• rpc.nfsd — This process is the NFS server. It works with the Linux kernel to meet thedynamic demands of NFS clients, such as providing server threads each time an NFS clientconnects. This process corresponds to the nfs service.• rpc.lockd — An optional process that allows NFS clients to lock files on the server. Thisprocess corresponds to the nfslock service. This is not used with NFSv4.• rpc.statd — This process implements the Network Status Monitor (NSM) RPC protocolwhich notifies NFS clients when an NFS server is restarted without being gracefully broughtdown. This process is started automatically by the nfslock service and does not require userconfiguration. This is not used with NFSv4.• rpc.rquotad — This process provides user quota information for remote users. This processis started automatically by the nfs service and does not require user configuration.• rpc.idmapd — This process provides NFSv4 client and server upcalls which map betweenon-the-wire NFSv4 names (which are strings in the form of user@domain) and local UIDs andGIDs. For idmapd to function with NFSv4, the /etc/idmapd.conf must be configured. Thisservice is required for use with NFSv4.• rpc.svcgssd — This process is used by the NFS server to perform user authentication and isstarted only when SECURE_NFS=yes is set in the /etc/sysconfig/nfs file.• rpc.gssd — This process is used by the NFS server to perform user authentication and isstarted only when SECURE_NFS=yes is set in the /etc/sysconfig/nfs file.1.2. NFS and portmapNoteThe following section only applies to NFSv2 or NFSv3 implementations thatrequire the portmap service for backward compatibility.The portmap service under Linux maps RPC requests to the correct services. RPC processesnotify portmap when they start, revealing the port number they are monitoring and the RPCprogram numbers they expect to serve. The client system then contacts portmap on the serverwith a particular RPC program number. The portmap service redirects the client to the properport number so it can communicate with the requested service.Because RPC-based services rely on portmap to make all connections with incoming clientrequests, portmap must be available before any of these services start.The portmap service uses TCP wrappers for access control, and access control rules forportmap affect all RPC-based services. Alternatively, it is possible to specify access controlrules for each of the NFS RPC daemons. The man pages for rpc.mountd and rpc.statdcontain information regarding the precise syntax for these rules.NFS and portmap133
