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
       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.  Debugging can also be turned on by setting debug= in the
              [exportfs] section of /etc/nfs.conf.


       -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.


CONFIGURATION FILE
       The [exportfs] section of the /etc/nfs.conf configuration file can
       contain a debug value, which can be one or more from the list general,
       call, auth, parse, all.  When a list is given, the members should be
       comma-separated.

       exportfs will also recognize the state-directory-path value from the
       [mountd] section.


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), nfs.conf(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)