Make EBS block device mapping optional for ephemeral virtual names.

builder/amazon/common/block_device.go

@@ -4,6 +4,7 @@ import (
 	"github.com/aws/aws-sdk-go/aws"
 	"github.com/aws/aws-sdk-go/service/ec2"
 	"github.com/mitchellh/packer/template/interpolate"
+	"strings"
 )
 
 // BlockDevice
@@ -47,11 +48,14 @@ func buildBlockDevices(b []BlockDevice) []*ec2.BlockDeviceMapping {
 		}
 
 		mapping := &ec2.BlockDeviceMapping{
-			EBS:         ebsBlockDevice,
 		  DeviceName:  aws.String(blockDevice.DeviceName),
 		  VirtualName: aws.String(blockDevice.VirtualName),
 		}
 
+		if !strings.HasPrefix(blockDevice.VirtualName, "ephemeral") {
+		  mapping.EBS = ebsBlockDevice
+		}
+
 		if blockDevice.NoDevice {
 			mapping.NoDevice = aws.String("")
 		}