Assume that an NFS (described in Section 4.5) server contains a file /a/b and that an NFS client mounts the NFS server’s root directory in the location /x, so that the client can now name the file as /x/a/b. Further assume that this is the only client and that the client executes the following two commands:

The remove message from the client to the server gets through, and the server removes the file. Unfortunately, the response from the server to the client is lost and the client resends the message to remove the (now non-existent) file. The server receives the resent message. What happens next depends on the server implementation. Which of the following are correct statements?

A. If the server maintains an in-memory reply cache in which it records all operations it previously executed, and there are no server failures, the server will return “OK”.

B. If the server maintains an in-memory reply cache but the server has failed, restarted, and its reply cache is empty, both of the following responses are possible: the server may return “file not found” or “OK”.

C. If the server is stateless, it will return “file not found”.

D. Because remove is an idempotent operation, any server implementation will return “OK”.

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chdir /x/a rm b