--links copy symlinks as symlinks --delete 允许删除文件 --sparse handle sparse files efficiently --backup make backups (see --suffix & --backup-dir) --backup-dir=DIR make backups into hierarchy based in DIR --archive archive mode; equals -rlptgoD (no -H,-A,-X) --verbose 显示详细输出 --recursive 递归同步文件夹内容 --human-readable output numbers in a human-readable format