NFS uses a number of daemon processes to provide reliable file system access over a network. A number of clients may be accessing shared files, and it is the responsibility of the NFS system to guarantee file system integrity. NFS is a stateless server, which means that it does not keep a record of the state of files and clients that are accessing them. To keep consistency of files, a file locking mechanism is used through NFS daemons to ensure that files are properly locked when accessed by a client. Table 33-3 shows a list of NFS daemons and their functions on the client and server.
Table 33-3. NFS Daemons
Name | NFS System | Description |
portmap | Both client and server | RPC daemon used in HP-UX 10.20 and earlier versions. |
rpcbind | Both client and server | RPC daemon used in HP-UX 10.30 and later versions. |
rpc.statd | Both client and server | RPC daemon used with the rpc.lockd daemon to provide crash recovery functions. |
rpc.lockd | Both client and server | Used for file locking on both NFS servers and clients. Both client and server rpc.lockd daemons interact with each other to provide file locking functions. |
nfsd | Server | The NFS server daemon. A number of server daemon processes (by default, 4) are started at startup time. All of these processes register themselves with portmap or rpcbind . A heavily loaded NFS server may start more daemon processes. |
rpc.pcnfsd | Server | Used with PCNFS. Not required if all clients are UNIX machines. |
rpc. mountd | Server | Keeps a record of mounted and exported file systems. Replies to mount requests . |
biod | Client | Used to handle buffer cache in asynchronous I/O on NFS clients. |