+.\"@(#)exportfs.8"
.\"
-.\" exportfs(8)
-.\"
.\" Copyright (C) 1995 Olaf Kirch <okir@monad.swb.de>
.\" Modifications 1999-2003 Neil Brown <neilb@cse.unsw.edu.au>
-.TH exportfs 8 "18 July 2003"
+.\"
+.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
.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
+However, a system administrator can choose to add or delete
+exports without modifying
+.I /etc/exports
+by using the
.B exportfs
-and it's partner program
-.B mountd
-work in one of two modes, a legacy mode which applies to 2.4 and
+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
+2.6 and later versions, providing the
.B nfsd
virtual filesystem has been mounted at
-.B /proc/fs/nfsd
+.I /proc/fs/nfsd
or
-.BR /proc/fs/nfs .
-If this filesystem is not mounted in 2.6, the legacy mode is used.
-.P
+.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 only provides it to
-.B mountd
+does not give any information to the kernel, but provides it only to
+.B rpc.mountd
through the
-.B /var/lib/nfs/xtab
+.I /var/lib/nfs/etab
file.
-.B mountd
-will listen to requests from the kernel and will provide information
-as needed.
-.P
+.B rpc.mountd
+then manages kernel requests for information about exports, as needed.
+.PP
In the legacy mode,
-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
+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
.B -u
Unexport one or more directories.
.TP
.B -f
-In 'new' mode, flush everything out of the kernels export table. Any
-clients that are active will get new entries added by
-.B mountd
-when they make their next request.
+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 override 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 sync,ro,root_squash,wdelay .
-.\" -------------------- 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 individual 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
+.I /etc/exports
to
-.B /var/lib/nfs/xtab
+.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 no longer valid they will be removed.
-.P
-.\" -------------------- SEE ALSO --------------------------------
+.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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