Network File System (NFS)
NFS, defined by RFC 1094, is a method for client systems to use a file system on a remote host computer.
NFS uses the UDP protocol and is supported by RPC.
Remote Procedure Call (RPC)
RPC, defined by RFC 1057, is a set of function calls used by a client program to call functions in a remote server program. The port mapper program is the program used to keep track of which ports programs supporting RPC functions use. The port mappers port is 111. In Redhat Linux the portmapper daemon is started in the /etc/rc.d/init.d/portmap and the daemon program is called “portmap”.
The rpcinfo command
The command “rpcinfo -p” will show the port numbers that are assigned to the RPC services.
program vers proto port
100000 2 tcp 111 portmapper
100000 2 udp 111 portmapper
100011 1 udp 747 rquotad
100011 2 udp 747 rquotad
100005 1 udp 757 mountd
100005 1 tcp 759 mountd
100005 2 udp 762 mountd
100005 2 tcp 764 mountd
100003 2 udp 2049 nfs
Services that may be listed include:
- rquotad – Enforces the set quotas for remote mounted NFS systems.
- mountd – Performs the requested mounts.
- nfs – Handles the user interface to the kernel module that performs NFS.
NFS related services in Linux include:
- amd – Runs the automount daemon for automatic remote filesystem mounting such as nfs. It is especially worthwhile for working with removeable media such as floppies or CD ROM disks.
- autofs – This is the startup, stop, and status script for the automount program used to configure mount points for automatic mounting of file systems.
- nfs – Provides Network File System server services.
- netfs – Mounts and unmounts Network Fils System (NFS), Windows (SMB), and Netware (NCP) file systems. The mount command is used to perform this operation and no daemon is run in the background.
The /etc/exports file is used to configure exported filesystems.