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.\" 3. All advertising materials mentioning features or use of this software 13.\" must display the following acknowledgement: 14.\" This product includes software developed by the University of 15.\" California, Berkeley and its contributors. 16.\" 4. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" @(#)mount_nfs.8 8.3 (Berkeley) 3/29/95 33.\" 34.\" $Id: mount_nfs.8,v 1.13 1998/06/29 06:58:46 jkoshy Exp $ 35.\"" 36.Dd March 29, 1995 37.Dt MOUNT_NFS 8 38.Os BSD 4.4 39.Sh NAME 40.Nm mount_nfs 41.Nd mount nfs file systems 42.Sh SYNOPSIS 43.Nm mount_nfs 44.Op Fl 23KNPTUbcdilqs 45.Op Fl D Ar deadthresh 46.Op Fl I Ar readdirsize 47.Op Fl L Ar leaseterm 48.Op Fl R Ar retrycnt 49.Op Fl a Ar maxreadahead 50.Op Fl g Ar maxgroups 51.Op Fl m Ar realm 52.Op Fl o Ar options 53.Op Fl r Ar readsize 54.Op Fl t Ar timeout 55.Op Fl w Ar writesize 56.Op Fl x Ar retrans 57.Ar rhost:path node 58.Sh DESCRIPTION 59The 60.Nm 61command 62calls the 63.Xr mount 2 64system call to prepare and graft a remote nfs file system (rhost:path) 65on to the file system tree at the point 66.Ar node. 67This command is normally executed by 68.Xr mount 8 . 69It implements the mount protocol as described in RFC 1094, Appendix A and 70.%T "NFS: Network File System Version 3 Protocol Specification" , 71Appendix I. 72.Pp 73The options are: 74.Bl -tag -width indent 75.It Fl 2 76Use the NFS Version 2 protocol (the default is to try version 3 first 77then version 2). Note that NFS version 2 has a file size limit of 2 78gigabytes. 79.It Fl 3 80Use the NFS Version 3 protocol. 81.It Fl D 82Used with NQNFS to set the 83.Dq "dead server threshold" 84to the specified number of round trip timeout intervals. 85After a 86.Dq "dead server threshold" 87of retransmit timeouts, 88cached data for the unresponsive server is assumed to still be valid. 89Values may be set in the range of 1 - 9, with 9 referring to an 90.Dq "infinite dead threshold" 91(i.e. never assume cached data still valid). 92This option is not generally recommended and is really an experimental 93feature. 94.It Fl I 95Set the readdir read size to the specified value. The value should normally 96be a multiple of DIRBLKSIZ that is <= the read size for the mount. 97.It Fl K 98Pass Kerberos authenticators to the server for client-to-server 99user-credential mapping. 100This requires that the kernel be built with the NFSKERB option. 101(Refer to the INTERNET-DRAFT titled 102.%T "Authentication Mechanisms for ONC RPC" , 103for more information.) 104.It Fl L 105Used with NQNFS to set the lease term to the specified number of seconds. 106Only use this argument for mounts with a large round trip delay. 107Values are normally in the 10-30 second range. 108.It Fl N 109Do 110.Em not 111use a reserved socket port number (see below). 112.It Fl P 113Use a reserved socket port number. 114This flag is obsolete, and only retained for compatibility reasons. 115Reserved port numbers are used by default now. 116This is useful for mounting servers that require clients to use a 117reserved port number on the mistaken belief that this makes NFS 118more secure. (For the rare case where the client has a trusted root account 119but untrustworthy users and the network cables are in secure areas this does 120help, but for normal desktop clients this does not apply.) 121.It Fl R 122Set the retry count for doing the mount to the specified value. 123.It Fl T 124Use TCP transport instead of UDP. 125This is recommended for servers that are not on the same LAN cable as 126the client. 127(NB: This is NOT supported by most non-BSD servers.) 128.It Fl U 129Force the mount protocol to use UDP transport, even for TCP NFS mounts. 130(Necessary for some old BSD servers.) 131.It Fl a 132Set the read-ahead count to the specified value. 133This may be in the range of 0 - 4, and determines how many blocks 134will be read ahead when a large file is being read sequentially. 135Trying a value greater than 1 for this is suggested for 136mounts with a large bandwidth * delay product. 137.It Fl b 138If an initial attempt to contact the server fails, fork off a child to keep 139trying the mount in the background. 140Useful for 141.Xr fstab 5 , 142where the filesystem mount is not critical to multiuser operation. 143.It Fl c 144For UDP mount points, do not do a 145.Xr connect 2 . 146This must be used for servers that do not reply to requests from the 147standard NFS port number 2049. 148.It Fl d 149Turn off the dynamic retransmit timeout estimator. 150This may be useful for UDP mounts that exhibit high retry rates, 151since it is possible that the dynamically estimated timeout interval is too 152short. 153.It Fl g 154Set the maximum size of the group list for the credentials to the 155specified value. 156This should be used for mounts on old servers that cannot handle a 157group list size of 16, as specified in RFC 1057. 158Try 8, if users in a lot of groups cannot get response from the mount 159point. 160.It Fl i 161Make the mount interruptible, which implies that file system calls that 162are delayed due to an unresponsive server will fail with EINTR when a 163termination signal is posted for the process. 164.It Fl l 165Used with NQNFS and NFSV3 to specify that the \fBReaddirPlus\fR RPC should 166be used. 167This option reduces RPC traffic for cases such as 168.Dq "ls -l" , 169but tends to flood the attribute and name caches with prefetched entries. 170Try this option and see whether performance improves or degrades. Probably 171most useful for client to server network interconnects with a large bandwidth 172times delay product. 173.It Fl m 174Set the Kerberos realm to the string argument. 175Used with the 176.Fl K 177option for mounts to other realms. 178.It Fl o 179Options are specified with a 180.Fl o 181flag followed by a comma separated string of options. 182See the 183.Xr mount 8 184man page for possible options and their meanings. 185The following NFS specific option is also available: 186.Bl -tag -width indent 187.It port=<port_number> 188Use specified port number for NFS requests. 189The default is to query the portmapper for the NFS port. 190.It acregmin=<seconds> 191.It acregmax=<seconds> 192.It acdirmin=<seconds> 193.It acdirmax=<seconds> 194When attributes of files are cached, a timeout calculated to determine 195whether a given cache entry has expired. These four values determine the 196upper and lower bounds of the timeouts for ``directory'' attributes and 197``regular'' (ie: everything else). The default values are 3 -> 60 seconds 198for regular files, and 30 -> 60 seconds for directories. The algorithm to 199calculate the timeout is based on the age of the file. The older the file, 200the longer the cache is considered valid, subject to the limits above. 201.El 202.Pp 203.Bl -tag -width "dumbtimerXX" 204\fBHistoric \&-o options\fR 205.Pp 206Use of these options is deprecated, they are only mentioned here for 207compatibility with historic versions of 208.Nm Ns . 209.It bg 210Same as 211.Fl b . 212.It conn 213Same as not specifying 214.Fl c . 215.It dumbtimer 216Same as 217.Fl d . 218.It intr 219Same as 220.Fl i . 221.It kerb 222Same as 223.Fl K . 224.It nfsv2 225Same as 226.Fl 2 . 227.It nfsv3 228Same as 229.Fl 3 . 230.It rdirplus 231Same as 232.Fl l . 233.It mntudp 234Same as 235.Fl U . 236.It resvport 237Same as 238.Fl P . 239.It seqpacket 240Same as 241.Fl p . 242.It nqnfs 243Same as 244.Fl q . 245.It soft 246Same as 247.Fl s . 248.It tcp 249Same as 250.Fl T. 251.El 252.It Fl q 253Use the leasing extensions to the NFS Version 3 protocol 254to maintain cache consistency. 255This protocol Version 2, referred to as Not Quite Nfs (NQNFS), 256is only supported by this updated release of NFS code. 257(It is not backwards compatible with the release of NQNFS that went out on 2584.4BSD-Lite. To interoperate with a 4.4BSD-Lite NFS system you will have to 259avoid this option until you have had an opportunity to upgrade the NFS code 260on all your 4.4BSD-Lite based systems.) 261.It Fl r 262Set the read data size to the specified value. 263It should normally be a power of 2 greater than or equal to 1024. 264This should be used for UDP mounts when the 265.Dq "fragments dropped due to timeout" 266value is getting large while actively using a mount point. 267(Use 268.Xr netstat 1 269with the 270.Fl s 271option to see what the 272.Dq "fragments dropped due to timeout" 273value is.) 274See the 275.Fl w 276option as well. 277.It Fl s 278A soft mount, which implies that file system calls will fail 279after \fBRetry\fR round trip timeout intervals. 280.It Fl t 281Set the initial retransmit timeout to the specified value. 282May be useful for fine tuning UDP mounts over internetworks 283with high packet loss rates or an overloaded server. 284Try increasing the interval if 285.Xr nfsstat 1 286shows high retransmit rates while the file system is active or reducing the 287value if there is a low retransmit rate but long response delay observed. 288(Normally, the -d option should be specified when using this option to manually 289tune the timeout 290interval.) 291.It Fl w 292Set the write data size to the specified value. 293Ditto the comments w.r.t. the 294.Fl r 295option, but using the 296.Dq "fragments dropped due to timeout" 297value on the server instead of the client. 298Note that both the 299.Fl r 300and 301.Fl w 302options should only be used as a last ditch effort at improving performance 303when mounting servers that do not support TCP mounts. 304.It Fl x 305Set the retransmit timeout count for soft mounts to the specified value. 306.El 307.Sh SEE ALSO 308.Xr mount 2 , 309.Xr unmount 2 , 310.Xr fstab 5 , 311.Xr mount 8 312.Sh BUGS 313Due to the way that Sun RPC is implemented on top of UDP (unreliable datagram) 314transport, tuning such mounts is really a black art that can only be expected 315to have limited success. 316For clients mounting servers that are not on the same 317LAN cable or that tend to be overloaded, 318TCP transport is strongly recommended, 319but unfortunately this is restricted to mostly 4.4BSD servers. 320