func (p *PostProcessor) PostProcess(ui packer.Ui, artifact packer.Artifact) (packer.Artifact, bool, error) {
	if artifact.BuilderId() != dockertag.BuilderId {
		err := fmt.Errorf(
			"Unknown artifact type: %s\nCan only build with Dockerfile from Docker tag artifacts.",
			artifact.BuilderId())
		return nil, false, err
	}

	p.config.From = artifact.Id()

	template_str := `FROM {{ .From }}
{{ if .Maintainer }}MAINTAINER {{ .Maintainer }}
{{ end }}{{ if .Cmd }}CMD {{ process .Cmd }}
{{ end }}{{ if .Label }}{{ range $k, $v := .Label }}LABEL "{{ $k }}"="{{ $v }}"
{{ end }}{{ end }}{{ if .Expose }}EXPOSE {{ join .Expose " " }}
{{ end }}{{ if .Env }}{{ range $k, $v := .Env }}ENV {{ $k }} {{ $v }}
{{ end }}{{ end }}{{ if .Entrypoint }}ENTRYPOINT {{ process .Entrypoint }}
{{ end }}{{ if .Volume }}VOLUME {{ process .Volume }}
{{ end }}{{ if .User }}USER {{ .User }}
{{ end }}{{ if .WorkDir }}WORKDIR {{ .WorkDir }}{{ end }}`

	dockerfile := new(bytes.Buffer)
	template_writer := bufio.NewWriter(dockerfile)

	tmpl, err := template.New("Dockerfile").Funcs(template.FuncMap{
		"process": p.processVar,
		"join":    strings.Join,
	}).Parse(template_str)
	if err != nil {
		return nil, false, err
	}
	err = tmpl.Execute(template_writer, p.config)
	if err != nil {
		return nil, false, err
	}
	template_writer.Flush()
	log.Printf("Dockerfile:\n%s", dockerfile.String())

	driver := p.Driver
	if driver == nil {
		// If no driver is set, then we use the real driver
		driver = &DockerDriver{&docker.DockerDriver{Ctx: &p.config.ctx, Ui: ui}}
	}

	ui.Message("Building image from Dockerfile")
	id, err := driver.BuildImage(dockerfile)
	if err != nil {
		return nil, false, err
	}

	ui.Message("Destroying previously tagged image: " + p.config.From)
	err = artifact.Destroy()
	if err != nil {
		return nil, false, err
	}

	ui.Message("Tagging new image, " + id + ", as " + p.config.From)
	err = driver.TagImage(id, p.config.From, true)
	if err != nil {
		return nil, false, err
	}

	// Build the artifact
	artifact = &docker.ImportArtifact{
		BuilderIdValue: dockertag.BuilderId,
		Driver:         driver,
		IdValue:        p.config.From,
	}

	return artifact, true, nil
}