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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
63 it implements the mount protocol as described in RFC 1094, Appendix A and
65 For NFSv4, it uses the NFSv4 protocol as described in RFC 7530, RFC 5661 and
70 keeps retrying until the mount succeeds.
71 This behaviour is intended for file systems listed in
73 that are critical to the boot process.
74 For non-critical file systems, the
78 options provide mechanisms to prevent the boot process from hanging
79 if the server is unavailable.
81 If the server becomes unresponsive while an NFS file system is
82 mounted, any new or outstanding file operations on that file system
83 will hang uninterruptibly until the server comes back.
84 To modify this default behaviour, see the
91 .Bl -tag -width indent
93 Options are specified with a
95 flag followed by a comma separated string of options.
98 man page for possible options and their meanings.
99 The following NFS specific options are also available:
100 .Bl -tag -width indent
101 .It Cm acregmin Ns = Ns Aq Ar seconds
102 .It Cm acregmax Ns = Ns Aq Ar seconds
103 .It Cm acdirmin Ns = Ns Aq Ar seconds
104 .It Cm acdirmax Ns = Ns Aq Ar seconds
105 When attributes of files are cached, a timeout calculated to determine
106 whether a given cache entry has expired.
107 These four values determine the upper and lower bounds of the timeouts for
111 (ie: everything else).
112 The default values are 3 -> 60 seconds
113 for regular files, and 30 -> 60 seconds for directories.
114 The algorithm to calculate the timeout is based on the age of the file.
116 the longer the cache is considered valid, subject to the limits above.
117 .It Cm actimeo Ns = Ns Aq Ar seconds
118 Set four cache timeouts above to specified value.
120 This option can be used along with
122 to specify that all operations should use the host-based initiator
124 This may be used for clients that run system daemons that need to
125 access files on the NFSv4 mounted volume.
127 If an initial attempt to contact the server fails, fork off a child to keep
128 trying the mount in the background.
131 where the file system mount is not critical to multiuser operation.
132 .It Cm deadthresh Ns = Ns Aq Ar value
134 .Dq "dead server threshold"
135 to the specified number of round trip timeout intervals before a
136 .Dq "server not responding"
137 message is displayed.
139 Turn off the dynamic retransmit timeout estimator.
140 This may be useful for UDP mounts that exhibit high retry rates,
141 since it is possible that the dynamically estimated timeout interval is too
144 Same as not specifying
146 .It Cm gssname Ns = Ns Aq Ar service-principal-name
147 This option can be used with the KerberosV security flavors for NFSv4 mounts
149 .Dq "service-principal-name"
150 of a host-based entry in the default
151 keytab file that is used for system operations.
152 It allows the mount to be performed by
154 and avoids problems with
155 cached credentials for the system operations expiring.
157 .Dq "service-prinicpal-name"
158 should be specified without instance or domain and is typically
164 Same as not specifying
167 Make the mount interruptible, which implies that file system calls that
168 are delayed due to an unresponsive server will fail with EINTR when a
169 termination signal is posted for the process.
170 .It Cm maxgroups Ns = Ns Aq Ar value
171 Set the maximum size of the group list for the credentials to the
173 This should be used for mounts on old servers that cannot handle a
174 group list size of 16, as specified in RFC 1057.
175 Try 8, if users in a lot of groups cannot get response from the mount
178 Force the mount protocol to use UDP transport, even for TCP NFS mounts.
179 (Necessary for some old
182 .It Cm nametimeo Ns = Ns Aq Ar value
183 Override the default of NFS_DEFAULT_NAMETIMEO for the timeout (in seconds)
184 for positive name cache entries.
185 If this is set to 0 it disables positive name caching for the mount point.
186 .It Cm negnametimeo Ns = Ns Aq Ar value
187 Override the default of NFS_DEFAULT_NEGNAMETIMEO for the timeout (in seconds)
188 for negative name cache entries.
189 If this is set to 0 it disables negative name caching for the mount point.
191 Use the NFS Version 2 protocol (the default is to try version 3 first
193 Note that NFS version 2 has a file size limit of 2 gigabytes.
195 Use the NFS Version 3 protocol.
197 Use the NFS Version 4 protocol.
198 This option will force the mount to use
200 .It Cm minorversion Ns = Ns Aq Ar value
201 Override the default of 0 for the minor version of the NFS Version 4 protocol.
202 The minor versions other than 0 currently supported are 1 and 2.
203 This option is only meaningful when used with the
207 Make a minor version 1 or 2 of the NFS Version 4 protocol mount use a single
208 OpenOwner for all Opens.
209 This may be useful for a server with a very low limit on OpenOwners, such as
211 It ca only be used with an NFSv4.1 or NFSv4.2 mount.
212 It may not work correctly when Delegations are being issued by a server,
213 but note that the AmazonEFS server does not issued delegations at this time.
215 Enable support for parallel NFS (pNFS) for minor version 1 or 2 of the
216 NFS Version 4 protocol.
217 This option is only meaningful when used with the
221 Disable attribute caching.
223 For UDP mount points, do not do a
225 This must be used if the server does not reply to requests from the standard
226 NFS port number 2049 or replies to requests using a different IP address
227 (which can occur if the server is multi-homed).
229 .Va vfs.nfs.nfs_ip_paranoia
230 sysctl to 0 will make this option the default.
232 Normally, NFS clients maintain the close-to-open cache coherency.
233 This works by flushing at close time and checking at open time.
234 Checking at open time is implemented by getting attributes from
235 the server and purging the data cache if they do not match
236 attributes cached by the client.
238 This option disables checking at open time.
239 It may improve performance for read-only mounts,
240 but should only be used if the data on the server changes rarely.
241 Be sure to understand the consequences before enabling this option.
242 .It Cm noinet4 , noinet6
248 Useful for hosts that have
249 both an A record and an AAAA record for the same name.
255 locks over the wire via the NLM protocol for NFSv3 mounts.
256 All locks will be local and not seen by the server
257 and likewise not seen by other NFS clients for NFSv3 mounts.
258 This removes the need to run the
264 servers on the client.
265 Note that this option will only be honored when performing the
266 initial mount, it will be silently ignored if used while updating
268 Also, note that NFSv4 mounts do not use these daemons and handle locks over the
269 wire in the NFSv4 protocol.
270 As such, this option is meaningless for NFSv4 mounts.
272 This mount option allows the NFS client to
273 combine non-contiguous byte ranges being written
274 such that the dirty byte range becomes a superset of the bytes
276 This reduces the number of writes significantly for software
278 The merging of byte ranges is not done if the file has been file
279 locked, since most applications modifying a file from multiple
280 clients will use file locking.
281 As such, this option could result in a corrupted file for the
282 rare case of an application modifying the file from multiple
283 clients concurrently without using file locking.
285 For the RPCSEC_GSS security flavors, such as krb5, krb5i and krb5p,
286 this option sets the name of the host based principal name expected
288 This option overrides the default, which will be ``nfs@<server-fqdn>''
289 and should normally be sufficient.
293 use a reserved socket port number (see below).
294 .It Cm port Ns = Ns Aq Ar port_number
295 Use specified port number for NFS requests.
296 The default is to query the portmapper for the NFS port.
297 .It Cm proto Ns = Ns Aq Ar protocol
298 Specify transport protocol version to use.
301 udp - Use UDP over IPv4
302 tcp - Use TCP over IPv4
303 udp6 - Use UDP over IPv6
304 tcp6 - Use TCP over IPv6
307 Used with NFSV3 to specify that the \fBReaddirPlus\fR RPC should
309 For NFSV4, setting this option has a similar effect, in that it will make
310 the Readdir Operation get more attributes.
311 This option reduces RPC traffic for cases such as
313 but tends to flood the attribute and name caches with prefetched entries.
314 Try this option and see whether performance improves or degrades.
316 most useful for client to server network interconnects with a large bandwidth
318 .It Cm readahead Ns = Ns Aq Ar value
319 Set the read-ahead count to the specified value.
320 This may be in the range of 0 - 4, and determines how many blocks
321 will be read ahead when a large file is being read sequentially.
322 Trying a value greater than 1 for this is suggested for
323 mounts with a large bandwidth * delay product.
324 .It Cm readdirsize Ns = Ns Aq Ar value
325 Set the readdir read size to the specified value.
326 The value should normally
329 that is <= the read size for the mount.
331 Use a reserved socket port number.
332 This flag is obsolete, and only retained for compatibility reasons.
333 Reserved port numbers are used by default now.
334 (For the rare case where the client has a trusted root account
335 but untrustworthy users and the network cables are in secure areas this does
336 help, but for normal desktop clients this does not apply.)
337 .It Cm retrans Ns = Ns Aq Ar value
338 Set the retransmit timeout count for soft mounts to the specified value.
339 .It Cm retrycnt Ns = Ns Aq Ar count
340 Set the mount retry count to the specified value.
341 The default is a retry count of zero, which means to keep retrying
343 There is a 60 second delay between each attempt.
344 .It Cm rsize Ns = Ns Aq Ar value
345 Set the read data size to the specified value.
346 It should normally be a power of 2 greater than or equal to 1024.
347 This should be used for UDP mounts when the
348 .Dq "fragments dropped due to timeout"
349 value is getting large while actively using a mount point.
354 option to see what the
355 .Dq "fragments dropped due to timeout"
357 .It Cm sec Ns = Ns Aq Ar flavor
358 This option specifies what security flavor should be used for the mount.
361 krb5 - Use KerberosV authentication
362 krb5i - Use KerberosV authentication and
363 apply integrity checksums to RPCs
364 krb5p - Use KerberosV authentication and
366 sys - The default AUTH_SYS, which uses a
367 uid + gid list authenticator
370 A soft mount, which implies that file system calls will fail
373 round trip timeout intervals.
376 This is the default option, as it provides for increased reliability on both
377 LAN and WAN configurations compared to UDP.
378 Some old NFS servers do not support this method; UDP mounts may be required
379 for interoperability.
380 .It Cm timeout Ns = Ns Aq Ar value
381 Set the initial retransmit timeout to the specified value,
382 expressed in tenths of a second.
383 May be useful for fine tuning UDP mounts over internetworks
384 with high packet loss rates or an overloaded server.
385 Try increasing the interval if
387 shows high retransmit rates while the file system is active or reducing the
388 value if there is a low retransmit rate but long response delay observed.
391 option should be specified when using this option to manually
394 .It Cm timeo Ns = Ns Aq Ar value
399 .It Cm vers Ns = Ns Aq Ar vers_number
400 Use the specified version number for NFS requests.
407 .It Cm wcommitsize Ns = Ns Aq Ar value
408 Set the maximum pending write commit size to the specified value.
409 This determines the maximum amount of pending write data that the NFS
410 client is willing to cache for each file.
411 .It Cm wsize Ns = Ns Aq Ar value
412 Set the write data size to the specified value.
413 Ditto the comments w.r.t.\& the
415 option, but using the
416 .Dq "fragments dropped due to timeout"
417 value on the server instead of the client.
422 options should only be used as a last ditch effort at improving performance
423 when mounting servers that do not support TCP mounts.
427 The following command line flags are equivalent to
429 named options and are supported for compatibility with older
431 .Bl -tag -width indent
443 .Fl o Cm readdirsize Ns = Ns Aq Ar value
451 Use a reserved socket port number.
452 This flag is obsolete, and only retained for compatibility reasons.
453 (For the rare case where the client has a trusted root account
454 but untrustworthy users and the network cables are in secure areas this does
455 help, but for normal desktop clients this does not apply.)
458 .Fl o Cm retrycnt Ns = Ns Aq Ar value
467 .Fl o Cm readahead Ns = Ns Aq Ar value
488 .Fl o Cm rsize Ns = Ns Aq Ar value
494 .Fl o Cm retransmit Ns = Ns Aq Ar value
497 .Fl o Cm wsize Ns = Ns Aq Ar value
500 .Fl o Cm retrans Ns = Ns Aq Ar value
505 named options are equivalent to other
507 named options and are supported for compatibility with other
508 operating systems (e.g., Linux, Solaris, and OSX) to ease usage of
511 .Bl -tag -width indent
512 .It Fl o Cm vers Ns = Ns 2
515 .It Fl o Cm vers Ns = Ns 3
518 .It Fl o Cm vers Ns = Ns 4
538 Since nfsv4 performs open/lock operations that have their ordering strictly
539 enforced by the server, the options
543 cannot be safely used.
545 nfsv4 mounts are strongly recommended.