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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
155 Use the NFS Version 2 protocol (the default is to try version 3 first
157 Note that NFS version 2 has a file size limit of 2 gigabytes.
159 Use the NFS Version 3 protocol.
161 Use the NFS Version 4 protocol.
162 This option will force the mount to use the experimental nfs subsystem and
164 To use the experimental nfs subsystem for nfsv2 and nfsv3 mounts, you
165 must specify the ``newnfs'' file system type instead of ``nfs''.
167 For UDP mount points, do not do a
169 This must be used if the server does not reply to requests from the standard
170 NFS port number 2049 or replies to requests using a different IP address
171 (which can occur if the server is multi-homed).
173 .Va vfs.nfs.nfs_ip_paranoia
174 sysctl to 0 will make this option the default.
175 .It Cm noinet4 , noinet6
181 Useful for hosts that have
182 both an A record and an AAAA record for the same name.
189 All locks will be local and not seen by the server
190 and likewise not seen by other NFS clients.
191 This removes the need to run the
197 servers on the client.
198 Note that this option will only be honored when performing the
199 initial mount, it will be silently ignored if used while updating
202 For the RPCSEC_GSS security flavors, such as krb5, krb5i and krb5p,
203 this option sets the name of the host based principal name expected
204 by the server. This option overrides the default, which will be
205 ``nfs@<server-fqdn>'' and should normally be sufficient.
209 use a reserved socket port number (see below).
210 .It Cm port Ns = Ns Aq Ar port_number
211 Use specified port number for NFS requests.
212 The default is to query the portmapper for the NFS port.
214 Used with NFSV3 to specify that the \fBReaddirPlus\fR RPC should
216 For NFSV4, setting this option has a similar effect, in that it will make
217 the Readdir Operation get more attributes.
218 This option reduces RPC traffic for cases such as
220 but tends to flood the attribute and name caches with prefetched entries.
221 Try this option and see whether performance improves or degrades.
223 most useful for client to server network interconnects with a large bandwidth
225 .It Cm readahead Ns = Ns Aq Ar value
226 Set the read-ahead count to the specified value.
227 This may be in the range of 0 - 4, and determines how many blocks
228 will be read ahead when a large file is being read sequentially.
229 Trying a value greater than 1 for this is suggested for
230 mounts with a large bandwidth * delay product.
231 .It Cm readdirsize Ns = Ns Aq Ar value
232 Set the readdir read size to the specified value.
233 The value should normally
236 that is <= the read size for the mount.
238 Use a reserved socket port number.
239 This flag is obsolete, and only retained for compatibility reasons.
240 Reserved port numbers are used by default now.
241 (For the rare case where the client has a trusted root account
242 but untrustworthy users and the network cables are in secure areas this does
243 help, but for normal desktop clients this does not apply.)
244 .It Cm retrans Ns = Ns Aq Ar value
245 Set the retransmit timeout count for soft mounts to the specified value.
246 .It Cm retrycnt Ns = Ns Aq Ar count
247 Set the mount retry count to the specified value.
248 The default is a retry count of zero, which means to keep retrying
250 There is a 60 second delay between each attempt.
251 .It Cm rsize Ns = Ns Aq Ar value
252 Set the read data size to the specified value.
253 It should normally be a power of 2 greater than or equal to 1024.
254 This should be used for UDP mounts when the
255 .Dq "fragments dropped due to timeout"
256 value is getting large while actively using a mount point.
261 option to see what the
262 .Dq "fragments dropped due to timeout"
264 .It Cm sec Ns = Ns Aq Ar flavor
265 This option specifies what security flavor should be used for the mount.
268 krb5 - Use KerberosV authentication
269 krb5i - Use KerberosV authentication and
270 apply integrity checksums to RPCs
271 krb5p - Use KerberosV authentication and
273 sys - The default AUTH_SYS, which uses a
274 uid + gid list authenticator
277 A soft mount, which implies that file system calls will fail
280 round trip timeout intervals.
283 This is the default option, as it provides for increased reliability on both
284 LAN and WAN configurations compared to UDP.
285 Some old NFS servers do not support this method; UDP mounts may be required
286 for interoperability.
287 .It Cm timeout Ns = Ns Aq Ar value
288 Set the initial retransmit timeout to the specified value.
289 May be useful for fine tuning UDP mounts over internetworks
290 with high packet loss rates or an overloaded server.
291 Try increasing the interval if
293 shows high retransmit rates while the file system is active or reducing the
294 value if there is a low retransmit rate but long response delay observed.
297 option should be specified when using this option to manually
302 .It Cm wsize Ns = Ns Aq Ar value
303 Set the write data size to the specified value.
304 Ditto the comments w.r.t.\& the
306 option, but using the
307 .Dq "fragments dropped due to timeout"
308 value on the server instead of the client.
313 options should only be used as a last ditch effort at improving performance
314 when mounting servers that do not support TCP mounts.
318 The following command line flags are equivalent to
320 named options and are supported for compatibility with older
322 .Bl -tag -width indent
334 .Fl o Cm readdirsize Ns = Ns Aq Ar value
342 Use a reserved socket port number.
343 This flag is obsolete, and only retained for compatibility reasons.
344 (For the rare case where the client has a trusted root account
345 but untrustworthy users and the network cables are in secure areas this does
346 help, but for normal desktop clients this does not apply.)
349 .Fl o Cm retrycnt Ns = Ns Aq Ar value
358 .Fl o Cm readahead Ns = Ns Aq Ar value
379 .Fl o Cm rsize Ns = Ns Aq Ar value
385 .Fl o Cm retransmit Ns = Ns Aq Ar value
388 .Fl o Cm wsize Ns = Ns Aq Ar value
391 .Fl o Cm retrans Ns = Ns Aq Ar value
404 Since nfsv4 performs open/lock operations that have their ordering strictly
405 enforced by the server, the options
409 cannot be safely used.
411 nfsv4 mounts are strongly recommended.