exportfs - maintain list of NFS exported 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]


DESCRIPTION

       The exportfs command is used to maintain the current table
       of  exported  file systems for NFS. This list is kept in a
       separate file named /var/lib/nfs/xtab  which  is  read  by
       mountd  when a remote host requests access to mount a file
       tree, and parts of the list which are active are  kept  in
       the kernel's export table.

       Normally  this  xtab  file is initialized with the list of
       all  file  systems  named  in  /etc/exports  by   invoking
       exportfs -a.

       However, administrators can choose to add and delete indi­
       vidual file systems without modifying  /etc/exports  using
       exportfs.

       Any export requests which identify a specific host (rather
       than a subnet or netgroup etc) are entered  directly  into
       the  kernel's  export  table  as  well as being written to
       /var/lib/nfs/xtab.  Further, any mount  points  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 entered into 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, so that only default
              options and options given on the command  line  are
              used.

       -r     Reexport    all    directories.   It   synchronizes
              /var/lib/nfs/xtab  with  /etc/exports.  It  removes
              entries in /var/lib/nfs/xtab which are deleted from
              /etc/exports, and remove any entries from the  ker­
              nel export table which are no longer valid.

       -u     Unexport one or more directories.

              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 the command when
       adding new  entries  to  the  export  table.   When  using
       exportfs  -a,  all  directories in exports(5) are added to
       xtab and the resulting list is pushed into the kernel.

       The host:/path argument specifies the directory to  export
       along  with the host or hosts to export it to. All formats
       described in exports(5) are supported; to export a  direc­
       tory to the world, simply specify :/path.

       The  export  options  for a particular host/directory pair
       derive from several sources.  There is a  set  of  default
       options which can be overridden by entries in /etc/exports
       (unless the -i option is given).  In addition, the  admin­
       istrator  may overide any options from these sources using
       the -o argument which  takes  a  comma-separated  list  of
       options  in  the same fashion as one would specify them in
       exports(5).  Thus, exportfs can also be used to modify the
       export options of an already exported directory.

       Modifications  of  the kernel export table used by nfsd(8)
       take place immediately after parsing the command line  and
       updating the xtab file.

       The        default        export        options        are
       sync,ro,root_squash,no_delay.

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

       To remove individial export entries,  one  can  specify  a
       host:/path  pair.  This  deletes  the specified entry from
       xtab and removes the corresponding kernel entry (if  any).

   Dumping the Export Table
       Invoking  exportfs  without further options shows the cur­
       rent list of exported file systems.  When  giving  the  -v
       option,  the  list  of flags pertaining to each export are
       shown in addition.


EXAMPLES

       The following adds all directories listed in  /etc/exports
       to  /var/lib/nfs/xtab  and  pushes  the  resulting  export


       # exportfs -a

       To export the /usr/tmp directory to host djando,  allowing
       asynchronous writes, one would do this:

       # exportfs -o async django:/usr/tmp


DEPENDENCIES

       Exporting  to  IP  networks,  DNS and NIS domains does not
       enable clients from these groups  to  access  NFS  immedi­
       ately;  rather,  these  sorts  of  exports  are  hints  to
       mountd(8) to grant any mount requests from these  clients.
       This  is  usually  not a big 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
       nolonger valid they will be removed.


SEE ALSO

       exports(5), mountd(8)


AUTHORS

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


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