fixed generated cloud config

userdata.go

@@ -8,6 +8,8 @@ import (
 	"net/url"
 )
 
+var cloudConfig = []byte("#cloud-config\n")
+
 func parseUserData(s string) (u *UserData, err error) {
 	s, err = url.QueryUnescape(s)
 	if err != nil {
@@ -29,7 +31,11 @@ func MarshalUserData(u *UserData) ([]byte, error) {
 	if u == nil {
 		return nil, nil
 	}
-	return yaml.Marshal(u)
+	b, err := yaml.Marshal(u)
+	if err == nil {
+		b = append(cloudConfig, b...)
+	}
+	return b, err
 }
 
 type UserData struct {