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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.
199 .It Cm nconnect Ns = Ns Aq Ar value
200 Specify the number of TCP connections (1-16) to be used
201 for an NFS Version 4, minor version 1 or 2 mount.
202 Multiple TCP connections can provide more client to server network
203 bandwidth for certain network configurations such as:
205 - Multiple network interfaces that are aggregated together.
206 - A fast network interface that uses multiple queues.
209 The first TCP connection will be used for all RPCs that consist
210 entirely of small RPC messages.
211 The RPCs that can have large RPC messages (Read/Readdir/Write) are
212 distributed over the additional TCP connections in a round robin
214 This option will result in more IP port#s being used.
215 This option requires the
219 Use the NFS Version 2 protocol (the default is to try version 3 first
221 Note that NFS version 2 has a file size limit of 2 gigabytes.
223 Use the NFS Version 3 protocol.
225 Use the NFS Version 4 protocol.
226 This option will force the mount to use
228 By default, the highest minor version of NFS Version 4 that is
229 supported by the NFS Version 4 server will be used.
233 .It Cm minorversion Ns = Ns Aq Ar value
234 Use the specified minor version for a NFS Version 4 mount,
235 overriding the default.
236 The minor versions supported are 0, 1, and 2.
237 This option is only meaningful when used with the
241 Make a minor version 1 or 2 of the NFS Version 4 protocol mount use a single
242 OpenOwner for all Opens.
243 This may be useful for a server with a very low limit on OpenOwners, such as
245 It may be required when an accumulation of NFS version 4 Opens occurs,
254 command-line options.
255 A common case for an accumulation of Opens is a shared library within
256 the NFS mount that is used by several
257 processes, where at least one of these processes is always running.
258 This option cannot be used for an NFS Version 4, minor version 0 mount.
259 It may not work correctly when Delegations are being issued by a server,
260 but note that the AmazonEFS server does not issued delegations at this time.
261 This option is only meaningful when used with the
265 Enable support for parallel NFS (pNFS) for minor version 1 or 2 of the
266 NFS Version 4 protocol.
267 This option is only meaningful when used with the
271 Disable attribute caching.
273 For UDP mount points, do not do a
275 This must be used if the server does not reply to requests from the standard
276 NFS port number 2049 or replies to requests using a different IP address
277 (which can occur if the server is multi-homed).
279 .Va vfs.nfs.nfs_ip_paranoia
280 sysctl to 0 will make this option the default.
282 Normally, NFS clients maintain the close-to-open cache coherency.
283 This works by flushing at close time and checking at open time.
284 Checking at open time is implemented by getting attributes from
285 the server and purging the data cache if they do not match
286 attributes cached by the client.
288 This option disables checking at open time.
289 It may improve performance for read-only mounts,
290 but should only be used if the data on the server changes rarely.
291 Be sure to understand the consequences before enabling this option.
292 .It Cm noinet4 , noinet6
298 Useful for hosts that have
299 both an A record and an AAAA record for the same name.
305 locks over the wire via the NLM protocol for NFSv3 mounts.
306 All locks will be local and not seen by the server
307 and likewise not seen by other NFS clients for NFSv3 mounts.
308 This removes the need to run the
314 servers on the client.
315 Note that this option will only be honored when performing the
316 initial mount, it will be silently ignored if used while updating
318 Also, note that NFSv4 mounts do not use these daemons and handle locks over the
319 wire in the NFSv4 protocol.
320 As such, this option is meaningless for NFSv4 mounts.
322 This mount option allows the NFS client to
323 combine non-contiguous byte ranges being written
324 such that the dirty byte range becomes a superset of the bytes
326 This reduces the number of writes significantly for software
328 The merging of byte ranges is not done if the file has been file
329 locked, since most applications modifying a file from multiple
330 clients will use file locking.
331 As such, this option could result in a corrupted file for the
332 rare case of an application modifying the file from multiple
333 clients concurrently without using file locking.
335 For the RPCSEC_GSS security flavors, such as krb5, krb5i and krb5p,
336 this option sets the name of the host based principal name expected
338 This option overrides the default, which will be ``nfs@<server-fqdn>''
339 and should normally be sufficient.
343 use a reserved socket port number (see below).
344 .It Cm port Ns = Ns Aq Ar port_number
345 Use specified port number for NFS requests.
346 The default is to query the portmapper for the NFS port.
347 .It Cm proto Ns = Ns Aq Ar protocol
348 Specify transport protocol version to use.
351 udp - Use UDP over IPv4
352 tcp - Use TCP over IPv4
353 udp6 - Use UDP over IPv6
354 tcp6 - Use TCP over IPv6
357 Used with NFSV3 to specify that the \fBReaddirPlus\fR RPC should
359 For NFSV4, setting this option has a similar effect, in that it will make
360 the Readdir Operation get more attributes.
361 This option reduces RPC traffic for cases such as
363 but tends to flood the attribute and name caches with prefetched entries.
364 Try this option and see whether performance improves or degrades.
366 most useful for client to server network interconnects with a large bandwidth
368 .It Cm readahead Ns = Ns Aq Ar value
369 Set the read-ahead count to the specified value.
370 This may be in the range of 0 - 4, and determines how many blocks
371 will be read ahead when a large file is being read sequentially.
372 Trying a value greater than 1 for this is suggested for
373 mounts with a large bandwidth * delay product.
374 .It Cm readdirsize Ns = Ns Aq Ar value
375 Set the readdir read size to the specified value.
376 The value should normally
379 that is <= the read size for the mount.
381 Use a reserved socket port number.
382 This flag is obsolete, and only retained for compatibility reasons.
383 Reserved port numbers are used by default now.
384 (For the rare case where the client has a trusted root account
385 but untrustworthy users and the network cables are in secure areas this does
386 help, but for normal desktop clients this does not apply.)
387 .It Cm retrans Ns = Ns Aq Ar value
388 Set the retransmit timeout count for soft mounts to the specified value.
389 .It Cm retrycnt Ns = Ns Aq Ar count
390 Set the mount retry count to the specified value.
391 The default is a retry count of zero, which means to keep retrying
393 There is a 60 second delay between each attempt.
394 .It Cm rsize Ns = Ns Aq Ar value
395 Set the read data size to the specified value.
396 It should normally be a power of 2 greater than or equal to 1024.
397 This should be used for UDP mounts when the
398 .Dq "fragments dropped due to timeout"
399 value is getting large while actively using a mount point.
404 option to see what the
405 .Dq "fragments dropped due to timeout"
407 .It Cm sec Ns = Ns Aq Ar flavor
408 This option specifies what security flavor should be used for the mount.
411 krb5 - Use KerberosV authentication
412 krb5i - Use KerberosV authentication and
413 apply integrity checksums to RPCs
414 krb5p - Use KerberosV authentication and
416 sys - The default AUTH_SYS, which uses a
417 uid + gid list authenticator
420 A soft mount, which implies that file system calls will fail
423 round trip timeout intervals.
426 This is the default option, as it provides for increased reliability on both
427 LAN and WAN configurations compared to UDP.
428 Some old NFS servers do not support this method; UDP mounts may be required
429 for interoperability.
430 .It Cm timeout Ns = Ns Aq Ar value
431 Set the initial retransmit timeout to the specified value,
432 expressed in tenths of a second.
433 May be useful for fine tuning UDP mounts over internetworks
434 with high packet loss rates or an overloaded server.
435 Try increasing the interval if
437 shows high retransmit rates while the file system is active or reducing the
438 value if there is a low retransmit rate but long response delay observed.
441 option should be specified when using this option to manually
444 .It Cm timeo Ns = Ns Aq Ar value
448 This option specifies that the connection to the server must use TLS
450 TLS is only supported for TCP connections and the
452 daemon must be running for an NFS over TCP connection to use TLS.
453 .It Cm tlscertname Ns = Ns Aq Ar name
454 This option specifies the name of an alternate certificate to be
455 presented to the NFS server during TLS handshake.
456 The default certificate file names are
460 When this option is specified,
464 in the above file names.
465 For example, if the value of
469 the certificate file names to be used will be
473 These files are stored in
474 .Pa /etc/rpc.tlsclntd
476 This option is only meaningful when used with the
482 command line flag set.
485 .It Cm vers Ns = Ns Aq Ar vers_number
486 Use the specified version number for NFS requests.
493 .It Cm wcommitsize Ns = Ns Aq Ar value
494 Set the maximum pending write commit size to the specified value.
495 This determines the maximum amount of pending write data that the NFS
496 client is willing to cache for each file.
497 .It Cm wsize Ns = Ns Aq Ar value
498 Set the write data size to the specified value.
499 Ditto the comments w.r.t.\& the
501 option, but using the
502 .Dq "fragments dropped due to timeout"
503 value on the server instead of the client.
508 options should only be used as a last ditch effort at improving performance
509 when mounting servers that do not support TCP mounts.
513 The following command line flags are equivalent to
515 named options and are supported for compatibility with older
517 .Bl -tag -width indent
529 .Fl o Cm readdirsize Ns = Ns Aq Ar value
537 Use a reserved socket port number.
538 This flag is obsolete, and only retained for compatibility reasons.
539 (For the rare case where the client has a trusted root account
540 but untrustworthy users and the network cables are in secure areas this does
541 help, but for normal desktop clients this does not apply.)
544 .Fl o Cm retrycnt Ns = Ns Aq Ar value
553 .Fl o Cm readahead Ns = Ns Aq Ar value
574 .Fl o Cm rsize Ns = Ns Aq Ar value
580 .Fl o Cm retransmit Ns = Ns Aq Ar value
583 .Fl o Cm wsize Ns = Ns Aq Ar value
586 .Fl o Cm retrans Ns = Ns Aq Ar value
591 named options are equivalent to other
593 named options and are supported for compatibility with other
594 operating systems (e.g., Linux, Solaris, and OSX) to ease usage of
597 .Bl -tag -width indent
598 .It Fl o Cm vers Ns = Ns 2
601 .It Fl o Cm vers Ns = Ns 3
604 .It Fl o Cm vers Ns = Ns 4
608 .Sh IMPLEMENTATION NOTES
613 options are specified, the I/O size will be set to the largest value
614 supported by both the NFS client and server.
615 The largest value supported by the NFS client is defined by
618 which can be set to a power of two up to
625 command line option will show what
627 option settings are actually in use for the mount.
647 Since nfsv4 performs open/lock operations that have their ordering strictly
648 enforced by the server, the options
652 cannot be safely used.
654 nfsv4 mounts are strongly recommended.