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Describe NFS Daemons & explain all types of NFS Daemons ?

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 NFS isn't a single program, but a suite of interrelated programs that work together to

get the job done. The following are several daemons that are started when a system
goes into run level 3 or multi-user mode. The mounted and nfsd daemons are run on
systems that are servers. The automatic startup of the server daemons depends on the
existence of entries that are labeled with the NFS file-system type in /etc./ds/share tab.
To support NFS file locking, the locked and stated daemons are run on NFS clients and
servers.

i) automounted Daemon

This daemon handles the mounting and unmounting requests from the autos
service. The syntax of the command is as follows:
automounted [ -Tnv ] [ -D name=value ]
The command behaves in the following ways:

-T enables tracing.
-n disables browsing on all autofs nodes.
-v selects to log all status messages to the console.
-D name=value substitutes value for the automount map variable that is
indicated by name.

The default value for the automount map is /etc/auto_master. Use the -T option
for troubleshooting

ii) Lockd Daemon
This daemon supports record-locking operations on NFS files. The lockd daemon
manages RPC connections between the client and the server for the Network
Lock Manager (NLM) protocol.

iii) Mountd Daemon
This daemon handles file-system mount requests from remote systems and
provides access control. The mountd daemon checks /etc/dfs/sharetab to
determine which file systems are available for remote mounting and which
systems are allowed to do the remote mounting. One can use the -v option and the
-r option with this command.

The -v option runs the command in verbose mode. Every time an NFS server
determines the access that a client should be granted, a message is printed on the
console. The information that is generated can be useful when trying to determine
why a client cannot access a file system.

The -r option rejects all future mount requests from clients. This option does not
affect clients that already have a file system mounted.

iv) nfs4cbd Daemon
This daemon is for the exclusive use of the NFS version 4 client that manages the
communication endpoints for the NFS version 4 callback program. The daemon
has no user-accessible interface.

v) nfslogd Daemon
This daemon provides operational logging. NFS operations that are logged
against a server are based on the configuration options that are defined in
/etc/default/nfslogd. When NFS server logging is enabled, records of all RPC
operations on a selected file system are written to a buffer file by the kernel

vi) statd Daemon
This daemon works with lockd daemon to provide crash and recovery functions
for the lock manager. The statd daemon tracks the clients that hold locks on an
NFS server. If a server crashes, on rebooting, statd daemon on the server contacts
statd on the client. The client statd can then attempt to reclaim any locks on the
server. The client statd also informs the server statd when a client has crashed so
that the client's locks on the server can be cleared.

vii) rpcbind: (portmap in older versions of Linux)
The primary daemon upon which all the others rely, rpcbind manages
connections for applications that use the RPC specification. By default, rpcbind
listens to TCP port 111 on which an initial connection is made. This is then used
to negotiate a range of TCP ports, usually above port 1024, to be used for
subsequent data transfers. You need to run rpcbind on both the NFS server and
client.

viii) nfs
Starts the RPC processes needed to serve shared NFS file systems. The nfs
daemon needs to be run on the NFS server only.

ix) nfslock
Used to allow NFS clients to lock files on the server via RPC processes. The
nfslock daemon needs to be run on both the NFS server and client.

x) netfs
It allows RPC processes run on NFS clients to mount NFS filesystems on the
server. The netfs daemon needs to be run on the NFS client only.



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