usr.sbin/nfsd/nfsd.8

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.\"	@(#)nfsd.8	8.4 (Berkeley) 3/29/95
.\" $FreeBSD$
.\"
.Dd April 25, 2015
.Dt NFSD 8
.Os
.Sh NAME
.Nm nfsd
.Nd remote
.Tn NFS
server
.Sh SYNOPSIS
.Nm
.Op Fl ardute
.Op Fl n Ar num_servers
.Op Fl h Ar bindip
.Op Fl Fl maxthreads Ar max_threads
.Op Fl Fl minthreads Ar min_threads
.Sh DESCRIPTION
The
.Nm
utility runs on a server machine to service
.Tn NFS
requests from client machines.
At least one
.Nm
must be running for a machine to operate as a server.
.Pp
Unless otherwise specified, eight servers per CPU for
.Tn UDP
transport are started.
.Pp
The following options are available:
.Bl -tag -width Ds
.It Fl r
Register the
.Tn NFS
service with
.Xr rpcbind 8
without creating any servers.
This option can be used along with the
.Fl u
or
.Fl t
options to re-register NFS if the rpcbind server is restarted.
.It Fl d
Unregister the
.Tn NFS
service with
.Xr rpcbind 8
without creating any servers.
.It Fl n Ar threads
Specifies how many servers to create.  This option is equivalent to specifying
.Fl Fl maxthreads
and
.Fl Fl minthreads
with their respective arguments to
.Ar threads .
.It Fl Fl maxthreads Ar threads
Specifies the maximum servers that will be kept around to service requests.
.It Fl Fl minthreads Ar threads
Specifies the minimum servers that will be kept around to service requests.
.It Fl h Ar bindip
Specifies which IP address or hostname to bind to on the local host.
This option is recommended when a host has multiple interfaces.
Multiple
.Fl h
options may be specified.
.It Fl a
Specifies that nfsd should bind to the wildcard IP address.
This is the default if no
.Fl h
options are given.
It may also be specified in addition to any
.Fl h
options given.
Note that NFS/UDP does not operate properly when
bound to the wildcard IP address whether you use -a or do not use -h.
.It Fl t
Serve
.Tn TCP NFS
clients.
.It Fl u
Serve
.Tn UDP NFS
clients.
.It Fl e
Ignored; included for backward compatibility.
.El
.Pp
For example,
.Dq Li "nfsd -u -t -n 6"
serves
.Tn UDP
and
.Tn TCP
transports using six daemons.
.Pp
A server should run enough daemons to handle
the maximum level of concurrency from its clients,
typically four to six.
.Pp
The
.Nm
utility listens for service requests at the port indicated in the
.Tn NFS
server specification; see
.%T "Network File System Protocol Specification" ,
RFC1094,
.%T "NFS: Network File System Version 3 Protocol Specification" ,
RFC1813 and
.%T "Network File System (NFS) Version 4 Protocol" ,
RFC3530.
.Pp
If
.Nm
detects that
.Tn NFS
is not loaded in the running kernel, it will attempt
to load a loadable kernel module containing
.Tn NFS
support using
.Xr kldload 2 .
If this fails, or no
.Tn NFS
KLD is available,
.Nm
will exit with an error.
.Pp
If
.Nm
is to be run on a host with multiple interfaces or interface aliases, use
of the
.Fl h
option is recommended.
If you do not use the option NFS may not respond to
UDP packets from the same IP address they were sent to.
Use of this option
is also recommended when securing NFS exports on a firewalling machine such
that the NFS sockets can only be accessed by the inside interface.
The
.Nm ipfw
utility
would then be used to block nfs-related packets that come in on the outside
interface.
.Pp
If the server has stopped servicing clients and has generated a console message
like
.Dq Li "nfsd server cache flooded..." ,
the value for vfs.nfsd.tcphighwater needs to be increased.
This should allow the server to again handle requests without a reboot.
Also, you may want to consider decreasing the value for
vfs.nfsd.tcpcachetimeo to several minutes (in seconds) instead of 12 hours
when this occurs.
.Pp
Unfortunately making vfs.nfsd.tcphighwater too large can result in the mbuf
limit being reached, as indicated by a console message
like
.Dq Li "kern.ipc.nmbufs limit reached" .
If you cannot find values of the above
.Nm sysctl
values that work, you can disable the DRC cache for TCP by setting
vfs.nfsd.cachetcp to 0.
.Pp
The
.Nm
utility has to be terminated with
.Dv SIGUSR1
and cannot be killed with
.Dv SIGTERM
or
.Dv SIGQUIT .
The
.Nm
utility needs to ignore these signals in order to stay alive as long
as possible during a shutdown, otherwise loopback mounts will
not be able to unmount.
If you have to kill
.Nm
just do a
.Dq Li "kill -USR1 <PID of master nfsd>"
.Sh EXIT STATUS
.Ex -std
.Sh SEE ALSO
.Xr nfsstat 1 ,
.Xr kldload 2 ,
.Xr nfssvc 2 ,
.Xr nfsv4 4 ,
.Xr exports 5 ,
.Xr stablerestart 5 ,
.Xr gssd 8 ,
.Xr ipfw 8 ,
.Xr mountd 8 ,
.Xr nfsiod 8 ,
.Xr nfsrevoke 8 ,
.Xr nfsuserd 8 ,
.Xr rpcbind 8
.Sh HISTORY
The
.Nm
utility first appeared in
.Bx 4.4 .
.Sh BUGS
If
.Nm
is started when
.Xr gssd 8
is not running, it will service AUTH_SYS requests only. To fix the problem
you must kill
.Nm
and then restart it, after the
.Xr gssd 8
is running.