xref: /freebsd/sbin/mount_nfs/mount_nfs.8 (revision acd3428b7d3e94cef0e1881c868cb4b131d4ff41)
1.\" Copyright (c) 1992, 1993, 1994, 1995
2.\"	The Regents of the University of California.  All rights reserved.
3.\"
4.\" Redistribution and use in source and binary forms, with or without
5.\" modification, are permitted provided that the following conditions
6.\" are met:
7.\" 1. Redistributions of source code must retain the above copyright
8.\"    notice, this list of conditions and the following disclaimer.
9.\" 2. Redistributions in binary form must reproduce the above copyright
10.\"    notice, this list of conditions and the following disclaimer in the
11.\"    documentation and/or other materials provided with the distribution.
12.\" 4. Neither the name of the University nor the names of its contributors
13.\"    may be used to endorse or promote products derived from this software
14.\"    without specific prior written permission.
15.\"
16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26.\" SUCH DAMAGE.
27.\"
28.\"	@(#)mount_nfs.8	8.3 (Berkeley) 3/29/95
29.\" $FreeBSD$
30.\"
31.Dd December 25, 2005
32.Dt MOUNT_NFS 8
33.Os
34.Sh NAME
35.Nm mount_nfs
36.Nd mount NFS file systems
37.Sh SYNOPSIS
38.Nm
39.Op Fl 23bcdiLlNPsTU
40.Op Fl a Ar maxreadahead
41.Op Fl D Ar deadthresh
42.Op Fl g Ar maxgroups
43.Op Fl I Ar readdirsize
44.Op Fl o Ar options
45.Op Fl R Ar retrycnt
46.Op Fl r Ar readsize
47.Op Fl t Ar timeout
48.Op Fl w Ar writesize
49.Op Fl x Ar retrans
50.Ar rhost : Ns Ar path node
51.Sh DESCRIPTION
52The
53.Nm
54utility calls the
55.Xr mount 2
56system call to prepare and graft a remote NFS file system
57.Pq Ar rhost : Ns Ar path
58on to the file system tree at the point
59.Ar node .
60This command is normally executed by
61.Xr mount 8 .
62It implements the mount protocol as described in RFC 1094, Appendix A and
63.%T "NFS: Network File System Version 3 Protocol Specification" ,
64Appendix I.
65.Pp
66By default,
67.Nm
68keeps retrying until the mount succeeds.
69This behaviour is intended for file systems listed in
70.Xr fstab 5
71that are critical to the boot process.
72For non-critical file systems, the
73.Fl b
74and
75.Fl R
76flags provide mechanisms to prevent the boot process from hanging
77if the server is unavailable.
78.Pp
79If the server becomes unresponsive while an NFS file system is
80mounted, any new or outstanding file operations on that file system
81will hang uninterruptibly until the server comes back.
82To modify this default behaviour, see the
83.Fl i
84and
85.Fl s
86flags.
87.Pp
88The options are:
89.Bl -tag -width indent
90.It Fl 2
91Use the NFS Version 2 protocol (the default is to try version 3 first
92then version 2).
93Note that NFS version 2 has a file size limit of 2 gigabytes.
94.It Fl 3
95Use the NFS Version 3 protocol.
96.It Fl D
97Set the
98.Dq "dead server threshold"
99to the specified number of round trip timeout intervals before a
100.Dq "server not responding"
101message is displayed.
102.It Fl I
103Set the readdir read size to the specified value.
104The value should normally
105be a multiple of
106.Dv DIRBLKSIZ
107that is <= the read size for the mount.
108.It Fl L
109Do
110.Em not
111forward
112.Xr fcntl 2
113locks over the wire.
114All locks will be local and not seen by the server
115and likewise not seen by other NFS clients.
116This removes the need to run the
117.Xr rpcbind 8
118service and the
119.Xr rpc.statd 8
120and
121.Xr rpc.lockd 8
122servers on the client.
123Note that this option will only be honored when performing the
124initial mount, it will be silently ignored if used while updating
125the mount options.
126.It Fl N
127Do
128.Em not
129use a reserved socket port number (see below).
130.It Fl P
131Use a reserved socket port number.
132This flag is obsolete, and only retained for compatibility reasons.
133Reserved port numbers are used by default now.
134(For the rare case where the client has a trusted root account
135but untrustworthy users and the network cables are in secure areas this does
136help, but for normal desktop clients this does not apply.)
137.It Fl R
138Set the mount retry count to the specified value.
139The default is a retry count of zero, which means to keep retrying
140forever.
141There is a 60 second delay between each attempt.
142.It Fl T
143Use TCP transport instead of UDP.
144This is recommended for servers that are not on the same LAN cable as
145the client.
146Not all NFS servers support this method, especially older ones;
147caution should be observed in these cases.
148.It Fl U
149Force the mount protocol to use UDP transport, even for TCP NFS mounts.
150(Necessary for some old
151.Bx
152servers.)
153.It Fl a
154Set the read-ahead count to the specified value.
155This may be in the range of 0 - 4, and determines how many blocks
156will be read ahead when a large file is being read sequentially.
157Trying a value greater than 1 for this is suggested for
158mounts with a large bandwidth * delay product.
159.It Fl b
160If an initial attempt to contact the server fails, fork off a child to keep
161trying the mount in the background.
162Useful for
163.Xr fstab 5 ,
164where the file system mount is not critical to multiuser operation.
165.It Fl c
166For UDP mount points, do not do a
167.Xr connect 2 .
168This must be used if the server does not reply to requests from the standard
169NFS port number 2049 or replies to requests using a different IP address
170(which can occur if the server is multi-homed).
171Setting the
172.Va vfs.nfs.nfs_ip_paranoia
173sysctl to 0 will make this option the default.
174.It Fl d
175Turn off the dynamic retransmit timeout estimator.
176This may be useful for UDP mounts that exhibit high retry rates,
177since it is possible that the dynamically estimated timeout interval is too
178short.
179.It Fl g
180Set the maximum size of the group list for the credentials to the
181specified value.
182This should be used for mounts on old servers that cannot handle a
183group list size of 16, as specified in RFC 1057.
184Try 8, if users in a lot of groups cannot get response from the mount
185point.
186.It Fl i
187Make the mount interruptible, which implies that file system calls that
188are delayed due to an unresponsive server will fail with EINTR when a
189termination signal is posted for the process.
190.It Fl l
191Used with NQNFS and NFSV3 to specify that the \fBReaddirPlus\fR RPC should
192be used.
193This option reduces RPC traffic for cases such as
194.Dq "ls -l" ,
195but tends to flood the attribute and name caches with prefetched entries.
196Try this option and see whether performance improves or degrades.
197Probably
198most useful for client to server network interconnects with a large bandwidth
199times delay product.
200.It Fl o
201Options are specified with a
202.Fl o
203flag followed by a comma separated string of options.
204See the
205.Xr mount 8
206man page for possible options and their meanings.
207The following NFS specific options are also available:
208.Bl -tag -width indent
209.It Cm port Ns = Ns Aq Ar port_number
210Use specified port number for NFS requests.
211The default is to query the portmapper for the NFS port.
212.It Cm acregmin Ns = Ns Aq Ar seconds
213.It Cm acregmax Ns = Ns Aq Ar seconds
214.It Cm acdirmin Ns = Ns Aq Ar seconds
215.It Cm acdirmax Ns = Ns Aq Ar seconds
216When attributes of files are cached, a timeout calculated to determine
217whether a given cache entry has expired.
218These four values determine the upper and lower bounds of the timeouts for
219.Dq directory
220attributes and
221.Dq regular
222(ie: everything else).
223The default values are 3 -> 60 seconds
224for regular files, and 30 -> 60 seconds for directories.
225The algorithm to calculate the timeout is based on the age of the file.
226The older the file,
227the longer the cache is considered valid, subject to the limits above.
228.It Cm noinet4 , noinet6
229Disables
230.Dv AF_INET
231or
232.Dv AF_INET6
233connections.
234Useful for hosts that have
235both an A record and an AAAA record for the same name.
236.El
237.Pp
238.Sy Historic Fl o Sy Options
239.Pp
240Use of these options is deprecated, they are only mentioned here for
241compatibility with historic versions of
242.Nm .
243.Bl -tag -width ".Cm dumbtimer"
244.It Cm bg
245Same as
246.Fl b .
247.It Cm conn
248Same as not specifying
249.Fl c .
250.It Cm dumbtimer
251Same as
252.Fl d .
253.It Cm intr
254Same as
255.Fl i .
256.It Cm lockd
257Same as not specifying
258.Fl L .
259.It Cm nfsv2
260Same as
261.Fl 2 .
262.It Cm nfsv3
263Same as
264.Fl 3 .
265.It Cm rdirplus
266Same as
267.Fl l .
268.It Cm mntudp
269Same as
270.Fl U .
271.It Cm resvport
272Same as
273.Fl P .
274.It Cm soft
275Same as
276.Fl s .
277.It Cm tcp
278Same as
279.Fl T .
280.El
281.It Fl r
282Set the read data size to the specified value.
283It should normally be a power of 2 greater than or equal to 1024.
284This should be used for UDP mounts when the
285.Dq "fragments dropped due to timeout"
286value is getting large while actively using a mount point.
287(Use
288.Xr netstat 1
289with the
290.Fl s
291option to see what the
292.Dq "fragments dropped due to timeout"
293value is.)
294See the
295.Fl w
296option as well.
297.It Fl s
298A soft mount, which implies that file system calls will fail
299after
300.Ar retrycnt
301round trip timeout intervals.
302.It Fl t
303Set the initial retransmit timeout to the specified value.
304May be useful for fine tuning UDP mounts over internetworks
305with high packet loss rates or an overloaded server.
306Try increasing the interval if
307.Xr nfsstat 1
308shows high retransmit rates while the file system is active or reducing the
309value if there is a low retransmit rate but long response delay observed.
310(Normally, the
311.Fl d
312option should be specified when using this option to manually
313tune the timeout
314interval.)
315.It Fl w
316Set the write data size to the specified value.
317Ditto the comments w.r.t.\& the
318.Fl r
319option, but using the
320.Dq "fragments dropped due to timeout"
321value on the server instead of the client.
322Note that both the
323.Fl r
324and
325.Fl w
326options should only be used as a last ditch effort at improving performance
327when mounting servers that do not support TCP mounts.
328.It Fl x
329Set the retransmit timeout count for soft mounts to the specified value.
330.El
331.Sh SEE ALSO
332.Xr mount 2 ,
333.Xr unmount 2 ,
334.Xr fstab 5 ,
335.Xr mount 8 ,
336.Xr nfsd 8 ,
337.Xr nfsiod 8 ,
338.Xr showmount 8
339