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 39.Sh NAME 40.Nm mount_nfs 41.Nd mount nfs file systems 42.Sh SYNOPSIS 43.Nm 44.Op Fl 23NPTUbcdiLls 45.Op Fl D Ar deadthresh 46.Op Fl I Ar readdirsize 47.Op Fl R Ar retrycnt 48.Op Fl a Ar maxreadahead 49.Op Fl g Ar maxgroups 50.Op Fl o Ar options 51.Op Fl r Ar readsize 52.Op Fl t Ar timeout 53.Op Fl w Ar writesize 54.Op Fl x Ar retrans 55.Ar rhost : Ns Ar path node 56.Sh DESCRIPTION 57The 58.Nm 59command 60calls the 61.Xr mount 2 62system call to prepare and graft a remote nfs file system 63.Pq Ar rhost : Ns Ar path 64on to the file system tree at the point 65.Ar node . 66This command is normally executed by 67.Xr mount 8 . 68It implements the mount protocol as described in RFC 1094, Appendix A and 69.%T "NFS: Network File System Version 3 Protocol Specification" , 70Appendix I. 71.Pp 72By default, 73.Nm 74keeps retrying until the mount succeeds. 75This behaviour is intended for filesystems listed in 76.Xr fstab 5 77that are critical to the boot process. 78For non-critical filesystems, the 79.Fl b 80and 81.Fl R 82flags provide mechanisms to prevent the boot process from hanging 83if the server is unavailable. 84.Pp 85If the server becomes unresponsive while an NFS filesystem is 86mounted, any new or outstanding file operations on that filesystem 87will hang uninterruptibly until the server comes back. 88To modify this default behaviour, see the 89.Fl i 90and 91.Fl s 92flags. 93.Pp 94The options are: 95.Bl -tag -width indent 96.It Fl 2 97Use the NFS Version 2 protocol (the default is to try version 3 first 98then version 2). Note that NFS version 2 has a file size limit of 2 99gigabytes. 100.It Fl 3 101Use the NFS Version 3 protocol. 102.It Fl D 103Set the 104.Dq "dead server threshold" 105to the specified number of round trip timeout intervals before a 106.Dq "server not responding" 107message is displayed. 108.It Fl I 109Set the readdir read size to the specified value. 110The value should normally 111be a multiple of DIRBLKSIZ that is <= the read size for the mount. 112.It Fl L 113Do 114.Em not 115forward 116.Xr fcntl 2 117locks over the wire. 118All locks will be local and not seen by the server 119and likewise not seen by other NFS clients. This removes 120the need to run the 121.Xr rpcbind 8 122service and the 123.Xr rpc.statd 8 124and 125.Xr rpc.lockd 8 126servers on the client. 127Note that this option will only be honored when performing the 128initial mount, it will be silently ignored if used while updating 129the mount options. 130.It Fl N 131Do 132.Em not 133use a reserved socket port number (see below). 134.It Fl P 135Use a reserved socket port number. 136This flag is obsolete, and only retained for compatibility reasons. 137Reserved port numbers are used by default now. 138This is useful for mounting servers that require clients to use a 139reserved port number on the mistaken belief that this makes NFS 140more secure. 141(For the rare case where the client has a trusted root account 142but untrustworthy users and the network cables are in secure areas this does 143help, but for normal desktop clients this does not apply.) 144.It Fl R 145Set the mount retry count to the specified value. 146The default is a retry count of zero, which means to keep retrying 147forever. 148There is a 60 second delay between each attempt. 149.It Fl T 150Use TCP transport instead of UDP. 151This is recommended for servers that are not on the same LAN cable as 152the client. 153(NB: This is NOT supported by most 154.No non- Ns Bx 155servers.) 156.It Fl U 157Force the mount protocol to use UDP transport, even for TCP NFS mounts. 158(Necessary for some old 159.Bx 160servers.) 161.It Fl a 162Set the read-ahead count to the specified value. 163This may be in the range of 0 - 4, and determines how many blocks 164will be read ahead when a large file is being read sequentially. 165Trying a value greater than 1 for this is suggested for 166mounts with a large bandwidth * delay product. 167.It Fl b 168If an initial attempt to contact the server fails, fork off a child to keep 169trying the mount in the background. 170Useful for 171.Xr fstab 5 , 172where the filesystem mount is not critical to multiuser operation. 173.It Fl c 174For UDP mount points, do not do a 175.Xr connect 2 . 176This must be used for servers that do not reply to requests from the 177standard NFS port number 2049. 178.It Fl d 179Turn off the dynamic retransmit timeout estimator. 180This may be useful for UDP mounts that exhibit high retry rates, 181since it is possible that the dynamically estimated timeout interval is too 182short. 183.It Fl g 184Set the maximum size of the group list for the credentials to the 185specified value. 186This should be used for mounts on old servers that cannot handle a 187group list size of 16, as specified in RFC 1057. 188Try 8, if users in a lot of groups cannot get response from the mount 189point. 190.It Fl i 191Make the mount interruptible, which implies that file system calls that 192are delayed due to an unresponsive server will fail with EINTR when a 193termination signal is posted for the process. 194.It Fl l 195Used with NQNFS and NFSV3 to specify that the \fBReaddirPlus\fR RPC should 196be used. 197This option reduces RPC traffic for cases such as 198.Dq "ls -l" , 199but tends to flood the attribute and name caches with prefetched entries. 200Try this option and see whether performance improves or degrades. 201Probably 202most useful for client to server network interconnects with a large bandwidth 203times delay product. 204.It Fl o 205Options are specified with a 206.Fl o 207flag followed by a comma separated string of options. 208See the 209.Xr mount 8 210man page for possible options and their meanings. 211The following NFS specific option is also available: 212.Bl -tag -width indent 213.It port=<port_number> 214Use specified port number for NFS requests. 215The default is to query the portmapper for the NFS port. 216.It acregmin=<seconds> 217.It acregmax=<seconds> 218.It acdirmin=<seconds> 219.It acdirmax=<seconds> 220When attributes of files are cached, a timeout calculated to determine 221whether a given cache entry has expired. These four values determine the 222upper and lower bounds of the timeouts for ``directory'' attributes and 223``regular'' (ie: everything else). The default values are 3 -> 60 seconds 224for regular files, and 30 -> 60 seconds for directories. The algorithm to 225calculate the timeout is based on the age of the file. The older the file, 226the longer the cache is considered valid, subject to the limits above. 227.El 228.Pp 229.Bl -tag -width "dumbtimerXX" 230\fBHistoric \&-o options\fR 231.Pp 232Use of these options is deprecated, they are only mentioned here for 233compatibility with historic versions of 234.Nm . 235.It bg 236Same as 237.Fl b . 238.It conn 239Same as not specifying 240.Fl c . 241.It dumbtimer 242Same as 243.Fl d . 244.It intr 245Same as 246.Fl i . 247.It lockd 248Same as not specifying 249.Fl L . 250.It nfsv2 251Same as 252.Fl 2 . 253.It nfsv3 254Same as 255.Fl 3 . 256.It rdirplus 257Same as 258.Fl l . 259.It mntudp 260Same as 261.Fl U . 262.It resvport 263Same as 264.Fl P . 265.It seqpacket 266Same as 267.Fl p . 268.It soft 269Same as 270.Fl s . 271.It tcp 272Same as 273.Fl T . 274.El 275.It Fl r 276Set the read data size to the specified value. 277It should normally be a power of 2 greater than or equal to 1024. 278This should be used for UDP mounts when the 279.Dq "fragments dropped due to timeout" 280value is getting large while actively using a mount point. 281(Use 282.Xr netstat 1 283with the 284.Fl s 285option to see what the 286.Dq "fragments dropped due to timeout" 287value is.) 288See the 289.Fl w 290option as well. 291.It Fl s 292A soft mount, which implies that file system calls will fail 293after \fBRetry\fR round trip timeout intervals. 294.It Fl t 295Set the initial retransmit timeout to the specified value. 296May be useful for fine tuning UDP mounts over internetworks 297with high packet loss rates or an overloaded server. 298Try increasing the interval if 299.Xr nfsstat 1 300shows high retransmit rates while the file system is active or reducing the 301value if there is a low retransmit rate but long response delay observed. 302(Normally, the -d option should be specified when using this option to manually 303tune the timeout 304interval.) 305.It Fl w 306Set the write data size to the specified value. 307Ditto the comments w.r.t. the 308.Fl r 309option, but using the 310.Dq "fragments dropped due to timeout" 311value on the server instead of the client. 312Note that both the 313.Fl r 314and 315.Fl w 316options should only be used as a last ditch effort at improving performance 317when mounting servers that do not support TCP mounts. 318.It Fl x 319Set the retransmit timeout count for soft mounts to the specified value. 320.El 321.Sh SEE ALSO 322.Xr mount 2 , 323.Xr unmount 2 , 324.Xr fstab 5 , 325.Xr mount 8 , 326.Xr nfsd 8 , 327.Xr nfsiod 8 , 328.Xr showmount 8 329.Sh BUGS 330Due to the way that Sun RPC is implemented on top of UDP (unreliable datagram) 331transport, tuning such mounts is really a black art that can only be expected 332to have limited success. 333For clients mounting servers that are not on the same 334LAN cable or that tend to be overloaded, 335TCP transport is strongly recommended, 336but unfortunately this is restricted to mostly 337.Bx 4.4 338servers. 339