This is the first time I've heard of a whiteout node, so I did some Google searching.
A whiteout node is used are part of a union file system mount, where a 2nd file system is mounted over a base file system, and the files in both file systems appear to be merged.
When you delete a file in the union file system which happens to be in the bottom layer (which is effectively read-only), the top layer gets a whiteout node created to indicate that the bottom layer file should not be returned on a directory lookup.
So while I did not find anything about deleting a whiteout node, my theory is that maybe if you create a real file or directory with the exact same name as the whiteout node you created, the file system will automatically remove the whiteout node. Or try renaming a file to the same name as the whiteout node.
This is all just while speculation, as today is the first time I've heard of whiteout nodes (and I make my living writing file systems 🙂 ).
