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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 December 25, 2005 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 mount 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 66By default, 67.Nm 68keeps retrying until the mount succeeds. 69This behaviour is intended for file systems listed in 70.Xr fstab 5 71that are critical to the boot process. 72For non-critical file systems, the 73.Fl b 74and 75.Fl R 76flags provide mechanisms to prevent the boot process from hanging 77if the server is unavailable. 78.Pp 79If the server becomes unresponsive while an NFS file system is 80mounted, any new or outstanding file operations on that file system 81will hang uninterruptibly until the server comes back. 82To modify this default behaviour, see the 83.Fl i 84and 85.Fl s 86flags. 87.Pp 88The options are: 89.Bl -tag -width indent 90.It Fl 2 91Use the NFS Version 2 protocol (the default is to try version 3 first 92then version 2). 93Note that NFS version 2 has a file size limit of 2 gigabytes. 94.It Fl 3 95Use the NFS Version 3 protocol. 96.It Fl D 97Set the 98.Dq "dead server threshold" 99to the specified number of round trip timeout intervals before a 100.Dq "server not responding" 101message is displayed. 102.It Fl I 103Set the readdir read size to the specified value. 104The value should normally 105be a multiple of 106.Dv DIRBLKSIZ 107that is <= the read size for the mount. 108.It Fl L 109Do 110.Em not 111forward 112.Xr fcntl 2 113locks over the wire. 114All locks will be local and not seen by the server 115and likewise not seen by other NFS clients. 116This removes the need to run the 117.Xr rpcbind 8 118service and the 119.Xr rpc.statd 8 120and 121.Xr rpc.lockd 8 122servers on the client. 123Note that this option will only be honored when performing the 124initial mount, it will be silently ignored if used while updating 125the mount options. 126.It Fl N 127Do 128.Em not 129use a reserved socket port number (see below). 130.It Fl P 131Use a reserved socket port number. 132This flag is obsolete, and only retained for compatibility reasons. 133Reserved port numbers are used by default now. 134(For the rare case where the client has a trusted root account 135but untrustworthy users and the network cables are in secure areas this does 136help, but for normal desktop clients this does not apply.) 137.It Fl R 138Set the mount retry count to the specified value. 139The default is a retry count of zero, which means to keep retrying 140forever. 141There is a 60 second delay between each attempt. 142.It Fl T 143Use TCP transport instead of UDP. 144This is recommended for servers that are not on the same LAN cable as 145the client. 146Not all NFS servers support this method, especially older ones; 147caution should be observed in these cases. 148.It Fl U 149Force the mount protocol to use UDP transport, even for TCP NFS mounts. 150(Necessary for some old 151.Bx 152servers.) 153.It Fl a 154Set the read-ahead count to the specified value. 155This may be in the range of 0 - 4, and determines how many blocks 156will be read ahead when a large file is being read sequentially. 157Trying a value greater than 1 for this is suggested for 158mounts with a large bandwidth * delay product. 159.It Fl b 160If an initial attempt to contact the server fails, fork off a child to keep 161trying the mount in the background. 162Useful for 163.Xr fstab 5 , 164where the file system mount is not critical to multiuser operation. 165.It Fl c 166For UDP mount points, do not do a 167.Xr connect 2 . 168This must be used if the server does not reply to requests from the standard 169NFS port number 2049 or replies to requests using a different IP address 170(which can occur if the server is multi-homed). 171Setting the 172.Va vfs.nfs.nfs_ip_paranoia 173sysctl to 0 will make this option the default. 174.It Fl d 175Turn off the dynamic retransmit timeout estimator. 176This may be useful for UDP mounts that exhibit high retry rates, 177since it is possible that the dynamically estimated timeout interval is too 178short. 179.It Fl g 180Set the maximum size of the group list for the credentials to the 181specified value. 182This should be used for mounts on old servers that cannot handle a 183group list size of 16, as specified in RFC 1057. 184Try 8, if users in a lot of groups cannot get response from the mount 185point. 186.It Fl i 187Make the mount interruptible, which implies that file system calls that 188are delayed due to an unresponsive server will fail with EINTR when a 189termination signal is posted for the process. 190.It Fl l 191Used with NQNFS and NFSV3 to specify that the \fBReaddirPlus\fR RPC should 192be used. 193This option reduces RPC traffic for cases such as 194.Dq "ls -l" , 195but tends to flood the attribute and name caches with prefetched entries. 196Try this option and see whether performance improves or degrades. 197Probably 198most useful for client to server network interconnects with a large bandwidth 199times delay product. 200.It Fl o 201Options are specified with a 202.Fl o 203flag followed by a comma separated string of options. 204See the 205.Xr mount 8 206man page for possible options and their meanings. 207The following NFS specific options are also available: 208.Bl -tag -width indent 209.It Cm port Ns = Ns Aq Ar port_number 210Use specified port number for NFS requests. 211The default is to query the portmapper for the NFS port. 212.It Cm acregmin Ns = Ns Aq Ar seconds 213.It Cm acregmax Ns = Ns Aq Ar seconds 214.It Cm acdirmin Ns = Ns Aq Ar seconds 215.It Cm acdirmax Ns = Ns Aq Ar seconds 216When attributes of files are cached, a timeout calculated to determine 217whether a given cache entry has expired. 218These four values determine the upper and lower bounds of the timeouts for 219.Dq directory 220attributes and 221.Dq regular 222(ie: everything else). 223The default values are 3 -> 60 seconds 224for regular files, and 30 -> 60 seconds for directories. 225The algorithm to calculate the timeout is based on the age of the file. 226The older the file, 227the longer the cache is considered valid, subject to the limits above. 228.It Cm noinet4 , noinet6 229Disables 230.Dv AF_INET 231or 232.Dv AF_INET6 233connections. 234Useful for hosts that have 235both an A record and an AAAA record for the same name. 236.El 237.Pp 238.Sy Historic Fl o Sy Options 239.Pp 240Use of these options is deprecated, they are only mentioned here for 241compatibility with historic versions of 242.Nm . 243.Bl -tag -width ".Cm dumbtimer" 244.It Cm bg 245Same as 246.Fl b . 247.It Cm conn 248Same as not specifying 249.Fl c . 250.It Cm dumbtimer 251Same as 252.Fl d . 253.It Cm intr 254Same as 255.Fl i . 256.It Cm lockd 257Same as not specifying 258.Fl L . 259.It Cm nfsv2 260Same as 261.Fl 2 . 262.It Cm nfsv3 263Same as 264.Fl 3 . 265.It Cm rdirplus 266Same as 267.Fl l . 268.It Cm mntudp 269Same as 270.Fl U . 271.It Cm resvport 272Same as 273.Fl P . 274.It Cm soft 275Same as 276.Fl s . 277.It Cm tcp 278Same as 279.Fl T . 280.El 281.It Fl r 282Set the read data size to the specified value. 283It should normally be a power of 2 greater than or equal to 1024. 284This should be used for UDP mounts when the 285.Dq "fragments dropped due to timeout" 286value is getting large while actively using a mount point. 287(Use 288.Xr netstat 1 289with the 290.Fl s 291option to see what the 292.Dq "fragments dropped due to timeout" 293value is.) 294See the 295.Fl w 296option as well. 297.It Fl s 298A soft mount, which implies that file system calls will fail 299after 300.Ar retrycnt 301round trip timeout intervals. 302.It Fl t 303Set the initial retransmit timeout to the specified value. 304May be useful for fine tuning UDP mounts over internetworks 305with high packet loss rates or an overloaded server. 306Try increasing the interval if 307.Xr nfsstat 1 308shows high retransmit rates while the file system is active or reducing the 309value if there is a low retransmit rate but long response delay observed. 310(Normally, the 311.Fl d 312option should be specified when using this option to manually 313tune the timeout 314interval.) 315.It Fl w 316Set the write data size to the specified value. 317Ditto the comments w.r.t.\& the 318.Fl r 319option, but using the 320.Dq "fragments dropped due to timeout" 321value on the server instead of the client. 322Note that both the 323.Fl r 324and 325.Fl w 326options should only be used as a last ditch effort at improving performance 327when mounting servers that do not support TCP mounts. 328.It Fl x 329Set the retransmit timeout count for soft mounts to the specified value. 330.El 331.Sh SEE ALSO 332.Xr mount 2 , 333.Xr unmount 2 , 334.Xr fstab 5 , 335.Xr mount 8 , 336.Xr nfsd 8 , 337.Xr nfsiod 8 , 338.Xr showmount 8 339