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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.
122 If an initial attempt to contact the server fails, fork off a child to keep
123 trying the mount in the background.
126 where the file system mount is not critical to multiuser operation.
127 .It Cm deadthresh Ns = Ns Aq Ar value
129 .Dq "dead server threshold"
130 to the specified number of round trip timeout intervals before a
131 .Dq "server not responding"
132 message is displayed.
134 Turn off the dynamic retransmit timeout estimator.
135 This may be useful for UDP mounts that exhibit high retry rates,
136 since it is possible that the dynamically estimated timeout interval is too
139 Same as not specifying
142 Same as not specifying
145 Make the mount interruptible, which implies that file system calls that
146 are delayed due to an unresponsive server will fail with EINTR when a
147 termination signal is posted for the process.
148 .It Cm maxgroups Ns = Ns Aq Ar value
149 Set the maximum size of the group list for the credentials to the
151 This should be used for mounts on old servers that cannot handle a
152 group list size of 16, as specified in RFC 1057.
153 Try 8, if users in a lot of groups cannot get response from the mount
156 Force the mount protocol to use UDP transport, even for TCP NFS mounts.
157 (Necessary for some old
160 .It Cm nametimeo Ns = Ns Aq Ar value
161 Override the default of NFS_DEFAULT_NAMETIMEO for the timeout (in seconds)
162 for positive name cache entries.
163 If this is set to 0 it disables positive name caching for the mount point.
164 .It Cm negnametimeo Ns = Ns Aq Ar value
165 Override the default of NFS_DEFAULT_NEGNAMETIMEO for the timeout (in seconds)
166 for negative name cache entries. If this is set to 0 it disables negative
167 name caching for the mount point.
169 Use the NFS Version 2 protocol (the default is to try version 3 first
171 Note that NFS version 2 has a file size limit of 2 gigabytes.
173 Use the NFS Version 3 protocol.
175 Use the NFS Version 4 protocol.
176 This option will force the mount to use
178 .It Cm minorversion Ns = Ns Aq Ar value
179 Override the default of 0 for the minor version of the NFS Version 4 protocol.
180 The only minor version currently supported is 1.
181 This option is only meaningful when used with the
185 Enable support for parallel NFS (pNFS) for minor version 1 of the
186 NFS Version 4 protocol.
187 This option is only meaningful when used with the
191 For UDP mount points, do not do a
193 This must be used if the server does not reply to requests from the standard
194 NFS port number 2049 or replies to requests using a different IP address
195 (which can occur if the server is multi-homed).
197 .Va vfs.nfs.nfs_ip_paranoia
198 sysctl to 0 will make this option the default.
200 Normally, NFS clients maintain the close-to-open cache coherency.
201 This works by flushing at close time and checking at open time.
202 Checking at open time is implemented by getting attributes from
203 the server and purging the data cache if they do not match
204 attributes cached by the client.
206 This option disables checking at open time.
207 It may improve performance for read-only mounts,
208 but should only be used if the data on the server changes rarely.
209 Be sure to understand the consequences before enabling this option.
210 .It Cm noinet4 , noinet6
216 Useful for hosts that have
217 both an A record and an AAAA record for the same name.
224 All locks will be local and not seen by the server
225 and likewise not seen by other NFS clients.
226 This removes the need to run the
232 servers on the client.
233 Note that this option will only be honored when performing the
234 initial mount, it will be silently ignored if used while updating
237 For the RPCSEC_GSS security flavors, such as krb5, krb5i and krb5p,
238 this option sets the name of the host based principal name expected
239 by the server. This option overrides the default, which will be
240 ``nfs@<server-fqdn>'' and should normally be sufficient.
244 use a reserved socket port number (see below).
245 .It Cm port Ns = Ns Aq Ar port_number
246 Use specified port number for NFS requests.
247 The default is to query the portmapper for the NFS port.
249 Used with NFSV3 to specify that the \fBReaddirPlus\fR RPC should
251 For NFSV4, setting this option has a similar effect, in that it will make
252 the Readdir Operation get more attributes.
253 This option reduces RPC traffic for cases such as
255 but tends to flood the attribute and name caches with prefetched entries.
256 Try this option and see whether performance improves or degrades.
258 most useful for client to server network interconnects with a large bandwidth
260 .It Cm readahead Ns = Ns Aq Ar value
261 Set the read-ahead count to the specified value.
262 This may be in the range of 0 - 4, and determines how many blocks
263 will be read ahead when a large file is being read sequentially.
264 Trying a value greater than 1 for this is suggested for
265 mounts with a large bandwidth * delay product.
266 .It Cm readdirsize Ns = Ns Aq Ar value
267 Set the readdir read size to the specified value.
268 The value should normally
271 that is <= the read size for the mount.
273 Use a reserved socket port number.
274 This flag is obsolete, and only retained for compatibility reasons.
275 Reserved port numbers are used by default now.
276 (For the rare case where the client has a trusted root account
277 but untrustworthy users and the network cables are in secure areas this does
278 help, but for normal desktop clients this does not apply.)
279 .It Cm retrans Ns = Ns Aq Ar value
280 Set the retransmit timeout count for soft mounts to the specified value.
281 .It Cm retrycnt Ns = Ns Aq Ar count
282 Set the mount retry count to the specified value.
283 The default is a retry count of zero, which means to keep retrying
285 There is a 60 second delay between each attempt.
286 .It Cm rsize Ns = Ns Aq Ar value
287 Set the read data size to the specified value.
288 It should normally be a power of 2 greater than or equal to 1024.
289 This should be used for UDP mounts when the
290 .Dq "fragments dropped due to timeout"
291 value is getting large while actively using a mount point.
296 option to see what the
297 .Dq "fragments dropped due to timeout"
299 .It Cm sec Ns = Ns Aq Ar flavor
300 This option specifies what security flavor should be used for the mount.
303 krb5 - Use KerberosV authentication
304 krb5i - Use KerberosV authentication and
305 apply integrity checksums to RPCs
306 krb5p - Use KerberosV authentication and
308 sys - The default AUTH_SYS, which uses a
309 uid + gid list authenticator
312 A soft mount, which implies that file system calls will fail
315 round trip timeout intervals.
318 This is the default option, as it provides for increased reliability on both
319 LAN and WAN configurations compared to UDP.
320 Some old NFS servers do not support this method; UDP mounts may be required
321 for interoperability.
322 .It Cm timeout Ns = Ns Aq Ar value
323 Set the initial retransmit timeout to the specified value.
324 May be useful for fine tuning UDP mounts over internetworks
325 with high packet loss rates or an overloaded server.
326 Try increasing the interval if
328 shows high retransmit rates while the file system is active or reducing the
329 value if there is a low retransmit rate but long response delay observed.
332 option should be specified when using this option to manually
337 .It Cm wcommitsize Ns = Ns Aq Ar value
338 Set the maximum pending write commit size to the specified value.
339 This determines the maximum amount of pending write data that the NFS
340 client is willing to cache for each file.
341 .It Cm wsize Ns = Ns Aq Ar value
342 Set the write data size to the specified value.
343 Ditto the comments w.r.t.\& the
345 option, but using the
346 .Dq "fragments dropped due to timeout"
347 value on the server instead of the client.
352 options should only be used as a last ditch effort at improving performance
353 when mounting servers that do not support TCP mounts.
357 The following command line flags are equivalent to
359 named options and are supported for compatibility with older
361 .Bl -tag -width indent
373 .Fl o Cm readdirsize Ns = Ns Aq Ar value
381 Use a reserved socket port number.
382 This flag is obsolete, and only retained for compatibility reasons.
383 (For the rare case where the client has a trusted root account
384 but untrustworthy users and the network cables are in secure areas this does
385 help, but for normal desktop clients this does not apply.)
388 .Fl o Cm retrycnt Ns = Ns Aq Ar value
397 .Fl o Cm readahead Ns = Ns Aq Ar value
418 .Fl o Cm rsize Ns = Ns Aq Ar value
424 .Fl o Cm retransmit Ns = Ns Aq Ar value
427 .Fl o Cm wsize Ns = Ns Aq Ar value
430 .Fl o Cm retrans Ns = Ns Aq Ar value
443 Since nfsv4 performs open/lock operations that have their ordering strictly
444 enforced by the server, the options
448 cannot be safely used.
450 nfsv4 mounts are strongly recommended.