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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.
179 .It Cm noinet4 , noinet6
185 Useful for hosts that have
186 both an A record and an AAAA record for the same name.
193 All locks will be local and not seen by the server
194 and likewise not seen by other NFS clients.
195 This removes the need to run the
201 servers on the client.
202 Note that this option will only be honored when performing the
203 initial mount, it will be silently ignored if used while updating
206 For the RPCSEC_GSS security flavors, such as krb5, krb5i and krb5p,
207 this option sets the name of the host based principal name expected
208 by the server. This option overrides the default, which will be
209 ``nfs@<server-fqdn>'' and should normally be sufficient.
213 use a reserved socket port number (see below).
214 .It Cm port Ns = Ns Aq Ar port_number
215 Use specified port number for NFS requests.
216 The default is to query the portmapper for the NFS port.
218 Used with NFSV3 to specify that the \fBReaddirPlus\fR RPC should
220 For NFSV4, setting this option has a similar effect, in that it will make
221 the Readdir Operation get more attributes.
222 This option reduces RPC traffic for cases such as
224 but tends to flood the attribute and name caches with prefetched entries.
225 Try this option and see whether performance improves or degrades.
227 most useful for client to server network interconnects with a large bandwidth
229 .It Cm readahead Ns = Ns Aq Ar value
230 Set the read-ahead count to the specified value.
231 This may be in the range of 0 - 4, and determines how many blocks
232 will be read ahead when a large file is being read sequentially.
233 Trying a value greater than 1 for this is suggested for
234 mounts with a large bandwidth * delay product.
235 .It Cm readdirsize Ns = Ns Aq Ar value
236 Set the readdir read size to the specified value.
237 The value should normally
240 that is <= the read size for the mount.
242 Use a reserved socket port number.
243 This flag is obsolete, and only retained for compatibility reasons.
244 Reserved port numbers are used by default now.
245 (For the rare case where the client has a trusted root account
246 but untrustworthy users and the network cables are in secure areas this does
247 help, but for normal desktop clients this does not apply.)
248 .It Cm retrans Ns = Ns Aq Ar value
249 Set the retransmit timeout count for soft mounts to the specified value.
250 .It Cm retrycnt Ns = Ns Aq Ar count
251 Set the mount retry count to the specified value.
252 The default is a retry count of zero, which means to keep retrying
254 There is a 60 second delay between each attempt.
255 .It Cm rsize Ns = Ns Aq Ar value
256 Set the read data size to the specified value.
257 It should normally be a power of 2 greater than or equal to 1024.
258 This should be used for UDP mounts when the
259 .Dq "fragments dropped due to timeout"
260 value is getting large while actively using a mount point.
265 option to see what the
266 .Dq "fragments dropped due to timeout"
268 .It Cm sec Ns = Ns Aq Ar flavor
269 This option specifies what security flavor should be used for the mount.
272 krb5 - Use KerberosV authentication
273 krb5i - Use KerberosV authentication and
274 apply integrity checksums to RPCs
275 krb5p - Use KerberosV authentication and
277 sys - The default AUTH_SYS, which uses a
278 uid + gid list authenticator
281 A soft mount, which implies that file system calls will fail
284 round trip timeout intervals.
287 This is the default option, as it provides for increased reliability on both
288 LAN and WAN configurations compared to UDP.
289 Some old NFS servers do not support this method; UDP mounts may be required
290 for interoperability.
291 .It Cm timeout Ns = Ns Aq Ar value
292 Set the initial retransmit timeout to the specified value.
293 May be useful for fine tuning UDP mounts over internetworks
294 with high packet loss rates or an overloaded server.
295 Try increasing the interval if
297 shows high retransmit rates while the file system is active or reducing the
298 value if there is a low retransmit rate but long response delay observed.
301 option should be specified when using this option to manually
306 .It Cm wsize Ns = Ns Aq Ar value
307 Set the write data size to the specified value.
308 Ditto the comments w.r.t.\& the
310 option, but using the
311 .Dq "fragments dropped due to timeout"
312 value on the server instead of the client.
317 options should only be used as a last ditch effort at improving performance
318 when mounting servers that do not support TCP mounts.
322 The following command line flags are equivalent to
324 named options and are supported for compatibility with older
326 .Bl -tag -width indent
338 .Fl o Cm readdirsize Ns = Ns Aq Ar value
346 Use a reserved socket port number.
347 This flag is obsolete, and only retained for compatibility reasons.
348 (For the rare case where the client has a trusted root account
349 but untrustworthy users and the network cables are in secure areas this does
350 help, but for normal desktop clients this does not apply.)
353 .Fl o Cm retrycnt Ns = Ns Aq Ar value
362 .Fl o Cm readahead Ns = Ns Aq Ar value
383 .Fl o Cm rsize Ns = Ns Aq Ar value
389 .Fl o Cm retransmit Ns = Ns Aq Ar value
392 .Fl o Cm wsize Ns = Ns Aq Ar value
395 .Fl o Cm retrans Ns = Ns Aq Ar value
408 Since nfsv4 performs open/lock operations that have their ordering strictly
409 enforced by the server, the options
413 cannot be safely used.
415 nfsv4 mounts are strongly recommended.