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Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.\" @(#)mount_nfs.8 8.3 (Berkeley) 3/29/95 29.\" $FreeBSD$ 30.\" 31.Dd May 3, 2011 32.Dt MOUNT_NFS 8 33.Os 34.Sh NAME 35.Nm mount_nfs 36.Nd mount NFS file systems 37.Sh SYNOPSIS 38.Nm 39.Op Fl 23bcdiLlNPsTU 40.Op Fl a Ar maxreadahead 41.Op Fl D Ar deadthresh 42.Op Fl g Ar maxgroups 43.Op Fl I Ar readdirsize 44.Op Fl o Ar options 45.Op Fl R Ar retrycnt 46.Op Fl r Ar readsize 47.Op Fl t Ar timeout 48.Op Fl w Ar writesize 49.Op Fl x Ar retrans 50.Ar rhost : Ns Ar path node 51.Sh DESCRIPTION 52The 53.Nm 54utility calls the 55.Xr nmount 2 56system call to prepare and graft a remote NFS file system 57.Pq Ar rhost : Ns Ar path 58on to the file system tree at the point 59.Ar node . 60This command is normally executed by 61.Xr mount 8 . 62It implements the mount protocol as described in RFC 1094, Appendix A and 63.%T "NFS: Network File System Version 3 Protocol Specification" , 64Appendix I. 65.Pp 66If the file system type is specified as ``oldnfs'', which implies this 67command is run as ``mount_oldnfs'', then it forces use of the old NFS 68client, which does not support the 69.Cm nfsv4 70option. 71.Pp 72By default, 73.Nm 74keeps retrying until the mount succeeds. 75This behaviour is intended for file systems listed in 76.Xr fstab 5 77that are critical to the boot process. 78For non-critical file systems, the 79.Cm bg 80and 81.Cm retrycnt 82options provide mechanisms to prevent the boot process from hanging 83if the server is unavailable. 84.Pp 85If the server becomes unresponsive while an NFS file system is 86mounted, any new or outstanding file operations on that file system 87will hang uninterruptibly until the server comes back. 88To modify this default behaviour, see the 89.Cm intr 90and 91.Cm soft 92options. 93.Pp 94The options are: 95.Bl -tag -width indent 96.It Fl o 97Options are specified with a 98.Fl o 99flag followed by a comma separated string of options. 100See the 101.Xr mount 8 102man page for possible options and their meanings. 103The 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 109When attributes of files are cached, a timeout calculated to determine 110whether a given cache entry has expired. 111These four values determine the upper and lower bounds of the timeouts for 112.Dq directory 113attributes and 114.Dq regular 115(ie: everything else). 116The default values are 3 -> 60 seconds 117for regular files, and 30 -> 60 seconds for directories. 118The algorithm to calculate the timeout is based on the age of the file. 119The older the file, 120the longer the cache is considered valid, subject to the limits above. 121.It Cm bg 122If an initial attempt to contact the server fails, fork off a child to keep 123trying the mount in the background. 124Useful for 125.Xr fstab 5 , 126where the file system mount is not critical to multiuser operation. 127.It Cm deadthresh Ns = Ns Aq Ar value 128Set the 129.Dq "dead server threshold" 130to the specified number of round trip timeout intervals before a 131.Dq "server not responding" 132message is displayed. 133.It Cm dumbtimer 134Turn off the dynamic retransmit timeout estimator. 135This may be useful for UDP mounts that exhibit high retry rates, 136since it is possible that the dynamically estimated timeout interval is too 137short. 138.It Cm fg 139Same as not specifying 140.Cm bg . 141.It Cm hard 142Same as not specifying 143.Cm soft . 144.It Cm intr 145Make the mount interruptible, which implies that file system calls that 146are delayed due to an unresponsive server will fail with EINTR when a 147termination signal is posted for the process. 148.It Cm maxgroups Ns = Ns Aq Ar value 149Set the maximum size of the group list for the credentials to the 150specified value. 151This should be used for mounts on old servers that cannot handle a 152group list size of 16, as specified in RFC 1057. 153Try 8, if users in a lot of groups cannot get response from the mount 154point. 155.It Cm mntudp 156Force the mount protocol to use UDP transport, even for TCP NFS mounts. 157(Necessary for some old 158.Bx 159servers.) 160.It Cm negnametimeo Ns = Ns Aq Ar value 161Override the default of NFS_DEFAULT_NEGNAMETIMEO for the timeout (in seconds) 162for negative name cache entries. If this is set to 0 it disables negative 163name caching for the mount point. 164.It Cm nfsv2 165Use the NFS Version 2 protocol (the default is to try version 3 first 166then version 2). 167Note that NFS version 2 has a file size limit of 2 gigabytes. 168.It Cm nfsv3 169Use the NFS Version 3 protocol. 170.It Cm nfsv4 171Use the NFS Version 4 protocol. 172This option will force the mount to use 173TCP transport. 174.It Cm noconn 175For UDP mount points, do not do a 176.Xr connect 2 . 177This must be used if the server does not reply to requests from the standard 178NFS port number 2049 or replies to requests using a different IP address 179(which can occur if the server is multi-homed). 180Setting the 181.Va vfs.nfs.nfs_ip_paranoia 182sysctl to 0 will make this option the default. 183.It Cm nocto 184Normally, NFS clients maintain the close-to-open cache coherency. 185This works by flushing at close time and checking at open time. 186Checking at open time is implemented by getting attributes from 187the server and purging the data cache if they do not match 188attributes cached by the client. 189.Pp 190This option disables checking at open time. 191It may improve performance for read-only mounts, 192but should only be used if the data on the server changes rarely. 193Be sure to understand the consequences before enabling this option. 194.It Cm noinet4 , noinet6 195Disables 196.Dv AF_INET 197or 198.Dv AF_INET6 199connections. 200Useful for hosts that have 201both an A record and an AAAA record for the same name. 202.It Cm nolockd 203Do 204.Em not 205forward 206.Xr fcntl 2 207locks over the wire. 208All locks will be local and not seen by the server 209and likewise not seen by other NFS clients. 210This removes the need to run the 211.Xr rpcbind 8 212service and the 213.Xr rpc.statd 8 214and 215.Xr rpc.lockd 8 216servers on the client. 217Note that this option will only be honored when performing the 218initial mount, it will be silently ignored if used while updating 219the mount options. 220.It Cm principal 221For the RPCSEC_GSS security flavors, such as krb5, krb5i and krb5p, 222this option sets the name of the host based principal name expected 223by the server. This option overrides the default, which will be 224``nfs@<server-fqdn>'' and should normally be sufficient. 225.It Cm noresvport 226Do 227.Em not 228use a reserved socket port number (see below). 229.It Cm port Ns = Ns Aq Ar port_number 230Use specified port number for NFS requests. 231The default is to query the portmapper for the NFS port. 232.It Cm rdirplus 233Used with NFSV3 to specify that the \fBReaddirPlus\fR RPC should 234be used. 235For NFSV4, setting this option has a similar effect, in that it will make 236the Readdir Operation get more attributes. 237This option reduces RPC traffic for cases such as 238.Dq "ls -l" , 239but tends to flood the attribute and name caches with prefetched entries. 240Try this option and see whether performance improves or degrades. 241Probably 242most useful for client to server network interconnects with a large bandwidth 243times delay product. 244.It Cm readahead Ns = Ns Aq Ar value 245Set the read-ahead count to the specified value. 246This may be in the range of 0 - 4, and determines how many blocks 247will be read ahead when a large file is being read sequentially. 248Trying a value greater than 1 for this is suggested for 249mounts with a large bandwidth * delay product. 250.It Cm readdirsize Ns = Ns Aq Ar value 251Set the readdir read size to the specified value. 252The value should normally 253be a multiple of 254.Dv DIRBLKSIZ 255that is <= the read size for the mount. 256.It Cm resvport 257Use a reserved socket port number. 258This flag is obsolete, and only retained for compatibility reasons. 259Reserved port numbers are used by default now. 260(For the rare case where the client has a trusted root account 261but untrustworthy users and the network cables are in secure areas this does 262help, but for normal desktop clients this does not apply.) 263.It Cm retrans Ns = Ns Aq Ar value 264Set the retransmit timeout count for soft mounts to the specified value. 265.It Cm retrycnt Ns = Ns Aq Ar count 266Set the mount retry count to the specified value. 267The default is a retry count of zero, which means to keep retrying 268forever. 269There is a 60 second delay between each attempt. 270.It Cm rsize Ns = Ns Aq Ar value 271Set the read data size to the specified value. 272It should normally be a power of 2 greater than or equal to 1024. 273This should be used for UDP mounts when the 274.Dq "fragments dropped due to timeout" 275value is getting large while actively using a mount point. 276(Use 277.Xr netstat 1 278with the 279.Fl s 280option to see what the 281.Dq "fragments dropped due to timeout" 282value is.) 283.It Cm sec Ns = Ns Aq Ar flavor 284This option specifies what security flavor should be used for the mount. 285Currently, they are: 286.Bd -literal 287krb5 - Use KerberosV authentication 288krb5i - Use KerberosV authentication and 289 apply integrity checksums to RPCs 290krb5p - Use KerberosV authentication and 291 encrypt the RPC data 292sys - The default AUTH_SYS, which uses a 293 uid + gid list authenticator 294.Ed 295.It Cm soft 296A soft mount, which implies that file system calls will fail 297after 298.Ar retrycnt 299round trip timeout intervals. 300.It Cm tcp 301Use TCP transport. 302This is the default option, as it provides for increased reliability on both 303LAN and WAN configurations compared to UDP. 304Some old NFS servers do not support this method; UDP mounts may be required 305for interoperability. 306.It Cm timeout Ns = Ns Aq Ar value 307Set the initial retransmit timeout to the specified value. 308May be useful for fine tuning UDP mounts over internetworks 309with high packet loss rates or an overloaded server. 310Try increasing the interval if 311.Xr nfsstat 1 312shows high retransmit rates while the file system is active or reducing the 313value if there is a low retransmit rate but long response delay observed. 314(Normally, the 315.Cm dumbtimer 316option should be specified when using this option to manually 317tune the timeout 318interval.) 319.It Cm udp 320Use UDP transport. 321.It Cm wsize Ns = Ns Aq Ar value 322Set the write data size to the specified value. 323Ditto the comments w.r.t.\& the 324.Cm rsize 325option, but using the 326.Dq "fragments dropped due to timeout" 327value on the server instead of the client. 328Note that both the 329.Cm rsize 330and 331.Cm wsize 332options should only be used as a last ditch effort at improving performance 333when mounting servers that do not support TCP mounts. 334.El 335.El 336.Sh COMPATIBILITY 337The following command line flags are equivalent to 338.Fl o 339named options and are supported for compatibility with older 340installations. 341.Bl -tag -width indent 342.It Fl 2 343Same as 344.Fl o Cm nfsv2 345.It Fl 3 346Same as 347.Fl o Cm nfsv3 348.It Fl D 349Same as 350.Fl o Cm deadthresh 351.It Fl I 352Same as 353.Fl o Cm readdirsize Ns = Ns Aq Ar value 354.It Fl L 355Same as 356.Fl o Cm nolockd 357.It Fl N 358Same as 359.Fl o Cm noresvport 360.It Fl P 361Use a reserved socket port number. 362This flag is obsolete, and only retained for compatibility reasons. 363(For the rare case where the client has a trusted root account 364but untrustworthy users and the network cables are in secure areas this does 365help, but for normal desktop clients this does not apply.) 366.It Fl R 367Same as 368.Fl o Cm retrycnt Ns = Ns Aq Ar value 369.It Fl T 370Same as 371.Fl o Cm tcp 372.It Fl U 373Same as 374.Fl o Cm mntudp 375.It Fl a 376Same as 377.Fl o Cm readahead Ns = Ns Aq Ar value 378.It Fl b 379Same as 380.Fl o Cm bg 381.It Fl c 382Same as 383.Fl o Cm noconn 384.It Fl d 385Same as 386.Fl o Cm dumbtimer 387.It Fl g 388Same as 389.Fl o Cm maxgroups 390.It Fl i 391Same as 392.Fl o Cm intr 393.It Fl l 394Same as 395.Fl o Cm rdirplus 396.It Fl r 397Same as 398.Fl o Cm rsize Ns = Ns Aq Ar value 399.It Fl s 400Same as 401.Fl o Cm soft 402.It Fl t 403Same as 404.Fl o Cm retransmit Ns = Ns Aq Ar value 405.It Fl w 406Same as 407.Fl o Cm wsize Ns = Ns Aq Ar value 408.It Fl x 409Same as 410.Fl o Cm retrans Ns = Ns Aq Ar value 411.El 412.Sh SEE ALSO 413.Xr nmount 2 , 414.Xr unmount 2 , 415.Xr nfsv4 4 , 416.Xr fstab 5 , 417.Xr gssd 8 , 418.Xr mount 8 , 419.Xr nfsd 8 , 420.Xr nfsiod 8 , 421.Xr showmount 8 422.Sh BUGS 423Since nfsv4 performs open/lock operations that have their ordering strictly 424enforced by the server, the options 425.Cm intr 426and 427.Cm soft 428cannot be safely used. 429.Cm hard 430nfsv4 mounts are strongly recommended. 431