspiOS.  
-The Packer config will run some scripts through the Shell provisioner in order to setup and configure the device image.  
+Build a ARM64 device image based on RaspiOS.  
+The Packer config will run some scripts located at `./scripts` through the Shell provisioner in order to setup and configure the device image.  
 In addition, `Firstboot` will be configured to run an additional setup scripts during first boot of the device.  
 
+## Provisioning
+
+```
+# run the Packer build
+terraform init
+terraform apply
+
+# show build progress
+docker logs -f $(docker ps -q -f name=packer-builder-arm)
+```
+
 ## Firstboot
 
-This example contains a Systemd service and script that will run at first boot and sets the hostname to `rpi-SERIAL`.  
+This example contains a Systemd service and script that will run at first boot and sets the hostname to `rpi-SERIAL` so that each device gets a unique hostname.    
 Adopted from https://github.com/nmcclain/raspberian-firstboot

examples/raspios/main.tf

@@ -3,7 +3,7 @@ module "raspios" {
   packer_config = "packer/raspios.pkr.hcl"
   packer_variables = {
     image_path = "rpi-arm64.img"
-      scripts = [
+    scripts = [
       "scripts/pi.sh",
       "scripts/docker.sh",
       "scripts/hashi.sh"