1mount_nfs(1M) System Administration Commands mount_nfs(1M)
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6 mount_nfs - mount remote NFS resources
7
9 mount [-F nfs] [generic_options] [-o specific_options] [-O] resource
10 mount [-F nfs] [generic_options] [-o specific_options] [-O] mount_point
13 mount [-F nfs] [generic_options] [-o specific_options]
16 [-O] resource mount_point
17
20 The mount utility attaches a named resource to the file system hierar‐
21 chy at the pathname location mount_point, which must already exist. If
22 mount_point has any contents prior to the mount operation, the contents
23 remain hidden until the resource is once again unmounted.
24 mount_nfs starts the lockd(1M) and statd(1M) daemons if they are not
27 already running.
28 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 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 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 specify‐
42 ing an IPv6 address string. Otherwise the first occurrence of a colon
43 can be interpreted as the separator between the host name and path, for
44 example, [1080::8:800:200C:417A]:tmp/file. See inet(7P) and inet6(7P).
45 host:pathname
47 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 nfs://host[:port]/pathname
56 This is an NFS URL and follows the standard convention for NFS URLs
58 as described in NFS URL Scheme, RFC 2224. See the discussion of
59 URL's and the public option under NFS FILE SYSTEMS for a more
60 detailed discussion.
61 host:pathname nfs://host[:port]/pathname
64 host:pathname is a comma-separated list of host:pathname.
67 See the discussion of replicated file systems and failover under
69 NFS FILE SYSTEMS for a more detailed discussion.
70 hostlist pathname
73 hostlist is a comma-separated list of hosts.
75 See the discussion of replicated file systems and failover under
77 NFS FILE SYSTEMS for a more detailed discussion.
78 The mount command maintains a table of mounted file systems in
82 /etc/mnttab, described in mnttab(4).
83 mount_nfs supports both NFSv3 and NFSv4 mounts. The default NFS version
86 is NFSv4.
87
89 See mount(1M) for the list of supported generic_options. See
90 share_nfs(1M) for a description of server options.
91 -o specific_options
93 Set file system specific options according to a comma-separated
95 list with no intervening spaces.
96 acdirmax=n
98 Hold cached attributes for no more than n seconds after direc‐
100 tory update. The default value is 60.
101 acdirmin=n
104 Hold cached attributes for at least n seconds after directory
106 update. The default value is 30.
107 acregmax=n
110 Hold cached attributes for no more than n seconds after file
112 modification. The default value is 60.
113 acregmin=n
116 Hold cached attributes for at least n seconds after file modi‐
118 fication. The default value is 3.
119 actimeo=n
122 Set min and max times for regular files and directories to n
124 seconds. See "File Attributes," below, for a description of the
125 effect of setting this option to 0.
126 See "Specifying Values for Attribute Cache Duration Options,"
128 below, for a description of how acdirmax, acdirmin, acregmax,
129 acregmin, and actimeo are parsed on a mount command line.
130 bg | fg
133 If the first attempt fails, retry in the background, or, in the
135 foreground. The default is fg.
136 forcedirectio | noforcedirectio
139 If forcedirectio is specified, then for the duration of the
141 mount, forced direct I/O is used. If the filesystem is mounted
142 using forcedirectio, data is transferred directly between
143 client and server, with no buffering on the client. If the
144 filesystem is mounted using noforcedirectio, data is buffered
145 on the client. forcedirectio is a performance option that is of
146 benefit only in large sequential data transfers. The default
147 behavior is noforcedirectio.
148 grpid
151 By default, the GID associated with a newly created file obeys
153 the System V semantics; that is, the GID is set to the effec‐
154 tive GID of the calling process. This behavior can be overrid‐
155 den on a per-directory basis by setting the set-GID bit of the
156 parent directory; in this case, the GID of a newly created file
157 is set to the GID of the parent directory (see open(2) and
158 mkdir(2)). Files created on file systems that are mounted with
159 the grpid option obeys BSD semantics independent of whether the
160 set-GID bit of the parent directory is set; that is, the GID is
161 unconditionally inherited from that of the parent directory.
162 hard | soft
165 Continue to retry requests until the server responds (hard) or
167 give up and return an error (soft). The default value is hard.
168 Note that NFSv4 clients do not support soft mounts.
169 intr | nointr
172 Allow (do not allow) keyboard interrupts to kill a process that
174 is hung while waiting for a response on a hard-mounted file
175 system. The default is intr, which makes it possible for
176 clients to interrupt applications that can be waiting for a
177 remote mount.
178 noac
181 Suppress data and attribute caching. The data caching that is
183 suppressed is the write-behind. The local page cache is still
184 maintained, but data copied into it is immediately written to
185 the server.
186 nocto
189 Do not perform the normal close-to-open consistency. When a
191 file is closed, all modified data associated with the file is
192 flushed to the server and not held on the client. When a file
193 is opened the client sends a request to the server to validate
194 the client's local caches. This behavior ensures a file's con‐
195 sistency across multiple NFS clients. When -nocto is in effect,
196 the client does not perform the flush on close and the request
197 for validation, allowing the possiblity of differences among
198 copies of the same file as stored on multiple clients.
199 This option can be used where it can be guaranteed that
201 accesses to a specified file system are made from only one
202 client and only that client. Under such a condition, the effect
203 of -nocto can be a slight performance gain.
204 port=n
207 The server IP port number. The default is NFS_PORT. If the port
209 option is specified, and if the resource includes one or more
210 NFS URLs, and if any of the URLs include a port number, then
211 the port number in the option and in the URL must be the same.
212 posix
215 Request POSIX.1 semantics for the file system. Requires a mount
217 Version 2 mountd(1M) on the server. See standards(5) for infor‐
218 mation regarding POSIX.
219 proto=netid | rdma
222 By default, the transport protocol that the NFS mount uses is
224 the first available RDMA transport supported both by the client
225 and the server. If no RDMA transport is found, then it attempts
226 to use a TCP transport or, failing that, a UDP transport, as
227 ordered in the /etc/netconfig file. If it does not find a con‐
228 nection oriented transport, it uses the first available connec‐
229 tionless transport.
230 Use this option to override the default behavior.
232 proto is set to the value of netid or rdma. netid is the value
234 of the network_id field entry in the /etc/netconfig file.
235 The UDP protocol is not supported for NFS Version 4. If you
237 specify a UDP protocol with the proto option, NFS version 4 is
238 not used.
239 public
242 The public option forces the use of the public file handle when
244 connecting to the NFS server. The resource specified might not
245 have an NFS URL. See the discussion of URLs and the public
246 option under NFS FILE SYSTEMS for a more detailed discussion.
247 quota | noquota
250 Enable or prevent quota(1M) to check whether the user is over
252 quota on this file system; if the file system has quotas
253 enabled on the server, quotas are still checked for operations
254 on this file system.
255 remount
258 Remounts a read-only file system as read-write (using the rw
260 option). This option cannot be used with other -o options, and
261 this option works only on currently mounted read-only file sys‐
262 tems.
263 retrans=n
266 Set the number of NFS retransmissions to n. The default value
268 is 5. For connection-oriented transports, this option has no
269 effect because it is assumed that the transport performs
270 retransmissions on behalf of NFS.
271 retry=n
274 The number of times to retry the mount operation. The default
276 for the mount command is 10000.
277 The default for the automounter is 0, in other words, do not
279 retry. You might find it useful to increase this value on heav‐
280 ily loaded servers, where automounter traffic is dropped, caus‐
281 ing unnecessary server not responding errors.
282 rsize=n
285 Set the read buffer size to a maximum of n bytes. The default
287 value is 1048576 when using connection-orientated transports
288 with Version 3 or Version 4 of the NFS protocol, and 32768 when
289 using connection-less transports. The default can be negotiated
290 down if the server prefers a smaller transfer size. "Read"
291 operations may not necessarily use the maximum buffer size.
292 When using Version 2, the default value is 32768 for all trans‐
293 ports.
294 sec=mode
297 Set the security mode for NFS transactions. If sec= is not
299 specified, then the default action is to use AUTH_SYS over NFS
300 Version 2 mounts, use a user-configured default auth over NFS
301 version 3 mounts, or to negotiate a mode over Version 4
302 mounts.
303 The preferred mode for NFS Version 3 mounts is the default mode
305 specified in /etc/nfssec.conf (see nfssec.conf(4)) on the
306 client. If there is no default configured in this file or if
307 the server does not export using the client's default mode,
308 then the client picks the first mode that it supports in the
309 array of modes returned by the server. These alternatives are
310 limited to the security flavors listed in /etc/nfssec.conf.
311 NFS Version 4 mounts negotiate a security mode when the server
313 returns an array of security modes. The client attempts the
314 mount with each security mode, in order, until one is success‐
315 ful.
316 Only one mode can be specified with the sec= option. See
318 nfssec(5) for the available mode options.
319 secure
322 This option has been deprecated in favor of the sec=dh option.
324 timeo=n
327 Set the NFS timeout to n tenths of a second. The default value
329 is 11 tenths of a second for connectionless transports, and 600
330 tenths of a second for connection-oriented transports. This
331 value is ignored for connectionless transports. Such transports
332 might implement their own timeouts, which are outside the con‐
333 trol of NFS.
334 vers=NFS version number
337 By default, the version of NFS protocol used between the client
339 and the server is the highest one available on both systems.
340 The default maximum for the client is Version 4. This can be
341 changed by setting the NFS_CLIENT_VERSMAX parameter in
342 /etc/default/nfs to a valid version (2, 3, or 4). If the NFS
343 server does not support the client's default maximum, the next
344 lowest version attempted until a matching version is found.
345 wsize=n
348 Set the write buffer size to a maximum of n bytes. The default
350 value is 1048576 when using connection-orientated transports
351 with Version 3 or Version 4 of the NFS protocol, and 32768 when
352 using connection-less transports. The default can be negotiated
353 down if the server prefers a smaller transfer size. "Write"
354 operations may not necessarily use the maximum buffer size.
355 When using Version 2, the default value is 32768 for all trans‐
356 ports.
357 xattr | noxattr
360 Allow or disallow the creation and manipulation of extended
362 attributes. The default is xattr. See fsattr(5) for a descrip‐
363 tion of extended attributes.
364 -O
368 Overlay mount. Allow the file system to be mounted over an existing
370 mount point, making the underlying file system inaccessible. If a
371 mount is attempted on a pre-existing mount point without setting
372 this flag, the mount fails, producing the error "device busy."
373
376 Background versus Foreground
377 File systems mounted with the bg option indicate that mount is to
379 retry in the background if the server's mount daemon (mountd(1M))
380 does not respond. mount retries the request up to the count speci‐
381 fied in the retry=n option. (Note that the default value for retry
382 differs between mount and automount. See the description of retry,
383 above.) Once the file system is mounted, each NFS request made in
384 the kernel waits timeo=n tenths of a second for a response. If no
385 response arrives, the time-out is multiplied by 2 and the request
386 is retransmitted. When the number of retransmissions has reached
387 the number specified in the retrans=n option, a file system mounted
388 with the soft option returns an error on the request; one mounted
389 with the hard option prints a warning message and continues to
390 retry the request.
391 Hard versus Soft
394 File systems that are mounted read-write or that contain executable
396 files should always be mounted with the hard option. Applications
397 using soft mounted file systems can incur unexpected I/O errors,
398 file corruption, and unexpected program core dumps. The soft option
399 is not recommended.
400 Authenticated requests
403 The server can require authenticated NFS requests from the client.
405 sec=dh authentication might be required. See nfssec(5).
406 URLs and the public option
409 If the public option is specified, or if the resource includes and
411 NFS URL, mount attempts to connect to the server using the public
412 file handle lookup protocol. See WebNFS Client Specification, RFC
413 2054. If the server supports the public file handle, the attempt is
414 successful; mount does not need to contact the server's rpcbind(1M)
415 and the mountd(1M) daemons to get the port number of the mount
416 server and the initial file handle of pathname, respectively. If
417 the NFS client and server are separated by a firewall that allows
418 all outbound connections through specific ports, such as NFS_PORT,
419 then this enables NFS operations through the firewall. The public
420 option and the NFS URL can be specified independently or together.
421 They interact as specified in the following matrix:
422 Resource Style
424 host:pathname NFS URL
426 public option Force public file Force public file
428 handle and fail handle and fail
429 mount if not supported. mount if not supported.
430 Use Native paths. Use Canonical paths.
432 default Use MOUNT protocol. Try public file handle
434 with Canonical paths.
435 Fall back to MOUNT
436 protocol if not
437 supported.
438 A Native path is a path name that is interpreted according to con‐
440 ventions used on the native operating system of the NFS server. A
441 Canonical path is a path name that is interpreted according to the
442 URL rules. See Uniform Resource Locators (URL), RFC 1738. See for
443 uses of Native and Canonical paths.
444 Replicated file systems and failover
447 resource can list multiple read−only file systems to be used to
449 provide data. These file systems should contain equivalent direc‐
450 tory structures and identical files. It is also recommended that
451 they be created by a utility such as rdist(1). The file systems can
452 be specified either with a comma−separated list of host:/pathname
453 entries and/or NFS URL entries, or with a comma −separated list of
454 hosts, if all file system names are the same. If multiple file sys‐
455 tems are named and the first server in the list is down, failover
456 uses the next alternate server to access files. If the read−only
457 option is not chosen, replication is disabled. File access, for NFS
458 Versions 2 and 3, is blocked on the original if NFS locks are
459 active for that file.
460 File Attributes
463 To improve NFS read performance, files and file attributes are cached.
464 File modification times get updated whenever a write occurs. However,
465 file access times can be temporarily out-of-date until the cache gets
466 refreshed.
467 The attribute cache retains file attributes on the client. Attributes
470 for a file are assigned a time to be flushed. If the file is modified
471 before the flush time, then the flush time is extended by the time
472 since the last modification (under the assumption that files that
473 changed recently are likely to change soon). There is a minimum and
474 maximum flush time extension for regular files and for directories.
475 Setting actimeo=n sets flush time to n seconds for both regular files
476 and directories.
477 Setting actimeo=0 disables attribute caching on the client. This means
480 that every reference to attributes is satisfied directly from the
481 server though file data is still cached. While this guarantees that the
482 client always has the latest file attributes from the server, it has an
483 adverse effect on performance through additional latency, network load,
484 and server load.
485 Setting the noac option also disables attribute caching, but has the
488 further effect of disabling client write caching. While this guarantees
489 that data written by an application is written directly to a server,
490 where it can be viewed immediately by other clients, it has a signifi‐
491 cant adverse effect on client write performance. Data written into mem‐
492 ory-mapped file pages (mmap(2)) are not written directly to this
493 server.
494 Specifying Values for Attribute Cache Duration Options
496 The attribute cache duration options are acdirmax, acdirmin, acregmax,
497 acregmin, and actimeo, as described under OPTIONS. A value specified
498 for actimeo sets the values of all attribute cache duration options
499 except for any of these options specified following actimeo on a mount
500 command line. For example, consider the following command:
501 example# mount -o acdirmax=10,actimeo=1000 server:/path /localpath
503 Because actimeo is the last duration option in the command line, its
507 value (1000) becomes the setting for all of the duration options,
508 including acdirmax. Now consider:
509 example# mount -o actimeo=1000,acdirmax=10 server:/path /localpath
511 Because the acdirmax option follows actimeo on the command line, it is
515 assigned the value specified (10). The remaining duration options are
516 set to the value of actimeo (1000).
517
519 Example 1 Mounting an NFS File System
520 To mount an NFS file system:
523 example# mount serv:/usr/src /usr/src
526 Example 2 Mounting An NFS File System Read-Only With No suid Privileges
530 To mount an NFS file system read-only with no suid privileges:
533 example# mount -r -o nosuid serv:/usr/src /usr/src
536 Example 3 Mounting An NFS File System Over Version 2, with the UDP
540 Transport
541 To mount an NFS file system over Version 2, with the UDP transport:
544 example# mount -o vers=2,proto=udp serv:/usr/src /usr/src
547 Example 4 Mounting an NFS File System Using An NFS URL
551 To mount an NFS file system using an NFS URL (a canonical path):
554 example# mount nfs://serv/usr/man /usr/man
557 Example 5 Mounting An NFS File System Forcing Use Of The Public File
561 Handle
562 To mount an NFS file system and force the use of the public file handle
565 and an NFS URL (a canonical path) that has a non 7-bit ASCII escape
566 sequence:
567 example# mount -o public nfs://serv/usr/%A0abc /mnt/test
570 Example 6 Mounting an NFS File System Using a Native Path
574 To mount an NFS file system using a native path (where the server uses
577 colons (":") as the component separator) and the public file handle:
578 example# mount -o public serv:C:doc:new /usr/doc
581 Example 7 Mounting a Replicated Set of NFS File Systems with the Same
585 Pathnames
586 To mount a replicated set of NFS file systems with the same pathnames:
589 example# mount serv−a,serv−b,serv−c:/usr/man /usr/man
592 Example 8 Mounting a Replicated Set of NFS File Systems with Different
596 Pathnames
597 To mount a replicated set of NFS file systems with different pathnames:
600 example# mount serv−x:/usr/man,serv−y:/var/man,nfs://serv-z/man /usr/man
603
607 /etc/mnttab
608 table of mounted file systems
610 /etc/dfs/fstypes
613 default distributed file system type
615 /etc/vfstab
618 table of automatically mounted resources
620
623 See attributes(5) for descriptions of the following attributes:
624 ┌─────────────────────────────┬─────────────────────────────┐
629 │ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
630 ├─────────────────────────────┼─────────────────────────────┤
631 │Availability │SUNWnfscu │
632 └─────────────────────────────┴─────────────────────────────┘
633
635 rdist(1), lockd(1M), mountall(1M), mountd(1M), nfsd(1M), quota(1M),
636 statd(1M), mkdir(2), mmap(2), mount(2), open(2), umount(2), mnttab(4),
637 nfs(4), nfssec.conf(4), attributes(5), fsattr(5), nfssec(5), stan‐
638 dards(5), inet(7P), inet6(7P), lofs(7FS)
639 Callaghan, Brent, WebNFS Client Specification, RFC 2054, October 1996.
642 Callaghan, Brent, NFS URL Scheme, RFC 2224, October 1997.
645 Berners-Lee, Masinter & McCahill , Uniform Resource Locators (URL), RFC
648 1738, December 1994.
649
651 An NFS server should not attempt to mount its own file systems. See
652 lofs(7FS).
653 If the directory on which a file system is to be mounted is a symbolic
656 link, the file system is mounted on the directory to which the symbolic
657 link refers, rather than being mounted on top of the symbolic link
658 itself.
659 SunOS 4.x used the biod maintenance procedure to perform parallel read-
662 ahead and write-behind on NFS clients. SunOS 5.x made biod obsolete
663 with multi-threaded processing, which transparently performs parallel
664 read-ahead and write-behind.
665 Since the root (/) file system is mounted read-only by the kernel dur‐
668 ing the boot process, only the remount option (and options that can be
669 used in conjunction with remount) affect the root (/) entry in the
670 /etc/vfstab file.
671 mount_cachefs cannot be used with replicated NFS mounts or any NFS Ver‐
674 sion 4 mount.
675 The NFS client service is managed by the service management facility,
678 smf(5), under the service identifier:
679 svc:/network/nfs/client:default
681 Administrative actions on this service, such as enabling, disabling, or
686 requesting restart, can be performed using svcadm(1M). The service's
687 status can be queried using the svcs(1) command.
688SunOS 5.11 26 Jul 2009 mount_nfs(1M)