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 3, 2023 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-principal-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. 191To avoid leaving file locks in an indeterminate state on the NFS 192server, it is recommended that the 193.Cm nolockd 194option be used with this option. 195.It Cm maxgroups Ns = Ns Aq Ar value 196Set the maximum size of the group list for the credentials to the 197specified value. 198This should be used for mounts on old servers that cannot handle a 199group list size of 16, as specified in RFC 1057. 200Try 8, if users in a lot of groups cannot get response from the mount 201point. 202.It Cm mntudp 203Force the mount protocol to use UDP transport, even for TCP NFS mounts. 204(Necessary for some old 205.Bx 206servers.) 207.It Cm nametimeo Ns = Ns Aq Ar value 208Override the default of NFS_DEFAULT_NAMETIMEO for the timeout (in seconds) 209for positive name cache entries. 210If this is set to 0 it disables positive name caching for the mount point. 211.It Cm negnametimeo Ns = Ns Aq Ar value 212Override the default of NFS_DEFAULT_NEGNAMETIMEO for the timeout (in seconds) 213for negative name cache entries. 214If this is set to 0 it disables negative name caching for the mount point. 215.It Cm nconnect Ns = Ns Aq Ar value 216Specify the number of TCP connections (1-16) to be used 217for an NFS Version 4, minor version 1 or 2 mount. 218Multiple TCP connections can provide more client to server network 219bandwidth for certain network configurations such as: 220.Bd -literal 221- Multiple network interfaces that are aggregated together. 222- A fast network interface that uses multiple queues. 223.Ed 224.sp 225The first TCP connection will be used for all RPCs that consist 226entirely of small RPC messages. 227The RPCs that can have large RPC messages (Read/Readdir/Write) are 228distributed over the additional TCP connections in a round robin 229fashion. 230This option will result in more IP port#s being used. 231This option requires the 232.Cm nfsv4 233option. 234.It Cm nfsv2 235Use the NFS Version 2 protocol (the default is to try version 3 first 236then version 2). 237Note that NFS version 2 has a file size limit of 2 gigabytes. 238.It Cm nfsv3 239Use the NFS Version 3 protocol. 240.It Cm nfsv4 241Use the NFS Version 4 protocol. 242This option will force the mount to use 243TCP transport. 244By default, the highest minor version of NFS Version 4 that is 245supported by the NFS Version 4 server will be used. 246See the 247.Cm minorversion 248option. 249Make sure that all your NFS Version 4 clients have unique 250values in 251.Pa /etc/hostid . 252.It Cm minorversion Ns = Ns Aq Ar value 253Use the specified minor version for a NFS Version 4 mount, 254overriding the default. 255The minor versions supported are 0, 1, and 2. 256This option is only meaningful when used with the 257.Cm nfsv4 258option. 259.It Cm oneopenown 260Make a minor version 1 or 2 of the NFS Version 4 protocol mount use a single 261OpenOwner for all Opens. 262This may be useful for a server with a very low limit on OpenOwners, such as 263AmazonEFS. 264It may be required when an accumulation of NFS version 4 Opens occurs, 265as indicated by the 266.Dq Opens 267count displayed by 268.Xr nfsstat 1 269with the 270.Fl c 271and 272.Fl E 273command-line options. 274A common case for an accumulation of Opens is a shared library within 275the NFS mount that is used by several 276processes, where at least one of these processes is always running. 277This option cannot be used for an NFS Version 4, minor version 0 mount. 278It may not work correctly when Delegations are being issued by a server, 279but note that the AmazonEFS server does not issued delegations at this time. 280This option is only meaningful when used with the 281.Cm nfsv4 282option. 283.It Cm pnfs 284Enable support for parallel NFS (pNFS) for minor version 1 or 2 of the 285NFS Version 4 protocol. 286This option is only meaningful when used with the 287.Cm nfsv4 288option. 289.It Cm noac 290Disable attribute caching. 291.It Cm noconn 292For UDP mount points, do not do a 293.Xr connect 2 . 294This must be used if the server does not reply to requests from the standard 295NFS port number 2049 or replies to requests using a different IP address 296(which can occur if the server is multi-homed). 297Setting the 298.Va vfs.nfs.nfs_ip_paranoia 299sysctl to 0 will make this option the default. 300.It Cm nocto 301Normally, NFS clients maintain the close-to-open cache coherency. 302This works by flushing at close time and checking at open time. 303Checking at open time is implemented by getting attributes from 304the server and purging the data cache if they do not match 305attributes cached by the client. 306.Pp 307This option disables checking at open time. 308It may improve performance for read-only mounts, 309but should only be used if the data on the server changes rarely. 310Be sure to understand the consequences before enabling this option. 311.It Cm noinet4 , noinet6 312Disables 313.Dv AF_INET 314or 315.Dv AF_INET6 316connections. 317Useful for hosts that have 318both an A record and an AAAA record for the same name. 319.It Cm nolockd 320Do 321.Em not 322forward 323.Xr fcntl 2 324locks over the wire via the NLM protocol for NFSv3 mounts 325or via the NFSv4 protocol for NFSv4 mounts. 326All locks will be local and not seen by the server 327and likewise not seen by other NFS clients for NFSv3 or NFSv4 mounts. 328This removes the need to run the 329.Xr rpcbind 8 330service and the 331.Xr rpc.statd 8 332and 333.Xr rpc.lockd 8 334servers on the client for NFSv3 mounts. 335Note that this option will only be honored when performing the 336initial mount, it will be silently ignored if used while updating 337the mount options. 338Also, note that NFSv4 mounts do not use these daemons. 339The NFSv4 protocol handles locks, 340unless this option is specified. 341.It Cm noncontigwr 342This mount option allows the NFS client to 343combine non-contiguous byte ranges being written 344such that the dirty byte range becomes a superset of the bytes 345that are dirty. 346This reduces the number of writes significantly for software 347builds. 348The merging of byte ranges is not done if the file has been file 349locked, since most applications modifying a file from multiple 350clients will use file locking. 351As such, this option could result in a corrupted file for the 352rare case of an application modifying the file from multiple 353clients concurrently without using file locking. 354.It Cm principal 355For the RPCSEC_GSS security flavors, such as krb5, krb5i and krb5p, 356this option sets the name of the host based principal name expected 357by the server. 358This option overrides the default, which will be ``nfs@<server-fqdn>'' 359and should normally be sufficient. 360.It Cm noresvport 361Do 362.Em not 363use a reserved socket port number (see below). 364.It Cm port Ns = Ns Aq Ar port_number 365Use specified port number for NFS requests. 366The default is to query the portmapper for the NFS port. 367.It Cm proto Ns = Ns Aq Ar protocol 368Specify transport protocol version to use. 369Currently, they are: 370.Bd -literal 371udp - Use UDP over IPv4 372tcp - Use TCP over IPv4 373udp6 - Use UDP over IPv6 374tcp6 - Use TCP over IPv6 375.Ed 376.It Cm rdirplus 377Used with NFSV3 to specify that the \fBReaddirPlus\fR RPC should 378be used. 379For NFSV4, setting this option has a similar effect, in that it will make 380the Readdir Operation get more attributes. 381This option reduces RPC traffic for cases such as 382.Dq "ls -l" , 383but tends to flood the attribute and name caches with prefetched entries. 384Try this option and see whether performance improves or degrades. 385Probably 386most useful for client to server network interconnects with a large bandwidth 387times delay product. 388.It Cm readahead Ns = Ns Aq Ar value 389Set the read-ahead count to the specified value. 390This may be in the range of 0 - 4, and determines how many blocks 391will be read ahead when a large file is being read sequentially. 392Trying a value greater than 1 for this is suggested for 393mounts with a large bandwidth * delay product. 394.It Cm readdirsize Ns = Ns Aq Ar value 395Set the readdir read size to the specified value. 396The value should normally 397be a multiple of 398.Dv DIRBLKSIZ 399that is <= the read size for the mount. 400.It Cm resvport 401Use a reserved socket port number. 402This flag is obsolete, and only retained for compatibility reasons. 403Reserved port numbers are used by default now. 404(For the rare case where the client has a trusted root account 405but untrustworthy users and the network cables are in secure areas this does 406help, but for normal desktop clients this does not apply.) 407.It Cm retrans Ns = Ns Aq Ar value 408Set the retransmit timeout count for soft mounts to the specified value. 409.It Cm retrycnt Ns = Ns Aq Ar count 410Set the mount retry count to the specified value. 411The default is a retry count of zero, which means to keep retrying 412forever. 413There is a 60 second delay between each attempt. 414.It Cm rsize Ns = Ns Aq Ar value 415Set the read data size to the specified value. 416It should normally be a power of 2 greater than or equal to 1024. 417This should be used for UDP mounts when the 418.Dq "fragments dropped due to timeout" 419value is getting large while actively using a mount point. 420(Use 421.Xr netstat 1 422with the 423.Fl s 424option to see what the 425.Dq "fragments dropped due to timeout" 426value is.) 427.It Cm sec Ns = Ns Aq Ar flavor 428This option specifies what security flavor should be used for the mount. 429Currently, they are: 430.Bd -literal 431krb5 - Use KerberosV authentication 432krb5i - Use KerberosV authentication and 433 apply integrity checksums to RPCs 434krb5p - Use KerberosV authentication and 435 encrypt the RPC data 436sys - The default AUTH_SYS, which uses a 437 uid + gid list authenticator 438.Ed 439.It Cm soft 440A soft mount, which implies that file system calls will fail 441after 442.Ar retrycnt 443round trip timeout intervals. 444.It Cm syskrb5 445This option specifies that a KerberosV NFSv4 minor version 1 or 2 mount 446uses AUTH_SYS for system operations. 447Using this option avoids the need for a KerberosV mount to have a 448host-based principal entry in the default keytab file 449(no 450.Cm gssname 451option) or a requirement for the user doing the mount to have a 452valid KerberosV ticket granting ticket (TGT) when the mount is done. 453This option is intended to be used with the 454.Cm sec Ns = Ns krb5 455and 456.Cm tls 457options and can only be used for 458NFSv4 mounts with minor version 1 or 2. 459.It Cm tcp 460Use TCP transport. 461This is the default option, as it provides for increased reliability on both 462LAN and WAN configurations compared to UDP. 463Some old NFS servers do not support this method; UDP mounts may be required 464for interoperability. 465.It Cm timeout Ns = Ns Aq Ar value 466Set the initial retransmit timeout to the specified value, 467expressed in tenths of a second. 468May be useful for fine tuning UDP mounts over internetworks 469with high packet loss rates or an overloaded server. 470Try increasing the interval if 471.Xr nfsstat 1 472shows high retransmit rates while the file system is active or reducing the 473value if there is a low retransmit rate but long response delay observed. 474(Normally, the 475.Cm dumbtimer 476option should be specified when using this option to manually 477tune the timeout 478interval.) 479.It Cm timeo Ns = Ns Aq Ar value 480Alias for 481.Cm timeout . 482.It Cm tls 483This option specifies that the connection to the server must use TLS 484per RFC 9289. 485TLS is only supported for TCP connections and the 486.Xr rpc.tlsclntd 8 487daemon must be running for an NFS over TCP connection to use TLS. 488.It Cm tlscertname Ns = Ns Aq Ar name 489This option specifies the name of an alternate certificate to be 490presented to the NFS server during TLS handshake. 491The default certificate file names are 492.Dq cert.pem 493and 494.Dq certkey.pem . 495When this option is specified, 496.Ar name 497replaces 498.Dq cert 499in the above file names. 500For example, if the value of 501.Ar name 502is specified as 503.Dq other 504the certificate file names to be used will be 505.Dq other.pem 506and 507.Dq otherkey.pem . 508These files are stored in 509.Pa /etc/rpc.tlsclntd 510by default. 511This option is only meaningful when used with the 512.Cm tls 513option and the 514.Xr rpc.tlsclntd 8 515is running with the 516.Fl m 517command line flag set. 518.It Cm udp 519Use UDP transport. 520.It Cm vers Ns = Ns Aq Ar vers_number 521Use the specified version number for NFS requests. 522See the 523.Cm nfsv2 , 524.Cm nfsv3 , 525and 526.Cm nfsv4 527options for details. 528.It Cm wcommitsize Ns = Ns Aq Ar value 529Set the maximum pending write commit size to the specified value. 530This determines the maximum amount of pending write data that the NFS 531client is willing to cache for each file. 532.It Cm wsize Ns = Ns Aq Ar value 533Set the write data size to the specified value. 534Ditto the comments w.r.t.\& the 535.Cm rsize 536option, but using the 537.Dq "fragments dropped due to timeout" 538value on the server instead of the client. 539Note that both the 540.Cm rsize 541and 542.Cm wsize 543options should only be used as a last ditch effort at improving performance 544when mounting servers that do not support TCP mounts. 545.El 546.El 547.Sh IMPLEMENTATION NOTES 548When neither the 549.Cm rsize 550nor 551.Cm wsize 552options are specified, the I/O size will be set to the largest value 553supported by both the NFS client and server. 554The largest value supported by the NFS client is defined by 555the tunable 556.Cd vfs.maxbcachebuf 557which can be set to a power of two up to 558.Cd kern.maxphys . 559.Pp 560The 561.Xr nfsstat 1 562command with the 563.Ic -m 564command line option will show what 565.Nm 566option settings are actually in use for the mount. 567.Sh COMPATIBILITY 568The following command line flags are equivalent to 569.Fl o 570named options and are supported for compatibility with older 571installations. 572.Bl -tag -width indent 573.It Fl 2 574Same as 575.Fl o Cm nfsv2 576.It Fl 3 577Same as 578.Fl o Cm nfsv3 579.It Fl D 580Same as 581.Fl o Cm deadthresh 582.It Fl I 583Same as 584.Fl o Cm readdirsize Ns = Ns Aq Ar value 585.It Fl L 586Same as 587.Fl o Cm nolockd 588.It Fl N 589Same as 590.Fl o Cm noresvport 591.It Fl P 592Use a reserved socket port number. 593This flag is obsolete, and only retained for compatibility reasons. 594(For the rare case where the client has a trusted root account 595but untrustworthy users and the network cables are in secure areas this does 596help, but for normal desktop clients this does not apply.) 597.It Fl R 598Same as 599.Fl o Cm retrycnt Ns = Ns Aq Ar value 600.It Fl T 601Same as 602.Fl o Cm tcp 603.It Fl U 604Same as 605.Fl o Cm mntudp 606.It Fl a 607Same as 608.Fl o Cm readahead Ns = Ns Aq Ar value 609.It Fl b 610Same as 611.Fl o Cm bg 612.It Fl c 613Same as 614.Fl o Cm noconn 615.It Fl d 616Same as 617.Fl o Cm dumbtimer 618.It Fl g 619Same as 620.Fl o Cm maxgroups 621.It Fl i 622Same as 623.Fl o Cm intr 624.It Fl l 625Same as 626.Fl o Cm rdirplus 627.It Fl r 628Same as 629.Fl o Cm rsize Ns = Ns Aq Ar value 630.It Fl s 631Same as 632.Fl o Cm soft 633.It Fl t 634Same as 635.Fl o Cm retransmit Ns = Ns Aq Ar value 636.It Fl w 637Same as 638.Fl o Cm wsize Ns = Ns Aq Ar value 639.It Fl x 640Same as 641.Fl o Cm retrans Ns = Ns Aq Ar value 642.El 643.Pp 644The following 645.Fl o 646named options are equivalent to other 647.Fl o 648named options and are supported for compatibility with other 649operating systems (e.g., Linux, Solaris, and OSX) to ease usage of 650.Xr autofs 5 651support. 652.Bl -tag -width indent 653.It Fl o Cm vers Ns = Ns 2 654Same as 655.Fl o Cm nfsv2 656.It Fl o Cm vers Ns = Ns 3 657Same as 658.Fl o Cm nfsv3 659.It Fl o Cm vers Ns = Ns 4 660Same as 661.Fl o Cm nfsv4 662.El 663.Sh SEE ALSO 664.Xr nfsstat 1 , 665.Xr nmount 2 , 666.Xr unmount 2 , 667.Xr lagg 4 , 668.Xr nfsv4 4 , 669.Xr fstab 5 , 670.Xr gssd 8 , 671.Xr mount 8 , 672.Xr nfsd 8 , 673.Xr nfsiod 8 , 674.Xr rpc.tlsclntd 8 , 675.Xr showmount 8 676.Sh HISTORY 677A version of the 678.Nm 679utility appeared in 680.Bx 4.4 . 681.Sh BUGS 682Since NFSv4 performs open/lock operations that have their ordering strictly 683enforced by the server, the options 684.Cm intr 685and 686.Cm soft 687cannot be safely used. 688For NFSv4 minor version 1 or 2 mounts, the ordering is done 689via session slots and the NFSv4 client now handles broken session slots 690fairly well. 691As such, if the 692.Cm nolockd 693option is used along with 694.Cm intr 695and/or 696.Cm soft , 697an NFSv4 minor version 1 or 2 mount 698should work fairly well, although still not completely correctly. 699For NFSv4 minor version 0 mounts, 700.Cm hard 701mounts without the 702.Cm intr 703mount option is strongly recommended. 704