xref: /freebsd/sbin/mount_nfs/mount_nfs.8 (revision ce834215a70ff69e7e222827437116eee2f9ac6f)
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32.\"	@(#)mount_nfs.8	8.3 (Berkeley) 3/29/95
33.\"
34.\" $Id: mount_nfs.8,v 1.8 1997/03/11 12:31:54 peter Exp $
35.\""
36.Dd March 29, 1995
37.Dt MOUNT_NFS 8
38.Os BSD 4.4
39.Sh NAME
40.Nm mount_nfs
41.Nd mount nfs file systems
42.Sh SYNOPSIS
43.Nm mount_nfs
44.Op Fl 23KPTUbcdilqs
45.Op Fl D Ar deadthresh
46.Op Fl I Ar readdirsize
47.Op Fl L Ar leaseterm
48.Op Fl R Ar retrycnt
49.Op Fl a Ar maxreadahead
50.Op Fl g Ar maxgroups
51.Op Fl m Ar realm
52.Op Fl o Ar options
53.Op Fl r Ar readsize
54.Op Fl t Ar timeout
55.Op Fl w Ar writesize
56.Op Fl x Ar retrans
57.Ar rhost:path node
58.Sh DESCRIPTION
59The
60.Nm mount_nfs
61command
62calls the
63.Xr mount 2
64system call to prepare and graft a remote nfs file system (rhost:path)
65on to the file system tree at the point
66.Ar node.
67This command is normally executed by
68.Xr mount 8 .
69It implements the mount protocol as described in RFC 1094, Appendix A and
70.%T "NFS: Network File System Version 3 Protocol Specification" ,
71Appendix I.
72.Pp
73The options are:
74.Bl -tag -width indent
75.It Fl 2
76Use the NFS Version 2 protocol (the default is to try version 3 first
77then version 2).
78.It Fl 3
79Use the NFS Version 3 protocol.
80.It Fl D
81Used with NQNFS to set the
82.Dq "dead server threshold"
83to the specified number of round trip timeout intervals.
84After a
85.Dq "dead server threshold"
86of retransmit timeouts,
87cached data for the unresponsive server is assumed to still be valid.
88Values may be set in the range of 1 - 9, with 9 referring to an
89.Dq "infinite dead threshold"
90(i.e. never assume cached data still valid).
91This option is not generally recommended and is really an experimental
92feature.
93.It Fl I
94Set the readdir read size to the specified value. The value should normally
95be a multiple of DIRBLKSIZ that is <= the read size for the mount.
96.It Fl K
97Pass Kerberos authenticators to the server for client-to-server
98user-credential mapping.
99This requires that the kernel be built with the NFSKERB option.
100(Refer to the INTERNET-DRAFT titled
101.%T "Authentication Mechanisms for ONC RPC" ,
102for more information.)
103.It Fl L
104Used with NQNFS to set the lease term to the specified number of seconds.
105Only use this argument for mounts with a large round trip delay.
106Values are normally in the 10-30 second range.
107.It Fl P
108Use a reserved socket port number.
109This is useful for mounting servers that require clients to use a
110reserved port number on the mistaken belief that this makes NFS
111more secure. (For the rare case where the client has a trusted root account
112but untrustworthy users and the network cables are in secure areas this does
113help, but for normal desktop clients this does not apply.)
114.It Fl R
115Set the retry count for doing the mount to the specified value.
116.It Fl T
117Use TCP transport instead of UDP.
118This is recommended for servers that are not on the same LAN cable as
119the client.
120(NB: This is NOT supported by most non-BSD servers.)
121.It Fl U
122Force the mount protocol to use UDP transport, even for TCP NFS mounts.
123(Necessary for some old BSD servers.)
124.It Fl a
125Set the read-ahead count to the specified value.
126This may be in the range of 0 - 4, and determines how many blocks
127will be read ahead when a large file is being read sequentially.
128Trying a value greater than 1 for this is suggested for
129mounts with a large bandwidth * delay product.
130.It Fl b
131If an initial attempt to contact the server fails, fork off a child to keep
132trying the mount in the background.
133Useful for
134.Xr fstab 5 ,
135where the filesystem mount is not critical to multiuser operation.
136.It Fl c
137For UDP mount points, do not do a
138.Xr connect 2 .
139This must be used for servers that do not reply to requests from the
140standard NFS port number 2049.
141.It Fl d
142Turn off the dynamic retransmit timeout estimator.
143This may be useful for UDP mounts that exhibit high retry rates,
144since it is possible that the dynamically estimated timeout interval is too
145short.
146.It Fl g
147Set the maximum size of the group list for the credentials to the
148specified value.
149This should be used for mounts on old servers that cannot handle a
150group list size of 16, as specified in RFC 1057.
151Try 8, if users in a lot of groups cannot get response from the mount
152point.
153.It Fl i
154Make the mount interruptible, which implies that file system calls that
155are delayed due to an unresponsive server will fail with EINTR when a
156termination signal is posted for the process.
157.It Fl l
158Used with NQNFS and NFSV3 to specify that the \fBReaddirPlus\fR RPC should
159be used.
160This option reduces RPC traffic for cases such as
161.Dq "ls -l" ,
162but tends to flood the attribute and name caches with prefetched entries.
163Try this option and see whether performance improves or degrades. Probably
164most useful for client to server network interconnects with a large bandwidth
165times delay product.
166.It Fl m
167Set the Kerberos realm to the string argument.
168Used with the
169.Fl K
170option for mounts to other realms.
171.It Fl o
172Options are specified with a
173.Fl o
174flag followed by a comma separated string of options.
175See the
176.Xr mount 8
177man page for possible options and their meanings.
178The following NFS specific option is also available:
179.Bl -tag -width indent
180.It port=<port_number>
181Use specified port number for NFS requests.
182The default is to query the portmapper for the NFS port.
183.El
184.Pp
185.Bl -tag -width "dumbtimerXX"
186\fBHistoric \&-o options\fR
187.Pp
188Use of these options is deprecated, they are only mentioned here for
189compatibility with historic versions of
190.Nm mount_nfs .
191.It bg
192Same as
193.Fl b .
194.It conn
195Same as
196.Fl c .
197.It dumbtimer
198Same as
199.Fl d .
200.It intr
201Same as
202.Fl i .
203.It kerb
204Same as
205.Fl K .
206.It nfsv2
207Same as
208.Fl 2 .
209.It nfsv3
210Same as
211.Fl 3 .
212.It rdirplus
213Same as
214.Fl l .
215.It mntudp
216Same as
217.Fl U .
218.It resvport
219Same as
220.Fl P .
221.It seqpacket
222Same as
223.Fl p .
224.It nqnfs
225Same as
226.Fl q .
227.It soft
228Same as
229.Fl s .
230.It tcp
231Same as
232.Fl T.
233.El
234.It Fl q
235Use the leasing extensions to the NFS Version 3 protocol
236to maintain cache consistency.
237This protocol Version 2, referred to as Not Quite Nfs (NQNFS),
238is only supported by this updated release of NFS code.
239(It is not backwards compatible with the release of NQNFS that went out on
2404.4BSD-Lite. To interoperate with a 4.4BSD-Lite NFS system you will have to
241avoid this option until you have had an opportunity to upgrade the NFS code
242on all your 4.4BSD-Lite based systems.)
243.It Fl r
244Set the read data size to the specified value.
245It should normally be a power of 2 greater than or equal to 1024.
246This should be used for UDP mounts when the
247.Dq "fragments dropped due to timeout"
248value is getting large while actively using a mount point.
249(Use
250.Xr netstat 1
251with the
252.Fl s
253option to see what the
254.Dq "fragments dropped due to timeout"
255value is.)
256See the
257.Fl w
258option as well.
259.It Fl s
260A soft mount, which implies that file system calls will fail
261after \fBRetry\fR round trip timeout intervals.
262.It Fl t
263Set the initial retransmit timeout to the specified value.
264May be useful for fine tuning UDP mounts over internetworks
265with high packet loss rates or an overloaded server.
266Try increasing the interval if
267.Xr nfsstat 1
268shows high retransmit rates while the file system is active or reducing the
269value if there is a low retransmit rate but long response delay observed.
270(Normally, the -d option should be specified when using this option to manually
271tune the timeout
272interval.)
273.It Fl w
274Set the write data size to the specified value.
275Ditto the comments w.r.t. the
276.Fl r
277option, but using the
278.Dq "fragments dropped due to timeout"
279value on the server instead of the client.
280Note that both the
281.Fl r
282and
283.Fl w
284options should only be used as a last ditch effort at improving performance
285when mounting servers that do not support TCP mounts.
286.It Fl x
287Set the retransmit timeout count for soft mounts to the specified value.
288.El
289.Sh SEE ALSO
290.Xr mount 2 ,
291.Xr unmount 2 ,
292.Xr fstab 5 ,
293.Xr mount 8
294.Sh BUGS
295Due to the way that Sun RPC is implemented on top of UDP (unreliable datagram)
296transport, tuning such mounts is really a black art that can only be expected
297to have limited success.
298For clients mounting servers that are not on the same
299LAN cable or that tend to be overloaded,
300TCP transport is strongly recommended,
301but unfortunately this is restricted to mostly 4.4BSD servers.
302