exportfs(8) System Manager's Manual exportfs(8)
exportfs - maintain table of exported NFS file systems
/usr/sbin/exportfs [-avi] [-o options,..] [client:/path ..]
/usr/sbin/exportfs -r [-v]
/usr/sbin/exportfs [-av] -u [client:/path ..]
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 ker-
nel, 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,
In the legacy mode, exports which identify a specific host, rather than
a subnet or netgroup, are entered directly into the kernel's export ta-
ble, 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.
-a Export or unexport all directories.
Specify a list of export options in the same manner as in
-i Ignore the /etc/exports file and files under /etc/exports.d
directory. Only default options and options given on the com-
mand 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entries from the kernel export table which are no longer valid.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.
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
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 for-
mats. 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-sep-
arated 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.
The third synopsis shows how to unexport a currently exported direc-
tory. 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 speci-
fied 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.
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
# exportfs -au
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 mem-
bers of this group will be checked against the remaining valid exports
and if they themselves are no longer valid they will be removed.
/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
/var/lib/nfs/etab master table of exports
/var/lib/nfs/rmtab table of clients accessing server's exports
exports(5), rpc.mountd(8), netgroup(5)
Olaf Kirch <firstname.lastname@example.org>
Neil Brown <email@example.com>
31 December 2009 exportfs(8)
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