xref: /freebsd/usr.sbin/mountd/exports.5 (revision 6780ab54325a71e7e70112b11657973edde8655e)
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32.\"     @(#)exports.5	8.3 (Berkeley) 3/29/95
33.\" $FreeBSD$
34.\"
35.Dd March 29, 1995
36.Dt EXPORTS 5
37.Os
38.Sh NAME
39.Nm exports
40.Nd define remote mount points for
41.Tn NFS
42mount requests
43.Sh SYNOPSIS
44.Nm
45.Sh DESCRIPTION
46The
47.Nm
48file specifies remote mount points for the
49.Tn NFS
50mount protocol per the
51.Tn NFS
52server specification; see
53.%T "Network File System Protocol Specification" ,
54RFC1094, Appendix A and
55.%T "NFS: Network File System Version 3 Specification" ,
56Appendix I.
57.Pp
58Each line in the file
59(other than comment lines that begin with a #)
60specifies the mount point(s) and export flags within one local server
61file system for one or more hosts.
62A long line may be split over several lines by ending all but the
63last line with a backslash
64.Pq Ql \e .
65A host may be specified only once for each local file system on the
66server and there may be only one default entry for each server
67file system that applies to all other hosts.
68The latter exports the file system to the ``world'' and should
69be used only when the file system contains public information.
70.Pp
71In a mount entry,
72the first field(s) specify the directory path(s) within a server file system
73that can be mounted on by the corresponding client(s).
74There are two forms of this specification.
75The first is to list all mount points as absolute
76directory paths separated by whitespace.
77The second is to specify the pathname of the root of the file system
78followed by the
79.Fl alldirs
80flag;
81this form allows the host(s) to mount at any point within the file system,
82including regular files if the
83.Fl r
84option is used on
85.Xr mountd 8 .
86The pathnames must not have any symbolic links in them and should not have
87any "." or ".." components.
88Mount points for a file system may appear on multiple lines each with
89different sets of hosts and export options.
90.Pp
91The second component of a line specifies how the file system is to be
92exported to the host set.
93The option flags specify whether the file system
94is exported read-only or read-write and how the client uid is mapped to
95user credentials on the server.
96.Pp
97Export options are specified as follows:
98.Pp
99.Sm off
100.Fl maproot No = Sy user
101.Sm on
102The credential of the specified user is used for remote access by root.
103The credential includes all the groups to which the user is a member
104on the local machine (see
105.Xr id 1 ) .
106The user may be specified by name or number.
107.Pp
108.Sm off
109.Fl maproot No = Sy user:group1:group2:...
110.Sm on
111The colon separated list is used to specify the precise credential
112to be used for remote access by root.
113The elements of the list may be either names or numbers.
114Note that user: should be used to distinguish a credential containing
115no groups from a complete credential for that user.
116.Pp
117.Sm off
118.Fl mapall No = Sy user
119.Sm on
120or
121.Sm off
122.Fl mapall No = Sy user:group1:group2:...
123.Sm on
124specifies a mapping for all client uids (including root)
125using the same semantics as
126.Fl maproot .
127.Pp
128The option
129.Fl r
130is a synonym for
131.Fl maproot
132in an effort to be backward compatible with older export file formats.
133.Pp
134In the absence of
135.Fl maproot
136and
137.Fl mapall
138options, remote accesses by root will result in using a credential of -2:-2.
139All other users will be mapped to their remote credential.
140If a
141.Fl maproot
142option is given,
143remote access by root will be mapped to that credential instead of -2:-2.
144If a
145.Fl mapall
146option is given,
147all users (including root) will be mapped to that credential in
148place of their own.
149.Pp
150The
151.Fl ro
152option specifies that the file system should be exported read-only
153(default read/write).
154The option
155.Fl o
156is a synonym for
157.Fl ro
158in an effort to be backward compatible with older export file formats.
159.Pp
160.Tn WebNFS
161exports strictly according to the spec (RFC 2054 and RFC 2055) can
162be done with the
163.Fl public
164flag.
165However, this flag in itself allows r/w access to all files in
166the file system, not requiring reserved ports and not remapping uids.
167It
168is only provided to conform to the spec, and should normally not be used.
169For a
170.Tn WebNFS
171export,
172use the
173.Fl webnfs
174flag, which implies
175.Fl public ,
176.Sm off
177.Fl mapall No = Sy nobody
178.Sm on
179and
180.Fl ro .
181.Pp
182A
183.Sm off
184.Fl index No = Sy file
185.Sm on
186option can be used to specify a file whose handle will be returned if
187a directory is looked up using the public filehandle
188.Pq Tn WebNFS .
189This is to mimic the behavior of URLs.
190If no
191.Fl index
192option is specified, a directory filehandle will be returned as usual.
193The
194.Fl index
195option only makes sense in combination with the
196.Fl public
197or
198.Fl webnfs
199flags.
200.Pp
201Specifying the
202.Fl quiet
203option will inhibit some of the syslog diagnostics for bad lines in
204.Pa /etc/exports .
205This can be useful to avoid annoying error messages for known possible
206problems (see
207.Sx EXAMPLES
208below).
209.Pp
210The third component of a line specifies the host set to which the line applies.
211The set may be specified in three ways.
212The first way is to list the host name(s) separated by white space.
213(Standard Internet ``dot'' addresses may be used in place of names.)
214The second way is to specify a ``netgroup'' as defined in the netgroup file (see
215.Xr netgroup 5 ) .
216The third way is to specify an Internet subnetwork using a network and
217network mask that is defined as the set of all hosts with addresses within
218the subnetwork.
219This latter approach requires less overhead within the
220kernel and is recommended for cases where the export line refers to a
221large number of clients within an administrative subnet.
222.Pp
223The first two cases are specified by simply listing the name(s) separated
224by whitespace.
225All names are checked to see if they are ``netgroup'' names
226first and are assumed to be hostnames otherwise.
227Using the full domain specification for a hostname can normally
228circumvent the problem of a host that has the same name as a netgroup.
229The third case is specified by the flag
230.Sm off
231.Fl network No = Sy netname
232.Sm on
233and optionally
234.Sm off
235.Fl mask No = Sy netmask .
236.Sm on
237If the mask is not specified, it will default to the mask for that network
238class (A, B or C; see
239.Xr inet 4 ) .
240See the
241.Sx EXAMPLES
242section below.
243.Pp
244The
245.Xr mountd 8
246utility can be made to re-read the
247.Nm
248file by sending it a hangup signal as follows:
249.Bd -literal -offset indent
250kill -s HUP `cat /var/run/mountd.pid`
251.Ed
252.Pp
253After sending the
254.Dv SIGHUP ,
255check the
256.Xr syslogd 8
257output to see whether
258.Xr mountd 8
259logged any parsing errors in the
260.Nm
261file.
262.Sh FILES
263.Bl -tag -width /etc/exports -compact
264.It Pa /etc/exports
265the default remote mount-point file
266.El
267.Sh EXAMPLES
268.Bd -literal -offset indent
269/usr /usr/local -maproot=0:10 friends
270/usr -maproot=daemon grumpy.cis.uoguelph.ca 131.104.48.16
271/usr -ro -mapall=nobody
272/u -maproot=bin: -network 131.104.48 -mask 255.255.255.0
273/u2 -maproot=root friends
274/u2 -alldirs -network cis-net -mask cis-mask
275/cdrom -alldirs,quiet,ro -network 192.168.33.0 -mask 255.255.255.0
276.Ed
277.Pp
278Given that
279.Sy /usr ,
280.Sy /u
281and
282.Sy /u2
283are
284local file system mount points, the above example specifies the following:
285.Sy /usr
286is exported to hosts
287.Em friends
288where friends is specified in the netgroup file
289with users mapped to their remote credentials and
290root mapped to uid 0 and group 10.
291It is exported read-write and the hosts in ``friends'' can mount either /usr
292or /usr/local.
293It is exported to
294.Em 131.104.48.16
295and
296.Em grumpy.cis.uoguelph.ca
297with users mapped to their remote credentials and
298root mapped to the user and groups associated with ``daemon'';
299it is exported to the rest of the world as read-only with
300all users mapped to the user and groups associated with ``nobody''.
301.Pp
302.Sy /u
303is exported to all hosts on the subnetwork
304.Em 131.104.48
305with root mapped to the uid for ``bin'' and with no group access.
306.Pp
307.Sy /u2
308is exported to the hosts in ``friends'' with root mapped to uid and groups
309associated with ``root'';
310it is exported to all hosts on network ``cis-net'' allowing mounts at any
311directory within /u2.
312.Pp
313The file system rooted at
314.Sy /cdrom
315will exported read-only to the entire network 192.168.33.0/24, including
316all its subdirectories.
317Since
318.Sy /cdrom
319is the conventional mountpoint for a CD-ROM device, this export will
320fail if no CD-ROM medium is currently mounted there since that line
321would then attempt to export a subdirectory of the root file system
322with the
323.Fl alldirs
324option which is not allowed.
325The
326.Fl quiet
327option will then suppress the error message for this condition that
328would normally be syslogged.
329As soon as an actual CD-ROM is going to be mounted,
330.Xr mount 8
331will notify
332.Xr mountd 8
333about this situation, and the
334.Sy /cdrom
335file system will be exported as intended.
336Note that without using the
337.Fl alldirs
338option, the export would always succeed.
339While there is no CD-ROM medium mounted under
340.Sy /cdrom ,
341it would export the (normally empty) directory
342.Sy /cdrom
343of the root file system instead.
344.Sh SEE ALSO
345.Xr netgroup 5 ,
346.Xr mountd 8 ,
347.Xr nfsd 8 ,
348.Xr showmount 8
349.Sh BUGS
350The export options are tied to the local mount points in the kernel and
351must be non-contradictory for any exported subdirectory of the local
352server mount point.
353It is recommended that all exported directories within the same server
354file system be specified on adjacent lines going down the tree.
355You cannot specify a hostname that is also the name of a netgroup.
356Specifying the full domain specification for a hostname can normally
357circumvent the problem.
358