Chapter 29 NFS Network File System
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TCP/IP 卷一详解版
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29.4 Port Mapper
The RPC server programs containing the remote procedures use ephemeral ports, not well-known ports.
29.5 NFS Protocol
NFS provides transparent file access for clients to files and filesystems on a server.
File Handles
A fundamental concept in NFS is the file handle. It is an opaque object used to reference a file or directory on the server.
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.
NFS Procedures
The NFS server provides 15 procedures, which we now describe. Although NFS was designed to work between different operating systems, and not just Unix systems, some of the procedures provide Unix functionality that might not be supported by other operating systems.
UDP or TCP?
NFS was originally written to use UDP, and that's what all verdors provide.
NFS Over TCP
The Berkeley Net/2 implementation of NFS supports either UDP or TCP.
29.6 NFS Examples
Let's use tcpdump to see which NFS procedures are invoked by the client for typical file operations.
Simple Example: Reading a File
Simple Example: Creating a Directory
Statelessness
Example: Server Crash
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29.7 NFS Version 3
29.1 Introduction
In this chapter we describe NFS, the Network FIle System, another popular application that provides transparent file access for client application.
29.2 Sum Remote Procedure Call
Most network programming is done by writing application programs that call system-provided functions to perform specific network operations.
Sun RPC
Sun RPC comes in two flavors. One version is built using the sockets API and works with TCP and UDP. Another , called TI-RPC , is built using the TLI API and works with any transport layer provided by the kernel.
29.3 XDR: External Data Representation
XDR, External Data Representation , is the standard used to encode the values in the RPC call and reply message-the RPC header field , the procedure parameters, and the procedure results.
29.8 Summary
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