Network File System (NFS)

NFS Overview

The Network File System (NFS) is one of the network services that have quickly gained a leading role in the emerging networked environment. NFS allows directories and files to be shared across anetwork.
It is supported by virtually all UNIX flavors and many non−UNIX platforms. Through NFS,
users and programs can access files residing at remote systems as if they were local files. In an
ideal NFS environment, users neither know nor care where files are actually located.
The benefits of such an approach are obvious:

NFS reduces local disk storage requirements because a network can store a single copy of
a directory accessible by everyone on the network.
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NFS simplifies common support tasks, because files can be updated centrally (at the single
site) and yet be available through the network.
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NFS allows users to use familiar UNIX commands to manipulate remote files instead of
learning new ones; from the user standpoint everything is fully transparent.
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NFS is built on the RPC protocol (remote procedure call) and imposes a client−server relationship on the hosts that use NFS. An NFS server is a host that owns one or more filesystems and makes them available on the network; an NFS client mounts remote filesystems from one or more servers, and uses them in a way equivalent to local filesystems.
There are two aspects related to system administration when using NFS: choosing a filesystem
naming and mounting scheme, and then configuring the servers and clients to adhere to this
scheme. Users themselves do not know a lot about NFS, they simply benefit from using it.
Certain actions are required on both the server and client sides to configure NFS. NFS has
introduced new terminology to identify the required steps in the procedure itself. On the server side, to advertise and make a filesystem available on the network is known as to export a filesystem, or to share a filesystem (as in Solaris 2.x); on the client side, to implement an exported filesystem is known as to mount a remote filesystem.
The two actions are complementary: nonexported
filesystems cannot be mounted, and non−mounted exported filesystems cannot be used. We will
discuss these issues in greater detail later.

NFS Daemons
NFS requires the full support of several daemons, which perform basic server and client
NFS−related functions. Based on the RPC model and protocol, NFS includes a number of
processes involved on both sides. The NFS related daemons are:

nfsd = The NFS server daemon, which runs on the server side. The daemon services the
[option] client's NFS requests. The option specifies how many daemons should be started;
the common value is eight.
biod = The NFS block I/O daemon handles the client side of the NFS I/O. The option
[option] specifies the number of daemons to be started; the common value is eight.
rpc.lockd = The NFS lock daemon, which handles file lock requests on both sides; a client
requests file locks and a server grants them.
rpc.statd = The NFS status monitor daemon, which provides monitoring services requested
by the rpc.lockd daemon. More specifically, this daemon allows locks to be reset