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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 flags 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 Use the NFS Version 2 protocol (the default is to try version 3 first
93 Note that NFS version 2 has a file size limit of 2 gigabytes.
95 Use the NFS Version 3 protocol.
98 .Dq "dead server threshold"
99 to the specified number of round trip timeout intervals before a
100 .Dq "server not responding"
101 message is displayed.
103 Set the readdir read size to the specified value.
104 The value should normally
107 that is <= the read size for the mount.
114 All locks will be local and not seen by the server
115 and likewise not seen by other NFS clients.
116 This removes the need to run the
122 servers on the client.
123 Note that this option will only be honored when performing the
124 initial mount, it will be silently ignored if used while updating
129 use a reserved socket port number (see below).
131 Use a reserved socket port number.
132 This flag is obsolete, and only retained for compatibility reasons.
133 Reserved port numbers are used by default now.
134 (For the rare case where the client has a trusted root account
135 but untrustworthy users and the network cables are in secure areas this does
136 help, but for normal desktop clients this does not apply.)
138 Set the mount retry count to the specified value.
139 The default is a retry count of zero, which means to keep retrying
141 There is a 60 second delay between each attempt.
143 Use TCP transport instead of UDP.
144 This is recommended for servers that are not on the same LAN cable as
146 (NB: This is NOT supported by most
150 Force the mount protocol to use UDP transport, even for TCP NFS mounts.
151 (Necessary for some old
155 Set the read-ahead count to the specified value.
156 This may be in the range of 0 - 4, and determines how many blocks
157 will be read ahead when a large file is being read sequentially.
158 Trying a value greater than 1 for this is suggested for
159 mounts with a large bandwidth * delay product.
161 If an initial attempt to contact the server fails, fork off a child to keep
162 trying the mount in the background.
165 where the file system mount is not critical to multiuser operation.
167 For UDP mount points, do not do a
169 This must be used if the server does not reply to requests from the standard
170 NFS port number 2049 or replies to requests using a different IP address
171 (which can occur if the server is multi-homed).
173 .Va vfs.nfs.nfs_ip_paranoia
174 sysctl to 0 will make this option the default.
176 Turn off the dynamic retransmit timeout estimator.
177 This may be useful for UDP mounts that exhibit high retry rates,
178 since it is possible that the dynamically estimated timeout interval is too
181 Set the maximum size of the group list for the credentials to the
183 This should be used for mounts on old servers that cannot handle a
184 group list size of 16, as specified in RFC 1057.
185 Try 8, if users in a lot of groups cannot get response from the mount
188 Make the mount interruptible, which implies that file system calls that
189 are delayed due to an unresponsive server will fail with EINTR when a
190 termination signal is posted for the process.
192 Used with NQNFS and NFSV3 to specify that the \fBReaddirPlus\fR RPC should
194 This option reduces RPC traffic for cases such as
196 but tends to flood the attribute and name caches with prefetched entries.
197 Try this option and see whether performance improves or degrades.
199 most useful for client to server network interconnects with a large bandwidth
202 Options are specified with a
204 flag followed by a comma separated string of options.
207 man page for possible options and their meanings.
208 The following NFS specific options are also available:
209 .Bl -tag -width indent
210 .It Cm port Ns = Ns Aq Ar port_number
211 Use specified port number for NFS requests.
212 The default is to query the portmapper for the NFS port.
213 .It Cm acregmin Ns = Ns Aq Ar seconds
214 .It Cm acregmax Ns = Ns Aq Ar seconds
215 .It Cm acdirmin Ns = Ns Aq Ar seconds
216 .It Cm acdirmax Ns = Ns Aq Ar seconds
217 When attributes of files are cached, a timeout calculated to determine
218 whether a given cache entry has expired.
219 These four values determine the upper and lower bounds of the timeouts for
223 (ie: everything else).
224 The default values are 3 -> 60 seconds
225 for regular files, and 30 -> 60 seconds for directories.
226 The algorithm to calculate the timeout is based on the age of the file.
228 the longer the cache is considered valid, subject to the limits above.
229 .It Cm noinet4 , noinet6
235 Useful for hosts that have
236 both an A record and an AAAA record for the same name.
239 .Sy Historic Fl o Sy Options
241 Use of these options is deprecated, they are only mentioned here for
242 compatibility with historic versions of
244 .Bl -tag -width ".Cm dumbtimer"
249 Same as not specifying
258 Same as not specifying
283 Set the read data size to the specified value.
284 It should normally be a power of 2 greater than or equal to 1024.
285 This should be used for UDP mounts when the
286 .Dq "fragments dropped due to timeout"
287 value is getting large while actively using a mount point.
292 option to see what the
293 .Dq "fragments dropped due to timeout"
299 A soft mount, which implies that file system calls will fail
302 round trip timeout intervals.
304 Set the initial retransmit timeout to the specified value.
305 May be useful for fine tuning UDP mounts over internetworks
306 with high packet loss rates or an overloaded server.
307 Try increasing the interval if
309 shows high retransmit rates while the file system is active or reducing the
310 value if there is a low retransmit rate but long response delay observed.
313 option should be specified when using this option to manually
317 Set the write data size to the specified value.
318 Ditto the comments w.r.t.\& the
320 option, but using the
321 .Dq "fragments dropped due to timeout"
322 value on the server instead of the client.
327 options should only be used as a last ditch effort at improving performance
328 when mounting servers that do not support TCP mounts.
330 Set the retransmit timeout count for soft mounts to the specified value.
341 Due to the way that Sun RPC is implemented on top of UDP (unreliable datagram)
342 transport, tuning such mounts is really a black art that can only be expected
343 to have limited success.
344 For clients mounting servers that are not on the same
345 LAN cable or that tend to be overloaded,
346 TCP transport is strongly recommended,
347 but unfortunately this is restricted to mostly