Network file locking process

When an application wants to obtain a lock on a local file, it sends its request to the kernel using the lockf, fcntl, or flock subroutines.

The kernel then processes the lock request. However, if an application on an NFS client makes a lock request for a remote file, the Network Lock Manager client generates a Remote Procedure Call (RPC) to the server to handle the request.

When the client receives an initial remote lock request, it registers interest in the server with the client's rpc.statd daemon. The same is true for the network lock manager at the server. On the initial request from a client, it registers interest in the client with the local network status monitor.