Directory mirroring with cron


I have one folder in one of my hosted site (we can call it
to semplify).

And I have 5 FTP only user, each of one with:

Now, I want to keep in sync these folders because I need to give at these users the ability to upload in the main website, but without the permission to fisically access the “mainuser/directory”.

The problem is that i don’t want to have 6 copies of the same file, but I’m trying use hard-linking because i don’t want to waste space.

I tried with “cp -al” and with “find” but it get difficult because of permission.

Every one know a good way to achieve this result?

Or, if ceph support de-duplication can I simply copy all of this files without wondering about dupes?

Or do you think that I can ask to the support team?

Thank you everyone