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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  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 permit-
       ted 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  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 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 immedi-
       ately.   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 <okirATmonad.de>
       Neil Brown <neilbATcse.au>



                               31 December 2009                    exportfs(8)