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exportfs



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

       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.

       exportfs  and  it's  partner program 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.  If this filesystem is not mounted  in  2.6,
       the legacy mode is used.

       In the new mode, exportfs does not give any information to
       the kernel but only provides  it  to  mountd  through  the
       /var/lib/nfs/xtab  file.   mountd  will listen to requests
       from the kernel and will provide information as needed.

       In the legacy mode, 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).
              export  table. Any clients that are active will get
              new entries added by mountd when  they  make  their
              next 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 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,wdelay.

   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


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>

                           18 July 2003               exportfs(8)
  
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