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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.
116 If an initial attempt to contact the server fails, fork off a child to keep
117 trying the mount in the background.
120 where the file system mount is not critical to multiuser operation.
121 .It Cm deadthresh Ns = Ns Aq Ar value
123 .Dq "dead server threshold"
124 to the specified number of round trip timeout intervals before a
125 .Dq "server not responding"
126 message is displayed.
128 Turn off the dynamic retransmit timeout estimator.
129 This may be useful for UDP mounts that exhibit high retry rates,
130 since it is possible that the dynamically estimated timeout interval is too
133 Same as not specifying
136 Same as not specifying
139 Make the mount interruptible, which implies that file system calls that
140 are delayed due to an unresponsive server will fail with EINTR when a
141 termination signal is posted for the process.
142 .It Cm maxgroups Ns = Ns Aq Ar value
143 Set the maximum size of the group list for the credentials to the
145 This should be used for mounts on old servers that cannot handle a
146 group list size of 16, as specified in RFC 1057.
147 Try 8, if users in a lot of groups cannot get response from the mount
150 Force the mount protocol to use UDP transport, even for TCP NFS mounts.
151 (Necessary for some old
154 .It Cm negnametimeo Ns = Ns Aq Ar value
155 Override the default of NFS_DEFAULT_NEGNAMETIMEO for the timeout (in seconds)
156 for negative name cache entries. If this is set to 0 it disables negative
157 name caching for the mount point.
159 Use the NFS Version 2 protocol (the default is to try version 3 first
161 Note that NFS version 2 has a file size limit of 2 gigabytes.
163 Use the NFS Version 3 protocol.
165 Use the NFS Version 4 protocol.
166 This option will force the mount to use the experimental nfs subsystem and
168 To use the experimental nfs subsystem for nfsv2 and nfsv3 mounts, you
169 must specify the ``newnfs'' file system type instead of ``nfs''.
171 For UDP mount points, do not do a
173 This must be used if the server does not reply to requests from the standard
174 NFS port number 2049 or replies to requests using a different IP address
175 (which can occur if the server is multi-homed).
177 .Va vfs.nfs.nfs_ip_paranoia
178 sysctl to 0 will make this option the default.
180 Normally, NFS clients maintain the close-to-open cache coherency.
181 This works by flushing at close time and checking at open time.
182 Checking at open time is implemented by getting attributes from
183 the server and purging the data cache if they do not match
184 attributes cached by the client.
186 This option disables checking at open time.
187 It may improve performance for read-only mounts,
188 but should only be used if the data on the server changes rarely.
189 Be sure to understand the consequences before enabling this option.
190 .It Cm noinet4 , noinet6
196 Useful for hosts that have
197 both an A record and an AAAA record for the same name.
204 All locks will be local and not seen by the server
205 and likewise not seen by other NFS clients.
206 This removes the need to run the
212 servers on the client.
213 Note that this option will only be honored when performing the
214 initial mount, it will be silently ignored if used while updating
217 For the RPCSEC_GSS security flavors, such as krb5, krb5i and krb5p,
218 this option sets the name of the host based principal name expected
219 by the server. This option overrides the default, which will be
220 ``nfs@<server-fqdn>'' and should normally be sufficient.
224 use a reserved socket port number (see below).
225 .It Cm port Ns = Ns Aq Ar port_number
226 Use specified port number for NFS requests.
227 The default is to query the portmapper for the NFS port.
229 Used with NFSV3 to specify that the \fBReaddirPlus\fR RPC should
231 For NFSV4, setting this option has a similar effect, in that it will make
232 the Readdir Operation get more attributes.
233 This option reduces RPC traffic for cases such as
235 but tends to flood the attribute and name caches with prefetched entries.
236 Try this option and see whether performance improves or degrades.
238 most useful for client to server network interconnects with a large bandwidth
240 .It Cm readahead Ns = Ns Aq Ar value
241 Set the read-ahead count to the specified value.
242 This may be in the range of 0 - 4, and determines how many blocks
243 will be read ahead when a large file is being read sequentially.
244 Trying a value greater than 1 for this is suggested for
245 mounts with a large bandwidth * delay product.
246 .It Cm readdirsize Ns = Ns Aq Ar value
247 Set the readdir read size to the specified value.
248 The value should normally
251 that is <= the read size for the mount.
253 Use a reserved socket port number.
254 This flag is obsolete, and only retained for compatibility reasons.
255 Reserved port numbers are used by default now.
256 (For the rare case where the client has a trusted root account
257 but untrustworthy users and the network cables are in secure areas this does
258 help, but for normal desktop clients this does not apply.)
259 .It Cm retrans Ns = Ns Aq Ar value
260 Set the retransmit timeout count for soft mounts to the specified value.
261 .It Cm retrycnt Ns = Ns Aq Ar count
262 Set the mount retry count to the specified value.
263 The default is a retry count of zero, which means to keep retrying
265 There is a 60 second delay between each attempt.
266 .It Cm rsize Ns = Ns Aq Ar value
267 Set the read data size to the specified value.
268 It should normally be a power of 2 greater than or equal to 1024.
269 This should be used for UDP mounts when the
270 .Dq "fragments dropped due to timeout"
271 value is getting large while actively using a mount point.
276 option to see what the
277 .Dq "fragments dropped due to timeout"
279 .It Cm sec Ns = Ns Aq Ar flavor
280 This option specifies what security flavor should be used for the mount.
283 krb5 - Use KerberosV authentication
284 krb5i - Use KerberosV authentication and
285 apply integrity checksums to RPCs
286 krb5p - Use KerberosV authentication and
288 sys - The default AUTH_SYS, which uses a
289 uid + gid list authenticator
292 A soft mount, which implies that file system calls will fail
295 round trip timeout intervals.
298 This is the default option, as it provides for increased reliability on both
299 LAN and WAN configurations compared to UDP.
300 Some old NFS servers do not support this method; UDP mounts may be required
301 for interoperability.
302 .It Cm timeout Ns = Ns Aq Ar value
303 Set the initial retransmit timeout to the specified value.
304 May be useful for fine tuning UDP mounts over internetworks
305 with high packet loss rates or an overloaded server.
306 Try increasing the interval if
308 shows high retransmit rates while the file system is active or reducing the
309 value if there is a low retransmit rate but long response delay observed.
312 option should be specified when using this option to manually
317 .It Cm wsize Ns = Ns Aq Ar value
318 Set the write data size to the specified value.
319 Ditto the comments w.r.t.\& the
321 option, but using the
322 .Dq "fragments dropped due to timeout"
323 value on the server instead of the client.
328 options should only be used as a last ditch effort at improving performance
329 when mounting servers that do not support TCP mounts.
333 The following command line flags are equivalent to
335 named options and are supported for compatibility with older
337 .Bl -tag -width indent
349 .Fl o Cm readdirsize Ns = Ns Aq Ar value
357 Use a reserved socket port number.
358 This flag is obsolete, and only retained for compatibility reasons.
359 (For the rare case where the client has a trusted root account
360 but untrustworthy users and the network cables are in secure areas this does
361 help, but for normal desktop clients this does not apply.)
364 .Fl o Cm retrycnt Ns = Ns Aq Ar value
373 .Fl o Cm readahead Ns = Ns Aq Ar value
394 .Fl o Cm rsize Ns = Ns Aq Ar value
400 .Fl o Cm retransmit Ns = Ns Aq Ar value
403 .Fl o Cm wsize Ns = Ns Aq Ar value
406 .Fl o Cm retrans Ns = Ns Aq Ar value
419 Since nfsv4 performs open/lock operations that have their ordering strictly
420 enforced by the server, the options
424 cannot be safely used.
426 nfsv4 mounts are strongly recommended.