+.\"@(#)exportfs.8"
.\"
-.\" exportfs(8)
-.\"
.\" Copyright (C) 1995 Olaf Kirch <okir@monad.swb.de>
-.\" Modifications 1999 Neil Brown <neilb@cse.unsw.edu.au>
-.TH exportfs 8 "7 Sep 1999"
+.\" Modifications 1999-2003 Neil Brown <neilb@cse.unsw.edu.au>
+.\"
+.TH exportfs 8 "31 December 2009"
.SH NAME
-exportfs \- maintain list of NFS exported file systems
+exportfs \- maintain table of exported NFS file systems
.SH SYNOPSIS
.BI "/usr/sbin/exportfs [-avi] [-o " "options,.." "] [" "client:/path" " ..]
.br
.br
.BI "/usr/sbin/exportfs [-v]
.br
+.BI "/usr/sbin/exportfs -f"
+.br
.SH 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
+.IR "exported file system" ,
+or
+.IR export ,
+for short.
+.PP
The
.B exportfs
-command is used to maintain the current table of exported file systems for
-NFS. This list is kept in a separate file named
-.BR /var/lib/nfs/xtab
-which is read by
-.B 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.
-.P
-Normally this
-.B xtab
-file is initialized with the list of all file systems named in
-.B /etc/exports
+command maintains the current table of exports for the NFS server.
+The master export table is kept in a file named
+.IR /var/lib/nfs/etab .
+This file is read by
+.B rpc.mountd
+when a client sends an NFS MOUNT request.
+.PP
+Normally the master export table is initialized with the contents of
+.I /etc/exports
by invoking
.BR "exportfs -a" .
-.P
-However, administrators can choose to add and delete individual file systems
-without modifying
-.B /etc/exports
-using
-.BR exportfs .
-.P
-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
-.BR /var/lib/nfs/xtab .
-Further, any mount points listed in
-.B /var/lib/nfs/rmtab
+However, a system administrator can choose to add or delete
+exports without modifying
+.I /etc/exports
+by using the
+.B exportfs
+command.
+.PP
+.B exportfs
+and its partner program
+.B 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
+.B nfsd
+virtual filesystem has been mounted at
+.I /proc/fs/nfsd
+or
+.IR /proc/fs/nfs .
+On 2.6 kernels, if this filesystem is not mounted, the legacy mode is used.
+.PP
+In the new mode,
+.B exportfs
+does not give any information to the kernel, but provides it only to
+.B rpc.mountd
+through the
+.I /var/lib/nfs/etab
+file.
+.B rpc.mountd
+then manages kernel requests for information about exports, as needed.
+.PP
+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
+.IR /var/lib/nfs/etab .
+Further, exports listed in
+.I /var/lib/nfs/rmtab
which match a non host-specific export request will cause an
appropriate export entry for the host given in
-.B rmtab
-to be entered
-into the kernel's export table.
+.I rmtab
+to be added to the kernel's export table.
.SH OPTIONS
-.TP
+.TP
.B -a
Export or unexport all directories.
.TP
.BI "-o " options,...
Specify a list of export options in the same manner as in
-.BR exports(5) .
+.BR exports (5).
.TP
.B -i
Ignore the
-.B /etc/exports
-file, so that only default options and options given on the command
-line are used.
+.I /etc/exports
+file. Only default options and options given on the command line are used.
.TP
.B -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
+Reexport all directories, synchronizing
+.I /var/lib/nfs/etab
+with
+.IR /etc/exports .
+This option removes entries in
+.I /var/lib/nfs/etab
+which have been deleted from
+.I /etc/exports, and removes any entries from the
kernel export table which are no longer valid.
.TP
-.TP
.B -u
Unexport one or more directories.
.TP
+.B -f
+If
+.I /proc/fs/nfsd
+or
+.I /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
+.B rpc.mountd
+when they make their next NFS mount request.
+.TP
.B -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.
.SH DISCUSSION
-.\" -------------------- Exporting Directories --------------------
.SS Exporting Directories
-The first synopsis shows how to invoke the command when adding new
-entries to the export table. When using
+The first synopsis shows how to invoke
+.B exportfs
+when adding new entries to the export table. When using
.BR "exportfs -a" ,
-all directories in
-.B exports(5)
+all exports listed in
+.I /etc/exports
are added to
-.B xtab
-and the resulting list is pushed into the kernel.
-.P
+.IR /var/lib/nfs/etab .
+The kernel's export table is also updated as needed.
+.PP
The
.I host:/path
-argument specifies the directory to export along with the host or hosts to
-export it to. All formats described in
+argument specifies a local directory to export,
+along with the client or clients who are permitted to access it.
+See
.B exports(5)
-are supported; to export a directory to the world, simply specify
+for a description of supported options and access list formats.
+To export a directory to the world, simply specify
.IR :/path .
-.P
+.PP
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
-.B /etc/exports
-(unless the
-.B -i
-option is given).
-In addition, the administrator may overide any options from these sources
-using the
+several sources.
+The default export options are
+.BR sync,ro,root_squash,wdelay .
+These can be overridden by entries in
+.IR /etc/exports .
+.PP
+A system administrator may override options from these sources using the
.B -o
-argument which takes a comma-separated list of options in the same fashion
+command-line option on
+.BR exportfs .
+This option takes a comma-separated list of options in the same fashion
as one would specify them in
-.BR exports(5) .
-Thus,
+.IR /etc/exports .
+In this way
.B exportfs
-can also be used to modify the export options of an already exported
-directory.
-.P
-Modifications of the kernel export table used by
-.B nfsd(8)
-take place immediately after parsing the command line and updating the
-.B xtab
-file.
-.P
-The default export options are
-.BR async,ro,root_squash,no_delay .
-.\" -------------------- Unexporting Directories ------------------
+can be used to modify the export options of an already exported directory.
.SS Unexporting Directories
The third synopsis shows how to unexported a currently exported directory.
When using
.BR "exportfs -ua" ,
all entries listed in
-.B xtab
+.I /var/lib/nfs/etab
are removed from the kernel export tables, and the file is cleared. This
effectively shuts down all NFS activity.
-.P
-To remove individial export entries, one can specify a
+.PP
+To remove an export, specify a
.I host:/path
pair. This deletes the specified entry from
-.B xtab
+.I /var/lib/nfs/etab
and removes the corresponding kernel entry (if any).
-.P
-.\" -------------------- Dumping the Export Table -----------------
-.SS Dumping the Export Table
+.PP
+.SS Dumping the Export Table
Invoking
.B exportfs
-without further options shows the current list of exported file systems.
-When giving the
+without options shows the current list of exported file systems.
+Adding the
.B -v
-option, the list of flags pertaining to each export are shown in addition.
-.\" -------------------- EXAMPLES ---------------------------------
+option causes
+.B exportfs
+to display the export options for each export.
.SH EXAMPLES
The following adds all directories listed in
-.B /etc/exports to /var/lib/nfs/xtab
+.I /etc/exports
+to
+.I /var/lib/nfs/etab
and pushes the resulting export entries into the kernel:
-.P
+.PP
.nf
.B "# exportfs -a
.fi
-.P
+.PP
To export the
-.B /usr/tmp
-directory to host
-.BR djando ,
-allowing asynchronous writes, one would do this:
-.P
+.I /usr/tmp
+directory to host
+.BR django ,
+allowing insecure file locking requests from clients:
+.PP
+.nf
+.B "# exportfs -o insecure_locks django:/usr/tmp
+.fi
+.PP
+To unexport the
+.I /usr/tmp
+directory:
+.PP
+.nf
+.B "# exportfs -u django:/usr/tmp
+.fi
+.PP
+To unexport all exports listed in
+.IR /etc/exports :
+.PP
.nf
-.B "# exportfs -o async django:/usr/tmp
+.B "# exportfs -au
.fi
-.\" -------------------- DEPENDENCIES -----------------------------
-.SH 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
-.B mountd(8)
+.SH 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
+.BR rpc.mountd (8)
to grant any mount requests from these clients.
-This is usually not a big problem, because any existing mounts are preserved
-in
-.B rmtab
+This is usually not a problem, because any existing mounts are preserved in
+.I rmtab
across reboots.
-.P
+.PP
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.
-.P
-.\" -------------------- SEE ALSO --------------------------------
+if they themselves are no longer valid they will be removed.
+.SH FILES
+.TP 2.5i
+.I /etc/exports
+input file listing exports, export options, and access control lists
+.TP 2.5i
+.I /var/lib/nfs/etab
+master table of exports
+.TP 2.5i
+.I /var/lib/nfs/rmtab
+table of clients accessing server's exports
.SH SEE ALSO
-.BR exports(5) ", " mountd(8)
-.\" -------------------- AUTHOR ----------------------------------
+.BR exports (5),
+.BR rpc.mountd (8),
+.BR netgroup (5)
.SH AUTHORS
-Olaf Kirch, <okir@monad.swb.de>
+Olaf Kirch <okir@monad.swb.de>
.br
-Neil Brown, <neilb@cse.unsw.edu.au>
-
+Neil Brown <neilb@cse.unsw.edu.au>
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