File Systems

Security, authentication, file systems. NFS and AFS

What is a soft link in a file system?

a path that is resolved to another path

What is a hard link in a file system?

a mapping of a name to a file identifier

Can two Unix processes simultaneous write to different positions in a single file?

Yes, the two processes will have their own file table entries.

What is the purpose of the Unix lseek operation?

set the read/write pointer of an opened file

How is a NFS client-side cache entry validated?

if the validity was checked less than t seconds ago or if the server modification time is equal to the client modification time

How is authentication control handled in Sun NFS?

authentication is provided by RPC in each operation

How does a NFS server know at what position to read and write to?

each read and write operation holds the position

How is AFS client side caching implemented?

the server promise to notify the client if a file is modified by another client

Can two client have an inconsistent view of a file using AFS?

yes, if a call-back message is lost a cached copy can be used although the original has been modified

What is the advantage of using AFS over NFS?

the client need not periodically check validity