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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
62 It implements the mount protocol as described in RFC 1094, Appendix A and
63 .%T "NFS: Network File System Version 3 Protocol Specification" ,
68 keeps retrying until the mount succeeds.
69 This behaviour is intended for file systems listed in
71 that are critical to the boot process.
72 For non-critical file systems, the
76 options provide mechanisms to prevent the boot process from hanging
77 if the server is unavailable.
79 If the server becomes unresponsive while an NFS file system is
80 mounted, any new or outstanding file operations on that file system
81 will hang uninterruptibly until the server comes back.
82 To modify this default behaviour, see the
89 .Bl -tag -width indent
91 Options are specified with a
93 flag followed by a comma separated string of options.
96 man page for possible options and their meanings.
97 The following NFS specific options are also available:
98 .Bl -tag -width indent
99 .It Cm acregmin Ns = Ns Aq Ar seconds
100 .It Cm acregmax Ns = Ns Aq Ar seconds
101 .It Cm acdirmin Ns = Ns Aq Ar seconds
102 .It Cm acdirmax Ns = Ns Aq Ar seconds
103 When attributes of files are cached, a timeout calculated to determine
104 whether a given cache entry has expired.
105 These four values determine the upper and lower bounds of the timeouts for
109 (ie: everything else).
110 The default values are 3 -> 60 seconds
111 for regular files, and 30 -> 60 seconds for directories.
112 The algorithm to calculate the timeout is based on the age of the file.
114 the longer the cache is considered valid, subject to the limits above.
115 .It Cm actimeo Ns = Ns Aq Ar seconds
116 Set four cache timeouts above to specified value.
118 This option can be used along with
120 to specify that all operations should use the host-based initiator
122 This may be used for clients that run system daemons that need to
123 access files on the NFSv4 mounted volume.
125 If an initial attempt to contact the server fails, fork off a child to keep
126 trying the mount in the background.
129 where the file system mount is not critical to multiuser operation.
130 .It Cm deadthresh Ns = Ns Aq Ar value
132 .Dq "dead server threshold"
133 to the specified number of round trip timeout intervals before a
134 .Dq "server not responding"
135 message is displayed.
137 Turn off the dynamic retransmit timeout estimator.
138 This may be useful for UDP mounts that exhibit high retry rates,
139 since it is possible that the dynamically estimated timeout interval is too
142 Same as not specifying
144 .It Cm gssname Ns = Ns Aq Ar service-principal-name
145 This option can be used with the KerberosV security flavors for NFSv4 mounts
147 .Dq "service-principal-name"
148 of a host-based entry in the default
149 keytab file that is used for system operations.
150 It allows the mount to be performed by
152 and avoids problems with
153 cached credentials for the system operations expiring.
155 .Dq "service-prinicpal-name"
156 should be specified without instance or domain and is typically
162 Same as not specifying
165 Make the mount interruptible, which implies that file system calls that
166 are delayed due to an unresponsive server will fail with EINTR when a
167 termination signal is posted for the process.
168 .It Cm maxgroups Ns = Ns Aq Ar value
169 Set the maximum size of the group list for the credentials to the
171 This should be used for mounts on old servers that cannot handle a
172 group list size of 16, as specified in RFC 1057.
173 Try 8, if users in a lot of groups cannot get response from the mount
176 Force the mount protocol to use UDP transport, even for TCP NFS mounts.
177 (Necessary for some old
180 .It Cm nametimeo Ns = Ns Aq Ar value
181 Override the default of NFS_DEFAULT_NAMETIMEO for the timeout (in seconds)
182 for positive name cache entries.
183 If this is set to 0 it disables positive name caching for the mount point.
184 .It Cm negnametimeo Ns = Ns Aq Ar value
185 Override the default of NFS_DEFAULT_NEGNAMETIMEO for the timeout (in seconds)
186 for negative name cache entries. If this is set to 0 it disables negative
187 name caching for the mount point.
189 Use the NFS Version 2 protocol (the default is to try version 3 first
191 Note that NFS version 2 has a file size limit of 2 gigabytes.
193 Use the NFS Version 3 protocol.
195 Use the NFS Version 4 protocol.
196 This option will force the mount to use
198 .It Cm minorversion Ns = Ns Aq Ar value
199 Override the default of 0 for the minor version of the NFS Version 4 protocol.
200 The only minor version currently supported is 1.
201 This option is only meaningful when used with the
205 Make a minor version 1 of the NFS Version 4 protocol mount use a single OpenOwner
207 This may be useful for a server with a very low limit on OpenOwners, such as
209 It can only be used with an NFSv4.1 mount.
210 It may not work correctly when Delegations are being issued by a server,
211 but note that the AmazonEFS server does not issued delegations at this time.
213 Enable support for parallel NFS (pNFS) for minor version 1 of the
214 NFS Version 4 protocol.
215 This option is only meaningful when used with the
219 Disable attribute caching.
221 For UDP mount points, do not do a
223 This must be used if the server does not reply to requests from the standard
224 NFS port number 2049 or replies to requests using a different IP address
225 (which can occur if the server is multi-homed).
227 .Va vfs.nfs.nfs_ip_paranoia
228 sysctl to 0 will make this option the default.
230 Normally, NFS clients maintain the close-to-open cache coherency.
231 This works by flushing at close time and checking at open time.
232 Checking at open time is implemented by getting attributes from
233 the server and purging the data cache if they do not match
234 attributes cached by the client.
236 This option disables checking at open time.
237 It may improve performance for read-only mounts,
238 but should only be used if the data on the server changes rarely.
239 Be sure to understand the consequences before enabling this option.
240 .It Cm noinet4 , noinet6
246 Useful for hosts that have
247 both an A record and an AAAA record for the same name.
254 All locks will be local and not seen by the server
255 and likewise not seen by other NFS clients.
256 This removes the need to run the
262 servers on the client.
263 Note that this option will only be honored when performing the
264 initial mount, it will be silently ignored if used while updating
267 This mount option allows the NFS client to
268 combine non-contiguous byte ranges being written
269 such that the dirty byte range becomes a superset of the bytes
271 This reduces the number of writes significantly for software
273 The merging of byte ranges isn't done if the file has been file
274 locked, since most applications modifying a file from multiple
275 clients will use file locking.
276 As such, this option could result in a corrupted file for the
277 rare case of an application modifying the file from multiple
278 clients concurrently without using file locking.
280 For the RPCSEC_GSS security flavors, such as krb5, krb5i and krb5p,
281 this option sets the name of the host based principal name expected
282 by the server. This option overrides the default, which will be
283 ``nfs@<server-fqdn>'' and should normally be sufficient.
287 use a reserved socket port number (see below).
288 .It Cm port Ns = Ns Aq Ar port_number
289 Use specified port number for NFS requests.
290 The default is to query the portmapper for the NFS port.
291 .It Cm proto Ns = Ns Aq Ar protocol
292 Specify transport protocol version to use.
295 udp - Use UDP over IPv4
296 tcp - Use TCP over IPv4
297 udp6 - Use UDP over IPv6
298 tcp6 - Use TCP over IPv6
301 Used with NFSV3 to specify that the \fBReaddirPlus\fR RPC should
303 For NFSV4, setting this option has a similar effect, in that it will make
304 the Readdir Operation get more attributes.
305 This option reduces RPC traffic for cases such as
307 but tends to flood the attribute and name caches with prefetched entries.
308 Try this option and see whether performance improves or degrades.
310 most useful for client to server network interconnects with a large bandwidth
312 .It Cm readahead Ns = Ns Aq Ar value
313 Set the read-ahead count to the specified value.
314 This may be in the range of 0 - 4, and determines how many blocks
315 will be read ahead when a large file is being read sequentially.
316 Trying a value greater than 1 for this is suggested for
317 mounts with a large bandwidth * delay product.
318 .It Cm readdirsize Ns = Ns Aq Ar value
319 Set the readdir read size to the specified value.
320 The value should normally
323 that is <= the read size for the mount.
325 Use a reserved socket port number.
326 This flag is obsolete, and only retained for compatibility reasons.
327 Reserved port numbers are used by default now.
328 (For the rare case where the client has a trusted root account
329 but untrustworthy users and the network cables are in secure areas this does
330 help, but for normal desktop clients this does not apply.)
331 .It Cm retrans Ns = Ns Aq Ar value
332 Set the retransmit timeout count for soft mounts to the specified value.
333 .It Cm retrycnt Ns = Ns Aq Ar count
334 Set the mount retry count to the specified value.
335 The default is a retry count of zero, which means to keep retrying
337 There is a 60 second delay between each attempt.
338 .It Cm rsize Ns = Ns Aq Ar value
339 Set the read data size to the specified value.
340 It should normally be a power of 2 greater than or equal to 1024.
341 This should be used for UDP mounts when the
342 .Dq "fragments dropped due to timeout"
343 value is getting large while actively using a mount point.
348 option to see what the
349 .Dq "fragments dropped due to timeout"
351 .It Cm sec Ns = Ns Aq Ar flavor
352 This option specifies what security flavor should be used for the mount.
355 krb5 - Use KerberosV authentication
356 krb5i - Use KerberosV authentication and
357 apply integrity checksums to RPCs
358 krb5p - Use KerberosV authentication and
360 sys - The default AUTH_SYS, which uses a
361 uid + gid list authenticator
364 A soft mount, which implies that file system calls will fail
367 round trip timeout intervals.
370 This is the default option, as it provides for increased reliability on both
371 LAN and WAN configurations compared to UDP.
372 Some old NFS servers do not support this method; UDP mounts may be required
373 for interoperability.
374 .It Cm timeout Ns = Ns Aq Ar value
375 Set the initial retransmit timeout to the specified value,
376 expressed in tenths of a second.
377 May be useful for fine tuning UDP mounts over internetworks
378 with high packet loss rates or an overloaded server.
379 Try increasing the interval if
381 shows high retransmit rates while the file system is active or reducing the
382 value if there is a low retransmit rate but long response delay observed.
385 option should be specified when using this option to manually
388 .It Cm timeo Ns = Ns Aq Ar value
393 .It Cm vers Ns = Ns Aq Ar vers_number
394 Use the specified version number for NFS requests.
401 .It Cm wcommitsize Ns = Ns Aq Ar value
402 Set the maximum pending write commit size to the specified value.
403 This determines the maximum amount of pending write data that the NFS
404 client is willing to cache for each file.
405 .It Cm wsize Ns = Ns Aq Ar value
406 Set the write data size to the specified value.
407 Ditto the comments w.r.t.\& the
409 option, but using the
410 .Dq "fragments dropped due to timeout"
411 value on the server instead of the client.
416 options should only be used as a last ditch effort at improving performance
417 when mounting servers that do not support TCP mounts.
421 The following command line flags are equivalent to
423 named options and are supported for compatibility with older
425 .Bl -tag -width indent
437 .Fl o Cm readdirsize Ns = Ns Aq Ar value
445 Use a reserved socket port number.
446 This flag is obsolete, and only retained for compatibility reasons.
447 (For the rare case where the client has a trusted root account
448 but untrustworthy users and the network cables are in secure areas this does
449 help, but for normal desktop clients this does not apply.)
452 .Fl o Cm retrycnt Ns = Ns Aq Ar value
461 .Fl o Cm readahead Ns = Ns Aq Ar value
482 .Fl o Cm rsize Ns = Ns Aq Ar value
488 .Fl o Cm retransmit Ns = Ns Aq Ar value
491 .Fl o Cm wsize Ns = Ns Aq Ar value
494 .Fl o Cm retrans Ns = Ns Aq Ar value
499 named options are equivalent to other
501 named options and are supported for compatibility with other
502 operating systems (e.g., Linux, Solaris, and OSX) to ease usage of
505 .Bl -tag -width indent
506 .It Fl o Cm vers Ns = Ns 2
509 .It Fl o Cm vers Ns = Ns 3
512 .It Fl o Cm vers Ns = Ns 4
527 Since nfsv4 performs open/lock operations that have their ordering strictly
528 enforced by the server, the options
532 cannot be safely used.
534 nfsv4 mounts are strongly recommended.