about Linux read/write only permissions

Question

My question looks similar to another thread: Linux directory permissions read write but not delete

Here, I want to create a directory where I can give the permissions like:

• A user can create/upload any files.
• A user can re-upload and overwrite the files.
• A user cannot remove the file anymore.

I am on CentOS 5.5, basic user only. How can I do that? Or is there any third party software that can be installed to do this? Or, create a new process which will lock the permissions right after a new file is uploaded via ssh?

Answer 1

You cannot achieve that, even with ACLs, on Unix-derivative systems.

All else apart, if the user can overwrite the contents of the file, it is equivalent to delete (they can write nothing, leaving an empty file, or they can write junk).