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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 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 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 4 97Use the NFS Version 4 protocol. 98.It Fl D 99Set the 100.Dq "dead server threshold" 101to the specified number of round trip timeout intervals before a 102.Dq "server not responding" 103message is displayed. 104.It Fl I 105Set the readdir read size to the specified value. 106The value should normally 107be a multiple of 108.Dv DIRBLKSIZ 109that is <= the read size for the mount. 110.It Fl L 111Do 112.Em not 113forward 114.Xr fcntl 2 115locks over the wire. 116All locks will be local and not seen by the server 117and likewise not seen by other NFS clients. 118This removes the need to run the 119.Xr rpcbind 8 120service and the 121.Xr rpc.statd 8 122and 123.Xr rpc.lockd 8 124servers on the client. 125Note that this option will only be honored when performing the 126initial mount, it will be silently ignored if used while updating 127the mount options. 128.It Fl N 129Do 130.Em not 131use a reserved socket port number (see below). 132.It Fl P 133Use a reserved socket port number. 134This flag is obsolete, and only retained for compatibility reasons. 135Reserved port numbers are used by default now. 136(For the rare case where the client has a trusted root account 137but untrustworthy users and the network cables are in secure areas this does 138help, but for normal desktop clients this does not apply.) 139.It Fl R 140Set the mount retry count to the specified value. 141The default is a retry count of zero, which means to keep retrying 142forever. 143There is a 60 second delay between each attempt. 144.It Fl T 145Use TCP transport instead of UDP. 146This is recommended for servers that are not on the same LAN cable as 147the client. 148Not all NFS servers support this method, especially older ones; 149caution should be observed in these cases. 150.It Fl U 151Force the mount protocol to use UDP transport, even for TCP NFS mounts. 152(Necessary for some old 153.Bx 154servers.) 155.It Fl a 156Set the read-ahead count to the specified value. 157This may be in the range of 0 - 4, and determines how many blocks 158will be read ahead when a large file is being read sequentially. 159Trying a value greater than 1 for this is suggested for 160mounts with a large bandwidth * delay product. 161.It Fl b 162If an initial attempt to contact the server fails, fork off a child to keep 163trying the mount in the background. 164Useful for 165.Xr fstab 5 , 166where the file system mount is not critical to multiuser operation. 167.It Fl c 168For UDP mount points, do not do a 169.Xr connect 2 . 170This must be used if the server does not reply to requests from the standard 171NFS port number 2049 or replies to requests using a different IP address 172(which can occur if the server is multi-homed). 173Setting the 174.Va vfs.nfs.nfs_ip_paranoia 175sysctl to 0 will make this option the default. 176.It Fl d 177Turn off the dynamic retransmit timeout estimator. 178This may be useful for UDP mounts that exhibit high retry rates, 179since it is possible that the dynamically estimated timeout interval is too 180short. 181.It Fl g 182Set the maximum size of the group list for the credentials to the 183specified value. 184This should be used for mounts on old servers that cannot handle a 185group list size of 16, as specified in RFC 1057. 186Try 8, if users in a lot of groups cannot get response from the mount 187point. 188.It Fl i 189Make the mount interruptible, which implies that file system calls that 190are delayed due to an unresponsive server will fail with EINTR when a 191termination signal is posted for the process. 192.It Fl l 193Used with NQNFS and NFSV3 to specify that the \fBReaddirPlus\fR RPC should 194be used. 195This option reduces RPC traffic for cases such as 196.Dq "ls -l" , 197but tends to flood the attribute and name caches with prefetched entries. 198Try this option and see whether performance improves or degrades. 199Probably 200most useful for client to server network interconnects with a large bandwidth 201times delay product. 202.It Fl o 203Options are specified with a 204.Fl o 205flag followed by a comma separated string of options. 206See the 207.Xr mount 8 208man page for possible options and their meanings. 209The following NFS specific options are also available: 210.Bl -tag -width indent 211.It Cm port Ns = Ns Aq Ar port_number 212Use specified port number for NFS requests. 213The default is to query the portmapper for the NFS port. 214.It Cm acregmin Ns = Ns Aq Ar seconds 215.It Cm acregmax Ns = Ns Aq Ar seconds 216.It Cm acdirmin Ns = Ns Aq Ar seconds 217.It Cm acdirmax Ns = Ns Aq Ar seconds 218When attributes of files are cached, a timeout calculated to determine 219whether a given cache entry has expired. 220These four values determine the upper and lower bounds of the timeouts for 221.Dq directory 222attributes and 223.Dq regular 224(ie: everything else). 225The default values are 3 -> 60 seconds 226for regular files, and 30 -> 60 seconds for directories. 227The algorithm to calculate the timeout is based on the age of the file. 228The older the file, 229the longer the cache is considered valid, subject to the limits above. 230.It Cm noinet4 , noinet6 231Disables 232.Dv AF_INET 233or 234.Dv AF_INET6 235connections. 236Useful for hosts that have 237both an A record and an AAAA record for the same name. 238.El 239.Pp 240.Sy Historic Fl o Sy Options 241.Pp 242Use of these options is deprecated, they are only mentioned here for 243compatibility with historic versions of 244.Nm . 245.Bl -tag -width ".Cm dumbtimer" 246.It Cm bg 247Same as 248.Fl b . 249.It Cm conn 250Same as not specifying 251.Fl c . 252.It Cm dumbtimer 253Same as 254.Fl d . 255.It Cm intr 256Same as 257.Fl i . 258.It Cm lockd 259Same as not specifying 260.Fl L . 261.It Cm nfsv2 262Same as 263.Fl 2 . 264.It Cm nfsv3 265Same as 266.Fl 3 . 267.It Cm rdirplus 268Same as 269.Fl l . 270.It Cm mntudp 271Same as 272.Fl U . 273.It Cm resvport 274Same as 275.Fl P . 276.It Cm soft 277Same as 278.Fl s . 279.It Cm tcp 280Same as 281.Fl T . 282.El 283.It Fl r 284Set the read data size to the specified value. 285It should normally be a power of 2 greater than or equal to 1024. 286This should be used for UDP mounts when the 287.Dq "fragments dropped due to timeout" 288value is getting large while actively using a mount point. 289(Use 290.Xr netstat 1 291with the 292.Fl s 293option to see what the 294.Dq "fragments dropped due to timeout" 295value is.) 296See the 297.Fl w 298option as well. 299.It Fl s 300A soft mount, which implies that file system calls will fail 301after 302.Ar retrycnt 303round trip timeout intervals. 304.It Fl t 305Set the initial retransmit timeout to the specified value. 306May be useful for fine tuning UDP mounts over internetworks 307with high packet loss rates or an overloaded server. 308Try increasing the interval if 309.Xr nfsstat 1 310shows high retransmit rates while the file system is active or reducing the 311value if there is a low retransmit rate but long response delay observed. 312(Normally, the 313.Fl d 314option should be specified when using this option to manually 315tune the timeout 316interval.) 317.It Fl w 318Set the write data size to the specified value. 319Ditto the comments w.r.t.\& the 320.Fl r 321option, but using the 322.Dq "fragments dropped due to timeout" 323value on the server instead of the client. 324Note that both the 325.Fl r 326and 327.Fl w 328options should only be used as a last ditch effort at improving performance 329when mounting servers that do not support TCP mounts. 330.It Fl x 331Set the retransmit timeout count for soft mounts to the specified value. 332.El 333.Sh SEE ALSO 334.Xr nmount 2 , 335.Xr unmount 2 , 336.Xr fstab 5 , 337.Xr mount 8 , 338.Xr nfsd 8 , 339.Xr nfsiod 8 , 340.Xr showmount 8 341