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 November 30, 2020 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" , 163although the form 164.Sm off 165.Aq Ar service 166@ 167.Aq Ar fqdn 168.Sm on 169can also be used if the local system's 170.Xr gethostname 3 171value does not match the host-based principal in the keytab. 172.It Cm hard 173Same as not specifying 174.Cm soft . 175.It Cm intr 176Make the mount interruptible, which implies that file system calls that 177are delayed due to an unresponsive server will fail with EINTR when a 178termination signal is posted for the process. 179.It Cm maxgroups Ns = Ns Aq Ar value 180Set the maximum size of the group list for the credentials to the 181specified value. 182This should be used for mounts on old servers that cannot handle a 183group list size of 16, as specified in RFC 1057. 184Try 8, if users in a lot of groups cannot get response from the mount 185point. 186.It Cm mntudp 187Force the mount protocol to use UDP transport, even for TCP NFS mounts. 188(Necessary for some old 189.Bx 190servers.) 191.It Cm nametimeo Ns = Ns Aq Ar value 192Override the default of NFS_DEFAULT_NAMETIMEO for the timeout (in seconds) 193for positive name cache entries. 194If this is set to 0 it disables positive name caching for the mount point. 195.It Cm negnametimeo Ns = Ns Aq Ar value 196Override the default of NFS_DEFAULT_NEGNAMETIMEO for the timeout (in seconds) 197for negative name cache entries. 198If this is set to 0 it disables negative name caching for the mount point. 199.It Cm nfsv2 200Use the NFS Version 2 protocol (the default is to try version 3 first 201then version 2). 202Note that NFS version 2 has a file size limit of 2 gigabytes. 203.It Cm nfsv3 204Use the NFS Version 3 protocol. 205.It Cm nfsv4 206Use the NFS Version 4 protocol. 207This option will force the mount to use 208TCP transport. 209.It Cm minorversion Ns = Ns Aq Ar value 210Override the default of 0 for the minor version of the NFS Version 4 protocol. 211The minor versions other than 0 currently supported are 1 and 2. 212This option is only meaningful when used with the 213.Cm nfsv4 214option. 215.It Cm oneopenown 216Make a minor version 1 or 2 of the NFS Version 4 protocol mount use a single 217OpenOwner for all Opens. 218This may be useful for a server with a very low limit on OpenOwners, such as 219AmazonEFS. 220This option cannot be used for an NFS Version 4, minor version 0 mount. 221As such, this option requires the 222.Cm minorversion 223option be specified with a value of 1 for AmazonEFS, because AmazonEFS does 224not support minor version 2 at this time. 225It may not work correctly when Delegations are being issued by a server, 226but note that the AmazonEFS server does not issued delegations at this time. 227This option is only meaningful when used with the 228.Cm nfsv4 229and 230.Cm minorversion 231options. 232.It Cm pnfs 233Enable support for parallel NFS (pNFS) for minor version 1 or 2 of the 234NFS Version 4 protocol. 235This option is only meaningful when used with the 236.Cm minorversion 237option. 238.It Cm noac 239Disable attribute caching. 240.It Cm noconn 241For UDP mount points, do not do a 242.Xr connect 2 . 243This must be used if the server does not reply to requests from the standard 244NFS port number 2049 or replies to requests using a different IP address 245(which can occur if the server is multi-homed). 246Setting the 247.Va vfs.nfs.nfs_ip_paranoia 248sysctl to 0 will make this option the default. 249.It Cm nocto 250Normally, NFS clients maintain the close-to-open cache coherency. 251This works by flushing at close time and checking at open time. 252Checking at open time is implemented by getting attributes from 253the server and purging the data cache if they do not match 254attributes cached by the client. 255.Pp 256This option disables checking at open time. 257It may improve performance for read-only mounts, 258but should only be used if the data on the server changes rarely. 259Be sure to understand the consequences before enabling this option. 260.It Cm noinet4 , noinet6 261Disables 262.Dv AF_INET 263or 264.Dv AF_INET6 265connections. 266Useful for hosts that have 267both an A record and an AAAA record for the same name. 268.It Cm nolockd 269Do 270.Em not 271forward 272.Xr fcntl 2 273locks over the wire via the NLM protocol for NFSv3 mounts. 274All locks will be local and not seen by the server 275and likewise not seen by other NFS clients for NFSv3 mounts. 276This removes the need to run the 277.Xr rpcbind 8 278service and the 279.Xr rpc.statd 8 280and 281.Xr rpc.lockd 8 282servers on the client. 283Note that this option will only be honored when performing the 284initial mount, it will be silently ignored if used while updating 285the mount options. 286Also, note that NFSv4 mounts do not use these daemons and handle locks over the 287wire in the NFSv4 protocol. 288As such, this option is meaningless for NFSv4 mounts. 289.It Cm noncontigwr 290This mount option allows the NFS client to 291combine non-contiguous byte ranges being written 292such that the dirty byte range becomes a superset of the bytes 293that are dirty. 294This reduces the number of writes significantly for software 295builds. 296The merging of byte ranges is not done if the file has been file 297locked, since most applications modifying a file from multiple 298clients will use file locking. 299As such, this option could result in a corrupted file for the 300rare case of an application modifying the file from multiple 301clients concurrently without using file locking. 302.It Cm principal 303For the RPCSEC_GSS security flavors, such as krb5, krb5i and krb5p, 304this option sets the name of the host based principal name expected 305by the server. 306This option overrides the default, which will be ``nfs@<server-fqdn>'' 307and should normally be sufficient. 308.It Cm noresvport 309Do 310.Em not 311use a reserved socket port number (see below). 312.It Cm port Ns = Ns Aq Ar port_number 313Use specified port number for NFS requests. 314The default is to query the portmapper for the NFS port. 315.It Cm proto Ns = Ns Aq Ar protocol 316Specify transport protocol version to use. 317Currently, they are: 318.Bd -literal 319udp - Use UDP over IPv4 320tcp - Use TCP over IPv4 321udp6 - Use UDP over IPv6 322tcp6 - Use TCP over IPv6 323.Ed 324.It Cm rdirplus 325Used with NFSV3 to specify that the \fBReaddirPlus\fR RPC should 326be used. 327For NFSV4, setting this option has a similar effect, in that it will make 328the Readdir Operation get more attributes. 329This option reduces RPC traffic for cases such as 330.Dq "ls -l" , 331but tends to flood the attribute and name caches with prefetched entries. 332Try this option and see whether performance improves or degrades. 333Probably 334most useful for client to server network interconnects with a large bandwidth 335times delay product. 336.It Cm readahead Ns = Ns Aq Ar value 337Set the read-ahead count to the specified value. 338This may be in the range of 0 - 4, and determines how many blocks 339will be read ahead when a large file is being read sequentially. 340Trying a value greater than 1 for this is suggested for 341mounts with a large bandwidth * delay product. 342.It Cm readdirsize Ns = Ns Aq Ar value 343Set the readdir read size to the specified value. 344The value should normally 345be a multiple of 346.Dv DIRBLKSIZ 347that is <= the read size for the mount. 348.It Cm resvport 349Use a reserved socket port number. 350This flag is obsolete, and only retained for compatibility reasons. 351Reserved port numbers are used by default now. 352(For the rare case where the client has a trusted root account 353but untrustworthy users and the network cables are in secure areas this does 354help, but for normal desktop clients this does not apply.) 355.It Cm retrans Ns = Ns Aq Ar value 356Set the retransmit timeout count for soft mounts to the specified value. 357.It Cm retrycnt Ns = Ns Aq Ar count 358Set the mount retry count to the specified value. 359The default is a retry count of zero, which means to keep retrying 360forever. 361There is a 60 second delay between each attempt. 362.It Cm rsize Ns = Ns Aq Ar value 363Set the read data size to the specified value. 364It should normally be a power of 2 greater than or equal to 1024. 365This should be used for UDP mounts when the 366.Dq "fragments dropped due to timeout" 367value is getting large while actively using a mount point. 368(Use 369.Xr netstat 1 370with the 371.Fl s 372option to see what the 373.Dq "fragments dropped due to timeout" 374value is.) 375.It Cm sec Ns = Ns Aq Ar flavor 376This option specifies what security flavor should be used for the mount. 377Currently, they are: 378.Bd -literal 379krb5 - Use KerberosV authentication 380krb5i - Use KerberosV authentication and 381 apply integrity checksums to RPCs 382krb5p - Use KerberosV authentication and 383 encrypt the RPC data 384sys - The default AUTH_SYS, which uses a 385 uid + gid list authenticator 386.Ed 387.It Cm soft 388A soft mount, which implies that file system calls will fail 389after 390.Ar retrycnt 391round trip timeout intervals. 392.It Cm tcp 393Use TCP transport. 394This is the default option, as it provides for increased reliability on both 395LAN and WAN configurations compared to UDP. 396Some old NFS servers do not support this method; UDP mounts may be required 397for interoperability. 398.It Cm timeout Ns = Ns Aq Ar value 399Set the initial retransmit timeout to the specified value, 400expressed in tenths of a second. 401May be useful for fine tuning UDP mounts over internetworks 402with high packet loss rates or an overloaded server. 403Try increasing the interval if 404.Xr nfsstat 1 405shows high retransmit rates while the file system is active or reducing the 406value if there is a low retransmit rate but long response delay observed. 407(Normally, the 408.Cm dumbtimer 409option should be specified when using this option to manually 410tune the timeout 411interval.) 412.It Cm timeo Ns = Ns Aq Ar value 413Alias for 414.Cm timeout . 415.It Cm tls 416This option specifies that the connection to the server must use TLS 417per RFC NNNN. 418TLS is only supported for TCP connections and the 419.Xr rpc.tlsclntd 8 420daemon must be running for an NFS over TCP connection to use TLS. 421.It Cm udp 422Use UDP transport. 423.It Cm vers Ns = Ns Aq Ar vers_number 424Use the specified version number for NFS requests. 425See the 426.Cm nfsv2 , 427.Cm nfsv3 , 428and 429.Cm nfsv4 430options for details. 431.It Cm wcommitsize Ns = Ns Aq Ar value 432Set the maximum pending write commit size to the specified value. 433This determines the maximum amount of pending write data that the NFS 434client is willing to cache for each file. 435.It Cm wsize Ns = Ns Aq Ar value 436Set the write data size to the specified value. 437Ditto the comments w.r.t.\& the 438.Cm rsize 439option, but using the 440.Dq "fragments dropped due to timeout" 441value on the server instead of the client. 442Note that both the 443.Cm rsize 444and 445.Cm wsize 446options should only be used as a last ditch effort at improving performance 447when mounting servers that do not support TCP mounts. 448.El 449.El 450.Sh COMPATIBILITY 451The following command line flags are equivalent to 452.Fl o 453named options and are supported for compatibility with older 454installations. 455.Bl -tag -width indent 456.It Fl 2 457Same as 458.Fl o Cm nfsv2 459.It Fl 3 460Same as 461.Fl o Cm nfsv3 462.It Fl D 463Same as 464.Fl o Cm deadthresh 465.It Fl I 466Same as 467.Fl o Cm readdirsize Ns = Ns Aq Ar value 468.It Fl L 469Same as 470.Fl o Cm nolockd 471.It Fl N 472Same as 473.Fl o Cm noresvport 474.It Fl P 475Use a reserved socket port number. 476This flag is obsolete, and only retained for compatibility reasons. 477(For the rare case where the client has a trusted root account 478but untrustworthy users and the network cables are in secure areas this does 479help, but for normal desktop clients this does not apply.) 480.It Fl R 481Same as 482.Fl o Cm retrycnt Ns = Ns Aq Ar value 483.It Fl T 484Same as 485.Fl o Cm tcp 486.It Fl U 487Same as 488.Fl o Cm mntudp 489.It Fl a 490Same as 491.Fl o Cm readahead Ns = Ns Aq Ar value 492.It Fl b 493Same as 494.Fl o Cm bg 495.It Fl c 496Same as 497.Fl o Cm noconn 498.It Fl d 499Same as 500.Fl o Cm dumbtimer 501.It Fl g 502Same as 503.Fl o Cm maxgroups 504.It Fl i 505Same as 506.Fl o Cm intr 507.It Fl l 508Same as 509.Fl o Cm rdirplus 510.It Fl r 511Same as 512.Fl o Cm rsize Ns = Ns Aq Ar value 513.It Fl s 514Same as 515.Fl o Cm soft 516.It Fl t 517Same as 518.Fl o Cm retransmit Ns = Ns Aq Ar value 519.It Fl w 520Same as 521.Fl o Cm wsize Ns = Ns Aq Ar value 522.It Fl x 523Same as 524.Fl o Cm retrans Ns = Ns Aq Ar value 525.El 526.Pp 527The following 528.Fl o 529named options are equivalent to other 530.Fl o 531named options and are supported for compatibility with other 532operating systems (e.g., Linux, Solaris, and OSX) to ease usage of 533.Xr autofs 5 534support. 535.Bl -tag -width indent 536.It Fl o Cm vers Ns = Ns 2 537Same as 538.Fl o Cm nfsv2 539.It Fl o Cm vers Ns = Ns 3 540Same as 541.Fl o Cm nfsv3 542.It Fl o Cm vers Ns = Ns 4 543Same as 544.Fl o Cm nfsv4 545.El 546.Sh SEE ALSO 547.Xr nmount 2 , 548.Xr unmount 2 , 549.Xr nfsv4 4 , 550.Xr fstab 5 , 551.Xr gssd 8 , 552.Xr mount 8 , 553.Xr nfsd 8 , 554.Xr nfsiod 8 , 555.Xr rpc.tlsclntd 8 , 556.Xr showmount 8 557.Sh HISTORY 558A version of the 559.Nm 560utility appeared in 561.Bx 4.4 . 562.Sh BUGS 563Since nfsv4 performs open/lock operations that have their ordering strictly 564enforced by the server, the options 565.Cm intr 566and 567.Cm soft 568cannot be safely used. 569.Cm hard 570nfsv4 mounts are strongly recommended. 571