exportfs(2)							System Calls Manual						       exportfs(2)

NAME

       exportfs - Exports an NFS file system

SYNOPSIS

       #include <nfs/nfs.h>

       exportfs(access, cookie, exdata)
	       int access;
	       int *cookie;
	       struct exportfsdata *exdata;

DESCRIPTION

       The  exportfs  system  call  allows  the  specified local file system to be mounted remotely by an NFS client.  This system call is usually
       called from mountd. The system call allows access to the kernels export database.  The method of access is specified by the access flag	as
       follows:

       #define	EXPORTFS_CREATE 0x01	    /* create a new export record */ #define EXPORTFS_REMOVE 0x02	 /* remove an old export record */
       #define EXPORTFS_READ   0x03	   /* read an export record */

       Each entry in the export database has the following structure:

       struct exportfsdata {
	       dev_t   e_dev;	  /* ID of device containing the directory */
	       ino_t   e_ino;	  /* File serial number */
	       uint_t  e_gen;	  /* File generation number */
	       char e_path[MAXPATHLEN];  /* Name of the path to export */
	       int  e_flags;		 /* Export flags */
	       uid_t e_rootmap;   /* Map root to this uid (either 0 or -2) */
	       uid_t e_anon;	  /* Map anonymous users to this uid */
	       struct exportfsaddrlist e_rootaddrs;
				  /* List of hosts where root can be mapped
				   * to uid 0 */
	       struct exportfsaddrlist e_writeaddrs;
				  /* List of hosts allowed write access to
				   * read mostly export */
	       int     e_more;	  /* Used in EXPORTFS_READ */ };

       struct exportfsaddrlist {
	       unsigned naddrs;
	       struct sockaddr addrvec[EXMAXADDRS]; };

       The e_path argument is a pointer to a null-terminated string containing the path name of the file system or directory being exported.

       The e_dev, e_ino, and e_gen fields are inputs to the system call for creating an entry. They are returned when an entry is read.

       Security on the exported file systems can be improved by setting the root mapped user ID in, e_rootmap and the anonymous user id in  e_anon
       to  user  id -2. Setting the rootmap field to 0 specifies that all client superusers will be mapped to 0 and thus will have the same rights
       as the local superuser.	Anonymous remote users are those without UNIX credentials and superusers on client systems.   Setting  anon  to  a
       user  id other than -2 will map all anonymous users to that uid. Use of the rootmap field overrides values in e_anon for client superusers.
       Finally, to grant superuser privileges to only a select group of clients, set rootmap to -2 and use the e_rootaddrs  structure  to  specify
       the list of privileged systems.

       The export permissions flags are set in e_flags for the local file system path. The following flags are the only possible flags accepted by
       exportfs:

       #define M_EXRDONLY    /* export read-only */ #define M_EXRDMOSTLY  /* export read-write to hosts  in  e_writeaddrs  */  #define	M_EXPUBLIC
       /* exported for WebNFS public access */ #define M_EXPUBINDEX  /* WebNFS access with index */

       By  default,  exports  are  read-write.	To export a filesystem or directory read-only, set the M_EXRDONLY flag.  To export a filesystem or
       directory read-only to most clients and read-write to a select group, set the  M_EXRDMOSTLY  flag  and  include	the  list  of  clients	in
       e_writeaddrs.

       To export a filesystem or directory for WebNFS public access, set the M_EXPUBLIC flag. Note that only one exported filesystem can have this
       flag set.  By default, the filesystem is exported read-write.

       The M_EXPUBINDEX flag enables the WebNFS server to look for an index.html file when given a directory name. This flag is used  in  conjunc-
       tion with the M_EXPUBLIC flag.

       The  e_more  field  is used in conjunction with the cookie parameter to sequentially read the kernel's export database using EXPORTFS_READ.
       The contents of cookie should be set to zero to read the first record. After reading the record into  exdata,  the  system  call  will  set
       e_more to a non-zero value if there are more records to read and will update the value of cookie. If there are no more records in the data-
       base, e_more will be zero after the system call completes.

       The exportfs system call returns a value of 0 upon successful completion of an operation, and -1 upon failure.

ERRORS

       Not superuser.  Not enough memory in the system to service the request.	Bad address for exdata or cookie.  Access  is  EXPORTFS_CREATE	or
       EXPORTFS_REMOVE	and e_path does not exist, or access is EXPORTFS_REMOVE and e_path is not an exported path, or access is EXPORTFS_READ and
       there are no exportfsdata records to read.  Access is EXPORTFS_CREATE and e_path is an NFS mounted directory.  Only local  directories  can
       be exported.  The exdata pointer is NULL, the cookie value is negative, or the access flag is invalid.

SEE ALSO

       Files:  exports(4)

       Daemons:  mountd(8)

																       exportfs(2)