1 .\" Copyright (c) 1992, 1993, 1994, 1995
2 .\" The Regents of the University of California. All rights reserved.
4 .\" Redistribution and use in source and binary forms, with or without
5 .\" modification, are permitted provided that the following conditions
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.
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
28 .\" @(#)mount_nfs.8 8.3 (Berkeley) 3/29/95
36 .Nd mount NFS file systems
40 .Op Fl a Ar maxreadahead
41 .Op Fl D Ar deadthresh
43 .Op Fl I Ar readdirsize
50 .Ar rhost : Ns Ar path node
56 system call to prepare and graft a remote NFS file system
57 .Pq Ar rhost : Ns Ar path
58 on to the file system tree at the point
60 This command is normally executed by
62 It implements the mount protocol as described in RFC 1094, Appendix A and
63 .%T "NFS: Network File System Version 3 Protocol Specification" ,
68 keeps retrying until the mount succeeds.
69 This behaviour is intended for file systems listed in
71 that are critical to the boot process.
72 For non-critical file systems, the
76 options provide mechanisms to prevent the boot process from hanging
77 if the server is unavailable.
79 If the server becomes unresponsive while an NFS file system is
80 mounted, any new or outstanding file operations on that file system
81 will hang uninterruptibly until the server comes back.
82 To modify this default behaviour, see the
89 .Bl -tag -width indent
91 Options are specified with a
93 flag followed by a comma separated string of options.
96 man page for possible options and their meanings.
97 The following NFS specific options are also available:
98 .Bl -tag -width indent
99 .It Cm acregmin Ns = Ns Aq Ar seconds
100 .It Cm acregmax Ns = Ns Aq Ar seconds
101 .It Cm acdirmin Ns = Ns Aq Ar seconds
102 .It Cm acdirmax Ns = Ns Aq Ar seconds
103 When attributes of files are cached, a timeout calculated to determine
104 whether a given cache entry has expired.
105 These four values determine the upper and lower bounds of the timeouts for
109 (ie: everything else).
110 The default values are 3 -> 60 seconds
111 for regular files, and 30 -> 60 seconds for directories.
112 The algorithm to calculate the timeout is based on the age of the file.
114 the longer the cache is considered valid, subject to the limits above.
116 If an initial attempt to contact the server fails, fork off a child to keep
117 trying the mount in the background.
120 where the file system mount is not critical to multiuser operation.
121 .It Cm deadthresh Ns = Ns Aq Ar value
123 .Dq "dead server threshold"
124 to the specified number of round trip timeout intervals before a
125 .Dq "server not responding"
126 message is displayed.
128 Turn off the dynamic retransmit timeout estimator.
129 This may be useful for UDP mounts that exhibit high retry rates,
130 since it is possible that the dynamically estimated timeout interval is too
133 Same as not specifying
136 Same as not specifying
139 Make the mount interruptible, which implies that file system calls that
140 are delayed due to an unresponsive server will fail with EINTR when a
141 termination signal is posted for the process.
142 .It Cm maxgroups Ns = Ns Aq Ar value
143 Set the maximum size of the group list for the credentials to the
145 This should be used for mounts on old servers that cannot handle a
146 group list size of 16, as specified in RFC 1057.
147 Try 8, if users in a lot of groups cannot get response from the mount
150 Force the mount protocol to use UDP transport, even for TCP NFS mounts.
151 (Necessary for some old
154 .It Cm nametimeo Ns = Ns Aq Ar value
155 Override the default of NFS_DEFAULT_NAMETIMEO for the timeout (in seconds)
156 for positive name cache entries.
157 If this is set to 0 it disables positive name caching for the mount point.
158 .It Cm negnametimeo Ns = Ns Aq Ar value
159 Override the default of NFS_DEFAULT_NEGNAMETIMEO for the timeout (in seconds)
160 for negative name cache entries. If this is set to 0 it disables negative
161 name caching for the mount point.
163 Use the NFS Version 2 protocol (the default is to try version 3 first
165 Note that NFS version 2 has a file size limit of 2 gigabytes.
167 Use the NFS Version 3 protocol.
169 Use the NFS Version 4 protocol.
170 This option will force the mount to use the experimental nfs subsystem and
172 To use the experimental nfs subsystem for nfsv2 and nfsv3 mounts, you
173 must specify the ``newnfs'' file system type instead of ``nfs''.
175 For UDP mount points, do not do a
177 This must be used if the server does not reply to requests from the standard
178 NFS port number 2049 or replies to requests using a different IP address
179 (which can occur if the server is multi-homed).
181 .Va vfs.nfs.nfs_ip_paranoia
182 sysctl to 0 will make this option the default.
184 Normally, NFS clients maintain the close-to-open cache coherency.
185 This works by flushing at close time and checking at open time.
186 Checking at open time is implemented by getting attributes from
187 the server and purging the data cache if they do not match
188 attributes cached by the client.
190 This option disables checking at open time.
191 It may improve performance for read-only mounts,
192 but should only be used if the data on the server changes rarely.
193 Be sure to understand the consequences before enabling this option.
194 .It Cm noinet4 , noinet6
200 Useful for hosts that have
201 both an A record and an AAAA record for the same name.
208 All locks will be local and not seen by the server
209 and likewise not seen by other NFS clients.
210 This removes the need to run the
216 servers on the client.
217 Note that this option will only be honored when performing the
218 initial mount, it will be silently ignored if used while updating
221 For the RPCSEC_GSS security flavors, such as krb5, krb5i and krb5p,
222 this option sets the name of the host based principal name expected
223 by the server. This option overrides the default, which will be
224 ``nfs@<server-fqdn>'' and should normally be sufficient.
228 use a reserved socket port number (see below).
229 .It Cm port Ns = Ns Aq Ar port_number
230 Use specified port number for NFS requests.
231 The default is to query the portmapper for the NFS port.
233 Used with NFSV3 to specify that the \fBReaddirPlus\fR RPC should
235 For NFSV4, setting this option has a similar effect, in that it will make
236 the Readdir Operation get more attributes.
237 This option reduces RPC traffic for cases such as
239 but tends to flood the attribute and name caches with prefetched entries.
240 Try this option and see whether performance improves or degrades.
242 most useful for client to server network interconnects with a large bandwidth
244 .It Cm readahead Ns = Ns Aq Ar value
245 Set the read-ahead count to the specified value.
246 This may be in the range of 0 - 4, and determines how many blocks
247 will be read ahead when a large file is being read sequentially.
248 Trying a value greater than 1 for this is suggested for
249 mounts with a large bandwidth * delay product.
250 .It Cm readdirsize Ns = Ns Aq Ar value
251 Set the readdir read size to the specified value.
252 The value should normally
255 that is <= the read size for the mount.
257 Use a reserved socket port number.
258 This flag is obsolete, and only retained for compatibility reasons.
259 Reserved port numbers are used by default now.
260 (For the rare case where the client has a trusted root account
261 but untrustworthy users and the network cables are in secure areas this does
262 help, but for normal desktop clients this does not apply.)
263 .It Cm retrans Ns = Ns Aq Ar value
264 Set the retransmit timeout count for soft mounts to the specified value.
265 .It Cm retrycnt Ns = Ns Aq Ar count
266 Set the mount retry count to the specified value.
267 The default is a retry count of zero, which means to keep retrying
269 There is a 60 second delay between each attempt.
270 .It Cm rsize Ns = Ns Aq Ar value
271 Set the read data size to the specified value.
272 It should normally be a power of 2 greater than or equal to 1024.
273 This should be used for UDP mounts when the
274 .Dq "fragments dropped due to timeout"
275 value is getting large while actively using a mount point.
280 option to see what the
281 .Dq "fragments dropped due to timeout"
283 .It Cm sec Ns = Ns Aq Ar flavor
284 This option specifies what security flavor should be used for the mount.
287 krb5 - Use KerberosV authentication
288 krb5i - Use KerberosV authentication and
289 apply integrity checksums to RPCs
290 krb5p - Use KerberosV authentication and
292 sys - The default AUTH_SYS, which uses a
293 uid + gid list authenticator
296 A soft mount, which implies that file system calls will fail
299 round trip timeout intervals.
302 This is the default option, as it provides for increased reliability on both
303 LAN and WAN configurations compared to UDP.
304 Some old NFS servers do not support this method; UDP mounts may be required
305 for interoperability.
306 .It Cm timeout Ns = Ns Aq Ar value
307 Set the initial retransmit timeout to the specified value.
308 May be useful for fine tuning UDP mounts over internetworks
309 with high packet loss rates or an overloaded server.
310 Try increasing the interval if
312 shows high retransmit rates while the file system is active or reducing the
313 value if there is a low retransmit rate but long response delay observed.
316 option should be specified when using this option to manually
321 .It Cm wcommitsize Ns = Ns Aq Ar value
322 Set the maximum pending write commit size to the specified value.
323 This determines the maximum amount of pending write data that the NFS
324 client is willing to cache for each file.
325 .It Cm wsize Ns = Ns Aq Ar value
326 Set the write data size to the specified value.
327 Ditto the comments w.r.t.\& the
329 option, but using the
330 .Dq "fragments dropped due to timeout"
331 value on the server instead of the client.
336 options should only be used as a last ditch effort at improving performance
337 when mounting servers that do not support TCP mounts.
341 The following command line flags are equivalent to
343 named options and are supported for compatibility with older
345 .Bl -tag -width indent
357 .Fl o Cm readdirsize Ns = Ns Aq Ar value
365 Use a reserved socket port number.
366 This flag is obsolete, and only retained for compatibility reasons.
367 (For the rare case where the client has a trusted root account
368 but untrustworthy users and the network cables are in secure areas this does
369 help, but for normal desktop clients this does not apply.)
372 .Fl o Cm retrycnt Ns = Ns Aq Ar value
381 .Fl o Cm readahead Ns = Ns Aq Ar value
402 .Fl o Cm rsize Ns = Ns Aq Ar value
408 .Fl o Cm retransmit Ns = Ns Aq Ar value
411 .Fl o Cm wsize Ns = Ns Aq Ar value
414 .Fl o Cm retrans Ns = Ns Aq Ar value
427 Since nfsv4 performs open/lock operations that have their ordering strictly
428 enforced by the server, the options
432 cannot be safely used.
434 nfsv4 mounts are strongly recommended.