code: public void makePrivate() {
          if (getPublicMarkerFile().exists()) {
              if (getPublicMarkerFile().delete()) {
                  publicAccessCache.put(getName(), false);
              } else {
                  Storage.LOG.WARN("Failed to delete public marker for bucket %s - it remains public!", getName());
              }
          }
      }
docs: Marks the bucket as private accessible.