Rsync can be tricky, but it is the best way to synchronize the contents of directories. It is used when you don't want to simply delete one directory and replace it with another. For example, when replacing the contents of a directory under SVN version control you don't want the .svn directory to get removed or modified.
rsync -arvz [source] [destination]
-a "archive mode" which preserves links, permissions, etc.
-v verbose, multiple Vs increase the amount of data displayed. -vv, -vvv -vvvv.
-n Do a dry-run, to see what would happen.