Add mount_partition to amazon-chroot builder to specify a partition other than 1

builder/amazon/chroot/builder.go

@@ -37,6 +37,7 @@ type Config struct {
 	SourceAmi      string     `mapstructure:"source_ami"`
 	RootVolumeSize int64      `mapstructure:"root_volume_size"`
 	MountOptions   []string   `mapstructure:"mount_options"`
+	MountPartition int        `mapstructure:"mount_partition"`
 
 	ctx interpolate.Context
 }
@@ -97,6 +98,10 @@ func (b *Builder) Prepare(raws ...interface{}) ([]string, error) {
 		b.config.MountPath = "/mnt/packer-amazon-chroot-volumes/{{.Device}}"
 	}
 
+	if b.config.MountPartition == 0 {
+		b.config.MountPartition = 1
+	}
+
 	// Accumulate any errors
 	var errs *packer.MultiError
 	errs = packer.MultiErrorAppend(errs, b.config.AccessConfig.Prepare(&b.config.ctx)...)
@@ -170,6 +175,7 @@ func (b *Builder) Run(ui packer.Ui, hook packer.Hook, cache packer.Cache) (packe
 		&StepEarlyUnflock{},
 		&StepMountDevice{
 			MountOptions:   b.config.MountOptions,
+			MountPartition: b.config.MountPartition,
 		},
 		&StepMountExtra{},
 		&StepCopyFiles{},

builder/amazon/chroot/step_mount_device.go

@@ -25,6 +25,7 @@ type mountPathData struct {
 //   mount_device_cleanup CleanupFunc - To perform early cleanup
 type StepMountDevice struct {
 	MountOptions   []string
+	MountPartition int
 
 	mountPath string
 }
@@ -67,7 +68,7 @@ func (s *StepMountDevice) Run(state multistep.StateBag) multistep.StepAction {
 	log.Printf("Source image virtualization type is: %s", *image.VirtualizationType)
 	deviceMount := device
 	if *image.VirtualizationType == "hvm" {
-		deviceMount = fmt.Sprintf("%s%d", device, 1)
+		deviceMount = fmt.Sprintf("%s%d", device, s.MountPartition)
 	}
 	state.Put("deviceMount", deviceMount)
 

website/source/docs/builders/amazon-chroot.html.markdown

@@ -133,6 +133,9 @@ builder.
     where the `.Device` variable is replaced with the name of the device where
     the volume is attached.
 
+-   `mount_partition` (integer) - The partition number containing the /
+    partition. By default this is the first partition of the volume.
+
 -   `mount_options` (array of strings) - Options to supply the `mount` command
     when mounting devices. Each option will be prefixed with `-o` and supplied
     to the `mount` command ran by Packer. Because this command is ran in a