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EXPORTS(5)		    BSD	File Formats Manual		    EXPORTS(5)

     exports --	define remote mount points for NFS mount requests


     The exports file specifies	remote mount points for	the NFS	mount protocol
     per the NFS server	specification; see Network File	System Protocol
     Specification, RFC1094, Appendix A	and NFS: Network File System Version 3
     Specification, Appendix I.

     Each line in the file (other than comment lines that begin	with a #)
     specifies the mount point(s) and export flags within one local server
     filesystem	for one	or more	hosts.	A host may be specified	only once for
     each local	filesystem on the server and there may be only one default en-
     try for each server filesystem that applies to all	other hosts.  The lat-
     ter exports the filesystem	to the ``world'' and should be used only when
     the filesystem contains public information.

     In	a mount	entry, the first field(s) specify the directory	path(s)	within
     a server filesystem that can be mounted on	by the corresponding
     client(s).	 There are two forms of	this specification.  The first is to
     list all mount points as absolute directory paths separated by white-
     space.  The second	is to specify the pathname of the root of the filesys-
     tem followed by the -alldirs flag;	this form allows the host(s) to	mount
     at	any point within the filesystem, including regular files if the	-r op-
     tion is used on mountd(8).	 The pathnames must not	have any symbolic
     links in them and should not have any "." or ".." components.  Mount
     points for	a filesystem may appear	on multiple lines each with different
     sets of hosts and export options.

     The second	component of a line specifies how the filesystem is to be ex-
     ported to the host	set.  The option flags specify whether the filesystem
     is	exported read-only or read-write and how the client uid	is mapped to
     user credentials on the server.

     Export options are	specified as follows:

     -maproot=user The credential of the specified user	is used	for remote ac-
     cess by root.  The	credential includes all	the groups to which the	user
     is	a member on the	local machine (see id(1)).  The	user may be specified
     by	name or	number.

     -maproot=user:group1:group2:... The colon separated list is used to spec-
     ify the precise credential	to be used for remote access by	root.  The el-
     ements of the list	may be either names or numbers.	 Note that user:
     should be used to distinguish a credential	containing no groups from a
     complete credential for that user.

     -mapall=user or -mapall=user:group1:group2:... specifies a	mapping	for
     all client	uids (including	root) using the	same semantics as -maproot.

     The option	-r is a	synonym	for -maproot in	an effort to be	backward com-
     patible with older	export file formats.

     In	the absence of -maproot	and -mapall options, remote accesses by	root
     will result in using a credential of -2:-2.  All other users will be
     mapped to their remote credential.	 If a -maproot option is given,	remote
     access by root will be mapped to that credential instead of -2:-2.	 If a
     -mapall option is given, all users	(including root) will be mapped	to
     that credential in	place of their own.

     The -ro option specifies that the filesystem should be exported read-only
     (default read/write).  The	option -o is a synonym for -ro in an effort to
     be	backward compatible with older export file formats.

     WebNFS exports strictly according to the spec (RFC	2054 and RFC 2055) can
     be	done with the -public flag.  However, this flag	in itself allows r/w
     access to all files in the	filesystem, not	requiring reserved ports and
     not remapping uids.  It is	only provided to conform to the	spec, and
     should normally not be used.  For a WebNFS	export,	use the	-webnfs	flag,
     which implies -public, -mapall=nobody and -ro.  Note that only one	file
     system can	be WebNFS exported on a	server.

     A -index=file option can be used to specify a file	whose handle will be
     returned if a directory is	looked up using	the public filehandle
     (WebNFS).	This is	to mimic the behavior of URLs.	If no -index option is
     specified,	a directory filehandle will be returned	as usual.  The -index
     option only makes sense in	combination with the -public or	-webnfs	flags.

     Specifying	the -quiet option will inhibit some of the syslog diagnostics
     for bad lines in /etc/exports.  This can be useful	to avoid annoying er-
     ror messages for known possible problems (see EXAMPLES below).

     The third component of a line specifies the host set to which the line
     applies.  The set may be specified	in three ways.	The first way is to
     list the host name(s) separated by	white space.  (Standard	Internet
     ``dot'' addresses may be used in place of names.)	The second way is to
     specify a ``netgroup'' as defined in the netgroup file (see netgroup(5)).
     The third way is to specify an Internet subnetwork	using a	network	and
     network mask that is defined as the set of	all hosts with addresses
     within the	subnetwork.  This latter approach requires less	overhead
     within the	kernel and is recommended for cases where the export line
     refers to a large number of clients within	an administrative subnet.

     The first two cases are specified by simply listing the name(s) separated
     by	whitespace.  All names are checked to see if they are ``netgroup''
     names first and are assumed to be hostnames otherwise.  Using the full
     domain specification for a	hostname can normally circumvent the problem
     of	a host that has	the same name as a netgroup.  The third	case is	speci-
     fied by the flag -network=netname and optionally -mask=netmask.  If the
     mask is not specified, it will default to the mask	for that network class
     (A, B or C; see inet(4)).	See the	EXAMPLES section below.

     The mountd(8) utility can be made to re-read the exports file by sending
     it	a hangup signal	as follows:

	   kill	-s HUP `cat /var/run/`

     After sending the SIGHUP, check the syslogd(8) output to see whether
     mountd(8) logged any parsing errors in the	exports	file.

     /etc/exports  the default remote mount-point file

	   /usr	/usr/local -maproot=0:10 friends
	   /usr	-maproot=daemon
	   /usr	-ro -mapall=nobody
	   /u -maproot=bin: -network 131.104.48	-mask
	   /u2 -maproot=root friends
	   /u2 -alldirs	-network cis-net -mask cis-mask
	   /cdrom -alldirs,quiet,ro -network -mask

     Given that	/usr, /u and /u2 are local filesystem mount points, the	above
     example specifies the following: /usr is exported to hosts	friends	where
     friends is	specified in the netgroup file with users mapped to their re-
     mote credentials and root mapped to uid 0 and group 10.  It is exported
     read-write	and the	hosts in ``friends'' can mount either /usr or /usr/lo-
     cal.  It is exported to and with
     users mapped to their remote credentials and root mapped to the user and
     groups associated with ``daemon'';	it is exported to the rest of the
     world as read-only	with all users mapped to the user and groups associ-
     ated with ``nobody''.

     /u	is exported to all hosts on the	subnetwork 131.104.48 with root	mapped
     to	the uid	for ``bin'' and	with no	group access.

     /u2 is exported to	the hosts in ``friends'' with root mapped to uid and
     groups associated with ``root''; it is exported to	all hosts on network
     ``cis-net'' allowing mounts at any	directory within /u2.

     The filesystem rooted at /cdrom will exported read-only to	the entire
     network, including	all its	subdirectories.	 Since /cdrom
     is	the conventional mountpoint for	a CD-ROM device, this export will fail
     if	no CD-ROM medium is currently mounted there since that line would then
     attempt to	export a subdirectory of the root filesystem with the -alldirs
     option which is not allowed.  The -quiet option will then suppress	the
     error message for this condition that would normally be syslogged.	 As
     soon as an	actual CD-ROM is going to be mounted, mount(8) will notify
     mountd(8) about this situation, and the /cdrom filesystem will be ex-
     ported as intented.  Note that without using the -alldirs option, the ex-
     port would	always succeed.	 While there is	no CD-ROM medium mounted under
     /cdrom, it	would export the (normally empty) directory /cdrom of the root
     filesystem	instead.

     netgroup(5), mountd(8), nfsd(8), showmount(8)

     The export	options	are tied to the	local mount points in the kernel and
     must be non-contradictory for any exported	subdirectory of	the local
     server mount point.  It is	recommended that all exported directories
     within the	same server filesystem be specified on adjacent	lines going
     down the tree.  You cannot	specify	a hostname that	is also	the name of a
     netgroup.	Specifying the full domain specification for a hostname	can
     normally circumvent the problem.

BSD				March 29, 1995				   BSD


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