how can we create a folder invisible to the userspace, i.e no flavor of "ls" should be able to retrieve it, it should exist and we should be able to work with it like any other folder.

Specifically, hat changes do we need to make in the kernel... I am thinking of a whiteout entry but not sure how to implement it.

Please Help.

Can you tell us what is the purpose on that ? Because, for example, if I create a folder, as root, like : "mkdir -p /home/users/testFolder", chown it for example with "chown user:user /home/users/testFolder", make "chmod -R 700 /home/users/testFolder" no one else besides root will be able to ls it. For other purposes, you can use BSD jails, here's an article on Wikipedia and an article at FreeBSD's site on what is beneath the technology.

I too would like to express that i wonder what the purpose of such a directory should be.

What you can do is: create a directory with filemode 700 like sysgate has told you. Only the owner (and root) can "ls" its contents. Now create a directory inside it with also filemode 700. Nobody will be able to find out about its existence because listing the contents of the parent directory is not possible.

I hope this helps.

bakunin

Hi,
Instead of "looking for the magic tricks", another alternative could be to use encryption and there are lots of them, one is: gpgdir - Recursively encrypt and decrypt directories (that i just came across today )
But just dont stop there, do explore the darkest of areas and share them with us ...