exportfs(8) exportfs(8)
NAME
exportfs - maintain list of NFS exported file systems
SYNOPSIS
/usr/sbin/exportfs [-av] [-o options,..] [client:/path ..]
/usr/sbin/exportfs [-rv] [-o options,..] [client:/path ..]
/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. Normally, this
file is initialized with the list of all file systems
named in /etc/exports by invoking exportfs -a, and modi-
fied by mountd(8) whenever receiving a mount request from
a host that is matched by a network or domain export.
However, administrators can choose to add and delete indi-
vidual file systems without modifying /etc/exports using
exportfs.
OPTIONS
-a Export or unexport all directories.
-o options,...
Specify a list of export options in the same manner
as in exports(5).
-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.
-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 direc-
tory to the world, simply specify /path.
The export options for a particular host/directory pair
derive from several sources. The set of default options
can be overridden by entries in /usr/etc/exports and
/var/lib/nfs/xtab, if they exists. 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 directory.
Modifications of the kernel export table used by nfsd(8)
take place immediately after parsing the command line and
updating the xtab file.
Unexporting Directories
The second 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.
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
entries into the kernel:
# exportfs -a
To export the /usr/tmp directory to host djando, allowing
asynchronous writes, one would do this:
# exportfs django:/usr/tmp -o async
If the directory was already exported,
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 xtab across reboots.
When unexporting a network or domain entry, any current
exports to members of this group are unaffected. The rea-
son for this is that exportfs cannot tell whether these
specific exports were created as a result of the group
export, or whether they have been exported independently.
SEE ALSO
exports(5), mountd(8)
AUTHOR
Olaf Kirch, <okir@monad.swb.de>
15 Feb 1996 1