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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
169 can also be used if the local system's
171 value does not match the host-based principal in the keytab.
173 Same as not specifying
176 Make the mount interruptible, which implies that file system calls that
177 are delayed due to an unresponsive server will fail with EINTR when a
178 termination signal is posted for the process.
179 .It Cm maxgroups Ns = Ns Aq Ar value
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 Force the mount protocol to use UDP transport, even for TCP NFS mounts.
188 (Necessary for some old
191 .It Cm nametimeo Ns = Ns Aq Ar value
192 Override the default of NFS_DEFAULT_NAMETIMEO for the timeout (in seconds)
193 for positive name cache entries.
194 If this is set to 0 it disables positive name caching for the mount point.
195 .It Cm negnametimeo Ns = Ns Aq Ar value
196 Override the default of NFS_DEFAULT_NEGNAMETIMEO for the timeout (in seconds)
197 for negative name cache entries.
198 If this is set to 0 it disables negative name caching for the mount point.
200 Use the NFS Version 2 protocol (the default is to try version 3 first
202 Note that NFS version 2 has a file size limit of 2 gigabytes.
204 Use the NFS Version 3 protocol.
206 Use the NFS Version 4 protocol.
207 This option will force the mount to use
209 .It Cm minorversion Ns = Ns Aq Ar value
210 Override the default of 0 for the minor version of the NFS Version 4 protocol.
211 The minor versions other than 0 currently supported are 1 and 2.
212 This option is only meaningful when used with the
216 Make a minor version 1 or 2 of the NFS Version 4 protocol mount use a single
217 OpenOwner for all Opens.
218 This may be useful for a server with a very low limit on OpenOwners, such as
220 It ca only be used with an NFSv4.1 or NFSv4.2 mount.
221 It may not work correctly when Delegations are being issued by a server,
222 but note that the AmazonEFS server does not issued delegations at this time.
224 Enable support for parallel NFS (pNFS) for minor version 1 or 2 of the
225 NFS Version 4 protocol.
226 This option is only meaningful when used with the
230 Disable attribute caching.
232 For UDP mount points, do not do a
234 This must be used if the server does not reply to requests from the standard
235 NFS port number 2049 or replies to requests using a different IP address
236 (which can occur if the server is multi-homed).
238 .Va vfs.nfs.nfs_ip_paranoia
239 sysctl to 0 will make this option the default.
241 Normally, NFS clients maintain the close-to-open cache coherency.
242 This works by flushing at close time and checking at open time.
243 Checking at open time is implemented by getting attributes from
244 the server and purging the data cache if they do not match
245 attributes cached by the client.
247 This option disables checking at open time.
248 It may improve performance for read-only mounts,
249 but should only be used if the data on the server changes rarely.
250 Be sure to understand the consequences before enabling this option.
251 .It Cm noinet4 , noinet6
257 Useful for hosts that have
258 both an A record and an AAAA record for the same name.
264 locks over the wire via the NLM protocol for NFSv3 mounts.
265 All locks will be local and not seen by the server
266 and likewise not seen by other NFS clients for NFSv3 mounts.
267 This removes the need to run the
273 servers on the client.
274 Note that this option will only be honored when performing the
275 initial mount, it will be silently ignored if used while updating
277 Also, note that NFSv4 mounts do not use these daemons and handle locks over the
278 wire in the NFSv4 protocol.
279 As such, this option is meaningless for NFSv4 mounts.
281 This mount option allows the NFS client to
282 combine non-contiguous byte ranges being written
283 such that the dirty byte range becomes a superset of the bytes
285 This reduces the number of writes significantly for software
287 The merging of byte ranges is not done if the file has been file
288 locked, since most applications modifying a file from multiple
289 clients will use file locking.
290 As such, this option could result in a corrupted file for the
291 rare case of an application modifying the file from multiple
292 clients concurrently without using file locking.
294 For the RPCSEC_GSS security flavors, such as krb5, krb5i and krb5p,
295 this option sets the name of the host based principal name expected
297 This option overrides the default, which will be ``nfs@<server-fqdn>''
298 and should normally be sufficient.
302 use a reserved socket port number (see below).
303 .It Cm port Ns = Ns Aq Ar port_number
304 Use specified port number for NFS requests.
305 The default is to query the portmapper for the NFS port.
306 .It Cm proto Ns = Ns Aq Ar protocol
307 Specify transport protocol version to use.
310 udp - Use UDP over IPv4
311 tcp - Use TCP over IPv4
312 udp6 - Use UDP over IPv6
313 tcp6 - Use TCP over IPv6
316 Used with NFSV3 to specify that the \fBReaddirPlus\fR RPC should
318 For NFSV4, setting this option has a similar effect, in that it will make
319 the Readdir Operation get more attributes.
320 This option reduces RPC traffic for cases such as
322 but tends to flood the attribute and name caches with prefetched entries.
323 Try this option and see whether performance improves or degrades.
325 most useful for client to server network interconnects with a large bandwidth
327 .It Cm readahead Ns = Ns Aq Ar value
328 Set the read-ahead count to the specified value.
329 This may be in the range of 0 - 4, and determines how many blocks
330 will be read ahead when a large file is being read sequentially.
331 Trying a value greater than 1 for this is suggested for
332 mounts with a large bandwidth * delay product.
333 .It Cm readdirsize Ns = Ns Aq Ar value
334 Set the readdir read size to the specified value.
335 The value should normally
338 that is <= the read size for the mount.
340 Use a reserved socket port number.
341 This flag is obsolete, and only retained for compatibility reasons.
342 Reserved port numbers are used by default now.
343 (For the rare case where the client has a trusted root account
344 but untrustworthy users and the network cables are in secure areas this does
345 help, but for normal desktop clients this does not apply.)
346 .It Cm retrans Ns = Ns Aq Ar value
347 Set the retransmit timeout count for soft mounts to the specified value.
348 .It Cm retrycnt Ns = Ns Aq Ar count
349 Set the mount retry count to the specified value.
350 The default is a retry count of zero, which means to keep retrying
352 There is a 60 second delay between each attempt.
353 .It Cm rsize Ns = Ns Aq Ar value
354 Set the read data size to the specified value.
355 It should normally be a power of 2 greater than or equal to 1024.
356 This should be used for UDP mounts when the
357 .Dq "fragments dropped due to timeout"
358 value is getting large while actively using a mount point.
363 option to see what the
364 .Dq "fragments dropped due to timeout"
366 .It Cm sec Ns = Ns Aq Ar flavor
367 This option specifies what security flavor should be used for the mount.
370 krb5 - Use KerberosV authentication
371 krb5i - Use KerberosV authentication and
372 apply integrity checksums to RPCs
373 krb5p - Use KerberosV authentication and
375 sys - The default AUTH_SYS, which uses a
376 uid + gid list authenticator
379 A soft mount, which implies that file system calls will fail
382 round trip timeout intervals.
385 This is the default option, as it provides for increased reliability on both
386 LAN and WAN configurations compared to UDP.
387 Some old NFS servers do not support this method; UDP mounts may be required
388 for interoperability.
389 .It Cm timeout Ns = Ns Aq Ar value
390 Set the initial retransmit timeout to the specified value,
391 expressed in tenths of a second.
392 May be useful for fine tuning UDP mounts over internetworks
393 with high packet loss rates or an overloaded server.
394 Try increasing the interval if
396 shows high retransmit rates while the file system is active or reducing the
397 value if there is a low retransmit rate but long response delay observed.
400 option should be specified when using this option to manually
403 .It Cm timeo Ns = Ns Aq Ar value
408 .It Cm vers Ns = Ns Aq Ar vers_number
409 Use the specified version number for NFS requests.
416 .It Cm wcommitsize Ns = Ns Aq Ar value
417 Set the maximum pending write commit size to the specified value.
418 This determines the maximum amount of pending write data that the NFS
419 client is willing to cache for each file.
420 .It Cm wsize Ns = Ns Aq Ar value
421 Set the write data size to the specified value.
422 Ditto the comments w.r.t.\& the
424 option, but using the
425 .Dq "fragments dropped due to timeout"
426 value on the server instead of the client.
431 options should only be used as a last ditch effort at improving performance
432 when mounting servers that do not support TCP mounts.
436 The following command line flags are equivalent to
438 named options and are supported for compatibility with older
440 .Bl -tag -width indent
452 .Fl o Cm readdirsize Ns = Ns Aq Ar value
460 Use a reserved socket port number.
461 This flag is obsolete, and only retained for compatibility reasons.
462 (For the rare case where the client has a trusted root account
463 but untrustworthy users and the network cables are in secure areas this does
464 help, but for normal desktop clients this does not apply.)
467 .Fl o Cm retrycnt Ns = Ns Aq Ar value
476 .Fl o Cm readahead Ns = Ns Aq Ar value
497 .Fl o Cm rsize Ns = Ns Aq Ar value
503 .Fl o Cm retransmit Ns = Ns Aq Ar value
506 .Fl o Cm wsize Ns = Ns Aq Ar value
509 .Fl o Cm retrans Ns = Ns Aq Ar value
514 named options are equivalent to other
516 named options and are supported for compatibility with other
517 operating systems (e.g., Linux, Solaris, and OSX) to ease usage of
520 .Bl -tag -width indent
521 .It Fl o Cm vers Ns = Ns 2
524 .It Fl o Cm vers Ns = Ns 3
527 .It Fl o Cm vers Ns = Ns 4
547 Since nfsv4 performs open/lock operations that have their ordering strictly
548 enforced by the server, the options
552 cannot be safely used.
554 nfsv4 mounts are strongly recommended.