builder/amazon/chroot: more settings, validation

builder/amazon/chroot/builder.go

@@ -24,7 +24,10 @@ type Config struct {
 	common.PackerConfig    `mapstructure:",squash"`
 	awscommon.AccessConfig `mapstructure:",squash"`
 
-	SourceAmi string `mapstructure:"source_ami"`
+	SourceAmi          string `mapstructure:"source_ami"`
+	AttachedDevicePath string `mapstructure:"attached_device_path"`
+	DevicePath         string `mapstructure:"device_path"`
+	MountPath          string `mapstructure:"mount_path"`
 }
 
 type Builder struct {
@@ -39,11 +42,22 @@ func (b *Builder) Prepare(raws ...interface{}) error {
 	}
 
 	// Defaults
+	if b.config.DevicePath == "" {
+		b.config.DevicePath = "/dev/sdh"
+	}
+
+	if b.config.MountPath == "" {
+		b.config.MountPath = "/var/packer-amazon-chroot/volumes/{{.Device}}"
+	}
 
 	// Accumulate any errors
 	errs := common.CheckUnusedConfig(md)
 	errs = packer.MultiErrorAppend(errs, b.config.AccessConfig.Prepare()...)
 
+	if b.config.SourceAmi == "" {
+		errs = packer.MultiErrorAppend(errs, errors.New("source_ami is required."))
+	}
+
 	if errs != nil && len(errs.Errors) > 0 {
 		return errs
 	}

builder/amazon/chroot/builder_test.go

@@ -6,7 +6,9 @@ import (
 )
 
 func testConfig() map[string]interface{} {
-	return map[string]interface{}{}
+	return map[string]interface{}{
+		"source_ami": "foo",
+	}
 }
 
 func TestBuilder_ImplementsBuilder(t *testing.T) {
@@ -16,3 +18,20 @@ func TestBuilder_ImplementsBuilder(t *testing.T) {
 		t.Fatalf("Builder should be a builder")
 	}
 }
+
+func TestBuilderPrepare_SourceAmi(t *testing.T) {
+	b := &Builder{}
+	config := testConfig()
+
+	config["source_ami"] = ""
+	err := b.Prepare(config)
+	if err == nil {
+		t.Fatal("should have error")
+	}
+
+	config["source_ami"] = "foo"
+	err = b.Prepare(config)
+	if err != nil {
+		t.Errorf("err: %s", err)
+	}
+}

builder/amazon/chroot/step_attach_volume.go

@@ -20,12 +20,13 @@ type StepAttachVolume struct {
 }
 
 func (s *StepAttachVolume) Run(state map[string]interface{}) multistep.StepAction {
+	config := state["config"].(*Config)
 	ec2conn := state["ec2"].(*ec2.EC2)
 	instance := state["instance"].(*ec2.Instance)
 	ui := state["ui"].(packer.Ui)
 	volumeId := state["volume_id"].(string)
 
-	device := "/dev/sdh"
+	device := config.DevicePath
 
 	ui.Say("Attaching the root volume...")
 	_, err := ec2conn.AttachVolume(volumeId, instance.InstanceId, device)