NFSSVC(2) System Calls Manual NFSSVC(2)

nfssvcNFS services

#include <unistd.h>
#include <nfs/nfs.h>

nfssvc(int flags, void *argstructp);

The () function is used by the NFS server daemon to pass information into and out of the kernel and also to enter the kernel as a server daemon. The flags argument consists of several bits that show what action is to be taken once in the kernel and the argstructp points to any corresponding data that the action may require.

() is called with the flag NFSSVC_NFSD and a NULL argstructp to enter the kernel as an nfsd(8) daemon. The NFSSVC_NFSD action normally does not return until the NFS server is stopped.

The nfsd(8) server daemon calls () with the flag NFSSVC_ADDSOCK and a pointer to a

struct nfsd_args {
	int	sock;		/* Socket to serve */
	caddr_t	name;		/* Client address for connection based sockets */
	int	namelen;	/* Length of name */

to pass a server side NFS socket into the kernel for servicing by the nfsd(8) daemons.

The nfsd(8) server daemon calls () with the flag NFSSVC_EXPORT and a pointer to a

struct nfs_export_args {
	uint32_t		nxa_fsid;	/* export FS ID */
	uint32_t		nxa_expid;	/* export ID */
	char			*nxa_fspath;	/* export FS path */
	char			*nxa_exppath;	/* export sub-path */
	uint32_t		nxa_flags;	/* export arg flags */
	uint32_t		nxa_netcount;	/* #entries in ex_nets array */
	struct nfs_export_net_args *nxa_nets;	/* array of net args */

to pass exported file system information into the kernel.

Additionally, the () is used by nfsstat(1) tool to receive statistic about the server from kernel. While used, argstructp points to struct iovec of size 2. The first iovec entry specifies the base address and length of an area in memory from which data should be written. The size of the available data will be returned in the location pointed by the second iovec entry. The following flags are supported :

Used to receive exported directory status.
Used to receive exported directory active user status.
Used to receive current count of active NFS users.
Used to zero NFS server statistics.
Used to receive NFS server statistics.

Upon successful completion, a value of 0 is returned. Otherwise, -1 is returned the global variable errno is set to specify the error.

The caller is not the super-user.
The action specified by the flags argument was not valid.
argstructp points to an invalid address.
A memory allocation failure prevented the action from completing.
An attempt was made to add a UDP socket via the NFSSVC_ADDSOCK action, but the UDP socket has already been added.

nfsstat(1), nfsd(8)

The nfssvc function first appeared in 4.4BSD.

The nfssvc system call is designed specifically for the NFS server daemons and as such is specific to their requirements. Several fields of the argument structures are assumed to be valid, such that nfssvc must be used with extreme care.

January 9, 2007 macOS 14.5