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.\" $FreeBSD$ 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. 96The value should normally 97be a multiple of DIRBLKSIZ that is <= the read size for the mount. 98.It Fl K 99Pass Kerberos authenticators to the server for client-to-server 100user-credential mapping. 101This requires that the kernel be built with the NFSKERB option. 102(Refer to the INTERNET-DRAFT titled 103.%T "Authentication Mechanisms for ONC RPC" , 104for more information.) 105.It Fl L 106Used with NQNFS to set the lease term to the specified number of seconds. 107Only use this argument for mounts with a large round trip delay. 108Values are normally in the 10-30 second range. 109.It Fl N 110Do 111.Em not 112use a reserved socket port number (see below). 113.It Fl P 114Use a reserved socket port number. 115This flag is obsolete, and only retained for compatibility reasons. 116Reserved port numbers are used by default now. 117This is useful for mounting servers that require clients to use a 118reserved port number on the mistaken belief that this makes NFS 119more secure. 120(For the rare case where the client has a trusted root account 121but untrustworthy users and the network cables are in secure areas this does 122help, but for normal desktop clients this does not apply.) 123.It Fl R 124Set the retry count for doing the mount to the specified value. 125.It Fl T 126Use TCP transport instead of UDP. 127This is recommended for servers that are not on the same LAN cable as 128the client. 129(NB: This is NOT supported by most non-BSD servers.) 130.It Fl U 131Force the mount protocol to use UDP transport, even for TCP NFS mounts. 132(Necessary for some old BSD servers.) 133.It Fl a 134Set the read-ahead count to the specified value. 135This may be in the range of 0 - 4, and determines how many blocks 136will be read ahead when a large file is being read sequentially. 137Trying a value greater than 1 for this is suggested for 138mounts with a large bandwidth * delay product. 139.It Fl b 140If an initial attempt to contact the server fails, fork off a child to keep 141trying the mount in the background. 142Useful for 143.Xr fstab 5 , 144where the filesystem mount is not critical to multiuser operation. 145.It Fl c 146For UDP mount points, do not do a 147.Xr connect 2 . 148This must be used for servers that do not reply to requests from the 149standard NFS port number 2049. 150.It Fl d 151Turn off the dynamic retransmit timeout estimator. 152This may be useful for UDP mounts that exhibit high retry rates, 153since it is possible that the dynamically estimated timeout interval is too 154short. 155.It Fl g 156Set the maximum size of the group list for the credentials to the 157specified value. 158This should be used for mounts on old servers that cannot handle a 159group list size of 16, as specified in RFC 1057. 160Try 8, if users in a lot of groups cannot get response from the mount 161point. 162.It Fl i 163Make the mount interruptible, which implies that file system calls that 164are delayed due to an unresponsive server will fail with EINTR when a 165termination signal is posted for the process. 166.It Fl l 167Used with NQNFS and NFSV3 to specify that the \fBReaddirPlus\fR RPC should 168be used. 169This option reduces RPC traffic for cases such as 170.Dq "ls -l" , 171but tends to flood the attribute and name caches with prefetched entries. 172Try this option and see whether performance improves or degrades. 173Probably 174most useful for client to server network interconnects with a large bandwidth 175times delay product. 176.It Fl m 177Set the Kerberos realm to the string argument. 178Used with the 179.Fl K 180option for mounts to other realms. 181.It Fl o 182Options are specified with a 183.Fl o 184flag followed by a comma separated string of options. 185See the 186.Xr mount 8 187man page for possible options and their meanings. 188The following NFS specific option is also available: 189.Bl -tag -width indent 190.It port=<port_number> 191Use specified port number for NFS requests. 192The default is to query the portmapper for the NFS port. 193.It acregmin=<seconds> 194.It acregmax=<seconds> 195.It acdirmin=<seconds> 196.It acdirmax=<seconds> 197When attributes of files are cached, a timeout calculated to determine 198whether a given cache entry has expired. These four values determine the 199upper and lower bounds of the timeouts for ``directory'' attributes and 200``regular'' (ie: everything else). The default values are 3 -> 60 seconds 201for regular files, and 30 -> 60 seconds for directories. The algorithm to 202calculate the timeout is based on the age of the file. The older the file, 203the longer the cache is considered valid, subject to the limits above. 204.El 205.Pp 206.Bl -tag -width "dumbtimerXX" 207\fBHistoric \&-o options\fR 208.Pp 209Use of these options is deprecated, they are only mentioned here for 210compatibility with historic versions of 211.Nm Ns . 212.It bg 213Same as 214.Fl b . 215.It conn 216Same as not specifying 217.Fl c . 218.It dumbtimer 219Same as 220.Fl d . 221.It intr 222Same as 223.Fl i . 224.It kerb 225Same as 226.Fl K . 227.It nfsv2 228Same as 229.Fl 2 . 230.It nfsv3 231Same as 232.Fl 3 . 233.It rdirplus 234Same as 235.Fl l . 236.It mntudp 237Same as 238.Fl U . 239.It resvport 240Same as 241.Fl P . 242.It seqpacket 243Same as 244.Fl p . 245.It nqnfs 246Same as 247.Fl q . 248.It soft 249Same as 250.Fl s . 251.It tcp 252Same as 253.Fl T. 254.El 255.It Fl q 256Use the leasing extensions to the NFS Version 3 protocol 257to maintain cache consistency. 258This protocol Version 2, referred to as Not Quite Nfs (NQNFS), 259is only supported by this updated release of NFS code. 260(It is not backwards compatible with the release of NQNFS that went out on 2614.4BSD-Lite. 262To interoperate with a 4.4BSD-Lite NFS system you will have to 263avoid this option until you have had an opportunity to upgrade the NFS code 264on all your 4.4BSD-Lite based systems.) 265.It Fl r 266Set the read data size to the specified value. 267It should normally be a power of 2 greater than or equal to 1024. 268This should be used for UDP mounts when the 269.Dq "fragments dropped due to timeout" 270value is getting large while actively using a mount point. 271(Use 272.Xr netstat 1 273with the 274.Fl s 275option to see what the 276.Dq "fragments dropped due to timeout" 277value is.) 278See the 279.Fl w 280option as well. 281.It Fl s 282A soft mount, which implies that file system calls will fail 283after \fBRetry\fR round trip timeout intervals. 284.It Fl t 285Set the initial retransmit timeout to the specified value. 286May be useful for fine tuning UDP mounts over internetworks 287with high packet loss rates or an overloaded server. 288Try increasing the interval if 289.Xr nfsstat 1 290shows high retransmit rates while the file system is active or reducing the 291value if there is a low retransmit rate but long response delay observed. 292(Normally, the -d option should be specified when using this option to manually 293tune the timeout 294interval.) 295.It Fl w 296Set the write data size to the specified value. 297Ditto the comments w.r.t. the 298.Fl r 299option, but using the 300.Dq "fragments dropped due to timeout" 301value on the server instead of the client. 302Note that both the 303.Fl r 304and 305.Fl w 306options should only be used as a last ditch effort at improving performance 307when mounting servers that do not support TCP mounts. 308.It Fl x 309Set the retransmit timeout count for soft mounts to the specified value. 310.El 311.Sh SEE ALSO 312.Xr mount 2 , 313.Xr unmount 2 , 314.Xr fstab 5 , 315.Xr mount 8 , 316.Xr nfsd 8 , 317.Xr nfsiod 8 , 318.Xr showmount 8 319.Sh BUGS 320Due to the way that Sun RPC is implemented on top of UDP (unreliable datagram) 321transport, tuning such mounts is really a black art that can only be expected 322to have limited success. 323For clients mounting servers that are not on the same 324LAN cable or that tend to be overloaded, 325TCP transport is strongly recommended, 326but unfortunately this is restricted to mostly 4.4BSD servers. 327