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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" ,
66 If the file system type is specified as ``oldnfs'', which implies this
67 command is run as ``mount_oldnfs'', then it forces use of the old NFS
68 client, which does not support the
74 keeps retrying until the mount succeeds.
75 This behaviour is intended for file systems listed in
77 that are critical to the boot process.
78 For non-critical file systems, the
82 options provide mechanisms to prevent the boot process from hanging
83 if the server is unavailable.
85 If the server becomes unresponsive while an NFS file system is
86 mounted, any new or outstanding file operations on that file system
87 will hang uninterruptibly until the server comes back.
88 To modify this default behaviour, see the
95 .Bl -tag -width indent
97 Options are specified with a
99 flag followed by a comma separated string of options.
102 man page for possible options and their meanings.
103 The following NFS specific options are also available:
104 .Bl -tag -width indent
105 .It Cm acregmin Ns = Ns Aq Ar seconds
106 .It Cm acregmax Ns = Ns Aq Ar seconds
107 .It Cm acdirmin Ns = Ns Aq Ar seconds
108 .It Cm acdirmax Ns = Ns Aq Ar seconds
109 When attributes of files are cached, a timeout calculated to determine
110 whether a given cache entry has expired.
111 These four values determine the upper and lower bounds of the timeouts for
115 (ie: everything else).
116 The default values are 3 -> 60 seconds
117 for regular files, and 30 -> 60 seconds for directories.
118 The algorithm to calculate the timeout is based on the age of the file.
120 the longer the cache is considered valid, subject to the limits above.
121 .It Cm actimeo Ns = Ns Aq Ar seconds
122 Set four cache timeouts above to specified value.
124 This option can be used along with
126 to specify that all operations should use the host-based initiator
128 This may be used for clients that run system daemons that need to
129 access files on the NFSv4 mounted volume.
131 If an initial attempt to contact the server fails, fork off a child to keep
132 trying the mount in the background.
135 where the file system mount is not critical to multiuser operation.
136 .It Cm deadthresh Ns = Ns Aq Ar value
138 .Dq "dead server threshold"
139 to the specified number of round trip timeout intervals before a
140 .Dq "server not responding"
141 message is displayed.
143 Turn off the dynamic retransmit timeout estimator.
144 This may be useful for UDP mounts that exhibit high retry rates,
145 since it is possible that the dynamically estimated timeout interval is too
148 Same as not specifying
150 .It Cm gssname Ns = Ns Aq Ar service-principal-name
151 This option can be used with the KerberosV security flavors for NFSv4 mounts
153 .Dq "service-principal-name"
154 of a host-based entry in the default
155 keytab file that is used for system operations.
156 It allows the mount to be performed by
158 and avoids problems with
159 cached credentials for the system operations expiring.
161 .Dq "service-prinicpal-name"
162 should be specified without instance or domain and is typically
168 Same as not specifying
171 Make the mount interruptible, which implies that file system calls that
172 are delayed due to an unresponsive server will fail with EINTR when a
173 termination signal is posted for the process.
174 .It Cm maxgroups Ns = Ns Aq Ar value
175 Set the maximum size of the group list for the credentials to the
177 This should be used for mounts on old servers that cannot handle a
178 group list size of 16, as specified in RFC 1057.
179 Try 8, if users in a lot of groups cannot get response from the mount
182 Force the mount protocol to use UDP transport, even for TCP NFS mounts.
183 (Necessary for some old
186 .It Cm nametimeo Ns = Ns Aq Ar value
187 Override the default of NFS_DEFAULT_NAMETIMEO for the timeout (in seconds)
188 for positive name cache entries.
189 If this is set to 0 it disables positive name caching for the mount point.
190 .It Cm negnametimeo Ns = Ns Aq Ar value
191 Override the default of NFS_DEFAULT_NEGNAMETIMEO for the timeout (in seconds)
192 for negative name cache entries. If this is set to 0 it disables negative
193 name caching for the mount point.
195 Use the NFS Version 2 protocol (the default is to try version 3 first
197 Note that NFS version 2 has a file size limit of 2 gigabytes.
199 Use the NFS Version 3 protocol.
201 Use the NFS Version 4 protocol.
202 This option will force the mount to use
204 .It Cm minorversion Ns = Ns Aq Ar value
205 Override the default of 0 for the minor version of the NFS Version 4 protocol.
206 The only minor version currently supported is 1.
207 This option is only meaningful when used with the
211 Enable support for parallel NFS (pNFS) for minor version 1 of the
212 NFS Version 4 protocol.
213 This option is only meaningful when used with the
217 Disable attribute caching.
219 For UDP mount points, do not do a
221 This must be used if the server does not reply to requests from the standard
222 NFS port number 2049 or replies to requests using a different IP address
223 (which can occur if the server is multi-homed).
225 .Va vfs.nfs.nfs_ip_paranoia
226 sysctl to 0 will make this option the default.
228 Normally, NFS clients maintain the close-to-open cache coherency.
229 This works by flushing at close time and checking at open time.
230 Checking at open time is implemented by getting attributes from
231 the server and purging the data cache if they do not match
232 attributes cached by the client.
234 This option disables checking at open time.
235 It may improve performance for read-only mounts,
236 but should only be used if the data on the server changes rarely.
237 Be sure to understand the consequences before enabling this option.
238 .It Cm noinet4 , noinet6
244 Useful for hosts that have
245 both an A record and an AAAA record for the same name.
252 All locks will be local and not seen by the server
253 and likewise not seen by other NFS clients.
254 This removes the need to run the
260 servers on the client.
261 Note that this option will only be honored when performing the
262 initial mount, it will be silently ignored if used while updating
265 This mount option allows the NFS client to
266 combine non-contiguous byte ranges being written
267 such that the dirty byte range becomes a superset of the bytes
269 This reduces the number of writes significantly for software
271 The merging of byte ranges isn't done if the file has been file
272 locked, since most applications modifying a file from multiple
273 clients will use file locking.
274 As such, this option could result in a corrupted file for the
275 rare case of an application modifying the file from multiple
276 clients concurrently without using file locking.
278 For the RPCSEC_GSS security flavors, such as krb5, krb5i and krb5p,
279 this option sets the name of the host based principal name expected
280 by the server. This option overrides the default, which will be
281 ``nfs@<server-fqdn>'' and should normally be sufficient.
285 use a reserved socket port number (see below).
286 .It Cm port Ns = Ns Aq Ar port_number
287 Use specified port number for NFS requests.
288 The default is to query the portmapper for the NFS port.
289 .It Cm proto Ns = Ns Aq Ar protocol
290 Specify transport protocol version to use.
293 udp - Use UDP over IPv4
294 tcp - Use TCP over IPv4
295 udp6 - Use UDP over IPv6
296 tcp6 - Use TCP over IPv6
299 Used with NFSV3 to specify that the \fBReaddirPlus\fR RPC should
301 For NFSV4, setting this option has a similar effect, in that it will make
302 the Readdir Operation get more attributes.
303 This option reduces RPC traffic for cases such as
305 but tends to flood the attribute and name caches with prefetched entries.
306 Try this option and see whether performance improves or degrades.
308 most useful for client to server network interconnects with a large bandwidth
310 .It Cm readahead Ns = Ns Aq Ar value
311 Set the read-ahead count to the specified value.
312 This may be in the range of 0 - 4, and determines how many blocks
313 will be read ahead when a large file is being read sequentially.
314 Trying a value greater than 1 for this is suggested for
315 mounts with a large bandwidth * delay product.
316 .It Cm readdirsize Ns = Ns Aq Ar value
317 Set the readdir read size to the specified value.
318 The value should normally
321 that is <= the read size for the mount.
323 Use a reserved socket port number.
324 This flag is obsolete, and only retained for compatibility reasons.
325 Reserved port numbers are used by default now.
326 (For the rare case where the client has a trusted root account
327 but untrustworthy users and the network cables are in secure areas this does
328 help, but for normal desktop clients this does not apply.)
329 .It Cm retrans Ns = Ns Aq Ar value
330 Set the retransmit timeout count for soft mounts to the specified value.
331 .It Cm retrycnt Ns = Ns Aq Ar count
332 Set the mount retry count to the specified value.
333 The default is a retry count of zero, which means to keep retrying
335 There is a 60 second delay between each attempt.
336 .It Cm rsize Ns = Ns Aq Ar value
337 Set the read data size to the specified value.
338 It should normally be a power of 2 greater than or equal to 1024.
339 This should be used for UDP mounts when the
340 .Dq "fragments dropped due to timeout"
341 value is getting large while actively using a mount point.
346 option to see what the
347 .Dq "fragments dropped due to timeout"
349 .It Cm sec Ns = Ns Aq Ar flavor
350 This option specifies what security flavor should be used for the mount.
353 krb5 - Use KerberosV authentication
354 krb5i - Use KerberosV authentication and
355 apply integrity checksums to RPCs
356 krb5p - Use KerberosV authentication and
358 sys - The default AUTH_SYS, which uses a
359 uid + gid list authenticator
362 A soft mount, which implies that file system calls will fail
365 round trip timeout intervals.
368 This is the default option, as it provides for increased reliability on both
369 LAN and WAN configurations compared to UDP.
370 Some old NFS servers do not support this method; UDP mounts may be required
371 for interoperability.
372 .It Cm timeout Ns = Ns Aq Ar value
373 Set the initial retransmit timeout to the specified value,
374 expressed in tenths of a second.
375 May be useful for fine tuning UDP mounts over internetworks
376 with high packet loss rates or an overloaded server.
377 Try increasing the interval if
379 shows high retransmit rates while the file system is active or reducing the
380 value if there is a low retransmit rate but long response delay observed.
383 option should be specified when using this option to manually
386 .It Cm timeo Ns = Ns Aq Ar value
391 .It Cm vers Ns = Ns Aq Ar vers_number
392 Use the specified version number for NFS requests.
399 .It Cm wcommitsize Ns = Ns Aq Ar value
400 Set the maximum pending write commit size to the specified value.
401 This determines the maximum amount of pending write data that the NFS
402 client is willing to cache for each file.
403 .It Cm wsize Ns = Ns Aq Ar value
404 Set the write data size to the specified value.
405 Ditto the comments w.r.t.\& the
407 option, but using the
408 .Dq "fragments dropped due to timeout"
409 value on the server instead of the client.
414 options should only be used as a last ditch effort at improving performance
415 when mounting servers that do not support TCP mounts.
419 The following command line flags are equivalent to
421 named options and are supported for compatibility with older
423 .Bl -tag -width indent
435 .Fl o Cm readdirsize Ns = Ns Aq Ar value
443 Use a reserved socket port number.
444 This flag is obsolete, and only retained for compatibility reasons.
445 (For the rare case where the client has a trusted root account
446 but untrustworthy users and the network cables are in secure areas this does
447 help, but for normal desktop clients this does not apply.)
450 .Fl o Cm retrycnt Ns = Ns Aq Ar value
459 .Fl o Cm readahead Ns = Ns Aq Ar value
480 .Fl o Cm rsize Ns = Ns Aq Ar value
486 .Fl o Cm retransmit Ns = Ns Aq Ar value
489 .Fl o Cm wsize Ns = Ns Aq Ar value
492 .Fl o Cm retrans Ns = Ns Aq Ar value
497 named options are equivalent to other
499 named options and are supported for compatibility with other
500 operating systems (e.g., Linux, Solaris, and OSX) to ease usage of
503 .Bl -tag -width indent
504 .It Fl o Cm vers Ns = Ns 2
507 .It Fl o Cm vers Ns = Ns 3
510 .It Fl o Cm vers Ns = Ns 4
525 Since nfsv4 performs open/lock operations that have their ordering strictly
526 enforced by the server, the options
530 cannot be safely used.
532 nfsv4 mounts are strongly recommended.