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. Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.\" @(#)mount_nfs.8 8.3 (Berkeley) 3/29/95 29.\" $FreeBSD$ 30.\" 31.Dd September 10, 2016 32.Dt MOUNT_NFS 8 33.Os 34.Sh NAME 35.Nm mount_nfs 36.Nd mount NFS file systems 37.Sh SYNOPSIS 38.Nm 39.Op Fl 23bcdiLlNPsTU 40.Op Fl a Ar maxreadahead 41.Op Fl D Ar deadthresh 42.Op Fl g Ar maxgroups 43.Op Fl I Ar readdirsize 44.Op Fl o Ar options 45.Op Fl R Ar retrycnt 46.Op Fl r Ar readsize 47.Op Fl t Ar timeout 48.Op Fl w Ar writesize 49.Op Fl x Ar retrans 50.Ar rhost : Ns Ar path node 51.Sh DESCRIPTION 52The 53.Nm 54utility calls the 55.Xr nmount 2 56system call to prepare and graft a remote NFS file system 57.Pq Ar rhost : Ns Ar path 58on to the file system tree at the point 59.Ar node . 60This command is normally executed by 61.Xr mount 8 . 62It implements the mount protocol as described in RFC 1094, Appendix A and 63.%T "NFS: Network File System Version 3 Protocol Specification" , 64Appendix I. 65.Pp 66By default, 67.Nm 68keeps retrying until the mount succeeds. 69This behaviour is intended for file systems listed in 70.Xr fstab 5 71that are critical to the boot process. 72For non-critical file systems, the 73.Cm bg 74and 75.Cm retrycnt 76options provide mechanisms to prevent the boot process from hanging 77if the server is unavailable. 78.Pp 79If the server becomes unresponsive while an NFS file system is 80mounted, any new or outstanding file operations on that file system 81will hang uninterruptibly until the server comes back. 82To modify this default behaviour, see the 83.Cm intr 84and 85.Cm soft 86options. 87.Pp 88The options are: 89.Bl -tag -width indent 90.It Fl o 91Options are specified with a 92.Fl o 93flag followed by a comma separated string of options. 94See the 95.Xr mount 8 96man page for possible options and their meanings. 97The following NFS specific options are also available: 98.Bl -tag -width indent 99.It Cm acregmin Ns = Ns Aq Ar seconds 100.It Cm acregmax Ns = Ns Aq Ar seconds 101.It Cm acdirmin Ns = Ns Aq Ar seconds 102.It Cm acdirmax Ns = Ns Aq Ar seconds 103When attributes of files are cached, a timeout calculated to determine 104whether a given cache entry has expired. 105These four values determine the upper and lower bounds of the timeouts for 106.Dq directory 107attributes and 108.Dq regular 109(ie: everything else). 110The default values are 3 -> 60 seconds 111for regular files, and 30 -> 60 seconds for directories. 112The algorithm to calculate the timeout is based on the age of the file. 113The older the file, 114the longer the cache is considered valid, subject to the limits above. 115.It Cm actimeo Ns = Ns Aq Ar seconds 116Set four cache timeouts above to specified value. 117.It Cm allgssname 118This option can be used along with 119.Fl o Cm gssname 120to specify that all operations should use the host-based initiator 121credential. 122This may be used for clients that run system daemons that need to 123access files on the NFSv4 mounted volume. 124.It Cm bg 125If an initial attempt to contact the server fails, fork off a child to keep 126trying the mount in the background. 127Useful for 128.Xr fstab 5 , 129where the file system mount is not critical to multiuser operation. 130.It Cm deadthresh Ns = Ns Aq Ar value 131Set the 132.Dq "dead server threshold" 133to the specified number of round trip timeout intervals before a 134.Dq "server not responding" 135message is displayed. 136.It Cm dumbtimer 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 Cm fg 142Same as not specifying 143.Cm bg . 144.It Cm gssname Ns = Ns Aq Ar service-principal-name 145This option can be used with the KerberosV security flavors for NFSv4 mounts 146to specify the 147.Dq "service-principal-name" 148of a host-based entry in the default 149keytab file that is used for system operations. 150It allows the mount to be performed by 151.Dq "root" 152and avoids problems with 153cached credentials for the system operations expiring. 154The 155.Dq "service-prinicpal-name" 156should be specified without instance or domain and is typically 157.Dq "host" , 158.Dq "nfs" 159or 160.Dq "root" . 161.It Cm hard 162Same as not specifying 163.Cm soft . 164.It Cm intr 165Make the mount interruptible, which implies that file system calls that 166are delayed due to an unresponsive server will fail with EINTR when a 167termination signal is posted for the process. 168.It Cm maxgroups Ns = Ns Aq Ar value 169Set the maximum size of the group list for the credentials to the 170specified value. 171This should be used for mounts on old servers that cannot handle a 172group list size of 16, as specified in RFC 1057. 173Try 8, if users in a lot of groups cannot get response from the mount 174point. 175.It Cm mntudp 176Force the mount protocol to use UDP transport, even for TCP NFS mounts. 177(Necessary for some old 178.Bx 179servers.) 180.It Cm nametimeo Ns = Ns Aq Ar value 181Override the default of NFS_DEFAULT_NAMETIMEO for the timeout (in seconds) 182for positive name cache entries. 183If this is set to 0 it disables positive name caching for the mount point. 184.It Cm negnametimeo Ns = Ns Aq Ar value 185Override the default of NFS_DEFAULT_NEGNAMETIMEO for the timeout (in seconds) 186for negative name cache entries. 187If this is set to 0 it disables negative name caching for the mount point. 188.It Cm nfsv2 189Use the NFS Version 2 protocol (the default is to try version 3 first 190then version 2). 191Note that NFS version 2 has a file size limit of 2 gigabytes. 192.It Cm nfsv3 193Use the NFS Version 3 protocol. 194.It Cm nfsv4 195Use the NFS Version 4 protocol. 196This option will force the mount to use 197TCP transport. 198.It Cm minorversion Ns = Ns Aq Ar value 199Override the default of 0 for the minor version of the NFS Version 4 protocol. 200The only minor version currently supported is 1. 201This option is only meaningful when used with the 202.Cm nfsv4 203option. 204.It Cm pnfs 205Enable support for parallel NFS (pNFS) for minor version 1 of the 206NFS Version 4 protocol. 207This option is only meaningful when used with the 208.Cm minorversion 209option. 210.It Cm noac 211Disable attribute caching. 212.It Cm noconn 213For UDP mount points, do not do a 214.Xr connect 2 . 215This must be used if the server does not reply to requests from the standard 216NFS port number 2049 or replies to requests using a different IP address 217(which can occur if the server is multi-homed). 218Setting the 219.Va vfs.nfs.nfs_ip_paranoia 220sysctl to 0 will make this option the default. 221.It Cm nocto 222Normally, NFS clients maintain the close-to-open cache coherency. 223This works by flushing at close time and checking at open time. 224Checking at open time is implemented by getting attributes from 225the server and purging the data cache if they do not match 226attributes cached by the client. 227.Pp 228This option disables checking at open time. 229It may improve performance for read-only mounts, 230but should only be used if the data on the server changes rarely. 231Be sure to understand the consequences before enabling this option. 232.It Cm noinet4 , noinet6 233Disables 234.Dv AF_INET 235or 236.Dv AF_INET6 237connections. 238Useful for hosts that have 239both an A record and an AAAA record for the same name. 240.It Cm nolockd 241Do 242.Em not 243forward 244.Xr fcntl 2 245locks over the wire. 246All locks will be local and not seen by the server 247and likewise not seen by other NFS clients. 248This removes the need to run the 249.Xr rpcbind 8 250service and the 251.Xr rpc.statd 8 252and 253.Xr rpc.lockd 8 254servers on the client. 255Note that this option will only be honored when performing the 256initial mount, it will be silently ignored if used while updating 257the mount options. 258.It Cm noncontigwr 259This mount option allows the NFS client to 260combine non-contiguous byte ranges being written 261such that the dirty byte range becomes a superset of the bytes 262that are dirty. 263This reduces the number of writes significantly for software 264builds. 265The merging of byte ranges is not done if the file has been file 266locked, since most applications modifying a file from multiple 267clients will use file locking. 268As such, this option could result in a corrupted file for the 269rare case of an application modifying the file from multiple 270clients concurrently without using file locking. 271.It Cm principal 272For the RPCSEC_GSS security flavors, such as krb5, krb5i and krb5p, 273this option sets the name of the host based principal name expected 274by the server. 275This option overrides the default, which will be ``nfs@<server-fqdn>'' 276and should normally be sufficient. 277.It Cm noresvport 278Do 279.Em not 280use a reserved socket port number (see below). 281.It Cm port Ns = Ns Aq Ar port_number 282Use specified port number for NFS requests. 283The default is to query the portmapper for the NFS port. 284.It Cm proto Ns = Ns Aq Ar protocol 285Specify transport protocol version to use. 286Currently, they are: 287.Bd -literal 288udp - Use UDP over IPv4 289tcp - Use TCP over IPv4 290udp6 - Use UDP over IPv6 291tcp6 - Use TCP over IPv6 292.Ed 293.It Cm rdirplus 294Used with NFSV3 to specify that the \fBReaddirPlus\fR RPC should 295be used. 296For NFSV4, setting this option has a similar effect, in that it will make 297the Readdir Operation get more attributes. 298This option reduces RPC traffic for cases such as 299.Dq "ls -l" , 300but tends to flood the attribute and name caches with prefetched entries. 301Try this option and see whether performance improves or degrades. 302Probably 303most useful for client to server network interconnects with a large bandwidth 304times delay product. 305.It Cm readahead Ns = Ns Aq Ar value 306Set the read-ahead count to the specified value. 307This may be in the range of 0 - 4, and determines how many blocks 308will be read ahead when a large file is being read sequentially. 309Trying a value greater than 1 for this is suggested for 310mounts with a large bandwidth * delay product. 311.It Cm readdirsize Ns = Ns Aq Ar value 312Set the readdir read size to the specified value. 313The value should normally 314be a multiple of 315.Dv DIRBLKSIZ 316that is <= the read size for the mount. 317.It Cm resvport 318Use a reserved socket port number. 319This flag is obsolete, and only retained for compatibility reasons. 320Reserved port numbers are used by default now. 321(For the rare case where the client has a trusted root account 322but untrustworthy users and the network cables are in secure areas this does 323help, but for normal desktop clients this does not apply.) 324.It Cm retrans Ns = Ns Aq Ar value 325Set the retransmit timeout count for soft mounts to the specified value. 326.It Cm retrycnt Ns = Ns Aq Ar count 327Set the mount retry count to the specified value. 328The default is a retry count of zero, which means to keep retrying 329forever. 330There is a 60 second delay between each attempt. 331.It Cm rsize Ns = Ns Aq Ar value 332Set the read data size to the specified value. 333It should normally be a power of 2 greater than or equal to 1024. 334This should be used for UDP mounts when the 335.Dq "fragments dropped due to timeout" 336value is getting large while actively using a mount point. 337(Use 338.Xr netstat 1 339with the 340.Fl s 341option to see what the 342.Dq "fragments dropped due to timeout" 343value is.) 344.It Cm sec Ns = Ns Aq Ar flavor 345This option specifies what security flavor should be used for the mount. 346Currently, they are: 347.Bd -literal 348krb5 - Use KerberosV authentication 349krb5i - Use KerberosV authentication and 350 apply integrity checksums to RPCs 351krb5p - Use KerberosV authentication and 352 encrypt the RPC data 353sys - The default AUTH_SYS, which uses a 354 uid + gid list authenticator 355.Ed 356.It Cm soft 357A soft mount, which implies that file system calls will fail 358after 359.Ar retrycnt 360round trip timeout intervals. 361.It Cm tcp 362Use TCP transport. 363This is the default option, as it provides for increased reliability on both 364LAN and WAN configurations compared to UDP. 365Some old NFS servers do not support this method; UDP mounts may be required 366for interoperability. 367.It Cm timeout Ns = Ns Aq Ar value 368Set the initial retransmit timeout to the specified value, 369expressed in tenths of a second. 370May be useful for fine tuning UDP mounts over internetworks 371with high packet loss rates or an overloaded server. 372Try increasing the interval if 373.Xr nfsstat 1 374shows high retransmit rates while the file system is active or reducing the 375value if there is a low retransmit rate but long response delay observed. 376(Normally, the 377.Cm dumbtimer 378option should be specified when using this option to manually 379tune the timeout 380interval.) 381.It Cm timeo Ns = Ns Aq Ar value 382Alias for 383.Cm timeout . 384.It Cm udp 385Use UDP transport. 386.It Cm vers Ns = Ns Aq Ar vers_number 387Use the specified version number for NFS requests. 388See the 389.Cm nfsv2 , 390.Cm nfsv3 , 391and 392.Cm nfsv4 393options for details. 394.It Cm wcommitsize Ns = Ns Aq Ar value 395Set the maximum pending write commit size to the specified value. 396This determines the maximum amount of pending write data that the NFS 397client is willing to cache for each file. 398.It Cm wsize Ns = Ns Aq Ar value 399Set the write data size to the specified value. 400Ditto the comments w.r.t.\& the 401.Cm rsize 402option, but using the 403.Dq "fragments dropped due to timeout" 404value on the server instead of the client. 405Note that both the 406.Cm rsize 407and 408.Cm wsize 409options should only be used as a last ditch effort at improving performance 410when mounting servers that do not support TCP mounts. 411.El 412.El 413.Sh COMPATIBILITY 414The following command line flags are equivalent to 415.Fl o 416named options and are supported for compatibility with older 417installations. 418.Bl -tag -width indent 419.It Fl 2 420Same as 421.Fl o Cm nfsv2 422.It Fl 3 423Same as 424.Fl o Cm nfsv3 425.It Fl D 426Same as 427.Fl o Cm deadthresh 428.It Fl I 429Same as 430.Fl o Cm readdirsize Ns = Ns Aq Ar value 431.It Fl L 432Same as 433.Fl o Cm nolockd 434.It Fl N 435Same as 436.Fl o Cm noresvport 437.It Fl P 438Use a reserved socket port number. 439This flag is obsolete, and only retained for compatibility reasons. 440(For the rare case where the client has a trusted root account 441but untrustworthy users and the network cables are in secure areas this does 442help, but for normal desktop clients this does not apply.) 443.It Fl R 444Same as 445.Fl o Cm retrycnt Ns = Ns Aq Ar value 446.It Fl T 447Same as 448.Fl o Cm tcp 449.It Fl U 450Same as 451.Fl o Cm mntudp 452.It Fl a 453Same as 454.Fl o Cm readahead Ns = Ns Aq Ar value 455.It Fl b 456Same as 457.Fl o Cm bg 458.It Fl c 459Same as 460.Fl o Cm noconn 461.It Fl d 462Same as 463.Fl o Cm dumbtimer 464.It Fl g 465Same as 466.Fl o Cm maxgroups 467.It Fl i 468Same as 469.Fl o Cm intr 470.It Fl l 471Same as 472.Fl o Cm rdirplus 473.It Fl r 474Same as 475.Fl o Cm rsize Ns = Ns Aq Ar value 476.It Fl s 477Same as 478.Fl o Cm soft 479.It Fl t 480Same as 481.Fl o Cm retransmit Ns = Ns Aq Ar value 482.It Fl w 483Same as 484.Fl o Cm wsize Ns = Ns Aq Ar value 485.It Fl x 486Same as 487.Fl o Cm retrans Ns = Ns Aq Ar value 488.El 489.Pp 490The following 491.Fl o 492named options are equivalent to other 493.Fl o 494named options and are supported for compatibility with other 495operating systems (e.g., Linux, Solaris, and OSX) to ease usage of 496.Xr autofs 5 497support. 498.Bl -tag -width indent 499.It Fl o Cm vers Ns = Ns 2 500Same as 501.Fl o Cm nfsv2 502.It Fl o Cm vers Ns = Ns 3 503Same as 504.Fl o Cm nfsv3 505.It Fl o Cm vers Ns = Ns 4 506Same as 507.Fl o Cm nfsv4 508.El 509.Sh SEE ALSO 510.Xr nmount 2 , 511.Xr unmount 2 , 512.Xr nfsv4 4 , 513.Xr fstab 5 , 514.Xr gssd 8 , 515.Xr mount 8 , 516.Xr nfsd 8 , 517.Xr nfsiod 8 , 518.Xr showmount 8 519.Sh HISTORY 520A version of the 521.Nm 522utility appeared in 523.Bx 4.4 . 524.Sh BUGS 525Since nfsv4 performs open/lock operations that have their ordering strictly 526enforced by the server, the options 527.Cm intr 528and 529.Cm soft 530cannot be safely used. 531.Cm hard 532nfsv4 mounts are strongly recommended. 533