To be able to build both PV and HVM images, it is not possible to use both...

To be able to build both PV and HVM images, it is not possible to use both /dev/sd[f-p] and [1-16] as the HVM images get attached at /dev/sdf but must be mounted a /dev/sdf1.

This reduces the number of simultaneous packer runs possible significantly, but unless you are Netflix, who have Aminator anyway, this is probably never going to be an issue

builder/amazon/chroot/device.go

@@ -27,11 +27,12 @@ func AvailableDevice() (string, error) {
 			continue
 		}
 
-		for i := 1; i < 16; i++ {
-			device := fmt.Sprintf("/dev/%s%c%d", prefix, letter, i)
-			if _, err := os.Stat(device); err != nil {
-				return device, nil
-			}
+		// To be able to build both Paravirtual and HVM images, the unnumbered
+		// device and the first numbered one must be available. 
+		// E.g. /dev/xvdf  and  /dev/xvdf1
+		numbered_device := fmt.Sprintf("%s%d", device, 1)
+		if _, err := os.Stat(numbered_device); err != nil {
+			return device, nil
 		}
 	}