exportfs
exportfs(8) exportfs(8)
NAME
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 sys-
tems named in /etc/exports by invoking exportfs -a.
However, administrators can choose to add and delete individual file
systems without modifying /etc/exports using exportfs.
Any export requests which identify a specific host (rather than a sub-
net or netgroup etc) are entered directly into the kernel's export ta-
ble 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nel export table which are no longer valid.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.
-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 directory 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 administrator 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 direc-
tory.
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 current 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 entries into
the kernel:
# exportfs -a
To export the /usr/tmp directory to host djando, allowing asyn-
chronous 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 immediately; 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>
7 Sep 1999 exportfs(8)
