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  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

       -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 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.

       -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 exports(5) for a description of supported options and access list formats.

       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
       brackets.  For IPv6 network addresses, place the prefix just after the closing 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-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 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  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

       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 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>

                                                30 September 2013                                    exportfs(8)