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 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 : Ns Ar 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 65.Pq Ar rhost : Ns Ar path 66on to the file system tree at the point 67.Ar node . 68This command is normally executed by 69.Xr mount 8 . 70It implements the mount protocol as described in RFC 1094, Appendix A and 71.%T "NFS: Network File System Version 3 Protocol Specification" , 72Appendix I. 73.Pp 74The options are: 75.Bl -tag -width indent 76.It Fl 2 77Use the NFS Version 2 protocol (the default is to try version 3 first 78then version 2). Note that NFS version 2 has a file size limit of 2 79gigabytes. 80.It Fl 3 81Use the NFS Version 3 protocol. 82.It Fl D 83Used with NQNFS to set the 84.Dq "dead server threshold" 85to the specified number of round trip timeout intervals. 86After a 87.Dq "dead server threshold" 88of retransmit timeouts, 89cached data for the unresponsive server is assumed to still be valid. 90Values may be set in the range of 1 - 9, with 9 referring to an 91.Dq "infinite dead threshold" 92(i.e. never assume cached data still valid). 93This option is not generally recommended and is really an experimental 94feature. 95.It Fl I 96Set the readdir read size to the specified value. 97The value should normally 98be a multiple of DIRBLKSIZ that is <= the read size for the mount. 99.It Fl K 100Pass Kerberos authenticators to the server for client-to-server 101user-credential mapping. 102This requires that the kernel be built with the NFSKERB option. 103The use of this option will prevent the kernel from compiling 104unless calls to the appropriate Kerberos encryption routines 105are provided in the NFS source. 106(Refer to the INTERNET-DRAFT titled 107.%T "Authentication Mechanisms for ONC RPC" , 108for more information.) 109.It Fl L 110Used with NQNFS to set the lease term to the specified number of seconds. 111Only use this argument for mounts with a large round trip delay. 112Values are normally in the 10-30 second range. 113.It Fl N 114Do 115.Em not 116use a reserved socket port number (see below). 117.It Fl P 118Use a reserved socket port number. 119This flag is obsolete, and only retained for compatibility reasons. 120Reserved port numbers are used by default now. 121This is useful for mounting servers that require clients to use a 122reserved port number on the mistaken belief that this makes NFS 123more secure. 124(For the rare case where the client has a trusted root account 125but untrustworthy users and the network cables are in secure areas this does 126help, but for normal desktop clients this does not apply.) 127.It Fl R 128Set the retry count for doing the mount to the specified value. 129.It Fl T 130Use TCP transport instead of UDP. 131This is recommended for servers that are not on the same LAN cable as 132the client. 133(NB: This is NOT supported by most non-BSD servers.) 134.It Fl U 135Force the mount protocol to use UDP transport, even for TCP NFS mounts. 136(Necessary for some old BSD servers.) 137.It Fl a 138Set the read-ahead count to the specified value. 139This may be in the range of 0 - 4, and determines how many blocks 140will be read ahead when a large file is being read sequentially. 141Trying a value greater than 1 for this is suggested for 142mounts with a large bandwidth * delay product. 143.It Fl b 144If an initial attempt to contact the server fails, fork off a child to keep 145trying the mount in the background. 146Useful for 147.Xr fstab 5 , 148where the filesystem mount is not critical to multiuser operation. 149.It Fl c 150For UDP mount points, do not do a 151.Xr connect 2 . 152This must be used for servers that do not reply to requests from the 153standard NFS port number 2049. 154.It Fl d 155Turn off the dynamic retransmit timeout estimator. 156This may be useful for UDP mounts that exhibit high retry rates, 157since it is possible that the dynamically estimated timeout interval is too 158short. 159.It Fl g 160Set the maximum size of the group list for the credentials to the 161specified value. 162This should be used for mounts on old servers that cannot handle a 163group list size of 16, as specified in RFC 1057. 164Try 8, if users in a lot of groups cannot get response from the mount 165point. 166.It Fl i 167Make the mount interruptible, which implies that file system calls that 168are delayed due to an unresponsive server will fail with EINTR when a 169termination signal is posted for the process. 170.It Fl l 171Used with NQNFS and NFSV3 to specify that the \fBReaddirPlus\fR RPC should 172be used. 173This option reduces RPC traffic for cases such as 174.Dq "ls -l" , 175but tends to flood the attribute and name caches with prefetched entries. 176Try this option and see whether performance improves or degrades. 177Probably 178most useful for client to server network interconnects with a large bandwidth 179times delay product. 180.It Fl m 181Set the Kerberos realm to the string argument. 182Used with the 183.Fl K 184option for mounts to other realms. 185.It Fl o 186Options are specified with a 187.Fl o 188flag followed by a comma separated string of options. 189See the 190.Xr mount 8 191man page for possible options and their meanings. 192The following NFS specific option is also available: 193.Bl -tag -width indent 194.It port=<port_number> 195Use specified port number for NFS requests. 196The default is to query the portmapper for the NFS port. 197.It acregmin=<seconds> 198.It acregmax=<seconds> 199.It acdirmin=<seconds> 200.It acdirmax=<seconds> 201When attributes of files are cached, a timeout calculated to determine 202whether a given cache entry has expired. These four values determine the 203upper and lower bounds of the timeouts for ``directory'' attributes and 204``regular'' (ie: everything else). The default values are 3 -> 60 seconds 205for regular files, and 30 -> 60 seconds for directories. The algorithm to 206calculate the timeout is based on the age of the file. The older the file, 207the longer the cache is considered valid, subject to the limits above. 208.El 209.Pp 210.Bl -tag -width "dumbtimerXX" 211\fBHistoric \&-o options\fR 212.Pp 213Use of these options is deprecated, they are only mentioned here for 214compatibility with historic versions of 215.Nm . 216.It bg 217Same as 218.Fl b . 219.It conn 220Same as not specifying 221.Fl c . 222.It dumbtimer 223Same as 224.Fl d . 225.It intr 226Same as 227.Fl i . 228.It kerb 229Same as 230.Fl K . 231.It nfsv2 232Same as 233.Fl 2 . 234.It nfsv3 235Same as 236.Fl 3 . 237.It rdirplus 238Same as 239.Fl l . 240.It mntudp 241Same as 242.Fl U . 243.It resvport 244Same as 245.Fl P . 246.It seqpacket 247Same as 248.Fl p . 249.It nqnfs 250Same as 251.Fl q . 252.It soft 253Same as 254.Fl s . 255.It tcp 256Same as 257.Fl T . 258.El 259.It Fl q 260Use the Not Quite NFS (NQNFS) protocol. 261This experimental protocol is NFS Version 2 with leasing extensions 262similar to those found in NFS Version 3. 263The interoperability of this protocol with other systems is 264very limited and its implementation is not widely used. 265Do not use this option unless you know exactly what you are doing! 266.It Fl r 267Set the read data size to the specified value. 268It should normally be a power of 2 greater than or equal to 1024. 269This should be used for UDP mounts when the 270.Dq "fragments dropped due to timeout" 271value is getting large while actively using a mount point. 272(Use 273.Xr netstat 1 274with the 275.Fl s 276option to see what the 277.Dq "fragments dropped due to timeout" 278value is.) 279See the 280.Fl w 281option as well. 282.It Fl s 283A soft mount, which implies that file system calls will fail 284after \fBRetry\fR round trip timeout intervals. 285.It Fl t 286Set the initial retransmit timeout to the specified value. 287May be useful for fine tuning UDP mounts over internetworks 288with high packet loss rates or an overloaded server. 289Try increasing the interval if 290.Xr nfsstat 1 291shows high retransmit rates while the file system is active or reducing the 292value if there is a low retransmit rate but long response delay observed. 293(Normally, the -d option should be specified when using this option to manually 294tune the timeout 295interval.) 296.It Fl w 297Set the write data size to the specified value. 298Ditto the comments w.r.t. the 299.Fl r 300option, but using the 301.Dq "fragments dropped due to timeout" 302value on the server instead of the client. 303Note that both the 304.Fl r 305and 306.Fl w 307options should only be used as a last ditch effort at improving performance 308when mounting servers that do not support TCP mounts. 309.It Fl x 310Set the retransmit timeout count for soft mounts to the specified value. 311.El 312.Sh SEE ALSO 313.Xr mount 2 , 314.Xr unmount 2 , 315.Xr fstab 5 , 316.Xr mount 8 , 317.Xr nfsd 8 , 318.Xr nfsiod 8 , 319.Xr showmount 8 320.Sh BUGS 321Due to the way that Sun RPC is implemented on top of UDP (unreliable datagram) 322transport, tuning such mounts is really a black art that can only be expected 323to have limited success. 324For clients mounting servers that are not on the same 325LAN cable or that tend to be overloaded, 326TCP transport is strongly recommended, 327but unfortunately this is restricted to mostly 4.4BSD servers. 328