1 MOUNT_NFS(1M) Maintenance Commands MOUNT_NFS(1M)
2
3
4
5 NAME
6 mount_nfs - mount remote NFS resources
7
8 SYNOPSIS
9 mount [-F nfs] [generic_options] [-o specific_options] [-O] resource
10
11
12 mount [-F nfs] [generic_options] [-o specific_options] [-O] mount_point
13
14
15 mount [-F nfs] [generic_options] [-o specific_options]
16 [-O] resource mount_point
17
18
19 DESCRIPTION
20 The mount utility attaches a named resource to the file system
21 hierarchy at the pathname location mount_point, which must already
22 exist. If mount_point has any contents prior to the mount operation,
23 the contents remain hidden until the resource is once again unmounted.
24
25
26 mount_nfs starts the lockd(1M) and statd(1M) daemons if they are not
27 already running.
28
29
30 If the resource is listed in the /etc/vfstab file, the command line can
31 specify either resource or mount_point, and mount consults /etc/vfstab
32 for more information. If the -F option is omitted, mount takes the file
33 system type from /etc/vfstab.
34
35
36 If the resource is not listed in the /etc/vfstab file, then the command
37 line must specify both the resource and the mount_point.
38
39
40 host can be an IPv4 or IPv6 address string. As IPv6 addresses already
41 contain colons, enclose host in a pair of square brackets when
42 specifying an IPv6 address string. Otherwise the first occurrence of a
43 colon can be interpreted as the separator between the host name and
44 path, for example, [1080::8:800:200C:417A]:tmp/file. See inet(7P) and
45 inet6(7P).
46
47 host:pathname
48 Where host is the name of the NFS server host, and pathname is the
49 path name of the directory on the server being mounted. The path
50 name is interpreted according to the server's path name parsing
51 rules and is not necessarily slash-separated, though on most
52 servers, this is the case.
53
54
55 nfs://host[:port]/pathname
56 This is an NFS URL and follows the standard convention for NFS URLs
57 as described in NFS URL Scheme, RFC 2224. See the discussion of
58 URL's and the public option under NFS FILE SYSTEMS for a more
59 detailed discussion.
60
61
62 host:pathname nfs://host[:port]/pathname
63 host:pathname is a comma-separated list of host:pathname.
64
65 See the discussion of replicated file systems and failover under
66 NFS FILE SYSTEMS for a more detailed discussion.
67
68
69 hostlist pathname
70 hostlist is a comma-separated list of hosts.
71
72 See the discussion of replicated file systems and failover under
73 NFS FILE SYSTEMS for a more detailed discussion.
74
75
76
77 The mount command maintains a table of mounted file systems in
78 /etc/mnttab, described in mnttab(4).
79
80
81 mount_nfs supports both NFSv3 and NFSv4 mounts. The default NFS version
82 is NFSv4.
83
84 OPTIONS
85 See mount(1M) for the list of supported generic_options. See
86 share_nfs(1M) for a description of server options.
87
88 -o specific_options
89 Set file system specific options according to a comma-separated list
90 with no intervening spaces.
91
92 acdirmax=n
93 Hold cached attributes for no more than n seconds after
94 directory update. The default value is 60.
95
96
97 acdirmin=n
98 Hold cached attributes for at least n seconds after directory
99 update. The default value is 30.
100
101
102 acregmax=n
103 Hold cached attributes for no more than n seconds after file
104 modification. The default value is 60.
105
106
107 acregmin=n
108 Hold cached attributes for at least n seconds after file
109 modification. The default value is 3.
110
111
112 actimeo=n
113 Set min and max times for regular files and directories to n
114 seconds. See "File Attributes," below, for a description of the
115 effect of setting this option to 0.
116
117 See "Specifying Values for Attribute Cache Duration Options,"
118 below, for a description of how acdirmax, acdirmin, acregmax,
119 acregmin, and actimeo are parsed on a mount command line.
120
121
122 bg | fg
123 If the first attempt fails, retry in the background, or, in the
124 foreground. The default is fg.
125
126
127 forcedirectio | noforcedirectio
128 If forcedirectio is specified, then for the duration of the
129 mount, forced direct I/O is used. If the filesystem is mounted
130 using forcedirectio, data is transferred directly between
131 client and server, with no buffering on the client. If the
132 filesystem is mounted using noforcedirectio, data is buffered
133 on the client. forcedirectio is a performance option that is of
134 benefit only in large sequential data transfers. The default
135 behavior is noforcedirectio.
136
137
138 grpid
139 By default, the GID associated with a newly created file obeys
140 the System V semantics; that is, the GID is set to the
141 effective GID of the calling process. This behavior can be
142 overridden on a per-directory basis by setting the set-GID bit of
143 the parent directory; in this case, the GID of a newly created
144 file is set to the GID of the parent directory (see open(2) and
145 mkdir(2)). Files created on file systems that are mounted with
146 the grpid option obeys BSD semantics independent of whether the
147 set-GID bit of the parent directory is set; that is, the GID is
148 unconditionally inherited from that of the parent directory.
149
150
151 hard | soft
152 Continue to retry requests until the server responds (hard) or
153 give up and return an error (soft). The default value is hard.
154 Note that NFSv4 clients do not support soft mounts.
155
156
157 intr | nointr
158 Allow (do not allow) keyboard interrupts to kill a process that
159 is hung while waiting for a response on a hard-mounted file
160 system. The default is intr, which makes it possible for
161 clients to interrupt applications that can be waiting for a
162 remote mount.
163
164
165 noac
166 Suppress data and attribute caching. The data caching that is
167 suppressed is the write-behind. The local page cache is still
168 maintained, but data copied into it is immediately written to
169 the server.
170
171
172 nocto
173 Do not perform the normal close-to-open consistency. When a file
174 is closed, all modified data associated with the file is
175 flushed to the server and not held on the client. When a file
176 is opened the client sends a request to the server to validate
177 the client's local caches. This behavior ensures a file's
178 consistency across multiple NFS clients. When -nocto is in
179 effect, the client does not perform the flush on close and the
180 request for validation, allowing the possiblity of differences
181 among copies of the same file as stored on multiple clients.
182
183 This option can be used where it can be guaranteed that
184 accesses to a specified file system are made from only one
185 client and only that client. Under such a condition, the effect
186 of -nocto can be a slight performance gain.
187
188
189 port=n
190 The server IP port number. The default is NFS_PORT. If the port
191 option is specified, and if the resource includes one or more
192 NFS URLs, and if any of the URLs include a port number, then
193 the port number in the option and in the URL must be the same.
194
195
196 posix
197 Request POSIX.1 semantics for the file system. Requires a mount
198 Version 2 mountd(1M) on the server. See standards(5) for
199 information regarding POSIX.
200
201
202 proto=netid | rdma
203 By default, the transport protocol that the NFS mount uses is
204 the first available RDMA transport supported both by the client
205 and the server. If no RDMA transport is found, then it attempts
206 to use a TCP transport or, failing that, a UDP transport, as
207 ordered in the /etc/netconfig file. If it does not find a
208 connection oriented transport, it uses the first available
209 connectionless transport.
210
211 Use this option to override the default behavior.
212
213 proto is set to the value of netid or rdma. netid is the value
214 of the network_id field entry in the /etc/netconfig file.
215
216 The UDP protocol is not supported for NFS Version 4. If you
217 specify a UDP protocol with the proto option, NFS version 4 is
218 not used.
219
220
221 public
222 The public option forces the use of the public file handle when
223 connecting to the NFS server. The resource specified might not
224 have an NFS URL. See the discussion of URLs and the public
225 option under NFS FILE SYSTEMS for a more detailed discussion.
226
227
228 quota | noquota
229 Enable or prevent quota(1M) to check whether the user is over
230 quota on this file system; if the file system has quotas
231 enabled on the server, quotas are still checked for operations
232 on this file system.
233
234
235 remount
236 Remounts a read-only file system as read-write (using the rw
237 option). This option cannot be used with other -o options, and
238 this option works only on currently mounted read-only file
239 systems.
240
241
242 retrans=n
243 Set the number of NFS retransmissions to n. The default value
244 is 5. For connection-oriented transports, this option has no
245 effect because it is assumed that the transport performs
246 retransmissions on behalf of NFS.
247
248
249 retry=n
250 The number of times to retry the mount operation. The default
251 for the mount command is 10000.
252
253 The default for the automounter is 0, in other words, do not
254 retry. You might find it useful to increase this value on
255 heavily loaded servers, where automounter traffic is dropped,
256 causing unnecessary server not responding errors.
257
258
259 rsize=n
260 Set the read buffer size to a maximum of n bytes. The default
261 value is 1048576 when using connection-oriented transports with
262 Version 3 or Version 4 of the NFS protocol, and 32768 when
263 using connection-less transports. The default can be negotiated
264 down if the server prefers a smaller transfer size. "Read"
265 operations may not necessarily use the maximum buffer size.
266 When using Version 2, the default value is 32768 for all
267 transports.
268
269
270 sec=mode
271 Set the security mode for NFS transactions. If sec= is not
272 specified, then the default action is to use AUTH_SYS over NFS
273 Version 2 mounts, use a user-configured default auth over NFS
274 version 3 mounts, or to negotiate a mode over Version 4
275 mounts.
276
277 The preferred mode for NFS Version 3 mounts is the default mode
278 specified in /etc/nfssec.conf (see nfssec.conf(4)) on the
279 client. If there is no default configured in this file or if
280 the server does not export using the client's default mode,
281 then the client picks the first mode that it supports in the
282 array of modes returned by the server. These alternatives are
283 limited to the security flavors listed in /etc/nfssec.conf.
284
285 NFS Version 4 mounts negotiate a security mode when the server
286 returns an array of security modes. The client attempts the
287 mount with each security mode, in order, until one is
288 successful.
289
290 Only one mode can be specified with the sec= option. See
291 nfssec(5) for the available mode options.
292
293
294 secure
295 This option has been deprecated in favor of the sec=dh option.
296
297
298 timeo=n
299 Set the NFS timeout to n tenths of a second. The default value
300 is 11 tenths of a second for connectionless transports, and 600
301 tenths of a second for connection-oriented transports. This
302 value is ignored for connectionless transports. Such transports
303 might implement their own timeouts, which are outside the
304 control of NFS.
305
306
307 vers=NFS version number
308 By default, the version of NFS protocol used between the client
309 and the server is the highest one available on both systems.
310 The default maximum for the client is Version 4. This can be
311 changed by setting the NFS_CLIENT_VERSMAX parameter in
312 /etc/default/nfs to a valid version (2, 3, or 4). If the NFS
313 server does not support the client's default maximum, the next
314 lowest version attempted until a matching version is found.
315
316
317 wsize=n
318 Set the write buffer size to a maximum of n bytes. The default
319 value is 1048576 when using connection-oriented transports with
320 Version 3 or Version 4 of the NFS protocol, and 32768 when
321 using connection-less transports. The default can be negotiated
322 down if the server prefers a smaller transfer size. "Write"
323 operations may not necessarily use the maximum buffer size.
324 When using Version 2, the default value is 32768 for all
325 transports.
326
327
328 xattr | noxattr
329 Allow or disallow the creation and manipulation of extended
330 attributes. The default is xattr. See fsattr(5) for a
331 description of extended attributes.
332
333
334
335 -O
336 Overlay mount. Allow the file system to be mounted over an existing
337 mount point, making the underlying file system inaccessible. If a
338 mount is attempted on a pre-existing mount point without setting
339 this flag, the mount fails, producing the error "device busy."
340
341
342 NFS FILE SYSTEMS
343 Background versus Foreground
344 File systems mounted with the bg option indicate that mount is to
345 retry in the background if the server's mount daemon (mountd(1M))
346 does not respond. mount retries the request up to the count
347 specified in the retry=n option. (Note that the default value for
348 retry differs between mount and automount. See the description of
349 retry, above.) Once the file system is mounted, each NFS request
350 made in the kernel waits timeo=n tenths of a second for a response.
351 If no response arrives, the time-out is multiplied by 2 and the
352 request is retransmitted. When the number of retransmissions has
353 reached the number specified in the retrans=n option, a file system
354 mounted with the soft option returns an error on the request; one
355 mounted with the hard option prints a warning message and continues
356 to retry the request.
357
358
359 Hard versus Soft
360 File systems that are mounted read-write or that contain executable
361 files should always be mounted with the hard option. Applications
362 using soft mounted file systems can incur unexpected I/O errors,
363 file corruption, and unexpected program core dumps. The soft option
364 is not recommended.
365
366
367 Authenticated requests
368 The server can require authenticated NFS requests from the client.
369 sec=dh authentication might be required. See nfssec(5).
370
371
372 URLs and the public option
373 If the public option is specified, or if the resource includes and
374 NFS URL, mount attempts to connect to the server using the public
375 file handle lookup protocol. See WebNFS Client Specification, RFC
376 2054. If the server supports the public file handle, the attempt is
377 successful; mount does not need to contact the server's rpcbind(1M)
378 and the mountd(1M) daemons to get the port number of the mount
379 server and the initial file handle of pathname, respectively. If
380 the NFS client and server are separated by a firewall that allows
381 all outbound connections through specific ports, such as NFS_PORT,
382 then this enables NFS operations through the firewall. The public
383 option and the NFS URL can be specified independently or together.
384 They interact as specified in the following matrix:
385
386 Resource Style
387
388 host:pathname NFS URL
389
390 public option Force public file Force public file
391 handle and fail handle and fail
392 mount if not supported. mount if not supported.
393
394 Use Native paths. Use Canonical paths.
395
396 default Use MOUNT protocol. Try public file handle
397 with Canonical paths.
398 Fall back to MOUNT
399 protocol if not
400 supported.
401
402 A Native path is a path name that is interpreted according to
403 conventions used on the native operating system of the NFS server.
404 A Canonical path is a path name that is interpreted according to
405 the URL rules. See Uniform Resource Locators (URL), RFC 1738. See
406 for uses of Native and Canonical paths.
407
408
409 Replicated file systems and failover
410 resource can list multiple readonly file systems to be used to
411 provide data. These file systems should contain equivalent
412 directory structures and identical files. It is also recommended
413 that they be created by a utility such as rdist(1). The file
414 systems can be specified either with a commaseparated list of
415 host:/pathname entries and/or NFS URL entries, or with a comma
416 separated list of hosts, if all file system names are the same. If
417 multiple file systems are named and the first server in the list is
418 down, failover uses the next alternate server to access files. If
419 the readonly option is not chosen, replication is disabled. File
420 access, for NFS Versions 2 and 3, is blocked on the original if NFS
421 locks are active for that file.
422
423
424 File Attributes
425 To improve NFS read performance, files and file attributes are cached.
426 File modification times get updated whenever a write occurs. However,
427 file access times can be temporarily out-of-date until the cache gets
428 refreshed.
429
430
431 The attribute cache retains file attributes on the client. Attributes
432 for a file are assigned a time to be flushed. If the file is modified
433 before the flush time, then the flush time is extended by the time
434 since the last modification (under the assumption that files that
435 changed recently are likely to change soon). There is a minimum and
436 maximum flush time extension for regular files and for directories.
437 Setting actimeo=n sets flush time to n seconds for both regular files
438 and directories.
439
440
441 Setting actimeo=0 disables attribute caching on the client. This means
442 that every reference to attributes is satisfied directly from the
443 server though file data is still cached. While this guarantees that the
444 client always has the latest file attributes from the server, it has an
445 adverse effect on performance through additional latency, network load,
446 and server load.
447
448
449 Setting the noac option also disables attribute caching, but has the
450 further effect of disabling client write caching. While this guarantees
451 that data written by an application is written directly to a server,
452 where it can be viewed immediately by other clients, it has a
453 significant adverse effect on client write performance. Data written
454 into memory-mapped file pages (mmap(2)) are not written directly to this
455 server.
456
457 Specifying Values for Attribute Cache Duration Options
458 The attribute cache duration options are acdirmax, acdirmin, acregmax,
459 acregmin, and actimeo, as described under OPTIONS. A value specified
460 for actimeo sets the values of all attribute cache duration options
461 except for any of these options specified following actimeo on a mount
462 command line. For example, consider the following command:
463
464 example# mount -o acdirmax=10,actimeo=1000 server:/path /localpath
465
466
467
468 Because actimeo is the last duration option in the command line, its
469 value (1000) becomes the setting for all of the duration options,
470 including acdirmax. Now consider:
471
472 example# mount -o actimeo=1000,acdirmax=10 server:/path /localpath
473
474
475
476 Because the acdirmax option follows actimeo on the command line, it is
477 assigned the value specified (10). The remaining duration options are
478 set to the value of actimeo (1000).
479
480 EXAMPLES
481 Example 1 Mounting an NFS File System
482
483
484 To mount an NFS file system:
485
486
487 example# mount serv:/usr/src /usr/src
488
489
490
491 Example 2 Mounting An NFS File System Read-Only With No suid Privileges
492
493
494 To mount an NFS file system read-only with no suid privileges:
495
496
497 example# mount -r -o nosuid serv:/usr/src /usr/src
498
499
500
501 Example 3 Mounting An NFS File System Over Version 2, with the UDP
502 Transport
503
504
505 To mount an NFS file system over Version 2, with the UDP transport:
506
507
508 example# mount -o vers=2,proto=udp serv:/usr/src /usr/src
509
510
511
512 Example 4 Mounting an NFS File System Using An NFS URL
513
514
515 To mount an NFS file system using an NFS URL (a canonical path):
516
517
518 example# mount nfs://serv/usr/man /usr/man
519
520
521
522 Example 5 Mounting An NFS File System Forcing Use Of The Public File
523 Handle
524
525
526 To mount an NFS file system and force the use of the public file handle
527 and an NFS URL (a canonical path) that has a non 7-bit ASCII escape
528 sequence:
529
530
531 example# mount -o public nfs://serv/usr/%A0abc /mnt/test
532
533
534
535 Example 6 Mounting an NFS File System Using a Native Path
536
537
538 To mount an NFS file system using a native path (where the server uses
539 colons (":") as the component separator) and the public file handle:
540
541
542 example# mount -o public serv:C:doc:new /usr/doc
543
544
545
546 Example 7 Mounting a Replicated Set of NFS File Systems with the Same
547 Pathnames
548
549
550 To mount a replicated set of NFS file systems with the same pathnames:
551
552
553 example# mount serva,servb,servc:/usr/man /usr/man
554
555
556
557 Example 8 Mounting a Replicated Set of NFS File Systems with Different
558 Pathnames
559
560
561 To mount a replicated set of NFS file systems with different pathnames:
562
563
564 example# mount servx:/usr/man,servy:/var/man,nfs://serv-z/man /usr/man
565
566
567
568 FILES
569 /etc/mnttab
570 table of mounted file systems
571
572
573 /etc/dfs/fstypes
574 default distributed file system type
575
576
577 /etc/vfstab
578 table of automatically mounted resources
579
580
581 SEE ALSO
582 rdist(1), lockd(1M), mountall(1M), mountd(1M), nfsd(1M), quota(1M),
583 statd(1M), mkdir(2), mmap(2), mount(2), open(2), umount(2), mnttab(4),
584 nfs(4), nfssec.conf(4), attributes(5), fsattr(5), nfssec(5),
585 standards(5), inet(7P), inet6(7P), lofs(7FS)
586
587
588 Callaghan, Brent, WebNFS Client Specification, RFC 2054, October 1996.
589
590
591 Callaghan, Brent, NFS URL Scheme, RFC 2224, October 1997.
592
593
594 Berners-Lee, Masinter & McCahill , Uniform Resource Locators (URL), RFC
595 1738, December 1994.
596
597 NOTES
598 An NFS server should not attempt to mount its own file systems. See
599 lofs(7FS).
600
601
602 If the directory on which a file system is to be mounted is a symbolic
603 link, the file system is mounted on the directory to which the symbolic
604 link refers, rather than being mounted on top of the symbolic link
605 itself.
606
607
608 SunOS 4.x used the biod maintenance procedure to perform parallel read-
609 ahead and write-behind on NFS clients. SunOS 5.x made biod obsolete with
610 multi-threaded processing, which transparently performs parallel read-
611 ahead and write-behind.
612
613
614 Since the root (/) file system is mounted read-only by the kernel during
615 the boot process, only the remount option (and options that can be used
616 in conjunction with remount) affect the root (/) entry in the
617 /etc/vfstab file.
618
619
620 mount_cachefs cannot be used with replicated NFS mounts or any NFS
621 Version 4 mount.
622
623
624 The NFS client service is managed by the service management facility,
625 smf(5), under the service identifier:
626
627 svc:/network/nfs/client:default
628
629
630
631
632 Administrative actions on this service, such as enabling, disabling, or
633 requesting restart, can be performed using svcadm(1M). The service's
634 status can be queried using the svcs(1) command.
635
636
637
638 June 3, 2015 MOUNT_NFS(1M)