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 August 31, 2022 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 bgnow 133Like 134.Cm bg , 135fork off a child to keep trying the mount in the background, 136but do not attempt to mount in the foreground first. 137This eliminates a 13860+ second timeout when the server is not responding. 139Useful for speeding up the boot process of a client when the server is 140likely to be unavailable. 141This is often the case for interdependent servers 142such as cross-mounted servers (each of two servers is an NFS client of 143the other) and for cluster nodes that must boot before the file servers. 144.It Cm deadthresh Ns = Ns Aq Ar value 145Set the 146.Dq "dead server threshold" 147to the specified number of round trip timeout intervals before a 148.Dq "server not responding" 149message is displayed. 150.It Cm dumbtimer 151Turn off the dynamic retransmit timeout estimator. 152This may be useful for UDP mounts that exhibit high retry rates, 153since it is possible that the dynamically estimated timeout interval is too 154short. 155.It Cm fg 156Same as not specifying 157.Cm bg . 158.It Cm gssname Ns = Ns Aq Ar service-principal-name 159This option can be used with the KerberosV security flavors for NFSv4 mounts 160to specify the 161.Dq "service-principal-name" 162of a host-based entry in the default 163keytab file that is used for system operations. 164It allows the mount to be performed by 165.Dq "root" 166and avoids problems with 167cached credentials for the system operations expiring. 168The 169.Dq "service-prinicpal-name" 170should be specified without instance or domain and is typically 171.Dq "host" , 172.Dq "nfs" 173or 174.Dq "root" , 175although the form 176.Sm off 177.Aq Ar service 178@ 179.Aq Ar fqdn 180.Sm on 181can also be used if the local system's 182.Xr gethostname 3 183value does not match the host-based principal in the keytab. 184.It Cm hard 185Same as not specifying 186.Cm soft . 187.It Cm intr 188Make the mount interruptible, which implies that file system calls that 189are delayed due to an unresponsive server will fail with EINTR when a 190termination signal is posted for the process. 191.It Cm maxgroups Ns = Ns Aq Ar value 192Set the maximum size of the group list for the credentials to the 193specified value. 194This should be used for mounts on old servers that cannot handle a 195group list size of 16, as specified in RFC 1057. 196Try 8, if users in a lot of groups cannot get response from the mount 197point. 198.It Cm mntudp 199Force the mount protocol to use UDP transport, even for TCP NFS mounts. 200(Necessary for some old 201.Bx 202servers.) 203.It Cm nametimeo Ns = Ns Aq Ar value 204Override the default of NFS_DEFAULT_NAMETIMEO for the timeout (in seconds) 205for positive name cache entries. 206If this is set to 0 it disables positive name caching for the mount point. 207.It Cm negnametimeo Ns = Ns Aq Ar value 208Override the default of NFS_DEFAULT_NEGNAMETIMEO for the timeout (in seconds) 209for negative name cache entries. 210If this is set to 0 it disables negative name caching for the mount point. 211.It Cm nconnect Ns = Ns Aq Ar value 212Specify the number of TCP connections (1-16) to be used 213for an NFS Version 4, minor version 1 or 2 mount. 214Multiple TCP connections can provide more client to server network 215bandwidth for certain network configurations such as: 216.Bd -literal 217- Multiple network interfaces that are aggregated together. 218- A fast network interface that uses multiple queues. 219.Ed 220.sp 221The first TCP connection will be used for all RPCs that consist 222entirely of small RPC messages. 223The RPCs that can have large RPC messages (Read/Readdir/Write) are 224distributed over the additional TCP connections in a round robin 225fashion. 226This option will result in more IP port#s being used. 227This option requires the 228.Cm nfsv4 229option. 230.It Cm nfsv2 231Use the NFS Version 2 protocol (the default is to try version 3 first 232then version 2). 233Note that NFS version 2 has a file size limit of 2 gigabytes. 234.It Cm nfsv3 235Use the NFS Version 3 protocol. 236.It Cm nfsv4 237Use the NFS Version 4 protocol. 238This option will force the mount to use 239TCP transport. 240By default, the highest minor version of NFS Version 4 that is 241supported by the NFS Version 4 server will be used. 242See the 243.Cm minorversion 244option. 245Make sure that all your NFS Version 4 clients have unique 246values in 247.Pa /etc/hostid . 248.It Cm minorversion Ns = Ns Aq Ar value 249Use the specified minor version for a NFS Version 4 mount, 250overriding the default. 251The minor versions supported are 0, 1, and 2. 252This option is only meaningful when used with the 253.Cm nfsv4 254option. 255.It Cm oneopenown 256Make a minor version 1 or 2 of the NFS Version 4 protocol mount use a single 257OpenOwner for all Opens. 258This may be useful for a server with a very low limit on OpenOwners, such as 259AmazonEFS. 260It may be required when an accumulation of NFS version 4 Opens occurs, 261as indicated by the 262.Dq Opens 263count displayed by 264.Xr nfsstat 1 265with the 266.Fl c 267and 268.Fl E 269command-line options. 270A common case for an accumulation of Opens is a shared library within 271the NFS mount that is used by several 272processes, where at least one of these processes is always running. 273This option cannot be used for an NFS Version 4, minor version 0 mount. 274It may not work correctly when Delegations are being issued by a server, 275but note that the AmazonEFS server does not issued delegations at this time. 276This option is only meaningful when used with the 277.Cm nfsv4 278option. 279.It Cm pnfs 280Enable support for parallel NFS (pNFS) for minor version 1 or 2 of the 281NFS Version 4 protocol. 282This option is only meaningful when used with the 283.Cm nfsv4 284option. 285.It Cm noac 286Disable attribute caching. 287.It Cm noconn 288For UDP mount points, do not do a 289.Xr connect 2 . 290This must be used if the server does not reply to requests from the standard 291NFS port number 2049 or replies to requests using a different IP address 292(which can occur if the server is multi-homed). 293Setting the 294.Va vfs.nfs.nfs_ip_paranoia 295sysctl to 0 will make this option the default. 296.It Cm nocto 297Normally, NFS clients maintain the close-to-open cache coherency. 298This works by flushing at close time and checking at open time. 299Checking at open time is implemented by getting attributes from 300the server and purging the data cache if they do not match 301attributes cached by the client. 302.Pp 303This option disables checking at open time. 304It may improve performance for read-only mounts, 305but should only be used if the data on the server changes rarely. 306Be sure to understand the consequences before enabling this option. 307.It Cm noinet4 , noinet6 308Disables 309.Dv AF_INET 310or 311.Dv AF_INET6 312connections. 313Useful for hosts that have 314both an A record and an AAAA record for the same name. 315.It Cm nolockd 316Do 317.Em not 318forward 319.Xr fcntl 2 320locks over the wire via the NLM protocol for NFSv3 mounts. 321All locks will be local and not seen by the server 322and likewise not seen by other NFS clients for NFSv3 mounts. 323This removes the need to run the 324.Xr rpcbind 8 325service and the 326.Xr rpc.statd 8 327and 328.Xr rpc.lockd 8 329servers on the client. 330Note that this option will only be honored when performing the 331initial mount, it will be silently ignored if used while updating 332the mount options. 333Also, note that NFSv4 mounts do not use these daemons and handle locks over the 334wire in the NFSv4 protocol. 335As such, this option is meaningless for NFSv4 mounts. 336.It Cm noncontigwr 337This mount option allows the NFS client to 338combine non-contiguous byte ranges being written 339such that the dirty byte range becomes a superset of the bytes 340that are dirty. 341This reduces the number of writes significantly for software 342builds. 343The merging of byte ranges is not done if the file has been file 344locked, since most applications modifying a file from multiple 345clients will use file locking. 346As such, this option could result in a corrupted file for the 347rare case of an application modifying the file from multiple 348clients concurrently without using file locking. 349.It Cm principal 350For the RPCSEC_GSS security flavors, such as krb5, krb5i and krb5p, 351this option sets the name of the host based principal name expected 352by the server. 353This option overrides the default, which will be ``nfs@<server-fqdn>'' 354and should normally be sufficient. 355.It Cm noresvport 356Do 357.Em not 358use a reserved socket port number (see below). 359.It Cm port Ns = Ns Aq Ar port_number 360Use specified port number for NFS requests. 361The default is to query the portmapper for the NFS port. 362.It Cm proto Ns = Ns Aq Ar protocol 363Specify transport protocol version to use. 364Currently, they are: 365.Bd -literal 366udp - Use UDP over IPv4 367tcp - Use TCP over IPv4 368udp6 - Use UDP over IPv6 369tcp6 - Use TCP over IPv6 370.Ed 371.It Cm rdirplus 372Used with NFSV3 to specify that the \fBReaddirPlus\fR RPC should 373be used. 374For NFSV4, setting this option has a similar effect, in that it will make 375the Readdir Operation get more attributes. 376This option reduces RPC traffic for cases such as 377.Dq "ls -l" , 378but tends to flood the attribute and name caches with prefetched entries. 379Try this option and see whether performance improves or degrades. 380Probably 381most useful for client to server network interconnects with a large bandwidth 382times delay product. 383.It Cm readahead Ns = Ns Aq Ar value 384Set the read-ahead count to the specified value. 385This may be in the range of 0 - 4, and determines how many blocks 386will be read ahead when a large file is being read sequentially. 387Trying a value greater than 1 for this is suggested for 388mounts with a large bandwidth * delay product. 389.It Cm readdirsize Ns = Ns Aq Ar value 390Set the readdir read size to the specified value. 391The value should normally 392be a multiple of 393.Dv DIRBLKSIZ 394that is <= the read size for the mount. 395.It Cm resvport 396Use a reserved socket port number. 397This flag is obsolete, and only retained for compatibility reasons. 398Reserved port numbers are used by default now. 399(For the rare case where the client has a trusted root account 400but untrustworthy users and the network cables are in secure areas this does 401help, but for normal desktop clients this does not apply.) 402.It Cm retrans Ns = Ns Aq Ar value 403Set the retransmit timeout count for soft mounts to the specified value. 404.It Cm retrycnt Ns = Ns Aq Ar count 405Set the mount retry count to the specified value. 406The default is a retry count of zero, which means to keep retrying 407forever. 408There is a 60 second delay between each attempt. 409.It Cm rsize Ns = Ns Aq Ar value 410Set the read data size to the specified value. 411It should normally be a power of 2 greater than or equal to 1024. 412This should be used for UDP mounts when the 413.Dq "fragments dropped due to timeout" 414value is getting large while actively using a mount point. 415(Use 416.Xr netstat 1 417with the 418.Fl s 419option to see what the 420.Dq "fragments dropped due to timeout" 421value is.) 422.It Cm sec Ns = Ns Aq Ar flavor 423This option specifies what security flavor should be used for the mount. 424Currently, they are: 425.Bd -literal 426krb5 - Use KerberosV authentication 427krb5i - Use KerberosV authentication and 428 apply integrity checksums to RPCs 429krb5p - Use KerberosV authentication and 430 encrypt the RPC data 431sys - The default AUTH_SYS, which uses a 432 uid + gid list authenticator 433.Ed 434.It Cm soft 435A soft mount, which implies that file system calls will fail 436after 437.Ar retrycnt 438round trip timeout intervals. 439.It Cm tcp 440Use TCP transport. 441This is the default option, as it provides for increased reliability on both 442LAN and WAN configurations compared to UDP. 443Some old NFS servers do not support this method; UDP mounts may be required 444for interoperability. 445.It Cm timeout Ns = Ns Aq Ar value 446Set the initial retransmit timeout to the specified value, 447expressed in tenths of a second. 448May be useful for fine tuning UDP mounts over internetworks 449with high packet loss rates or an overloaded server. 450Try increasing the interval if 451.Xr nfsstat 1 452shows high retransmit rates while the file system is active or reducing the 453value if there is a low retransmit rate but long response delay observed. 454(Normally, the 455.Cm dumbtimer 456option should be specified when using this option to manually 457tune the timeout 458interval.) 459.It Cm timeo Ns = Ns Aq Ar value 460Alias for 461.Cm timeout . 462.It Cm tls 463This option specifies that the connection to the server must use TLS 464per RFC NNNN. 465TLS is only supported for TCP connections and the 466.Xr rpc.tlsclntd 8 467daemon must be running for an NFS over TCP connection to use TLS. 468.It Cm tlscertname Ns = Ns Aq Ar name 469This option specifies the name of an alternate certificate to be 470presented to the NFS server during TLS handshake. 471The default certificate file names are 472.Dq cert.pem 473and 474.Dq certkey.pem . 475When this option is specified, 476.Ar name 477replaces 478.Dq cert 479in the above file names. 480For example, if the value of 481.Ar name 482is specified as 483.Dq other 484the certificate file names to be used will be 485.Dq other.pem 486and 487.Dq otherkey.pem . 488These files are stored in 489.Pa /etc/rpc.tlsclntd 490by default. 491This option is only meaningful when used with the 492.Cm tls 493option and the 494.Xr rpc.tlsclntd 8 495is running with the 496.Fl m 497command line flag set. 498.It Cm udp 499Use UDP transport. 500.It Cm vers Ns = Ns Aq Ar vers_number 501Use the specified version number for NFS requests. 502See the 503.Cm nfsv2 , 504.Cm nfsv3 , 505and 506.Cm nfsv4 507options for details. 508.It Cm wcommitsize Ns = Ns Aq Ar value 509Set the maximum pending write commit size to the specified value. 510This determines the maximum amount of pending write data that the NFS 511client is willing to cache for each file. 512.It Cm wsize Ns = Ns Aq Ar value 513Set the write data size to the specified value. 514Ditto the comments w.r.t.\& the 515.Cm rsize 516option, but using the 517.Dq "fragments dropped due to timeout" 518value on the server instead of the client. 519Note that both the 520.Cm rsize 521and 522.Cm wsize 523options should only be used as a last ditch effort at improving performance 524when mounting servers that do not support TCP mounts. 525.El 526.El 527.Sh COMPATIBILITY 528The following command line flags are equivalent to 529.Fl o 530named options and are supported for compatibility with older 531installations. 532.Bl -tag -width indent 533.It Fl 2 534Same as 535.Fl o Cm nfsv2 536.It Fl 3 537Same as 538.Fl o Cm nfsv3 539.It Fl D 540Same as 541.Fl o Cm deadthresh 542.It Fl I 543Same as 544.Fl o Cm readdirsize Ns = Ns Aq Ar value 545.It Fl L 546Same as 547.Fl o Cm nolockd 548.It Fl N 549Same as 550.Fl o Cm noresvport 551.It Fl P 552Use a reserved socket port number. 553This flag is obsolete, and only retained for compatibility reasons. 554(For the rare case where the client has a trusted root account 555but untrustworthy users and the network cables are in secure areas this does 556help, but for normal desktop clients this does not apply.) 557.It Fl R 558Same as 559.Fl o Cm retrycnt Ns = Ns Aq Ar value 560.It Fl T 561Same as 562.Fl o Cm tcp 563.It Fl U 564Same as 565.Fl o Cm mntudp 566.It Fl a 567Same as 568.Fl o Cm readahead Ns = Ns Aq Ar value 569.It Fl b 570Same as 571.Fl o Cm bg 572.It Fl c 573Same as 574.Fl o Cm noconn 575.It Fl d 576Same as 577.Fl o Cm dumbtimer 578.It Fl g 579Same as 580.Fl o Cm maxgroups 581.It Fl i 582Same as 583.Fl o Cm intr 584.It Fl l 585Same as 586.Fl o Cm rdirplus 587.It Fl r 588Same as 589.Fl o Cm rsize Ns = Ns Aq Ar value 590.It Fl s 591Same as 592.Fl o Cm soft 593.It Fl t 594Same as 595.Fl o Cm retransmit Ns = Ns Aq Ar value 596.It Fl w 597Same as 598.Fl o Cm wsize Ns = Ns Aq Ar value 599.It Fl x 600Same as 601.Fl o Cm retrans Ns = Ns Aq Ar value 602.El 603.Pp 604The following 605.Fl o 606named options are equivalent to other 607.Fl o 608named options and are supported for compatibility with other 609operating systems (e.g., Linux, Solaris, and OSX) to ease usage of 610.Xr autofs 5 611support. 612.Bl -tag -width indent 613.It Fl o Cm vers Ns = Ns 2 614Same as 615.Fl o Cm nfsv2 616.It Fl o Cm vers Ns = Ns 3 617Same as 618.Fl o Cm nfsv3 619.It Fl o Cm vers Ns = Ns 4 620Same as 621.Fl o Cm nfsv4 622.El 623.Sh IMPLEMENTATION NOTES 624When neither the 625.Cm rsize 626nor 627.Cm wsize 628options are specified, the I/O size will be set to the largest value 629supported by both the NFS client and server. 630The largest value supported by the NFS client is defined by 631the tunable 632.Cd vfs.maxbcachebuf 633which can be set to a power of two up to 634.Cd kern.maxphys . 635.Pp 636The 637.Xr nfsstat 1 638command with the 639.Ic -m 640command line option will show what 641.Nm 642option settings are actually in use for the mount. 643.Sh SEE ALSO 644.Xr nfsstat 1 , 645.Xr nmount 2 , 646.Xr unmount 2 , 647.Xr lagg 4 , 648.Xr nfsv4 4 , 649.Xr fstab 5 , 650.Xr gssd 8 , 651.Xr mount 8 , 652.Xr nfsd 8 , 653.Xr nfsiod 8 , 654.Xr rpc.tlsclntd 8 , 655.Xr showmount 8 656.Sh HISTORY 657A version of the 658.Nm 659utility appeared in 660.Bx 4.4 . 661.Sh BUGS 662Since nfsv4 performs open/lock operations that have their ordering strictly 663enforced by the server, the options 664.Cm intr 665and 666.Cm soft 667cannot be safely used. 668For NFSv4 minor version 1 or 2 mounts, these options may 669also result 670in hung mount points, due to corruption of session slots. 671.Cm hard 672nfsv4 mounts are strongly recommended. 673