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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
155 Use the NFS Version 2 protocol (the default is to try version 3 first
157 Note that NFS version 2 has a file size limit of 2 gigabytes.
159 Use the NFS Version 3 protocol.
161 Use the NFS Version 4 protocol.
163 For UDP mount points, do not do a
165 This must be used if the server does not reply to requests from the standard
166 NFS port number 2049 or replies to requests using a different IP address
167 (which can occur if the server is multi-homed).
169 .Va vfs.nfs.nfs_ip_paranoia
170 sysctl to 0 will make this option the default.
171 .It Cm noinet4 , noinet6
177 Useful for hosts that have
178 both an A record and an AAAA record for the same name.
185 All locks will be local and not seen by the server
186 and likewise not seen by other NFS clients.
187 This removes the need to run the
193 servers on the client.
194 Note that this option will only be honored when performing the
195 initial mount, it will be silently ignored if used while updating
200 use a reserved socket port number (see below).
201 .It Cm port Ns = Ns Aq Ar port_number
202 Use specified port number for NFS requests.
203 The default is to query the portmapper for the NFS port.
205 Used with NQNFS and NFSV3 to specify that the \fBReaddirPlus\fR RPC should
207 This option reduces RPC traffic for cases such as
209 but tends to flood the attribute and name caches with prefetched entries.
210 Try this option and see whether performance improves or degrades.
212 most useful for client to server network interconnects with a large bandwidth
214 .It Cm readahead Ns = Ns Aq Ar value
215 Set the read-ahead count to the specified value.
216 This may be in the range of 0 - 4, and determines how many blocks
217 will be read ahead when a large file is being read sequentially.
218 Trying a value greater than 1 for this is suggested for
219 mounts with a large bandwidth * delay product.
220 .It Cm readdirsize Ns = Ns Aq Ar value
221 Set the readdir read size to the specified value.
222 The value should normally
225 that is <= the read size for the mount.
227 Use a reserved socket port number.
228 This flag is obsolete, and only retained for compatibility reasons.
229 Reserved port numbers are used by default now.
230 (For the rare case where the client has a trusted root account
231 but untrustworthy users and the network cables are in secure areas this does
232 help, but for normal desktop clients this does not apply.)
233 .It Cm retrans Ns = Ns Aq Ar value
234 Set the retransmit timeout count for soft mounts to the specified value.
235 .It Cm retrycnt Ns = Ns Aq Ar count
236 Set the mount retry count to the specified value.
237 The default is a retry count of zero, which means to keep retrying
239 There is a 60 second delay between each attempt.
240 .It Cm rsize Ns = Ns Aq Ar value
241 Set the read data size to the specified value.
242 It should normally be a power of 2 greater than or equal to 1024.
243 This should be used for UDP mounts when the
244 .Dq "fragments dropped due to timeout"
245 value is getting large while actively using a mount point.
250 option to see what the
251 .Dq "fragments dropped due to timeout"
254 A soft mount, which implies that file system calls will fail
257 round trip timeout intervals.
260 This is the default option, as it provides for increased reliability on both
261 LAN and WAN configurations compared to UDP.
262 Some old NFS servers do not support this method; UDP mounts may be required
263 for interoperability.
264 .It Cm timeout Ns = Ns Aq Ar value
265 Set the initial retransmit timeout to the specified value.
266 May be useful for fine tuning UDP mounts over internetworks
267 with high packet loss rates or an overloaded server.
268 Try increasing the interval if
270 shows high retransmit rates while the file system is active or reducing the
271 value if there is a low retransmit rate but long response delay observed.
274 option should be specified when using this option to manually
279 .It Cm wsize Ns = Ns Aq Ar value
280 Set the write data size to the specified value.
281 Ditto the comments w.r.t.\& the
283 option, but using the
284 .Dq "fragments dropped due to timeout"
285 value on the server instead of the client.
290 options should only be used as a last ditch effort at improving performance
291 when mounting servers that do not support TCP mounts.
295 The following command line flags are equivalent to
297 named options and are supported for compatibility with older
299 .Bl -tag -width indent
314 .Fl o Cm readdirsize Ns = Ns Aq Ar value
322 Use a reserved socket port number.
323 This flag is obsolete, and only retained for compatibility reasons.
324 (For the rare case where the client has a trusted root account
325 but untrustworthy users and the network cables are in secure areas this does
326 help, but for normal desktop clients this does not apply.)
329 .Fl o Cm retrycnt Ns = Ns Aq Ar value
338 .Fl o Cm readahead Ns = Ns Aq Ar value
359 .Fl o Cm rsize Ns = Ns Aq Ar value
365 .Fl o Cm retransmit Ns = Ns Aq Ar value
368 .Fl o Cm wsize Ns = Ns Aq Ar value
371 .Fl o Cm retrans Ns = Ns Aq Ar value