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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 8.2 (Berkeley) 3/27/94 33.\" 34.Dd March 27, 1994 35.Dt MOUNT_NFS 8 36.Os BSD 4.4 37.Sh NAME 38.Nm mount_nfs 39.Nd mount nfs file systems 40.Sh SYNOPSIS 41.Nm mount_nfs 42.Op Fl 3KPTUbcdilqs 43.Op Fl D Ar deadthresh 44.Op Fl I Ar readdirsize 45.Op Fl L Ar leaseterm 46.Op Fl R Ar retrycnt 47.Op Fl a Ar maxreadahead 48.Op Fl g Ar maxgroups 49.Op Fl m Ar realm 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:path node 56.Sh DESCRIPTION 57The 58.Nm mount_nfs 59command 60calls the 61.Xr mount 2 62system call to prepare and graft a remote nfs file system (rhost:path) 63on to the file system tree at the point 64.Ar node. 65This command is normally executed by 66.Xr mount 8 . 67It implements the mount protocol as described in RFC 1094, Appendix A and 68.%T "NFS: Network File System Version 3 Protocol Specification" , 69Appendix I. 70.Pp 71The options are: 72.Bl -tag -width indent 73.It Fl 3 74Use the NFS Version 3 protocol (Version 2 is the default). 75.It Fl D 76Used with NQNFS to set the 77.Dq "dead server threshold" 78to the specified number of round trip timeout intervals. 79After a 80.Dq "dead server threshold" 81of retransmit timeouts, 82cached data for the unresponsive server is assumed to still be valid. 83Values may be set in the range of 1 - 9, with 9 referring to an 84.Dq "infinite dead threshold" 85(i.e. never assume cached data still valid). 86This option is not generally recommended and is really an experimental 87feature. 88.It Fl I 89Set the readdir read size to the specified value. The value should normally 90be a multiple of DIRBLKSIZ that is <= the read size for the mount. 91.It Fl K 92Pass Kerberos authenticators to the server for client-to-server 93user-credential mapping. 94This requires that the kernel be built with the NFSKERB option. 95(Refer to the INTERNET-DRAFT titled 96.%T "Authentication Mechanisms for ONC RPC" , 97for more information.) 98.It Fl L 99Used with NQNFS to set the lease term to the specified number of seconds. 100Only use this argument for mounts with a large round trip delay. 101Values are normally in the 10-30 second range. 102.It Fl P 103Use a reserved socket port number. 104This is useful for mounting servers that require clients to use a 105reserved port number on the mistaken belief that this makes NFS 106more secure. (For the rare case where the client has a trusted root account 107but untrustworthy users and the network cables are in secure areas this does 108help, but for normal desktop clients this does not apply.) 109.It Fl R 110Set the retry count for doing the mount to the specified value. 111.It Fl T 112Use TCP transport instead of UDP. 113This is recommended for servers that are not on the same LAN cable as 114the client. 115(NB: This is NOT supported by most non-BSD servers.) 116.It Fl U 117Force the mount protocol to use UDP transport, even for TCP NFS mounts. 118(Necessary for some old BSD servers.) 119.It Fl a 120Set the read-ahead count to the specified value. 121This may be in the range of 0 - 4, and determines how many blocks 122will be read ahead when a large file is being read sequentially. 123Trying a value greater than 1 for this is suggested for 124mounts with a large bandwidth * delay product. 125.It Fl b 126If an initial attempt to contact the server fails, fork off a child to keep 127trying the mount in the background. 128Useful for 129.Xr fstab 5 , 130where the filesystem mount is not critical to multiuser operation. 131.It Fl c 132For UDP mount points, do not do a 133.Xr connect 2 . 134This must be used for servers that do not reply to requests from the 135standard NFS port number 2049. 136.It Fl d 137Turn off the dynamic retransmit timeout estimator. 138This may be useful for UDP mounts that exhibit high retry rates, 139since it is possible that the dynamically estimated timeout interval is too 140short. 141.It Fl g 142Set the maximum size of the group list for the credentials to the 143specified value. 144This should be used for mounts on old servers that cannot handle a 145group list size of 16, as specified in RFC 1057. 146Try 8, if users in a lot of groups cannot get response from the mount 147point. 148.It Fl i 149Make the mount interruptible, which implies that file system calls that 150are delayed due to an unresponsive server will fail with EINTR when a 151termination signal is posted for the process. 152.It Fl l 153Used with NQNFS and NFSV3 to specify that the \fBReaddirPlus\fR RPC should 154be used. 155This option reduces RPC traffic for cases such as 156.Dq "ls -l" , 157but tends to flood the attribute and name caches with prefetched entries. 158Try this option and see whether performance improves or degrades. Probably 159most useful for client to server network interconnects with a large bandwidth 160times delay product. 161.It Fl m 162Set the Kerberos realm to the string argument. 163Used with the 164.Fl K 165option for mounts to other realms. 166.It Fl o 167Options are specified with a 168.Fl o 169flag followed by a comma separated string of options. 170See the 171.Xr mount 8 172man page for possible options and their meanings. 173The following NFS specific option is also available: 174.Bl -tag -width indent 175.It port=<port_number> 176Use specified port number for NFS requests. 177The default is to query the portmapper for the NFS port. 178.El 179.It Fl q 180Use the leasing extensions to the NFS Version 3 protocol to maintain cache consistency. 181This protocol Version 2, referred to as Not Quite Nfs (NQNFS), 182is only supported by this updated release of NFS code. 183(It is not backwards compatible with the release of NQNFS that went out on 1844.4BSD-Lite. To interoperate with a 4.4BSD-Lite NFS system you will have to 185avoid this option until you have had an opportunity to upgrade the NFS code 186on all your 4.4BSD-Lite based systems.) 187.It Fl r 188Set the read data size to the specified value. 189It should normally be a power of 2 greater than or equal to 1024. 190This should be used for UDP mounts when the 191.Dq "fragments dropped due to timeout" 192value is getting large while actively using a mount point. 193(Use 194.Xr netstat 1 195with the 196.Fl s 197option to see what the 198.Dq "fragments dropped due to timeout" 199value is.) 200See the 201.Fl w 202option as well. 203.It Fl s 204A soft mount, which implies that file system calls will fail 205after \fBRetry\fR round trip timeout intervals. 206.It Fl t 207Set the initial retransmit timeout to the specified value. 208May be useful for fine tuning UDP mounts over internetworks 209with high packet loss rates or an overloaded server. 210Try increasing the interval if 211.Xr nfsstat 1 212shows high retransmit rates while the file system is active or reducing the 213value if there is a low retransmit rate but long response delay observed. 214(Normally, the -d option should be specified when using this option to manually 215tune the timeout 216interval.) 217.It Fl w 218Set the write data size to the specified value. 219Ditto the comments w.r.t. the 220.Fl r 221option, but using the 222.Dq "fragments dropped due to timeout" 223value on the server instead of the client. 224Note that both the 225.Fl r 226and 227.Fl w 228options should only be used as a last ditch effort at improving performance 229when mounting servers that do not support TCP mounts. 230.It Fl x 231Set the retransmit timeout count for soft mounts to the specified value. 232.El 233.Sh SEE ALSO 234.Xr mount 2 , 235.Xr unmount 2 , 236.Xr fstab 5 , 237.Xr mount 8 238.Sh BUGS 239Due to the way that Sun RPC is implemented on top of UDP (unreliable datagram) 240transport, tuning such mounts is really a black art that can only be expected 241to have limited success. 242For clients mounting servers that are not on the same 243LAN cable or that tend to be overloaded, 244TCP transport is strongly recommended, 245but unfortunately this is restricted to mostly 4.4BSD servers. 246