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 April 13, 2017 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 oneopenown 205Make a minor version 1 of the NFS Version 4 protocol mount use a single OpenOwner 206for all Opens. 207This may be useful for a server with a very low limit on OpenOwners, such as 208AmazonEFS. 209It can only be used with an NFSv4.1 mount. 210It may not work correctly when Delegations are being issued by a server, 211but note that the AmazonEFS server does not issued delegations at this time. 212.It Cm pnfs 213Enable support for parallel NFS (pNFS) for minor version 1 of the 214NFS Version 4 protocol. 215This option is only meaningful when used with the 216.Cm minorversion 217option. 218.It Cm noac 219Disable attribute caching. 220.It Cm noconn 221For UDP mount points, do not do a 222.Xr connect 2 . 223This must be used if the server does not reply to requests from the standard 224NFS port number 2049 or replies to requests using a different IP address 225(which can occur if the server is multi-homed). 226Setting the 227.Va vfs.nfs.nfs_ip_paranoia 228sysctl to 0 will make this option the default. 229.It Cm nocto 230Normally, NFS clients maintain the close-to-open cache coherency. 231This works by flushing at close time and checking at open time. 232Checking at open time is implemented by getting attributes from 233the server and purging the data cache if they do not match 234attributes cached by the client. 235.Pp 236This option disables checking at open time. 237It may improve performance for read-only mounts, 238but should only be used if the data on the server changes rarely. 239Be sure to understand the consequences before enabling this option. 240.It Cm noinet4 , noinet6 241Disables 242.Dv AF_INET 243or 244.Dv AF_INET6 245connections. 246Useful for hosts that have 247both an A record and an AAAA record for the same name. 248.It Cm nolockd 249Do 250.Em not 251forward 252.Xr fcntl 2 253locks over the wire. 254All locks will be local and not seen by the server 255and likewise not seen by other NFS clients. 256This removes the need to run the 257.Xr rpcbind 8 258service and the 259.Xr rpc.statd 8 260and 261.Xr rpc.lockd 8 262servers on the client. 263Note that this option will only be honored when performing the 264initial mount, it will be silently ignored if used while updating 265the mount options. 266.It Cm noncontigwr 267This mount option allows the NFS client to 268combine non-contiguous byte ranges being written 269such that the dirty byte range becomes a superset of the bytes 270that are dirty. 271This reduces the number of writes significantly for software 272builds. 273The merging of byte ranges is not done if the file has been file 274locked, since most applications modifying a file from multiple 275clients will use file locking. 276As such, this option could result in a corrupted file for the 277rare case of an application modifying the file from multiple 278clients concurrently without using file locking. 279.It Cm principal 280For the RPCSEC_GSS security flavors, such as krb5, krb5i and krb5p, 281this option sets the name of the host based principal name expected 282by the server. 283This option overrides the default, which will be ``nfs@<server-fqdn>'' 284and should normally be sufficient. 285.It Cm noresvport 286Do 287.Em not 288use a reserved socket port number (see below). 289.It Cm port Ns = Ns Aq Ar port_number 290Use specified port number for NFS requests. 291The default is to query the portmapper for the NFS port. 292.It Cm proto Ns = Ns Aq Ar protocol 293Specify transport protocol version to use. 294Currently, they are: 295.Bd -literal 296udp - Use UDP over IPv4 297tcp - Use TCP over IPv4 298udp6 - Use UDP over IPv6 299tcp6 - Use TCP over IPv6 300.Ed 301.It Cm rdirplus 302Used with NFSV3 to specify that the \fBReaddirPlus\fR RPC should 303be used. 304For NFSV4, setting this option has a similar effect, in that it will make 305the Readdir Operation get more attributes. 306This option reduces RPC traffic for cases such as 307.Dq "ls -l" , 308but tends to flood the attribute and name caches with prefetched entries. 309Try this option and see whether performance improves or degrades. 310Probably 311most useful for client to server network interconnects with a large bandwidth 312times delay product. 313.It Cm readahead Ns = Ns Aq Ar value 314Set the read-ahead count to the specified value. 315This may be in the range of 0 - 4, and determines how many blocks 316will be read ahead when a large file is being read sequentially. 317Trying a value greater than 1 for this is suggested for 318mounts with a large bandwidth * delay product. 319.It Cm readdirsize Ns = Ns Aq Ar value 320Set the readdir read size to the specified value. 321The value should normally 322be a multiple of 323.Dv DIRBLKSIZ 324that is <= the read size for the mount. 325.It Cm resvport 326Use a reserved socket port number. 327This flag is obsolete, and only retained for compatibility reasons. 328Reserved port numbers are used by default now. 329(For the rare case where the client has a trusted root account 330but untrustworthy users and the network cables are in secure areas this does 331help, but for normal desktop clients this does not apply.) 332.It Cm retrans Ns = Ns Aq Ar value 333Set the retransmit timeout count for soft mounts to the specified value. 334.It Cm retrycnt Ns = Ns Aq Ar count 335Set the mount retry count to the specified value. 336The default is a retry count of zero, which means to keep retrying 337forever. 338There is a 60 second delay between each attempt. 339.It Cm rsize Ns = Ns Aq Ar value 340Set the read data size to the specified value. 341It should normally be a power of 2 greater than or equal to 1024. 342This should be used for UDP mounts when the 343.Dq "fragments dropped due to timeout" 344value is getting large while actively using a mount point. 345(Use 346.Xr netstat 1 347with the 348.Fl s 349option to see what the 350.Dq "fragments dropped due to timeout" 351value is.) 352.It Cm sec Ns = Ns Aq Ar flavor 353This option specifies what security flavor should be used for the mount. 354Currently, they are: 355.Bd -literal 356krb5 - Use KerberosV authentication 357krb5i - Use KerberosV authentication and 358 apply integrity checksums to RPCs 359krb5p - Use KerberosV authentication and 360 encrypt the RPC data 361sys - The default AUTH_SYS, which uses a 362 uid + gid list authenticator 363.Ed 364.It Cm soft 365A soft mount, which implies that file system calls will fail 366after 367.Ar retrycnt 368round trip timeout intervals. 369.It Cm tcp 370Use TCP transport. 371This is the default option, as it provides for increased reliability on both 372LAN and WAN configurations compared to UDP. 373Some old NFS servers do not support this method; UDP mounts may be required 374for interoperability. 375.It Cm timeout Ns = Ns Aq Ar value 376Set the initial retransmit timeout to the specified value, 377expressed in tenths of a second. 378May be useful for fine tuning UDP mounts over internetworks 379with high packet loss rates or an overloaded server. 380Try increasing the interval if 381.Xr nfsstat 1 382shows high retransmit rates while the file system is active or reducing the 383value if there is a low retransmit rate but long response delay observed. 384(Normally, the 385.Cm dumbtimer 386option should be specified when using this option to manually 387tune the timeout 388interval.) 389.It Cm timeo Ns = Ns Aq Ar value 390Alias for 391.Cm timeout . 392.It Cm udp 393Use UDP transport. 394.It Cm vers Ns = Ns Aq Ar vers_number 395Use the specified version number for NFS requests. 396See the 397.Cm nfsv2 , 398.Cm nfsv3 , 399and 400.Cm nfsv4 401options for details. 402.It Cm wcommitsize Ns = Ns Aq Ar value 403Set the maximum pending write commit size to the specified value. 404This determines the maximum amount of pending write data that the NFS 405client is willing to cache for each file. 406.It Cm wsize Ns = Ns Aq Ar value 407Set the write data size to the specified value. 408Ditto the comments w.r.t.\& the 409.Cm rsize 410option, but using the 411.Dq "fragments dropped due to timeout" 412value on the server instead of the client. 413Note that both the 414.Cm rsize 415and 416.Cm wsize 417options should only be used as a last ditch effort at improving performance 418when mounting servers that do not support TCP mounts. 419.El 420.El 421.Sh COMPATIBILITY 422The following command line flags are equivalent to 423.Fl o 424named options and are supported for compatibility with older 425installations. 426.Bl -tag -width indent 427.It Fl 2 428Same as 429.Fl o Cm nfsv2 430.It Fl 3 431Same as 432.Fl o Cm nfsv3 433.It Fl D 434Same as 435.Fl o Cm deadthresh 436.It Fl I 437Same as 438.Fl o Cm readdirsize Ns = Ns Aq Ar value 439.It Fl L 440Same as 441.Fl o Cm nolockd 442.It Fl N 443Same as 444.Fl o Cm noresvport 445.It Fl P 446Use a reserved socket port number. 447This flag is obsolete, and only retained for compatibility reasons. 448(For the rare case where the client has a trusted root account 449but untrustworthy users and the network cables are in secure areas this does 450help, but for normal desktop clients this does not apply.) 451.It Fl R 452Same as 453.Fl o Cm retrycnt Ns = Ns Aq Ar value 454.It Fl T 455Same as 456.Fl o Cm tcp 457.It Fl U 458Same as 459.Fl o Cm mntudp 460.It Fl a 461Same as 462.Fl o Cm readahead Ns = Ns Aq Ar value 463.It Fl b 464Same as 465.Fl o Cm bg 466.It Fl c 467Same as 468.Fl o Cm noconn 469.It Fl d 470Same as 471.Fl o Cm dumbtimer 472.It Fl g 473Same as 474.Fl o Cm maxgroups 475.It Fl i 476Same as 477.Fl o Cm intr 478.It Fl l 479Same as 480.Fl o Cm rdirplus 481.It Fl r 482Same as 483.Fl o Cm rsize Ns = Ns Aq Ar value 484.It Fl s 485Same as 486.Fl o Cm soft 487.It Fl t 488Same as 489.Fl o Cm retransmit Ns = Ns Aq Ar value 490.It Fl w 491Same as 492.Fl o Cm wsize Ns = Ns Aq Ar value 493.It Fl x 494Same as 495.Fl o Cm retrans Ns = Ns Aq Ar value 496.El 497.Pp 498The following 499.Fl o 500named options are equivalent to other 501.Fl o 502named options and are supported for compatibility with other 503operating systems (e.g., Linux, Solaris, and OSX) to ease usage of 504.Xr autofs 5 505support. 506.Bl -tag -width indent 507.It Fl o Cm vers Ns = Ns 2 508Same as 509.Fl o Cm nfsv2 510.It Fl o Cm vers Ns = Ns 3 511Same as 512.Fl o Cm nfsv3 513.It Fl o Cm vers Ns = Ns 4 514Same as 515.Fl o Cm nfsv4 516.El 517.Sh SEE ALSO 518.Xr nmount 2 , 519.Xr unmount 2 , 520.Xr nfsv4 4 , 521.Xr fstab 5 , 522.Xr gssd 8 , 523.Xr mount 8 , 524.Xr nfsd 8 , 525.Xr nfsiod 8 , 526.Xr showmount 8 527.Sh HISTORY 528A version of the 529.Nm 530utility appeared in 531.Bx 4.4 . 532.Sh BUGS 533Since nfsv4 performs open/lock operations that have their ordering strictly 534enforced by the server, the options 535.Cm intr 536and 537.Cm soft 538cannot be safely used. 539.Cm hard 540nfsv4 mounts are strongly recommended. 541