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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.
135 fork off a child to keep trying the mount in the background,
136 but do not attempt to mount in the foreground first.
138 60+ second timeout when the server is not responding.
139 Useful for speeding up the boot process of a client when the server is
140 likely to be unavailable.
141 This is often the case for interdependent servers
142 such as cross-mounted servers (each of two servers is an NFS client of
143 the other) and for cluster nodes that must boot before the file servers.
144 .It Cm deadthresh Ns = Ns Aq Ar value
146 .Dq "dead server threshold"
147 to the specified number of round trip timeout intervals before a
148 .Dq "server not responding"
149 message is displayed.
151 Turn off the dynamic retransmit timeout estimator.
152 This may be useful for UDP mounts that exhibit high retry rates,
153 since it is possible that the dynamically estimated timeout interval is too
156 Same as not specifying
158 .It Cm gssname Ns = Ns Aq Ar service-principal-name
159 This option can be used with the KerberosV security flavors for NFSv4 mounts
161 .Dq "service-principal-name"
162 of a host-based entry in the default
163 keytab file that is used for system operations.
164 It allows the mount to be performed by
166 and avoids problems with
167 cached credentials for the system operations expiring.
169 .Dq "service-prinicpal-name"
170 should be specified without instance or domain and is typically
181 can also be used if the local system's
183 value does not match the host-based principal in the keytab.
185 Same as not specifying
188 Make the mount interruptible, which implies that file system calls that
189 are delayed due to an unresponsive server will fail with EINTR when a
190 termination signal is posted for the process.
191 .It Cm maxgroups Ns = Ns Aq Ar value
192 Set the maximum size of the group list for the credentials to the
194 This should be used for mounts on old servers that cannot handle a
195 group list size of 16, as specified in RFC 1057.
196 Try 8, if users in a lot of groups cannot get response from the mount
199 Force the mount protocol to use UDP transport, even for TCP NFS mounts.
200 (Necessary for some old
203 .It Cm nametimeo Ns = Ns Aq Ar value
204 Override the default of NFS_DEFAULT_NAMETIMEO for the timeout (in seconds)
205 for positive name cache entries.
206 If this is set to 0 it disables positive name caching for the mount point.
207 .It Cm negnametimeo Ns = Ns Aq Ar value
208 Override the default of NFS_DEFAULT_NEGNAMETIMEO for the timeout (in seconds)
209 for negative name cache entries.
210 If this is set to 0 it disables negative name caching for the mount point.
211 .It Cm nconnect Ns = Ns Aq Ar value
212 Specify the number of TCP connections (1-16) to be used
213 for an NFS Version 4, minor version 1 or 2 mount.
214 Multiple TCP connections can provide more client to server network
215 bandwidth for certain network configurations such as:
217 - Multiple network interfaces that are aggregated together.
218 - A fast network interface that uses multiple queues.
221 The first TCP connection will be used for all RPCs that consist
222 entirely of small RPC messages.
223 The RPCs that can have large RPC messages (Read/Readdir/Write) are
224 distributed over the additional TCP connections in a round robin
226 This option will result in more IP port#s being used.
227 This option requires the
231 Use the NFS Version 2 protocol (the default is to try version 3 first
233 Note that NFS version 2 has a file size limit of 2 gigabytes.
235 Use the NFS Version 3 protocol.
237 Use the NFS Version 4 protocol.
238 This option will force the mount to use
240 By default, the highest minor version of NFS Version 4 that is
241 supported by the NFS Version 4 server will be used.
245 .It Cm minorversion Ns = Ns Aq Ar value
246 Use the specified minor version for a NFS Version 4 mount,
247 overriding the default.
248 The minor versions supported are 0, 1, and 2.
249 This option is only meaningful when used with the
253 Make a minor version 1 or 2 of the NFS Version 4 protocol mount use a single
254 OpenOwner for all Opens.
255 This may be useful for a server with a very low limit on OpenOwners, such as
257 It may be required when an accumulation of NFS version 4 Opens occurs,
266 command-line options.
267 A common case for an accumulation of Opens is a shared library within
268 the NFS mount that is used by several
269 processes, where at least one of these processes is always running.
270 This option cannot be used for an NFS Version 4, minor version 0 mount.
271 It may not work correctly when Delegations are being issued by a server,
272 but note that the AmazonEFS server does not issued delegations at this time.
273 This option is only meaningful when used with the
277 Enable support for parallel NFS (pNFS) for minor version 1 or 2 of the
278 NFS Version 4 protocol.
279 This option is only meaningful when used with the
283 Disable attribute caching.
285 For UDP mount points, do not do a
287 This must be used if the server does not reply to requests from the standard
288 NFS port number 2049 or replies to requests using a different IP address
289 (which can occur if the server is multi-homed).
291 .Va vfs.nfs.nfs_ip_paranoia
292 sysctl to 0 will make this option the default.
294 Normally, NFS clients maintain the close-to-open cache coherency.
295 This works by flushing at close time and checking at open time.
296 Checking at open time is implemented by getting attributes from
297 the server and purging the data cache if they do not match
298 attributes cached by the client.
300 This option disables checking at open time.
301 It may improve performance for read-only mounts,
302 but should only be used if the data on the server changes rarely.
303 Be sure to understand the consequences before enabling this option.
304 .It Cm noinet4 , noinet6
310 Useful for hosts that have
311 both an A record and an AAAA record for the same name.
317 locks over the wire via the NLM protocol for NFSv3 mounts.
318 All locks will be local and not seen by the server
319 and likewise not seen by other NFS clients for NFSv3 mounts.
320 This removes the need to run the
326 servers on the client.
327 Note that this option will only be honored when performing the
328 initial mount, it will be silently ignored if used while updating
330 Also, note that NFSv4 mounts do not use these daemons and handle locks over the
331 wire in the NFSv4 protocol.
332 As such, this option is meaningless for NFSv4 mounts.
334 This mount option allows the NFS client to
335 combine non-contiguous byte ranges being written
336 such that the dirty byte range becomes a superset of the bytes
338 This reduces the number of writes significantly for software
340 The merging of byte ranges is not done if the file has been file
341 locked, since most applications modifying a file from multiple
342 clients will use file locking.
343 As such, this option could result in a corrupted file for the
344 rare case of an application modifying the file from multiple
345 clients concurrently without using file locking.
347 For the RPCSEC_GSS security flavors, such as krb5, krb5i and krb5p,
348 this option sets the name of the host based principal name expected
350 This option overrides the default, which will be ``nfs@<server-fqdn>''
351 and should normally be sufficient.
355 use a reserved socket port number (see below).
356 .It Cm port Ns = Ns Aq Ar port_number
357 Use specified port number for NFS requests.
358 The default is to query the portmapper for the NFS port.
359 .It Cm proto Ns = Ns Aq Ar protocol
360 Specify transport protocol version to use.
363 udp - Use UDP over IPv4
364 tcp - Use TCP over IPv4
365 udp6 - Use UDP over IPv6
366 tcp6 - Use TCP over IPv6
369 Used with NFSV3 to specify that the \fBReaddirPlus\fR RPC should
371 For NFSV4, setting this option has a similar effect, in that it will make
372 the Readdir Operation get more attributes.
373 This option reduces RPC traffic for cases such as
375 but tends to flood the attribute and name caches with prefetched entries.
376 Try this option and see whether performance improves or degrades.
378 most useful for client to server network interconnects with a large bandwidth
380 .It Cm readahead Ns = Ns Aq Ar value
381 Set the read-ahead count to the specified value.
382 This may be in the range of 0 - 4, and determines how many blocks
383 will be read ahead when a large file is being read sequentially.
384 Trying a value greater than 1 for this is suggested for
385 mounts with a large bandwidth * delay product.
386 .It Cm readdirsize Ns = Ns Aq Ar value
387 Set the readdir read size to the specified value.
388 The value should normally
391 that is <= the read size for the mount.
393 Use a reserved socket port number.
394 This flag is obsolete, and only retained for compatibility reasons.
395 Reserved port numbers are used by default now.
396 (For the rare case where the client has a trusted root account
397 but untrustworthy users and the network cables are in secure areas this does
398 help, but for normal desktop clients this does not apply.)
399 .It Cm retrans Ns = Ns Aq Ar value
400 Set the retransmit timeout count for soft mounts to the specified value.
401 .It Cm retrycnt Ns = Ns Aq Ar count
402 Set the mount retry count to the specified value.
403 The default is a retry count of zero, which means to keep retrying
405 There is a 60 second delay between each attempt.
406 .It Cm rsize Ns = Ns Aq Ar value
407 Set the read data size to the specified value.
408 It should normally be a power of 2 greater than or equal to 1024.
409 This should be used for UDP mounts when the
410 .Dq "fragments dropped due to timeout"
411 value is getting large while actively using a mount point.
416 option to see what the
417 .Dq "fragments dropped due to timeout"
419 .It Cm sec Ns = Ns Aq Ar flavor
420 This option specifies what security flavor should be used for the mount.
423 krb5 - Use KerberosV authentication
424 krb5i - Use KerberosV authentication and
425 apply integrity checksums to RPCs
426 krb5p - Use KerberosV authentication and
428 sys - The default AUTH_SYS, which uses a
429 uid + gid list authenticator
432 A soft mount, which implies that file system calls will fail
435 round trip timeout intervals.
438 This is the default option, as it provides for increased reliability on both
439 LAN and WAN configurations compared to UDP.
440 Some old NFS servers do not support this method; UDP mounts may be required
441 for interoperability.
442 .It Cm timeout Ns = Ns Aq Ar value
443 Set the initial retransmit timeout to the specified value,
444 expressed in tenths of a second.
445 May be useful for fine tuning UDP mounts over internetworks
446 with high packet loss rates or an overloaded server.
447 Try increasing the interval if
449 shows high retransmit rates while the file system is active or reducing the
450 value if there is a low retransmit rate but long response delay observed.
453 option should be specified when using this option to manually
456 .It Cm timeo Ns = Ns Aq Ar value
460 This option specifies that the connection to the server must use TLS
462 TLS is only supported for TCP connections and the
464 daemon must be running for an NFS over TCP connection to use TLS.
465 .It Cm tlscertname Ns = Ns Aq Ar name
466 This option specifies the name of an alternate certificate to be
467 presented to the NFS server during TLS handshake.
468 The default certificate file names are
472 When this option is specified,
476 in the above file names.
477 For example, if the value of
481 the certificate file names to be used will be
485 These files are stored in
486 .Pa /etc/rpc.tlsclntd
488 This option is only meaningful when used with the
494 command line flag set.
497 .It Cm vers Ns = Ns Aq Ar vers_number
498 Use the specified version number for NFS requests.
505 .It Cm wcommitsize Ns = Ns Aq Ar value
506 Set the maximum pending write commit size to the specified value.
507 This determines the maximum amount of pending write data that the NFS
508 client is willing to cache for each file.
509 .It Cm wsize Ns = Ns Aq Ar value
510 Set the write data size to the specified value.
511 Ditto the comments w.r.t.\& the
513 option, but using the
514 .Dq "fragments dropped due to timeout"
515 value on the server instead of the client.
520 options should only be used as a last ditch effort at improving performance
521 when mounting servers that do not support TCP mounts.
525 The following command line flags are equivalent to
527 named options and are supported for compatibility with older
529 .Bl -tag -width indent
541 .Fl o Cm readdirsize Ns = Ns Aq Ar value
549 Use a reserved socket port number.
550 This flag is obsolete, and only retained for compatibility reasons.
551 (For the rare case where the client has a trusted root account
552 but untrustworthy users and the network cables are in secure areas this does
553 help, but for normal desktop clients this does not apply.)
556 .Fl o Cm retrycnt Ns = Ns Aq Ar value
565 .Fl o Cm readahead Ns = Ns Aq Ar value
586 .Fl o Cm rsize Ns = Ns Aq Ar value
592 .Fl o Cm retransmit Ns = Ns Aq Ar value
595 .Fl o Cm wsize Ns = Ns Aq Ar value
598 .Fl o Cm retrans Ns = Ns Aq Ar value
603 named options are equivalent to other
605 named options and are supported for compatibility with other
606 operating systems (e.g., Linux, Solaris, and OSX) to ease usage of
609 .Bl -tag -width indent
610 .It Fl o Cm vers Ns = Ns 2
613 .It Fl o Cm vers Ns = Ns 3
616 .It Fl o Cm vers Ns = Ns 4
620 .Sh IMPLEMENTATION NOTES
625 options are specified, the I/O size will be set to the largest value
626 supported by both the NFS client and server.
627 The largest value supported by the NFS client is defined by
630 which can be set to a power of two up to
637 command line option will show what
639 option settings are actually in use for the mount.
659 Since nfsv4 performs open/lock operations that have their ordering strictly
660 enforced by the server, the options
664 cannot be safely used.
666 nfsv4 mounts are strongly recommended.