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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" ,
66 If the file system type is specified as ``oldnfs'', which implies this
67 command is run as ``mount_oldnfs'', then it forces use of the old NFS
68 client, which does not support the
74 keeps retrying until the mount succeeds.
75 This behaviour is intended for file systems listed in
77 that are critical to the boot process.
78 For non-critical file systems, the
82 options provide mechanisms to prevent the boot process from hanging
83 if the server is unavailable.
85 If the server becomes unresponsive while an NFS file system is
86 mounted, any new or outstanding file operations on that file system
87 will hang uninterruptibly until the server comes back.
88 To modify this default behaviour, see the
95 .Bl -tag -width indent
97 Options are specified with a
99 flag followed by a comma separated string of options.
102 man page for possible options and their meanings.
103 The following NFS specific options are also available:
104 .Bl -tag -width indent
105 .It Cm acregmin Ns = Ns Aq Ar seconds
106 .It Cm acregmax Ns = Ns Aq Ar seconds
107 .It Cm acdirmin Ns = Ns Aq Ar seconds
108 .It Cm acdirmax Ns = Ns Aq Ar seconds
109 When attributes of files are cached, a timeout calculated to determine
110 whether a given cache entry has expired.
111 These four values determine the upper and lower bounds of the timeouts for
115 (ie: everything else).
116 The default values are 3 -> 60 seconds
117 for regular files, and 30 -> 60 seconds for directories.
118 The algorithm to calculate the timeout is based on the age of the file.
120 the longer the cache is considered valid, subject to the limits above.
122 This option can be used along with
124 to specify that all operations should use the host-based initiator
126 This may be used for clients that run system daemons that need to
127 access files on the NFSv4 mounted volume.
129 If an initial attempt to contact the server fails, fork off a child to keep
130 trying the mount in the background.
133 where the file system mount is not critical to multiuser operation.
134 .It Cm deadthresh Ns = Ns Aq Ar value
136 .Dq "dead server threshold"
137 to the specified number of round trip timeout intervals before a
138 .Dq "server not responding"
139 message is displayed.
141 Turn off the dynamic retransmit timeout estimator.
142 This may be useful for UDP mounts that exhibit high retry rates,
143 since it is possible that the dynamically estimated timeout interval is too
146 Same as not specifying
148 .It Cm gssname Ns = Ns Aq Ar service-principal-name
149 This option can be used with the KerberosV security flavors for NFSv4 mounts
151 .Dq "service-principal-name"
152 of a host-based entry in the default
153 keytab file that is used for system operations.
154 It allows the mount to be performed by
156 and avoids problems with
157 cached credentials for the system operations expiring.
159 .Dq "service-prinicpal-name"
160 should be specified without instance or domain and is typically
166 Same as not specifying
169 Make the mount interruptible, which implies that file system calls that
170 are delayed due to an unresponsive server will fail with EINTR when a
171 termination signal is posted for the process.
172 .It Cm maxgroups Ns = Ns Aq Ar value
173 Set the maximum size of the group list for the credentials to the
175 This should be used for mounts on old servers that cannot handle a
176 group list size of 16, as specified in RFC 1057.
177 Try 8, if users in a lot of groups cannot get response from the mount
180 Force the mount protocol to use UDP transport, even for TCP NFS mounts.
181 (Necessary for some old
184 .It Cm nametimeo Ns = Ns Aq Ar value
185 Override the default of NFS_DEFAULT_NAMETIMEO for the timeout (in seconds)
186 for positive name cache entries.
187 If this is set to 0 it disables positive name caching for the mount point.
188 .It Cm negnametimeo Ns = Ns Aq Ar value
189 Override the default of NFS_DEFAULT_NEGNAMETIMEO for the timeout (in seconds)
190 for negative name cache entries. If this is set to 0 it disables negative
191 name caching for the mount point.
193 Use the NFS Version 2 protocol (the default is to try version 3 first
195 Note that NFS version 2 has a file size limit of 2 gigabytes.
197 Use the NFS Version 3 protocol.
199 Use the NFS Version 4 protocol.
200 This option will force the mount to use
202 .It Cm minorversion Ns = Ns Aq Ar value
203 Override the default of 0 for the minor version of the NFS Version 4 protocol.
204 The only minor version currently supported is 1.
205 This option is only meaningful when used with the
209 Enable support for parallel NFS (pNFS) for minor version 1 of the
210 NFS Version 4 protocol.
211 This option is only meaningful when used with the
215 For UDP mount points, do not do a
217 This must be used if the server does not reply to requests from the standard
218 NFS port number 2049 or replies to requests using a different IP address
219 (which can occur if the server is multi-homed).
221 .Va vfs.nfs.nfs_ip_paranoia
222 sysctl to 0 will make this option the default.
224 Normally, NFS clients maintain the close-to-open cache coherency.
225 This works by flushing at close time and checking at open time.
226 Checking at open time is implemented by getting attributes from
227 the server and purging the data cache if they do not match
228 attributes cached by the client.
230 This option disables checking at open time.
231 It may improve performance for read-only mounts,
232 but should only be used if the data on the server changes rarely.
233 Be sure to understand the consequences before enabling this option.
234 .It Cm noinet4 , noinet6
240 Useful for hosts that have
241 both an A record and an AAAA record for the same name.
248 All locks will be local and not seen by the server
249 and likewise not seen by other NFS clients.
250 This removes the need to run the
256 servers on the client.
257 Note that this option will only be honored when performing the
258 initial mount, it will be silently ignored if used while updating
261 For the RPCSEC_GSS security flavors, such as krb5, krb5i and krb5p,
262 this option sets the name of the host based principal name expected
263 by the server. This option overrides the default, which will be
264 ``nfs@<server-fqdn>'' and should normally be sufficient.
268 use a reserved socket port number (see below).
269 .It Cm port Ns = Ns Aq Ar port_number
270 Use specified port number for NFS requests.
271 The default is to query the portmapper for the NFS port.
273 Used with NFSV3 to specify that the \fBReaddirPlus\fR RPC should
275 For NFSV4, setting this option has a similar effect, in that it will make
276 the Readdir Operation get more attributes.
277 This option reduces RPC traffic for cases such as
279 but tends to flood the attribute and name caches with prefetched entries.
280 Try this option and see whether performance improves or degrades.
282 most useful for client to server network interconnects with a large bandwidth
284 .It Cm readahead Ns = Ns Aq Ar value
285 Set the read-ahead count to the specified value.
286 This may be in the range of 0 - 4, and determines how many blocks
287 will be read ahead when a large file is being read sequentially.
288 Trying a value greater than 1 for this is suggested for
289 mounts with a large bandwidth * delay product.
290 .It Cm readdirsize Ns = Ns Aq Ar value
291 Set the readdir read size to the specified value.
292 The value should normally
295 that is <= the read size for the mount.
297 Use a reserved socket port number.
298 This flag is obsolete, and only retained for compatibility reasons.
299 Reserved port numbers are used by default now.
300 (For the rare case where the client has a trusted root account
301 but untrustworthy users and the network cables are in secure areas this does
302 help, but for normal desktop clients this does not apply.)
303 .It Cm retrans Ns = Ns Aq Ar value
304 Set the retransmit timeout count for soft mounts to the specified value.
305 .It Cm retrycnt Ns = Ns Aq Ar count
306 Set the mount retry count to the specified value.
307 The default is a retry count of zero, which means to keep retrying
309 There is a 60 second delay between each attempt.
310 .It Cm rsize Ns = Ns Aq Ar value
311 Set the read data size to the specified value.
312 It should normally be a power of 2 greater than or equal to 1024.
313 This should be used for UDP mounts when the
314 .Dq "fragments dropped due to timeout"
315 value is getting large while actively using a mount point.
320 option to see what the
321 .Dq "fragments dropped due to timeout"
323 .It Cm sec Ns = Ns Aq Ar flavor
324 This option specifies what security flavor should be used for the mount.
327 krb5 - Use KerberosV authentication
328 krb5i - Use KerberosV authentication and
329 apply integrity checksums to RPCs
330 krb5p - Use KerberosV authentication and
332 sys - The default AUTH_SYS, which uses a
333 uid + gid list authenticator
336 A soft mount, which implies that file system calls will fail
339 round trip timeout intervals.
342 This is the default option, as it provides for increased reliability on both
343 LAN and WAN configurations compared to UDP.
344 Some old NFS servers do not support this method; UDP mounts may be required
345 for interoperability.
346 .It Cm timeout Ns = Ns Aq Ar value
347 Set the initial retransmit timeout to the specified value.
348 May be useful for fine tuning UDP mounts over internetworks
349 with high packet loss rates or an overloaded server.
350 Try increasing the interval if
352 shows high retransmit rates while the file system is active or reducing the
353 value if there is a low retransmit rate but long response delay observed.
356 option should be specified when using this option to manually
361 .It Cm wcommitsize Ns = Ns Aq Ar value
362 Set the maximum pending write commit size to the specified value.
363 This determines the maximum amount of pending write data that the NFS
364 client is willing to cache for each file.
365 .It Cm wsize Ns = Ns Aq Ar value
366 Set the write data size to the specified value.
367 Ditto the comments w.r.t.\& the
369 option, but using the
370 .Dq "fragments dropped due to timeout"
371 value on the server instead of the client.
376 options should only be used as a last ditch effort at improving performance
377 when mounting servers that do not support TCP mounts.
381 The following command line flags are equivalent to
383 named options and are supported for compatibility with older
385 .Bl -tag -width indent
397 .Fl o Cm readdirsize Ns = Ns Aq Ar value
405 Use a reserved socket port number.
406 This flag is obsolete, and only retained for compatibility reasons.
407 (For the rare case where the client has a trusted root account
408 but untrustworthy users and the network cables are in secure areas this does
409 help, but for normal desktop clients this does not apply.)
412 .Fl o Cm retrycnt Ns = Ns Aq Ar value
421 .Fl o Cm readahead Ns = Ns Aq Ar value
442 .Fl o Cm rsize Ns = Ns Aq Ar value
448 .Fl o Cm retransmit Ns = Ns Aq Ar value
451 .Fl o Cm wsize Ns = Ns Aq Ar value
454 .Fl o Cm retrans Ns = Ns Aq Ar value
467 Since nfsv4 performs open/lock operations that have their ordering strictly
468 enforced by the server, the options
472 cannot be safely used.
474 nfsv4 mounts are strongly recommended.