Linux in a Nutshell, Fourth Edition

Overview of NFS

The Network File System (NFS) is a distributed filesystem that allows users to mount remote filesystems as if they were local. NFS uses a client/server model in which a server exports directories to be shared, and clients mount the directories to access the files in them. NFS eliminates the need to keep copies of files on several machines by letting the clients all share a single copy of a file on the server. NFS is an RPC-based application-level protocol. For more information on the architecture of network protocols, see Section 2.3 earlier in this chapter.

Administering NFS

To set up NFS clients and servers you must start the NFS daemons on the servers, export filesystems from the NFS servers, and mount the filesystems on the clients. The /etc/exports file is the NFS server configuration file; it controls which files and directories are exported and what kinds of access are allowed. Names and addresses for clients that should be allowed or denied access to NFS are kept in the /etc/hosts.allow and /etc/hosts.deny files.

Daemons

NFS server daemons, called nfsd daemons, run on the server and accept RPC calls from clients. NFS servers also run the mountd daemon to handle mount requests. On the client, caching and buffering are handled by biod , the block I/O daemon. The portmap daemon maps RPC program numbers to the appropriate TCP/IP port numbers.

Exporting Filesystems

To set up an NFS server, first check that all the hosts that will mount your filesystem can reach ...