code: protected String[] getFilesystemRoots() throws IOException {
  		File[] fileRoots=File.listRoots();
  		List<String> tempRoots=new ArrayList<>(fileRoots.length);
  		for (File fileRoot : fileRoots) {
  			String root = fileRoot.getPath();
  			// Only add if this root is used for at least one backup setting
  			FilesystemIteratorRule defaultRule = rules.get("");
  			if(
  				(defaultRule!=null && defaultRule.isIncluded(root))
  				|| hasIncludedChild(root)
  			) tempRoots.add(root);
  		}
  		return tempRoots.toArray(new String[tempRoots.size()]);
  	}
docs: Gets the file system roots.  It will only include the root if it has
  at least one backup-enabled rule.  An empty rule ("") will implicitly
  allow all roots.