You want to create a hard link from/to a directory but getting an error as below,
# ln test/ test2/ ln: `test/': hard link not allowed for directory
Hard link is not allowed for directories pointing. You need to use symbolic/soft link instead. Please refer to http://itsiti.com/ln-make-links-between-files-creating-hard-soft-links-steps for steps to create symbolic/soft link for directories.