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 December 14, 2019 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 . 62For NFSv2 and NFSv3, 63it implements the mount protocol as described in RFC 1094, Appendix A and 64RFC 1813, Appendix I. 65For NFSv4, it uses the NFSv4 protocol as described in RFC 7530, RFC 5661 and 66RFC 7862. 67.Pp 68By default, 69.Nm 70keeps retrying until the mount succeeds. 71This behaviour is intended for file systems listed in 72.Xr fstab 5 73that are critical to the boot process. 74For non-critical file systems, the 75.Cm bg 76and 77.Cm retrycnt 78options provide mechanisms to prevent the boot process from hanging 79if the server is unavailable. 80.Pp 81If the server becomes unresponsive while an NFS file system is 82mounted, any new or outstanding file operations on that file system 83will hang uninterruptibly until the server comes back. 84To modify this default behaviour, see the 85.Cm intr 86and 87.Cm soft 88options. 89.Pp 90The options are: 91.Bl -tag -width indent 92.It Fl o 93Options are specified with a 94.Fl o 95flag followed by a comma separated string of options. 96See the 97.Xr mount 8 98man page for possible options and their meanings. 99The following NFS specific options are also available: 100.Bl -tag -width indent 101.It Cm acregmin Ns = Ns Aq Ar seconds 102.It Cm acregmax Ns = Ns Aq Ar seconds 103.It Cm acdirmin Ns = Ns Aq Ar seconds 104.It Cm acdirmax Ns = Ns Aq Ar seconds 105When attributes of files are cached, a timeout calculated to determine 106whether a given cache entry has expired. 107These four values determine the upper and lower bounds of the timeouts for 108.Dq directory 109attributes and 110.Dq regular 111(ie: everything else). 112The default values are 3 -> 60 seconds 113for regular files, and 30 -> 60 seconds for directories. 114The algorithm to calculate the timeout is based on the age of the file. 115The older the file, 116the longer the cache is considered valid, subject to the limits above. 117.It Cm actimeo Ns = Ns Aq Ar seconds 118Set four cache timeouts above to specified value. 119.It Cm allgssname 120This option can be used along with 121.Fl o Cm gssname 122to specify that all operations should use the host-based initiator 123credential. 124This may be used for clients that run system daemons that need to 125access files on the NFSv4 mounted volume. 126.It Cm bg 127If an initial attempt to contact the server fails, fork off a child to keep 128trying the mount in the background. 129Useful for 130.Xr fstab 5 , 131where the file system mount is not critical to multiuser operation. 132.It Cm deadthresh Ns = Ns Aq Ar value 133Set the 134.Dq "dead server threshold" 135to the specified number of round trip timeout intervals before a 136.Dq "server not responding" 137message is displayed. 138.It Cm dumbtimer 139Turn off the dynamic retransmit timeout estimator. 140This may be useful for UDP mounts that exhibit high retry rates, 141since it is possible that the dynamically estimated timeout interval is too 142short. 143.It Cm fg 144Same as not specifying 145.Cm bg . 146.It Cm gssname Ns = Ns Aq Ar service-principal-name 147This option can be used with the KerberosV security flavors for NFSv4 mounts 148to specify the 149.Dq "service-principal-name" 150of a host-based entry in the default 151keytab file that is used for system operations. 152It allows the mount to be performed by 153.Dq "root" 154and avoids problems with 155cached credentials for the system operations expiring. 156The 157.Dq "service-prinicpal-name" 158should be specified without instance or domain and is typically 159.Dq "host" , 160.Dq "nfs" 161or 162.Dq "root" . 163.It Cm hard 164Same as not specifying 165.Cm soft . 166.It Cm intr 167Make the mount interruptible, which implies that file system calls that 168are delayed due to an unresponsive server will fail with EINTR when a 169termination signal is posted for the process. 170.It Cm maxgroups Ns = Ns Aq Ar value 171Set the maximum size of the group list for the credentials to the 172specified value. 173This should be used for mounts on old servers that cannot handle a 174group list size of 16, as specified in RFC 1057. 175Try 8, if users in a lot of groups cannot get response from the mount 176point. 177.It Cm mntudp 178Force the mount protocol to use UDP transport, even for TCP NFS mounts. 179(Necessary for some old 180.Bx 181servers.) 182.It Cm nametimeo Ns = Ns Aq Ar value 183Override the default of NFS_DEFAULT_NAMETIMEO for the timeout (in seconds) 184for positive name cache entries. 185If this is set to 0 it disables positive name caching for the mount point. 186.It Cm negnametimeo Ns = Ns Aq Ar value 187Override the default of NFS_DEFAULT_NEGNAMETIMEO for the timeout (in seconds) 188for negative name cache entries. 189If this is set to 0 it disables negative name caching for the mount point. 190.It Cm nfsv2 191Use the NFS Version 2 protocol (the default is to try version 3 first 192then version 2). 193Note that NFS version 2 has a file size limit of 2 gigabytes. 194.It Cm nfsv3 195Use the NFS Version 3 protocol. 196.It Cm nfsv4 197Use the NFS Version 4 protocol. 198This option will force the mount to use 199TCP transport. 200.It Cm minorversion Ns = Ns Aq Ar value 201Override the default of 0 for the minor version of the NFS Version 4 protocol. 202The minor versions other than 0 currently supported are 1 and 2. 203This option is only meaningful when used with the 204.Cm nfsv4 205option. 206.It Cm oneopenown 207Make a minor version 1 or 2 of the NFS Version 4 protocol mount use a single 208OpenOwner for all Opens. 209This may be useful for a server with a very low limit on OpenOwners, such as 210AmazonEFS. 211It ca only be used with an NFSv4.1 or NFSv4.2 mount. 212It may not work correctly when Delegations are being issued by a server, 213but note that the AmazonEFS server does not issued delegations at this time. 214.It Cm pnfs 215Enable support for parallel NFS (pNFS) for minor version 1 or 2 of the 216NFS Version 4 protocol. 217This option is only meaningful when used with the 218.Cm minorversion 219option. 220.It Cm noac 221Disable attribute caching. 222.It Cm noconn 223For UDP mount points, do not do a 224.Xr connect 2 . 225This must be used if the server does not reply to requests from the standard 226NFS port number 2049 or replies to requests using a different IP address 227(which can occur if the server is multi-homed). 228Setting the 229.Va vfs.nfs.nfs_ip_paranoia 230sysctl to 0 will make this option the default. 231.It Cm nocto 232Normally, NFS clients maintain the close-to-open cache coherency. 233This works by flushing at close time and checking at open time. 234Checking at open time is implemented by getting attributes from 235the server and purging the data cache if they do not match 236attributes cached by the client. 237.Pp 238This option disables checking at open time. 239It may improve performance for read-only mounts, 240but should only be used if the data on the server changes rarely. 241Be sure to understand the consequences before enabling this option. 242.It Cm noinet4 , noinet6 243Disables 244.Dv AF_INET 245or 246.Dv AF_INET6 247connections. 248Useful for hosts that have 249both an A record and an AAAA record for the same name. 250.It Cm nolockd 251Do 252.Em not 253forward 254.Xr fcntl 2 255locks over the wire via the NLM protocol for NFSv3 mounts. 256All locks will be local and not seen by the server 257and likewise not seen by other NFS clients for NFSv3 mounts. 258This removes the need to run the 259.Xr rpcbind 8 260service and the 261.Xr rpc.statd 8 262and 263.Xr rpc.lockd 8 264servers on the client. 265Note that this option will only be honored when performing the 266initial mount, it will be silently ignored if used while updating 267the mount options. 268Also, note that NFSv4 mounts do not use these daemons and handle locks over the 269wire in the NFSv4 protocol. 270As such, this option is meaningless for NFSv4 mounts. 271.It Cm noncontigwr 272This mount option allows the NFS client to 273combine non-contiguous byte ranges being written 274such that the dirty byte range becomes a superset of the bytes 275that are dirty. 276This reduces the number of writes significantly for software 277builds. 278The merging of byte ranges is not done if the file has been file 279locked, since most applications modifying a file from multiple 280clients will use file locking. 281As such, this option could result in a corrupted file for the 282rare case of an application modifying the file from multiple 283clients concurrently without using file locking. 284.It Cm principal 285For the RPCSEC_GSS security flavors, such as krb5, krb5i and krb5p, 286this option sets the name of the host based principal name expected 287by the server. 288This option overrides the default, which will be ``nfs@<server-fqdn>'' 289and should normally be sufficient. 290.It Cm noresvport 291Do 292.Em not 293use a reserved socket port number (see below). 294.It Cm port Ns = Ns Aq Ar port_number 295Use specified port number for NFS requests. 296The default is to query the portmapper for the NFS port. 297.It Cm proto Ns = Ns Aq Ar protocol 298Specify transport protocol version to use. 299Currently, they are: 300.Bd -literal 301udp - Use UDP over IPv4 302tcp - Use TCP over IPv4 303udp6 - Use UDP over IPv6 304tcp6 - Use TCP over IPv6 305.Ed 306.It Cm rdirplus 307Used with NFSV3 to specify that the \fBReaddirPlus\fR RPC should 308be used. 309For NFSV4, setting this option has a similar effect, in that it will make 310the Readdir Operation get more attributes. 311This option reduces RPC traffic for cases such as 312.Dq "ls -l" , 313but tends to flood the attribute and name caches with prefetched entries. 314Try this option and see whether performance improves or degrades. 315Probably 316most useful for client to server network interconnects with a large bandwidth 317times delay product. 318.It Cm readahead Ns = Ns Aq Ar value 319Set the read-ahead count to the specified value. 320This may be in the range of 0 - 4, and determines how many blocks 321will be read ahead when a large file is being read sequentially. 322Trying a value greater than 1 for this is suggested for 323mounts with a large bandwidth * delay product. 324.It Cm readdirsize Ns = Ns Aq Ar value 325Set the readdir read size to the specified value. 326The value should normally 327be a multiple of 328.Dv DIRBLKSIZ 329that is <= the read size for the mount. 330.It Cm resvport 331Use a reserved socket port number. 332This flag is obsolete, and only retained for compatibility reasons. 333Reserved port numbers are used by default now. 334(For the rare case where the client has a trusted root account 335but untrustworthy users and the network cables are in secure areas this does 336help, but for normal desktop clients this does not apply.) 337.It Cm retrans Ns = Ns Aq Ar value 338Set the retransmit timeout count for soft mounts to the specified value. 339.It Cm retrycnt Ns = Ns Aq Ar count 340Set the mount retry count to the specified value. 341The default is a retry count of zero, which means to keep retrying 342forever. 343There is a 60 second delay between each attempt. 344.It Cm rsize Ns = Ns Aq Ar value 345Set the read data size to the specified value. 346It should normally be a power of 2 greater than or equal to 1024. 347This should be used for UDP mounts when the 348.Dq "fragments dropped due to timeout" 349value is getting large while actively using a mount point. 350(Use 351.Xr netstat 1 352with the 353.Fl s 354option to see what the 355.Dq "fragments dropped due to timeout" 356value is.) 357.It Cm sec Ns = Ns Aq Ar flavor 358This option specifies what security flavor should be used for the mount. 359Currently, they are: 360.Bd -literal 361krb5 - Use KerberosV authentication 362krb5i - Use KerberosV authentication and 363 apply integrity checksums to RPCs 364krb5p - Use KerberosV authentication and 365 encrypt the RPC data 366sys - The default AUTH_SYS, which uses a 367 uid + gid list authenticator 368.Ed 369.It Cm soft 370A soft mount, which implies that file system calls will fail 371after 372.Ar retrycnt 373round trip timeout intervals. 374.It Cm tcp 375Use TCP transport. 376This is the default option, as it provides for increased reliability on both 377LAN and WAN configurations compared to UDP. 378Some old NFS servers do not support this method; UDP mounts may be required 379for interoperability. 380.It Cm timeout Ns = Ns Aq Ar value 381Set the initial retransmit timeout to the specified value, 382expressed in tenths of a second. 383May be useful for fine tuning UDP mounts over internetworks 384with high packet loss rates or an overloaded server. 385Try increasing the interval if 386.Xr nfsstat 1 387shows high retransmit rates while the file system is active or reducing the 388value if there is a low retransmit rate but long response delay observed. 389(Normally, the 390.Cm dumbtimer 391option should be specified when using this option to manually 392tune the timeout 393interval.) 394.It Cm timeo Ns = Ns Aq Ar value 395Alias for 396.Cm timeout . 397.It Cm udp 398Use UDP transport. 399.It Cm vers Ns = Ns Aq Ar vers_number 400Use the specified version number for NFS requests. 401See the 402.Cm nfsv2 , 403.Cm nfsv3 , 404and 405.Cm nfsv4 406options for details. 407.It Cm wcommitsize Ns = Ns Aq Ar value 408Set the maximum pending write commit size to the specified value. 409This determines the maximum amount of pending write data that the NFS 410client is willing to cache for each file. 411.It Cm wsize Ns = Ns Aq Ar value 412Set the write data size to the specified value. 413Ditto the comments w.r.t.\& the 414.Cm rsize 415option, but using the 416.Dq "fragments dropped due to timeout" 417value on the server instead of the client. 418Note that both the 419.Cm rsize 420and 421.Cm wsize 422options should only be used as a last ditch effort at improving performance 423when mounting servers that do not support TCP mounts. 424.El 425.El 426.Sh COMPATIBILITY 427The following command line flags are equivalent to 428.Fl o 429named options and are supported for compatibility with older 430installations. 431.Bl -tag -width indent 432.It Fl 2 433Same as 434.Fl o Cm nfsv2 435.It Fl 3 436Same as 437.Fl o Cm nfsv3 438.It Fl D 439Same as 440.Fl o Cm deadthresh 441.It Fl I 442Same as 443.Fl o Cm readdirsize Ns = Ns Aq Ar value 444.It Fl L 445Same as 446.Fl o Cm nolockd 447.It Fl N 448Same as 449.Fl o Cm noresvport 450.It Fl P 451Use a reserved socket port number. 452This flag is obsolete, and only retained for compatibility reasons. 453(For the rare case where the client has a trusted root account 454but untrustworthy users and the network cables are in secure areas this does 455help, but for normal desktop clients this does not apply.) 456.It Fl R 457Same as 458.Fl o Cm retrycnt Ns = Ns Aq Ar value 459.It Fl T 460Same as 461.Fl o Cm tcp 462.It Fl U 463Same as 464.Fl o Cm mntudp 465.It Fl a 466Same as 467.Fl o Cm readahead Ns = Ns Aq Ar value 468.It Fl b 469Same as 470.Fl o Cm bg 471.It Fl c 472Same as 473.Fl o Cm noconn 474.It Fl d 475Same as 476.Fl o Cm dumbtimer 477.It Fl g 478Same as 479.Fl o Cm maxgroups 480.It Fl i 481Same as 482.Fl o Cm intr 483.It Fl l 484Same as 485.Fl o Cm rdirplus 486.It Fl r 487Same as 488.Fl o Cm rsize Ns = Ns Aq Ar value 489.It Fl s 490Same as 491.Fl o Cm soft 492.It Fl t 493Same as 494.Fl o Cm retransmit Ns = Ns Aq Ar value 495.It Fl w 496Same as 497.Fl o Cm wsize Ns = Ns Aq Ar value 498.It Fl x 499Same as 500.Fl o Cm retrans Ns = Ns Aq Ar value 501.El 502.Pp 503The following 504.Fl o 505named options are equivalent to other 506.Fl o 507named options and are supported for compatibility with other 508operating systems (e.g., Linux, Solaris, and OSX) to ease usage of 509.Xr autofs 5 510support. 511.Bl -tag -width indent 512.It Fl o Cm vers Ns = Ns 2 513Same as 514.Fl o Cm nfsv2 515.It Fl o Cm vers Ns = Ns 3 516Same as 517.Fl o Cm nfsv3 518.It Fl o Cm vers Ns = Ns 4 519Same as 520.Fl o Cm nfsv4 521.El 522.Sh SEE ALSO 523.Xr nmount 2 , 524.Xr unmount 2 , 525.Xr nfsv4 4 , 526.Xr fstab 5 , 527.Xr gssd 8 , 528.Xr mount 8 , 529.Xr nfsd 8 , 530.Xr nfsiod 8 , 531.Xr showmount 8 532.Sh HISTORY 533A version of the 534.Nm 535utility appeared in 536.Bx 4.4 . 537.Sh BUGS 538Since nfsv4 performs open/lock operations that have their ordering strictly 539enforced by the server, the options 540.Cm intr 541and 542.Cm soft 543cannot be safely used. 544.Cm hard 545nfsv4 mounts are strongly recommended. 546