How many lookup calls are needed to resolve a 5-part pathname (for example, /usr/users/jim/code/ xyz.c) for a file that is stored on an NFS server? What is the reason for performing the translation step-by-step?
What will be an ideal response?
Five lookups, one for each part of the name.
Here are several reasons why pathnames are looked up one part at a time
i) pathnames may cross mount points;
ii) pathnames may contain symbolic links;
iii)pathnames may contain ‘..’;
iv)the syntax of pathnames could be client-specific.
Case (i) requires reference to the client mount tables, and a change in the server to which subsequent lookups are dispatched.
Case (ii) cannot be determined by the client.
Case (iii) requires a check in the client against the ‘pseudo-root’ of the client process making the request to make sure that the path doesn’t go above the pseudo- root.
Case (iv) requires parsing of the name at the client (not in itself a bar to multi-part lookups, since the parsed name could be passed to the server, but the NFSD protocol doesn’t provide for that).
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