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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132 This flag is obsolete, and only retained for compatibility reasons.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 Not all NFS servers support this method, especially older ones,
147 caution should be observed in these cases.
149 Force the mount protocol to use UDP transport, even for TCP NFS mounts.
150 (Necessary for some old
154 Set the read-ahead count to the specified value.
155 This may be in the range of 0 - 4, and determines how many blocks
156 will be read ahead when a large file is being read sequentially.
157 Trying a value greater than 1 for this is suggested for
158 mounts with a large bandwidth * delay product.
160 If an initial attempt to contact the server fails, fork off a child to keep
161 trying the mount in the background.
164 where the file system mount is not critical to multiuser operation.
166 For UDP mount points, do not do a
168 This must be used if the server does not reply to requests from the standard
169 NFS port number 2049 or replies to requests using a different IP address
170 (which can occur if the server is multi-homed).
172 .Va vfs.nfs.nfs_ip_paranoia
173 sysctl to 0 will make this option the default.
175 Turn off the dynamic retransmit timeout estimator.
176 This may be useful for UDP mounts that exhibit high retry rates,
177 since it is possible that the dynamically estimated timeout interval is too
180 Set the maximum size of the group list for the credentials to the
182 This should be used for mounts on old servers that cannot handle a
183 group list size of 16, as specified in RFC 1057.
184 Try 8, if users in a lot of groups cannot get response from the mount
187 Make the mount interruptible, which implies that file system calls that
188 are delayed due to an unresponsive server will fail with EINTR when a
189 termination signal is posted for the process.
191 Used with NQNFS and NFSV3 to specify that the \fBReaddirPlus\fR RPC should
193 This option reduces RPC traffic for cases such as
195 but tends to flood the attribute and name caches with prefetched entries.
196 Try this option and see whether performance improves or degrades.
198 most useful for client to server network interconnects with a large bandwidth
201 Options are specified with a
203 flag followed by a comma separated string of options.
206 man page for possible options and their meanings.
207 The following NFS specific options are also available:
208 .Bl -tag -width indent
209 .It Cm port Ns = Ns Aq Ar port_number
210 Use specified port number for NFS requests.
211 The 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
216 When attributes of files are cached, a timeout calculated to determine
217 whether a given cache entry has expired.
218 These four values determine the upper and lower bounds of the timeouts for
222 (ie: everything else).
223 The default values are 3 -> 60 seconds
224 for regular files, and 30 -> 60 seconds for directories.
225 The algorithm to calculate the timeout is based on the age of the file.
227 the longer the cache is considered valid, subject to the limits above.
228 .It Cm noinet4 , noinet6
234 Useful for hosts that have
235 both an A record and an AAAA record for the same name.
238 .Sy Historic Fl o Sy Options
240 Use of these options is deprecated, they are only mentioned here for
241 compatibility with historic versions of
243 .Bl -tag -width ".Cm dumbtimer"
248 Same as not specifying
257 Same as not specifying
282 Set the read data size to the specified value.
283 It should normally be a power of 2 greater than or equal to 1024.
284 This should be used for UDP mounts when the
285 .Dq "fragments dropped due to timeout"
286 value is getting large while actively using a mount point.
291 option to see what the
292 .Dq "fragments dropped due to timeout"
298 A soft mount, which implies that file system calls will fail
301 round trip timeout intervals.
303 Set the initial retransmit timeout to the specified value.
304 May be useful for fine tuning UDP mounts over internetworks
305 with high packet loss rates or an overloaded server.
306 Try increasing the interval if
308 shows high retransmit rates while the file system is active or reducing the
309 value if there is a low retransmit rate but long response delay observed.
312 option should be specified when using this option to manually
316 Set the write data size to the specified value.
317 Ditto the comments w.r.t.\& the
319 option, but using the
320 .Dq "fragments dropped due to timeout"
321 value on the server instead of the client.
326 options should only be used as a last ditch effort at improving performance
327 when mounting servers that do not support TCP mounts.
329 Set the retransmit timeout count for soft mounts to the specified value.