exportfs

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
       /usr/sbin/exportfs -s

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 ker-
       nel, 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 ta-
       ble, 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 re-
       quest will cause an appropriate export entry  for  the  host  given  in
       rmtab to be added to the kernel's export table.

OPTIONS
       -d kind  or  --debug kind
              Turn on debugging. Valid kinds are: all, auth, call, general and
              parse.

       -a     Export or unexport all directories.

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

       -i     Ignore  the /etc/exports file and files under /etc/exports.d di-
              rectory.  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  re-
              moves  entries in /var/lib/nfs/etab which have been deleted from
              /etc/exports or files under /etc/exports.d, and removes any  en-
              tries 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.

       -s     Display the current export list suitable for /etc/exports.

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 ex-
       ports(5) for a description of supported options and  access  list  for-
       mats.

       IPv6  presentation  addresses contain colons, which are already used to
       separate the "host" and "path" command line arguments.  When specifying
       a client using a raw IPv6 address, enclose the address in square brack-
       ets.  For IPv6 network addresses, place the prefix just after the clos-
       ing bracket.

       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-sep-
       arated 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  direc-
       tory.  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 speci-
       fied 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  ex-
       port options for each export.

EXAMPLES
       The following adds all directories listed in /etc/exports and files un-
       der /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/ex-
       ports.d:

       # exportfs -au

       To export the /usr/tmp directory to IPv6 link-local clients:

       # exportfs [fe80::]/64:/usr/tmp

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 mem-
       bers 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>

                               30 September 2013                   exportfs(8)