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 July 10, 2021 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 nconnect Ns = Ns Aq Ar value 200Specify the number of TCP connections (1-16) to be used 201for an NFS Version 4, minor version 1 or 2 mount. 202Multiple TCP connections can provide more client to server network 203bandwidth for certain network configurations such as: 204.Bd -literal 205- Multiple network interfaces that are aggregated together. 206- A fast network interface that uses multiple queues. 207.Ed 208.sp 209The first TCP connection will be used for all RPCs that consist 210entirely of small RPC messages. 211The RPCs that can have large RPC messages (Read/Readdir/Write) are 212distributed over the additional TCP connections in a round robin 213fashion. 214This option will result in more IP port#s being used. 215This option requires the 216.Cm nfsv4 217option. 218.It Cm nfsv2 219Use the NFS Version 2 protocol (the default is to try version 3 first 220then version 2). 221Note that NFS version 2 has a file size limit of 2 gigabytes. 222.It Cm nfsv3 223Use the NFS Version 3 protocol. 224.It Cm nfsv4 225Use the NFS Version 4 protocol. 226This option will force the mount to use 227TCP transport. 228By default, the highest minor version of NFS Version 4 that is 229supported by the NFS Version 4 server will be used. 230See the 231.Cm minorversion 232option. 233.It Cm minorversion Ns = Ns Aq Ar value 234Use the specified minor version for a NFS Version 4 mount, 235overriding the default. 236The minor versions supported are 0, 1, and 2. 237This option is only meaningful when used with the 238.Cm nfsv4 239option. 240.It Cm oneopenown 241Make a minor version 1 or 2 of the NFS Version 4 protocol mount use a single 242OpenOwner for all Opens. 243This may be useful for a server with a very low limit on OpenOwners, such as 244AmazonEFS. 245It may be required when an accumulation of NFS version 4 Opens occurs, 246as indicated by the 247.Dq Opens 248count displayed by 249.Xr nfsstat 1 250with the 251.Fl c 252and 253.Fl E 254command-line options. 255A common case for an accumulation of Opens is a shared library within 256the NFS mount that is used by several 257processes, where at least one of these processes is always running. 258This option cannot be used for an NFS Version 4, minor version 0 mount. 259It may not work correctly when Delegations are being issued by a server, 260but note that the AmazonEFS server does not issued delegations at this time. 261This option is only meaningful when used with the 262.Cm nfsv4 263option. 264.It Cm pnfs 265Enable support for parallel NFS (pNFS) for minor version 1 or 2 of the 266NFS Version 4 protocol. 267This option is only meaningful when used with the 268.Cm nfsv4 269option. 270.It Cm noac 271Disable attribute caching. 272.It Cm noconn 273For UDP mount points, do not do a 274.Xr connect 2 . 275This must be used if the server does not reply to requests from the standard 276NFS port number 2049 or replies to requests using a different IP address 277(which can occur if the server is multi-homed). 278Setting the 279.Va vfs.nfs.nfs_ip_paranoia 280sysctl to 0 will make this option the default. 281.It Cm nocto 282Normally, NFS clients maintain the close-to-open cache coherency. 283This works by flushing at close time and checking at open time. 284Checking at open time is implemented by getting attributes from 285the server and purging the data cache if they do not match 286attributes cached by the client. 287.Pp 288This option disables checking at open time. 289It may improve performance for read-only mounts, 290but should only be used if the data on the server changes rarely. 291Be sure to understand the consequences before enabling this option. 292.It Cm noinet4 , noinet6 293Disables 294.Dv AF_INET 295or 296.Dv AF_INET6 297connections. 298Useful for hosts that have 299both an A record and an AAAA record for the same name. 300.It Cm nolockd 301Do 302.Em not 303forward 304.Xr fcntl 2 305locks over the wire via the NLM protocol for NFSv3 mounts. 306All locks will be local and not seen by the server 307and likewise not seen by other NFS clients for NFSv3 mounts. 308This removes the need to run the 309.Xr rpcbind 8 310service and the 311.Xr rpc.statd 8 312and 313.Xr rpc.lockd 8 314servers on the client. 315Note that this option will only be honored when performing the 316initial mount, it will be silently ignored if used while updating 317the mount options. 318Also, note that NFSv4 mounts do not use these daemons and handle locks over the 319wire in the NFSv4 protocol. 320As such, this option is meaningless for NFSv4 mounts. 321.It Cm noncontigwr 322This mount option allows the NFS client to 323combine non-contiguous byte ranges being written 324such that the dirty byte range becomes a superset of the bytes 325that are dirty. 326This reduces the number of writes significantly for software 327builds. 328The merging of byte ranges is not done if the file has been file 329locked, since most applications modifying a file from multiple 330clients will use file locking. 331As such, this option could result in a corrupted file for the 332rare case of an application modifying the file from multiple 333clients concurrently without using file locking. 334.It Cm principal 335For the RPCSEC_GSS security flavors, such as krb5, krb5i and krb5p, 336this option sets the name of the host based principal name expected 337by the server. 338This option overrides the default, which will be ``nfs@<server-fqdn>'' 339and should normally be sufficient. 340.It Cm noresvport 341Do 342.Em not 343use a reserved socket port number (see below). 344.It Cm port Ns = Ns Aq Ar port_number 345Use specified port number for NFS requests. 346The default is to query the portmapper for the NFS port. 347.It Cm proto Ns = Ns Aq Ar protocol 348Specify transport protocol version to use. 349Currently, they are: 350.Bd -literal 351udp - Use UDP over IPv4 352tcp - Use TCP over IPv4 353udp6 - Use UDP over IPv6 354tcp6 - Use TCP over IPv6 355.Ed 356.It Cm rdirplus 357Used with NFSV3 to specify that the \fBReaddirPlus\fR RPC should 358be used. 359For NFSV4, setting this option has a similar effect, in that it will make 360the Readdir Operation get more attributes. 361This option reduces RPC traffic for cases such as 362.Dq "ls -l" , 363but tends to flood the attribute and name caches with prefetched entries. 364Try this option and see whether performance improves or degrades. 365Probably 366most useful for client to server network interconnects with a large bandwidth 367times delay product. 368.It Cm readahead Ns = Ns Aq Ar value 369Set the read-ahead count to the specified value. 370This may be in the range of 0 - 4, and determines how many blocks 371will be read ahead when a large file is being read sequentially. 372Trying a value greater than 1 for this is suggested for 373mounts with a large bandwidth * delay product. 374.It Cm readdirsize Ns = Ns Aq Ar value 375Set the readdir read size to the specified value. 376The value should normally 377be a multiple of 378.Dv DIRBLKSIZ 379that is <= the read size for the mount. 380.It Cm resvport 381Use a reserved socket port number. 382This flag is obsolete, and only retained for compatibility reasons. 383Reserved port numbers are used by default now. 384(For the rare case where the client has a trusted root account 385but untrustworthy users and the network cables are in secure areas this does 386help, but for normal desktop clients this does not apply.) 387.It Cm retrans Ns = Ns Aq Ar value 388Set the retransmit timeout count for soft mounts to the specified value. 389.It Cm retrycnt Ns = Ns Aq Ar count 390Set the mount retry count to the specified value. 391The default is a retry count of zero, which means to keep retrying 392forever. 393There is a 60 second delay between each attempt. 394.It Cm rsize Ns = Ns Aq Ar value 395Set the read data size to the specified value. 396It should normally be a power of 2 greater than or equal to 1024. 397This should be used for UDP mounts when the 398.Dq "fragments dropped due to timeout" 399value is getting large while actively using a mount point. 400(Use 401.Xr netstat 1 402with the 403.Fl s 404option to see what the 405.Dq "fragments dropped due to timeout" 406value is.) 407.It Cm sec Ns = Ns Aq Ar flavor 408This option specifies what security flavor should be used for the mount. 409Currently, they are: 410.Bd -literal 411krb5 - Use KerberosV authentication 412krb5i - Use KerberosV authentication and 413 apply integrity checksums to RPCs 414krb5p - Use KerberosV authentication and 415 encrypt the RPC data 416sys - The default AUTH_SYS, which uses a 417 uid + gid list authenticator 418.Ed 419.It Cm soft 420A soft mount, which implies that file system calls will fail 421after 422.Ar retrycnt 423round trip timeout intervals. 424.It Cm tcp 425Use TCP transport. 426This is the default option, as it provides for increased reliability on both 427LAN and WAN configurations compared to UDP. 428Some old NFS servers do not support this method; UDP mounts may be required 429for interoperability. 430.It Cm timeout Ns = Ns Aq Ar value 431Set the initial retransmit timeout to the specified value, 432expressed in tenths of a second. 433May be useful for fine tuning UDP mounts over internetworks 434with high packet loss rates or an overloaded server. 435Try increasing the interval if 436.Xr nfsstat 1 437shows high retransmit rates while the file system is active or reducing the 438value if there is a low retransmit rate but long response delay observed. 439(Normally, the 440.Cm dumbtimer 441option should be specified when using this option to manually 442tune the timeout 443interval.) 444.It Cm timeo Ns = Ns Aq Ar value 445Alias for 446.Cm timeout . 447.It Cm tls 448This option specifies that the connection to the server must use TLS 449per RFC NNNN. 450TLS is only supported for TCP connections and the 451.Xr rpc.tlsclntd 8 452daemon must be running for an NFS over TCP connection to use TLS. 453.It Cm tlscertname Ns = Ns Aq Ar name 454This option specifies the name of an alternate certificate to be 455presented to the NFS server during TLS handshake. 456The default certificate file names are 457.Dq cert.pem 458and 459.Dq certkey.pem . 460When this option is specified, 461.Ar name 462replaces 463.Dq cert 464in the above file names. 465For example, if the value of 466.Ar name 467is specified as 468.Dq other 469the certificate file names to be used will be 470.Dq other.pem 471and 472.Dq otherkey.pem . 473These files are stored in 474.Pa /etc/rpc.tlsclntd 475by default. 476This option is only meaningful when used with the 477.Cm tls 478option and the 479.Xr rpc.tlsclntd 8 480is running with the 481.Fl m 482command line flag set. 483.It Cm udp 484Use UDP transport. 485.It Cm vers Ns = Ns Aq Ar vers_number 486Use the specified version number for NFS requests. 487See the 488.Cm nfsv2 , 489.Cm nfsv3 , 490and 491.Cm nfsv4 492options for details. 493.It Cm wcommitsize Ns = Ns Aq Ar value 494Set the maximum pending write commit size to the specified value. 495This determines the maximum amount of pending write data that the NFS 496client is willing to cache for each file. 497.It Cm wsize Ns = Ns Aq Ar value 498Set the write data size to the specified value. 499Ditto the comments w.r.t.\& the 500.Cm rsize 501option, but using the 502.Dq "fragments dropped due to timeout" 503value on the server instead of the client. 504Note that both the 505.Cm rsize 506and 507.Cm wsize 508options should only be used as a last ditch effort at improving performance 509when mounting servers that do not support TCP mounts. 510.El 511.El 512.Sh COMPATIBILITY 513The following command line flags are equivalent to 514.Fl o 515named options and are supported for compatibility with older 516installations. 517.Bl -tag -width indent 518.It Fl 2 519Same as 520.Fl o Cm nfsv2 521.It Fl 3 522Same as 523.Fl o Cm nfsv3 524.It Fl D 525Same as 526.Fl o Cm deadthresh 527.It Fl I 528Same as 529.Fl o Cm readdirsize Ns = Ns Aq Ar value 530.It Fl L 531Same as 532.Fl o Cm nolockd 533.It Fl N 534Same as 535.Fl o Cm noresvport 536.It Fl P 537Use a reserved socket port number. 538This flag is obsolete, and only retained for compatibility reasons. 539(For the rare case where the client has a trusted root account 540but untrustworthy users and the network cables are in secure areas this does 541help, but for normal desktop clients this does not apply.) 542.It Fl R 543Same as 544.Fl o Cm retrycnt Ns = Ns Aq Ar value 545.It Fl T 546Same as 547.Fl o Cm tcp 548.It Fl U 549Same as 550.Fl o Cm mntudp 551.It Fl a 552Same as 553.Fl o Cm readahead Ns = Ns Aq Ar value 554.It Fl b 555Same as 556.Fl o Cm bg 557.It Fl c 558Same as 559.Fl o Cm noconn 560.It Fl d 561Same as 562.Fl o Cm dumbtimer 563.It Fl g 564Same as 565.Fl o Cm maxgroups 566.It Fl i 567Same as 568.Fl o Cm intr 569.It Fl l 570Same as 571.Fl o Cm rdirplus 572.It Fl r 573Same as 574.Fl o Cm rsize Ns = Ns Aq Ar value 575.It Fl s 576Same as 577.Fl o Cm soft 578.It Fl t 579Same as 580.Fl o Cm retransmit Ns = Ns Aq Ar value 581.It Fl w 582Same as 583.Fl o Cm wsize Ns = Ns Aq Ar value 584.It Fl x 585Same as 586.Fl o Cm retrans Ns = Ns Aq Ar value 587.El 588.Pp 589The following 590.Fl o 591named options are equivalent to other 592.Fl o 593named options and are supported for compatibility with other 594operating systems (e.g., Linux, Solaris, and OSX) to ease usage of 595.Xr autofs 5 596support. 597.Bl -tag -width indent 598.It Fl o Cm vers Ns = Ns 2 599Same as 600.Fl o Cm nfsv2 601.It Fl o Cm vers Ns = Ns 3 602Same as 603.Fl o Cm nfsv3 604.It Fl o Cm vers Ns = Ns 4 605Same as 606.Fl o Cm nfsv4 607.El 608.Sh IMPLEMENTATION NOTES 609When neither the 610.Cm rsize 611nor 612.Cm wsize 613options are specified, the I/O size will be set to the largest value 614supported by both the NFS client and server. 615The largest value supported by the NFS client is defined by 616the tunable 617.Cd vfs.maxbcachebuf 618which can be set to a power of two up to 619.Cd kern.maxphys . 620.Pp 621The 622.Xr nfsstat 1 623command with the 624.Ic -m 625command line option will show what 626.Nm 627option settings are actually in use for the mount. 628.Sh SEE ALSO 629.Xr nfsstat 1 , 630.Xr nmount 2 , 631.Xr unmount 2 , 632.Xr lagg 4 , 633.Xr nfsv4 4 , 634.Xr fstab 5 , 635.Xr gssd 8 , 636.Xr mount 8 , 637.Xr nfsd 8 , 638.Xr nfsiod 8 , 639.Xr rpc.tlsclntd 8 , 640.Xr showmount 8 641.Sh HISTORY 642A version of the 643.Nm 644utility appeared in 645.Bx 4.4 . 646.Sh BUGS 647Since nfsv4 performs open/lock operations that have their ordering strictly 648enforced by the server, the options 649.Cm intr 650and 651.Cm soft 652cannot be safely used. 653.Cm hard 654nfsv4 mounts are strongly recommended. 655