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32 .\" @(#)mount_nfs.8 8.3 (Berkeley) 3/29/95
34 .\" $FreeBSD: src/sbin/mount_nfs/mount_nfs.8,v 1.18.2.10 2003/05/13 14:45:40 trhodes Exp $
35 .\" $DragonFly: src/sbin/mount_nfs/mount_nfs.8,v 1.6 2008/05/01 23:36:43 swildner Exp $
42 .Nd mount nfs file systems
46 .Op Fl D Ar deadthresh
47 .Op Fl I Ar readdirsize
49 .Op Fl a Ar maxreadahead
57 .Ar rhost : Ns Ar path node
64 system call to prepare and graft a remote nfs file system
65 .Pq Ar rhost : Ns Ar path
66 on to the file system tree at the point
68 This command is normally executed by
70 It implements the mount protocol as described in RFC 1094, Appendix A and
71 .%T "NFS: Network File System Version 3 Protocol Specification" ,
76 keeps retrying until the mount succeeds.
77 This behaviour is intended for filesystems listed in
79 that are critical to the boot process.
80 For non-critical filesystems, the
84 flags provide mechanisms to prevent the boot process from hanging
85 if the server is unavailable.
87 If the server becomes unresponsive while an NFS filesystem is
88 mounted, any new or outstanding file operations on that filesystem
89 will hang uninterruptibly until the server comes back.
90 To modify this default behaviour, see the
97 .Bl -tag -width indent
99 Use the NFS Version 2 protocol (the default is to try version 3 first
101 Note that NFS version 2 has a file size limit of 2 gigabytes.
103 Use the NFS Version 3 protocol.
106 .Dq "dead server threshold"
107 to the specified number of round trip timeout intervals.
109 .Dq "dead server threshold"
110 of retransmit timeouts,
111 cached data for the unresponsive server is assumed to still be valid.
112 Values may be set in the range of 1 - 9, with 9 referring to an
113 .Dq "infinite dead threshold"
114 (i.e. never assume cached data still valid).
115 This option is not generally recommended and is really an experimental
118 Set the readdir read size to the specified value.
119 The value should normally
120 be a multiple of DIRBLKSIZ that is \(<= the read size for the mount.
122 Pass Kerberos authenticators to the server for client-to-server
123 user-credential mapping.
124 This requires that the kernel be built with the NFSKERB option.
125 The use of this option will prevent the kernel from compiling
126 unless calls to the appropriate Kerberos encryption routines
127 are provided in the NFS source.
129 .%T "Authentication Mechanisms for ONC RPC" ,
130 for more information.)
134 use a reserved socket port number (see below).
136 Use a reserved socket port number.
137 This flag is obsolete, and only retained for compatibility reasons.
138 Reserved port numbers are used by default now.
139 (For the rare case where the client has a trusted root account
140 but untrustworthy users and the network cables are in secure areas this does
141 help, but for normal desktop clients this does not apply.)
143 Set the mount retry count to the specified value.
144 The default is a retry count of zero, which means to keep retrying
146 There is a 60 second delay between each attempt.
148 Use TCP transport instead of UDP.
149 This is recommended for servers that are not on the same LAN cable as
153 Use UDP transport instead of TCP.
154 This is not recommended due to the ease of which
156 clients can blow out available socket buffer space on the server,
157 not to mention the impossibility of accurately calculating the
158 proper retry interval due to disk I/O backlogs on the server.
159 If you want to use the option anyway it is recommended that the
160 server reserve upwards of 2 MBytes of socket buffer space to hold
161 the received UDP packets.
163 Set the read-ahead count to the specified value.
164 This may be in the range of 0 - 32, and determines how many blocks
165 will be read ahead when a large file is being read sequentially.
166 Trying a value greater than 1 for this is suggested for
167 mounts with a large bandwidth * delay product.
169 If an initial attempt to contact the server fails, fork off a child to keep
170 trying the mount in the background.
173 where the filesystem mount is not critical to multiuser operation.
175 For UDP mount points, do not do a
177 This must be used if the server does not reply to requests from the standard
178 NFS port number 2049 or replies to requests using a different IP address
179 (which can occur if the server is multi-homed).
181 .Va vfs.nfs.nfs_ip_paranoia
182 sysctl to 0 will make this option the default.
184 Turn off the dynamic retransmit timeout estimator.
185 This may be useful for UDP mounts that exhibit high retry rates,
186 since it is possible that the dynamically estimated timeout interval is too
189 Set the maximum size of the group list for the credentials to the
191 This should be used for mounts on old servers that cannot handle a
192 group list size of 16, as specified in RFC 1057.
193 Try 8, if users in a lot of groups cannot get response from the mount
196 Make the mount interruptible, which implies that file system calls that
197 are delayed due to an unresponsive server will fail with
199 when a termination signal is posted for the process.
201 Used with NFSV3 to specify that the
204 This option reduces RPC traffic for cases such as
206 but tends to flood the attribute and name caches with prefetched entries.
207 Try this option and see whether performance improves or degrades.
209 most useful for client to server network interconnects with a large bandwidth
213 Set the Kerberos realm to the string argument.
216 option for mounts to other realms.
218 Options are specified with a
220 flag followed by a comma separated string of options.
223 man page for possible options and their meanings.
224 The following NFS specific option is also available:
225 .Bl -tag -width indent
226 .It Cm port Ns =<port_number>
227 Use specified port number for NFS requests.
228 The default is to query the portmapper for the NFS port.
229 .It Cm acregmin Ns =<seconds>
230 .It Cm acregmax Ns =<seconds>
231 .It Cm acdirmin Ns =<seconds>
232 .It Cm acdirmax Ns =<seconds>
233 When attributes of files are cached, a timeout calculated to determine
234 whether a given cache entry has expired.
235 These four values determine the
236 upper and lower bounds of the timeouts for ``directory'' attributes and
237 ``regular'' (i.e.: everything else).
238 The default values are 3 -> 60 seconds
239 for regular files, and 30 -> 60 seconds for directories.
241 calculate the timeout is based on the age of the file.
243 the longer the cache is considered valid, subject to the limits above.
251 flag on mount point (recursive, does not cross mounts).
254 this is alternate method to set flag.
259 Same as not specifying
297 Set the read data size to the specified value.
298 It should normally be a power of 2 greater than or equal to 1024.
299 This should be used for UDP mounts when the
300 .Dq "fragments dropped due to timeout"
301 value is getting large while actively using a mount point.
306 option to see what the
307 .Dq "fragments dropped due to timeout"
313 A soft mount, which implies that file system calls will fail after
315 round trip timeout intervals.
317 Set the initial retransmit timeout to the specified value.
318 May be useful for fine tuning UDP mounts over internetworks
319 with high packet loss rates or an overloaded server.
320 Try increasing the interval if
322 shows high retransmit rates while the file system is active or reducing the
323 value if there is a low retransmit rate but long response delay observed.
326 option should be specified when using this option to manually
330 Set the write data size to the specified value.
331 Ditto the comments w.r.t.\& the
333 option, but using the
334 .Dq "fragments dropped due to timeout"
335 value on the server instead of the client.
340 options should only be used as a last ditch effort at improving performance
341 when mounting servers that do not support TCP mounts.
343 Set the retransmit timeout count for soft mounts to the specified value.
356 Due to the way that Sun RPC is implemented on top of UDP (unreliable datagram)
357 transport, tuning such mounts is really a black art that can only be expected
358 to have limited success.
359 For clients mounting servers that are not on the same
360 LAN cable or that tend to be overloaded,
361 TCP transport is strongly recommended,
362 but unfortunately this is restricted to mostly