Stephen Worotynec sw@smoky.ca writes:

...

It is rather a long-established "trick" (it goes right back to the

original

...

Sun implementations) used by NFS client implementations to simulate the behaviour of local Unix filing systems when an open file is unlinked.

I'm not sure this "simulates" local filesystems, which I don't see creating such files.

OK, this is standard Unix filesystem semantics; if a file is unlinked while it is being held open by a process, the file remains accessible to that process until it closes the file (but not to any other process).

This doesn't work in general for NFS filesystems; it is the clients that keep track of open files. Even if a process holds a file open the file can be removed from under its feet by another client.

However, there is a standard trick to partly simulate the semantics of local filesystems; if a client removes a file that is being held open by some process on the same client, the client's NFS routines doesn't remove the file, but renames it to a temporary .nfs* file, which is still accessible to the process that has opened the file. When the process closes the file, it is removed.