1.\" Copyright (c) 1992, 1993, 1994, 1995 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 4. 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 11, 2003 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 23NPTUbcdiLls 40.Op Fl D Ar deadthresh 41.Op Fl I Ar readdirsize 42.Op Fl R Ar retrycnt 43.Op Fl a Ar maxreadahead 44.Op Fl g Ar maxgroups 45.Op Fl o Ar options 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. 146(NB: This is NOT supported by most 147.No non- Ns Bx 148servers.) 149.It Fl U 150Force the mount protocol to use UDP transport, even for TCP NFS mounts. 151(Necessary for some old 152.Bx 153servers.) 154.It Fl a 155Set the read-ahead count to the specified value. 156This may be in the range of 0 - 4, and determines how many blocks 157will be read ahead when a large file is being read sequentially. 158Trying a value greater than 1 for this is suggested for 159mounts with a large bandwidth * delay product. 160.It Fl b 161If an initial attempt to contact the server fails, fork off a child to keep 162trying the mount in the background. 163Useful for 164.Xr fstab 5 , 165where the file system mount is not critical to multiuser operation. 166.It Fl c 167For UDP mount points, do not do a 168.Xr connect 2 . 169This must be used if the server does not reply to requests from the standard 170NFS port number 2049 or replies to requests using a different IP address 171(which can occur if the server is multi-homed). 172Setting the 173.Va vfs.nfs.nfs_ip_paranoia 174sysctl to 0 will make this option the default. 175.It Fl d 176Turn off the dynamic retransmit timeout estimator. 177This may be useful for UDP mounts that exhibit high retry rates, 178since it is possible that the dynamically estimated timeout interval is too 179short. 180.It Fl g 181Set the maximum size of the group list for the credentials to the 182specified value. 183This should be used for mounts on old servers that cannot handle a 184group list size of 16, as specified in RFC 1057. 185Try 8, if users in a lot of groups cannot get response from the mount 186point. 187.It Fl i 188Make the mount interruptible, which implies that file system calls that 189are delayed due to an unresponsive server will fail with EINTR when a 190termination signal is posted for the process. 191.It Fl l 192Used with NQNFS and NFSV3 to specify that the \fBReaddirPlus\fR RPC should 193be used. 194This option reduces RPC traffic for cases such as 195.Dq "ls -l" , 196but tends to flood the attribute and name caches with prefetched entries. 197Try this option and see whether performance improves or degrades. 198Probably 199most useful for client to server network interconnects with a large bandwidth 200times delay product. 201.It Fl o 202Options are specified with a 203.Fl o 204flag followed by a comma separated string of options. 205See the 206.Xr mount 8 207man page for possible options and their meanings. 208The following NFS specific options are also available: 209.Bl -tag -width indent 210.It Cm port Ns = Ns Aq Ar port_number 211Use specified port number for NFS requests. 212The default is to query the portmapper for the NFS port. 213.It Cm acregmin Ns = Ns Aq Ar seconds 214.It Cm acregmax Ns = Ns Aq Ar seconds 215.It Cm acdirmin Ns = Ns Aq Ar seconds 216.It Cm acdirmax Ns = Ns Aq Ar seconds 217When attributes of files are cached, a timeout calculated to determine 218whether a given cache entry has expired. 219These four values determine the upper and lower bounds of the timeouts for 220.Dq directory 221attributes and 222.Dq regular 223(ie: everything else). 224The default values are 3 -> 60 seconds 225for regular files, and 30 -> 60 seconds for directories. 226The algorithm to calculate the timeout is based on the age of the file. 227The older the file, 228the longer the cache is considered valid, subject to the limits above. 229.It Cm noinet4 , noinet6 230Disables 231.Dv AF_INET 232or 233.Dv AF_INET6 234connections. 235Useful for hosts that have 236both an A record and an AAAA record for the same name. 237.El 238.Pp 239.Sy Historic Fl o Sy Options 240.Pp 241Use of these options is deprecated, they are only mentioned here for 242compatibility with historic versions of 243.Nm . 244.Bl -tag -width ".Cm dumbtimer" 245.It Cm bg 246Same as 247.Fl b . 248.It Cm conn 249Same as not specifying 250.Fl c . 251.It Cm dumbtimer 252Same as 253.Fl d . 254.It Cm intr 255Same as 256.Fl i . 257.It Cm lockd 258Same as not specifying 259.Fl L . 260.It Cm nfsv2 261Same as 262.Fl 2 . 263.It Cm nfsv3 264Same as 265.Fl 3 . 266.It Cm rdirplus 267Same as 268.Fl l . 269.It Cm mntudp 270Same as 271.Fl U . 272.It Cm resvport 273Same as 274.Fl P . 275.It Cm soft 276Same as 277.Fl s . 278.It Cm tcp 279Same as 280.Fl T . 281.El 282.It Fl r 283Set the read data size to the specified value. 284It should normally be a power of 2 greater than or equal to 1024. 285This should be used for UDP mounts when the 286.Dq "fragments dropped due to timeout" 287value is getting large while actively using a mount point. 288(Use 289.Xr netstat 1 290with the 291.Fl s 292option to see what the 293.Dq "fragments dropped due to timeout" 294value is.) 295See the 296.Fl w 297option as well. 298.It Fl s 299A soft mount, which implies that file system calls will fail 300after 301.Ar retrycnt 302round trip timeout intervals. 303.It Fl t 304Set the initial retransmit timeout to the specified value. 305May be useful for fine tuning UDP mounts over internetworks 306with high packet loss rates or an overloaded server. 307Try increasing the interval if 308.Xr nfsstat 1 309shows high retransmit rates while the file system is active or reducing the 310value if there is a low retransmit rate but long response delay observed. 311(Normally, the 312.Fl d 313option should be specified when using this option to manually 314tune the timeout 315interval.) 316.It Fl w 317Set the write data size to the specified value. 318Ditto the comments w.r.t.\& the 319.Fl r 320option, but using the 321.Dq "fragments dropped due to timeout" 322value on the server instead of the client. 323Note that both the 324.Fl r 325and 326.Fl w 327options should only be used as a last ditch effort at improving performance 328when mounting servers that do not support TCP mounts. 329.It Fl x 330Set the retransmit timeout count for soft mounts to the specified value. 331.El 332.Sh SEE ALSO 333.Xr mount 2 , 334.Xr unmount 2 , 335.Xr fstab 5 , 336.Xr mount 8 , 337.Xr nfsd 8 , 338.Xr nfsiod 8 , 339.Xr showmount 8 340.Sh BUGS 341Due to the way that Sun RPC is implemented on top of UDP (unreliable datagram) 342transport, tuning such mounts is really a black art that can only be expected 343to have limited success. 344For clients mounting servers that are not on the same 345LAN cable or that tend to be overloaded, 346TCP transport is strongly recommended, 347but unfortunately this is restricted to mostly 348.Bx 4.4 349servers. 350