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NFSD(8) System Manager's Manual NFSD(8)

nfsd — NFS server daemon

nfsd [command]

nfsd [-F exports_file] checkexports

nfsd [-NRrtuv] [-F exports_file] [-n num_servers] [-p nfsport] [-P mountport] [command]

nfsd runs on an NFS server machine to service NFS and MOUNT protocol requests from NFS client machines. In order for a machine to act as an NFS server an NFS exports file, /etc/exports, must exist and the nfsd service must be enabled.

nfsd listens for NFS service requests at the port indicated in the NFS server specification (2049) and the mountd thread listens for MOUNT service requests at an available port registered with portmap(8).

For more information on the NFS and MOUNT protocols see Network File System Protocol Specification, RFC1094 and NFS: Network File System Version 3 Protocol Specification.

The nfsd daemon is a multi-threaded process that includes a number of threads processing NFS requests, a thread to accept new socket connections and a thread that processes NFS MOUNT protocol requests.

When nfsd is started, it loads the export host addresses and options into the kernel using the nfssvc(2) system call. After changing the list of exports (either directly or indirectly via a change in netgroup membership), a hangup signal should be sent to the daemon to get it to reload the export information. This can be accomplished with the update command described below.

Any errors encountered while processing the export entries will be logged via syslog(3).

nfsd is normally launched by launchd(8); however, the nfsd command may also be used to manipulate the service using the following commands:

Enables the nfsd service.
Disables the nfsd service.
Starts the nfsd service. Note: if the service is disabled it will not be restarted on reboot. Use the enable command to make the change permanent.
Stops the nfsd service. Note: if the service is enabled it will be restarted on reboot. Use the disable command to make the change permanent.
Restarts the nfsd service (by stopping the service - it will restart automatically if the /etc/exports file exists).
Sends a SIGHUP to the running nfsd daemon to cause it to update its configuration.
Displays whether the nfsd service is enabled and whether the nfsd daemon is currently running.
Checks the exports file and reports any errors (to stderr). Note that this can be useful to verify the validity of an alternate exports file (using the -F option below) prior to putting the changes in place and updating nfsd.
Sends USR1 and/or USR2 signal(s) to the running nfsd daemon to cause it to increase and/or decrease its logging level. (See below for details about nfsd's logging).

Logging is performed via syslog(3) using the LOG_DAEMON facility. By default, only messages up to priority LOG_WARNING are logged. Setting the verbose level to one will add LOG_NOTICE messages which includes logging failed mount attempts. A verbose level of two will increase the log level to LOG_INFO which includes logging successful mount attempts. A log level of three or more will add LOG_DEBUG messages and cause increasing amounts of debug information to be logged. The debug information exposes lots of information about nfsd's inner workings which is typically only useful to developers. Note: the syslog(8) configuration may need to be adjusted in order to see the increased verbosity.

The nfsd utility exits 0 on success, and >0 if an error occurs. When given the status command, it exits 0 if the service is enabled, and 1 if the service is disabled.

The following is a list of command line options that are available. However, since nfsd is normally started by launchd(8), configuration of these options should be controlled using the equivalent settings in the NFS configuration file (see nfs.conf(5)).

exports_file
The exports_file argument specifies an alternate location for the exports file (useful with the checkexports command).
Allow non-root mount requests to be served. This should only be specified if there are clients that require it.
#
Specifies which port to use for the MOUNT service.
Allow mount RPCs requests for regular files to be served. Although this seems to violate the mount protocol specification, some diskless workstations do mount requests for their swapfiles and expect them to be regular files. Since a regular file cannot be specified in /etc/exports, the -alldirs option will need to be used on the export in which the swap files reside.
#
Specifies how many NFS server threads to create.
#
Specifies which port to use for the NFS service (instead of the default of 2049).
Register the NFS service with portmap(8). This option can be used to re-register the NFS services if the portmap server is restarted. This option is equivalent to the update command.
Serve TCP NFS clients. Note: only TCP will be used if no other options are specified.
Serve UDP NFS clients. Note: only UDP will be used if no other options are specified.
Increase nfsd's logging level by one (may be used multiple times).

Unless otherwise specified, eight NFS server threads are started and both UDP and TCP transports are supported.

A server should run enough threads to handle the maximum level of concurrency from its clients.

See nfs.conf(5) for a list of tunable parameters.

The exports list displayed via showmount(8) may contain additional information about the status of each export. This information is reported as entries in the export's group list.

If an export is currently unavailable, the group list will begin with the entry "<offline>" (or "<offline*>" if it is unavailable to some but not all clients exported to).

If an export allows non-default security mechanisms, the group list will contain an entry indicating what security mechanisms are allowed. For example: "<krb5:sys>". The mechanisms are listed in no particular order and may not be available to all clients.

If an export is available to all clients, the group list is usually empty. But if additional status information is returned in the group list, then the list will also contain an explicit "(Everyone)" entry to indicate that the export is available to all clients.

If nfsd does not have read access to an export, mount would fail with "Permission denied" and checkexports command would report the following error:

sandbox_check failed. nfsd has no read access to <path>
This could be resolved by granting nfsd "Full Disk Access" under "Privacy" tab of the "Security & Privacy" preference in the "System Preferences" followed by restart of nfsd service.

/etc/exports
The list of exported filesystems.
/var/run/nfsd.pid
The pid of the currently running nfsd.
/var/run/mountd.pid
The pid of the currently running mountd (provided for backwards compatibility with scripts that may HUP mountd to update exports).
/var/run/mountdtab
The current list of outstanding mounts served.
/var/run/mountdexptab
Information about exported file systems and directories (UUIDs, handles, ...).
/System/Library/LaunchDaemons/com.apple.nfsd.plist
The nfsd service's property list file for launchd(8).

exports(5), nfs.conf(5), showmount(8), nfsstat(1), nfssvc(2), portmap(8), rpc.rquotad(8), launchd(8)

The nfsd and mountd utilities first appeared in 4.4BSD. mountd functionality was merged into nfsd in Darwin 9.

November 10, 2008 macOS