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Unformatted text preview: twork File System obtains a file handle for that file from the NFS server. Each time the NFS client reads or
writes that file for the user process, the file handle is sent back to the server to identify the
file being accessed.
Normal user processes never deal with file handles - it is the NFS client code and the NFS
server code that pass them back and forth. In version 2 of NFS a file handle occupies 32
bytes, although this increases with version 3 to 64 bytes.
Unix servers normally store the following information in the file handle: the filesystem identifier (the
major and minor device numbers of the filesystem), the i-node number (a unique number within a
filesystem), and an i-node generation number (a number that changes each time an i-node is reused for a
different file). Mount Protocol
The client must use the NFS mount protocol to mount a server's filesystem, before the
client can access files on that filesystem. This is normally done when the client is
bootstrapped. The end result is for the client to obtain a file handle for the server's filesystem.
Figure 29.5 shows the sequence of steps that takes place when a Unix client issues the
mount (8) command, specifying an NFS mount. Figure 29.5 Mount protocol used by Unix mount command.
The following steps take place.
0. The port mapper is started on the server, normally when the server bootstraps.
1. The mount daemon (mountd) is started on the server, after the port mapper. It
creates a TCP end point and a UDP end point, and assigns ephemeral port number
to each. It then registers these port numbers with the port mapper. file:///D|/Documents%20and%20Settings/bigini/Docu...homenet2run/tcpip/tcp-ip-illustrated/nfs_netw.htm (10 of 23) [12/09/2001 14.47.56] Chapter 29. NFS: Network File System 2. The mount command is executed on the client and it issues an RPC call to the port
mapper on the server to obtain the port number of the server's mount daemon.
Either TCP or UDP can be used for this client exchange with the port mapper, but
UDP is normally used...
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This test prep was uploaded on 04/04/2014 for the course ECE EL5373 taught by Professor Guoyang during the Spring '12 term at NYU Poly.
- Spring '12