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Manual Pages  — NFSD


nfsd – remote NFS server



nfsd [-ardute] [-n num_servers] [-h bindip] [-maxthreads max_threads] [-minthreads min_threads]


The nfsd utility runs on a server machine to service NFS requests from client machines. At least one nfsd must be running for a machine to operate as a server.

Unless otherwise specified, eight servers per CPU for UDP transport are started.

The following options are available:
  Register the NFS service with rpcbind(8) without creating any servers. This option can be used along with the -u or -t options to re-register NFS if the rpcbind server is restarted.
  Unregister the NFS service with rpcbind(8) without creating any servers.
-n threads
  Specifies how many servers to create. This option is equivalent to specifying -maxthreads and -minthreads with their respective arguments to threads.
-maxthreads threads
  Specifies the maximum servers that will be kept around to service requests.
-minthreads threads
  Specifies the minimum servers that will be kept around to service requests.
-h 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 -h options may be specified.
  Specifies that nfsd should bind to the wildcard IP address. This is the default if no -h options are given. It may also be specified in addition to any -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.
  Serve TCP NFS clients.
  Serve UDP NFS clients.
  Ignored; included for backward compatibility.

For example, "nfsd -u -t -n 6" serves UDP and TCP transports using six daemons.

A server should run enough daemons to handle the maximum level of concurrency from its clients, typically four to six.

The nfsd utility listens for service requests at the port indicated in the NFS server specification; see Network File System Protocol Specification, RFC1094, NFS: Network File System Version 3 Protocol Specification, RFC1813 and Network File System (NFS) Version 4 Protocol, RFC3530.

If nfsd detects that NFS is not loaded in the running kernel, it will attempt to load a loadable kernel module containing NFS support using kldload(2). If this fails, or no NFS KLD is available, nfsd will exit with an error.

If nfsd is to be run on a host with multiple interfaces or interface aliases, use of the -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 ipfw utility would then be used to block nfs-related packets that come in on the outside interface.

If the server has stopped servicing clients and has generated a console message like "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.

Unfortunately making vfs.nfsd.tcphighwater too large can result in the mbuf limit being reached, as indicated by a console message like "kern.ipc.nmbufs limit reached". If you cannot find values of the above sysctl values that work, you can disable the DRC cache for TCP by setting vfs.nfsd.cachetcp to 0.

The nfsd utility has to be terminated with SIGUSR1 and cannot be killed with SIGTERM or SIGQUIT. The nfsd 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 nfsd just do a "kill -USR1 <PID of master nfsd>"


The utility exits 0 on success, and >0 if an error occurs.


nfsstat(1), kldload(2), nfssvc(2), nfsv4(4), exports(5), stablerestart(5), gssd(8), ipfw(8), mountd(8), nfsiod(8), nfsrevoke(8), nfsuserd(8), rpcbind(8)


The nfsd utility first appeared in BSD 4.4 .


If nfsd is started when gssd(8) is not running, it will service AUTH_SYS requests only. To fix the problem you must kill nfsd and then restart it, after the gssd(8) is running.

NFSD (8) April 25, 2015

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