1.\" Copyright (c) 1992, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" %sccs.include.redist.roff% 5.\" 6.\" @(#)mount_nfs.8 8.1 (Berkeley) 06/05/93 7.\" 8.Dd 9.Dt MOUNT_NFS 8 10.Os BSD 4.4 11.Sh NAME 12.Nm mount_nfs 13.Nd mount nfs file systems 14.Sh SYNOPSIS 15.Nm mount_nfs 16.Op Fl bsiTMlqdckPK 17.Op Fl R Ar retrycnt 18.Op Fl r Ar readsize 19.Op Fl w Ar writesize 20.Op Fl t Ar timeout 21.Op Fl x Ar retrans 22.Op Fl g Ar maxgroups 23.Op Fl a Ar maxreadahead 24.Op Fl L Ar leaseterm 25.Op Fl D Ar deadthresh 26.Op Fl m Ar realm 27.Ar rhost:path node 28.Sh DESCRIPTION 29The 30.Nm mount_nfs 31command 32calls the 33.Xr mount 2 34system call to prepare and graft a 35remote nfs file system 36(rhost:path) 37on to the file system tree at the point 38.Ar node. 39This command is normally executed by 40.Xr mount 8 41setting the options with the 42.Fl o 43flag. 44It implements the mount protocol as described in RFC 1094, Appendix A. 45.Pp 46The options are: 47.Bl -tag -width indent 48.It Fl b 49If an initial attempt to contact the server fails, fork off a child to keep 50trying the mount in the background. Useful for 51.Xr fstab 5 52where the filesystem mount is not critical to multiuser operation. 53.It Fl s 54A soft mount, which implies that file system calls will fail 55after \fBRetry\fR round trip timeout intervals. 56.It Fl i 57An interruptible mount, which implies that file system calls that are delayed 58due to an unresponsive server will fail with EINTR when a termination signal 59is posted for the process. 60.It Fl T 61Use TCP transport instead of UDP. 62This is recommended for servers that are not on the 63same LAN cable as the client. 64(NB: This is NOT supported by most non-BSD servers.) 65.It Fl M 66Assume that other clients are not writing a file concurrently with this client. 67This implements a slightly less strict 68consistency criteria than 4.3BSD Reno did, 69that is more in line with most commercial client implementations. 70This is recommended for servers that do not support leasing. 71.It Fl d 72Do not estimate retransmit timeout dynamically. 73This may be useful for UDP 74mounts that exhibit high retry rates. 75.It Fl c 76For UDP mount points, do not do a 77.Xr connect 2. 78This must be used for servers that do not reply to requests from the standard 79port number. 80.It Fl P 81Use a reserved socket port number. This is useful for mounting servers that 82require clients to use a reserved port number. 83.It Fl K 84Pass Kerberos authenticators to the server for 85client-to-server user-credential mapping. 86This may only be used over TCP mounts between 4.4BSD clients and 87servers. 88.It Fl q 89Use the leasing extensions to the protocol to maintain cache consistency. 90This protocol, referred to as Not Quite Nfs (NQNFS), 91is only supported by 4.4BSD servers. 92.It Fl l 93Used with NQNFS to specify that the 94\fBReaddir_and_Lookup\fR RPC should be used. 95This option reduces RPC traffic for cases such as ``ls -l'', 96but increases the lease load on the server. 97This is recommended unless the server is complaining 98about excessive lease load. 99.It Fl k 100Used with NQNFS to specify ``get a lease'' for the file name being looked up. 101This is recommended unless the server is complaining about excessive lease 102load. 103.El 104.Pp 105The following arguments take a value parameter that is either a decimal 106number or a character string specified as =<value> after the option flag. 107.Bl -tag -width indent 108.It Fl R 109Set the retry count for doing the mount to <value>. 110.It Fl x 111Set the retransmit timeout count for soft mounts to <value>. 112.It Fl r 113Set the read data size to <value>. 114It should be a power of 2 greater than 512. 115This should be used for UDP mounts when the 116``fragments dropped due to timeout'' 117value is getting large while actively using a mount point. 118(Use 119.Xr netstat 1 120with the 121.FL s 122option to see what the ``fragments dropped due to timeout'' value is.) 123.It Fl w 124Set the write data size to <value>. 125Ditto the comments w.r.t. the 126.Fl r 127option, but using the ``fragments dropped due to timeout'' value on the 128server instead of the client. 129Note that both the 130.Fl r 131and 132.Fl w 133options should only be used as a last ditch effort at improving performance 134when mounting servers that do not support TCP mounts. 135.It Fl t 136Set the initial retransmit timeout to <value>. 137May be useful for fine tuning UDP mounts over internetworks 138with high packet loss rates or an overloaded server. 139Try increasing the interval if 140.Xr nfsstat 1 141shows high retransmit rates while the file system is active or reducing the 142value if there is a low retransmit rate but long response delay observed. 143.It Fl g 144Set the maximum size of the group list for the credentials to <value>. 145This should be used for mounts on old servers that cannot handle a group list 146size of 16, as specified in RFC 1057. 147Try 8, if users in a lot of groups 148cannot get response from the mount point. 149.It Fl a 150Set the read-ahead count to <value>. 151This may be in the range of 0 - 4 and determines how many blocks 152will be read ahead when a large file is being read sequentially. 153This is recommended for mounts with a large 154bandwidth * delay product. 155.It Fl L 156Used with NQNFS to set the lease term to <value> seconds. 157Only use this argument for mounts with a large round trip delay. 158Values are normally in the 10-30 second range. 159.It Fl D 160Used with NQNFS to set the ``dead server threshold'' to <value> round trip 161timeout intervals. 162After a ``dead server threshold'' of retransmit timeouts, 163cached data for the unresponsive server is assumed to still be valid. 164Values may be set in the range of 1 - 9, with 9 referring to an ``infinite 165dead threshold'' (i.e. never assume cached data still valid). 166This option is not generally recommended and 167is really an experimental feature. 168.It Fl m 169Set the Kerberos realm to the string argument. Used with the 170.Fl K 171option for mounts to other realms. 172.El 173.Sh SEE ALSO 174.Xr mount 2 , 175.Xr unmount 2 , 176.Xr fstab 5 177.Sh BUGS 178Due to the way that Sun RPC is implemented on top of UDP (unreliable datagram) 179transport, tuning such mounts is really a black art that can only be expected 180to have limited success. 181For clients mounting servers that are not on the same 182LAN cable or that tend to be overloaded, 183TCP transport is strongly recommended, 184but unfortunately this is restricted to mostly 4.4BSD servers. 185