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

NAME

       exportfs - maintain table of exported NFS file systems

SYNOPSIS

       /usr/sbin/exportfs [-avi] [-o options,..] [client:/path ..]
       /usr/sbin/exportfs -r [-v]
       /usr/sbin/exportfs [-av] -u [client:/path ..]
       /usr/sbin/exportfs [-v]
       /usr/sbin/exportfs -f

DESCRIPTION

       An  NFS	server	maintains  a  table  of local physical file systems that are accessible to NFS clients.  Each file system in this table is
       referred to as an exported file system, or export, for short.

       The exportfs command maintains the current table of exports for the NFS	server.   The  master  export  table  is  kept	in  a  file  named
       /var/lib/nfs/etab.  This file is read by rpc.mountd when a client sends an NFS MOUNT request.

       Normally  the  master export table is initialized with the contents of /etc/exports and files under /etc/exports.d by invoking exportfs -a.
       However, a system administrator can choose to add or delete exports without modifying /etc/exports or files under /etc/exports.d  by  using
       the exportfs command.

       exportfs  and its partner program rpc.mountd work in one of two modes: a legacy mode which applies to 2.4 and earlier versions of the Linux
       kernel, and a new mode which applies to 2.6 and later versions, providing the nfsd virtual filesystem has been mounted at /proc/fs/nfsd	or
       /proc/fs/nfs.  On 2.6 kernels, if this filesystem is not mounted, the legacy mode is used.

       In  the	new  mode,  exportfs does not give any information to the kernel, but provides it only to rpc.mountd through the /var/lib/nfs/etab
       file.  rpc.mountd then manages kernel requests for information about exports, as needed.

       In the legacy mode, exports which identify a specific host, rather than a subnet or netgroup, are entered directly into the kernel's export
       table, as well as being written to /var/lib/nfs/etab.  Further, exports listed in /var/lib/nfs/rmtab which match a non host-specific export
       request will cause an appropriate export entry for the host given in rmtab to be added to the kernel's export table.

OPTIONS

       -a     Export or unexport all directories.

       -o options,...
	      Specify a list of export options in the same manner as in exports(5).

       -i     Ignore the /etc/exports file and files under /etc/exports.d directory.  Only default options and options given on the  command  line
	      are used.

       -r     Reexport	all  directories,  synchronizing  /var/lib/nfs/etab with /etc/exports and files under /etc/exports.d.  This option removes
	      entries in /var/lib/nfs/etab which have been deleted from /etc/exports or files under /etc/exports.d, and removes any  entries  from
	      the kernel export table which are no longer valid.

       -u     Unexport one or more directories.

       -f     If  /proc/fs/nfsd  or  /proc/fs/nfs is mounted, flush everything out of the kernel's export table.  Fresh entries for active clients
	      are added to the kernel's export table by rpc.mountd when they make their next NFS mount request.

       -v     Be verbose. When exporting or unexporting, show what's going on. When displaying the current export list, also display the  list	of
	      export options.

DISCUSSION

   Exporting Directories
       The first synopsis shows how to invoke exportfs when adding new entries to the export table.  When using exportfs -a, all exports listed in
       /etc/exports and files under /etc/exports.d are added to /var/lib/nfs/etab.  The kernel's export table is also updated as needed.

       The host:/path argument specifies a local directory to export, along with the client or clients	who  are  permitted  to  access  it.   See
       exports(5) for a description of supported options and access list formats.  To export a directory to the world, simply specify :/path.

       The   export   options	for   a   particular   host/directory	pair  derive  from  several  sources.	The  default  export  options  are
       sync,ro,root_squash,wdelay.  These can be overridden by entries in /etc/exports or files under /etc/exports.d.

       A system administrator may override options from these sources using the -o command-line option on exportfs.  This option  takes  a  comma-
       separated  list	of  options in the same fashion as one would specify them in /etc/exports.  In this way exportfs can be used to modify the
       export options of an already exported directory.

   Unexporting Directories
       The third synopsis shows how to unexport a currently exported directory.  When using exportfs -ua, all entries listed in  /var/lib/nfs/etab
       are removed from the kernel export tables, and the file is cleared. This effectively shuts down all NFS activity.

       To  remove an export, specify a host:/path pair. This deletes the specified entry from /var/lib/nfs/etab and removes the corresponding ker-
       nel entry (if any).

   Dumping the Export Table
       Invoking exportfs without options shows the current list of exported file systems.  Adding the -v option causes	exportfs  to  display  the
       export options for each export.

EXAMPLES

       The  following  adds  all  directories  listed in /etc/exports and files under /etc/exports.d to /var/lib/nfs/etab and pushes the resulting
       export entries into the kernel:

       # exportfs -a

       To export the /usr/tmp directory to host django, allowing insecure file locking requests from clients:

       # exportfs -o insecure_locks django:/usr/tmp

       To unexport the /usr/tmp directory:

       # exportfs -u django:/usr/tmp

       To unexport all exports listed in /etc/exports and files under /etc/exports.d:

       # exportfs -au

USAGE NOTES

       Exporting to IP networks or DNS and NIS domains does not enable clients from these groups to access NFS immediately.  Rather,  these  sorts
       of  exports are hints to rpc.mountd(8) to grant any mount requests from these clients.  This is usually not a problem, because any existing
       mounts are preserved in rmtab across reboots.

       When unexporting a network or domain entry, any current exports to members of this group  will  be  checked  against  the  remaining  valid
       exports and if they themselves are no longer valid they will be removed.

FILES

       /etc/exports		input file listing exports, export options, and access control lists

       /etc/exports.d		directory where extra input files are stored.  Note: only files that end with .exports are used.

       /var/lib/nfs/etab	master table of exports

       /var/lib/nfs/rmtab	table of clients accessing server's exports

SEE ALSO

       exports(5), rpc.mountd(8), netgroup(5)

AUTHORS

       Olaf Kirch <okir@monad.swb.de>
       Neil Brown <neilb@cse.unsw.edu.au>

								 31 December 2009						       exportfs(8)