exportfs(8)                                                                                                          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 by invoking exportfs -a.  However, a
       system administrator can choose to add or delete exports without modifying /etc/exports 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 ver-
       sions  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.  Only default options and options given on the command line are used.

       -r     Reexport  all  directories,  synchronizing  /var/lib/nfs/etab  with  /etc/exports.  This option removes entries in
              /var/lib/nfs/etab which have been deleted from /etc/exports, 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 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.

       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 unexported 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 kernel 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 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:

       # 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 usu-
       ally 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

       /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 <okirATmonad.de>
       Neil Brown <neilbATcse.au>



                                                        31 December 2009                                             exportfs(8)