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 June 14, 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. 234Note that for NFS servers such as AmazonEFS, where each new TCP 235connection can connect to a different cluster that maintains lock 236state separately, this option cannot be used. 237.It Cm nfsv2 238Use the NFS Version 2 protocol (the default is to try version 3 first 239then version 2). 240Note that NFS version 2 has a file size limit of 2 gigabytes. 241.It Cm nfsv3 242Use the NFS Version 3 protocol. 243.It Cm nfsv4 244Use the NFS Version 4 protocol. 245This option will force the mount to use 246TCP transport. 247By default, the highest minor version of NFS Version 4 that is 248supported by the NFS Version 4 server will be used. 249See the 250.Cm minorversion 251option. 252Make sure that all your NFS Version 4 clients have unique 253values in 254.Pa /etc/hostid . 255.It Cm minorversion Ns = Ns Aq Ar value 256Use the specified minor version for a NFS Version 4 mount, 257overriding the default. 258The minor versions supported are 0, 1, and 2. 259This option is only meaningful when used with the 260.Cm nfsv4 261option. 262.It Cm oneopenown 263Make a minor version 1 or 2 of the NFS Version 4 protocol mount use a single 264OpenOwner for all Opens. 265This may be useful for a server with a very low limit on OpenOwners, such as 266AmazonEFS. 267It may be required when an accumulation of NFS version 4 Opens occurs, 268as indicated by the 269.Dq Opens 270count displayed by 271.Xr nfsstat 1 272with the 273.Fl c 274and 275.Fl E 276command-line options. 277A common case for an accumulation of Opens is a shared library within 278the NFS mount that is used by several 279processes, where at least one of these processes is always running. 280This option cannot be used for an NFS Version 4, minor version 0 mount. 281It may not work correctly when Delegations are being issued by a server, 282but note that the AmazonEFS server does not issued delegations at this time. 283This option is only meaningful when used with the 284.Cm nfsv4 285option. 286.It Cm pnfs 287Enable support for parallel NFS (pNFS) for minor version 1 or 2 of the 288NFS Version 4 protocol. 289This option is only meaningful when used with the 290.Cm nfsv4 291option. 292.It Cm noac 293Disable attribute caching. 294.It Cm noconn 295For UDP mount points, do not do a 296.Xr connect 2 . 297This must be used if the server does not reply to requests from the standard 298NFS port number 2049 or replies to requests using a different IP address 299(which can occur if the server is multi-homed). 300Setting the 301.Va vfs.nfs.nfs_ip_paranoia 302sysctl to 0 will make this option the default. 303.It Cm nocto 304Normally, NFS clients maintain the close-to-open cache coherency. 305This works by flushing at close time and checking at open time. 306Checking at open time is implemented by getting attributes from 307the server and purging the data cache if they do not match 308attributes cached by the client. 309.Pp 310This option disables checking at open time. 311It may improve performance for read-only mounts, 312but should only be used if the data on the server changes rarely. 313Be sure to understand the consequences before enabling this option. 314.It Cm noinet4 , noinet6 315Disables 316.Dv AF_INET 317or 318.Dv AF_INET6 319connections. 320Useful for hosts that have 321both an A record and an AAAA record for the same name. 322.It Cm nolockd 323Do 324.Em not 325forward 326.Xr fcntl 2 327locks over the wire via the NLM protocol for NFSv3 mounts 328or via the NFSv4 protocol for NFSv4 mounts. 329All locks will be local and not seen by the server 330and likewise not seen by other NFS clients for NFSv3 or NFSv4 mounts. 331This removes the need to run the 332.Xr rpcbind 8 333service and the 334.Xr rpc.statd 8 335and 336.Xr rpc.lockd 8 337servers on the client for NFSv3 mounts. 338Note that this option will only be honored when performing the 339initial mount, it will be silently ignored if used while updating 340the mount options. 341Also, note that NFSv4 mounts do not use these daemons. 342The NFSv4 protocol handles locks, 343unless this option is specified. 344.It Cm noncontigwr 345This mount option allows the NFS client to 346combine non-contiguous byte ranges being written 347such that the dirty byte range becomes a superset of the bytes 348that are dirty. 349This reduces the number of writes significantly for software 350builds. 351The merging of byte ranges is not done if the file has been file 352locked, since most applications modifying a file from multiple 353clients will use file locking. 354As such, this option could result in a corrupted file for the 355rare case of an application modifying the file from multiple 356clients concurrently without using file locking. 357.It Cm principal 358For the RPCSEC_GSS security flavors, such as krb5, krb5i and krb5p, 359this option sets the name of the host based principal name expected 360by the server. 361This option overrides the default, which will be ``nfs@<server-fqdn>'' 362and should normally be sufficient. 363.It Cm noresvport 364Do 365.Em not 366use a reserved socket port number (see below). 367.It Cm port Ns = Ns Aq Ar port_number 368Use specified port number for NFS requests. 369The default is to query the portmapper for the NFS port. 370.It Cm proto Ns = Ns Aq Ar protocol 371Specify transport protocol version to use. 372Currently, they are: 373.Bd -literal 374udp - Use UDP over IPv4 375tcp - Use TCP over IPv4 376udp6 - Use UDP over IPv6 377tcp6 - Use TCP over IPv6 378.Ed 379.It Cm rdirplus 380Used with NFSV3 to specify that the \fBReaddirPlus\fR RPC should 381be used. 382For NFSV4, setting this option has a similar effect, in that it will make 383the Readdir Operation get more attributes. 384This option reduces RPC traffic for cases such as 385.Dq "ls -l" , 386but tends to flood the attribute and name caches with prefetched entries. 387Try this option and see whether performance improves or degrades. 388Probably 389most useful for client to server network interconnects with a large bandwidth 390times delay product. 391.It Cm readahead Ns = Ns Aq Ar value 392Set the read-ahead count to the specified value. 393This may be in the range of 0 - 4, and determines how many blocks 394will be read ahead when a large file is being read sequentially. 395Trying a value greater than 1 for this is suggested for 396mounts with a large bandwidth * delay product. 397.It Cm readdirsize Ns = Ns Aq Ar value 398Set the readdir read size to the specified value. 399The value should normally 400be a multiple of 401.Dv DIRBLKSIZ 402that is <= the read size for the mount. 403.It Cm resvport 404Use a reserved socket port number. 405This flag is obsolete, and only retained for compatibility reasons. 406Reserved port numbers are used by default now. 407(For the rare case where the client has a trusted root account 408but untrustworthy users and the network cables are in secure areas this does 409help, but for normal desktop clients this does not apply.) 410.It Cm retrans Ns = Ns Aq Ar value 411Set the retransmit timeout count for soft mounts to the specified value. 412.It Cm retrycnt Ns = Ns Aq Ar count 413Set the mount retry count to the specified value. 414The default is a retry count of zero, which means to keep retrying 415forever. 416There is a 60 second delay between each attempt. 417.It Cm rsize Ns = Ns Aq Ar value 418Set the read data size to the specified value. 419It should normally be a power of 2 greater than or equal to 1024. 420This should be used for UDP mounts when the 421.Dq "fragments dropped due to timeout" 422value is getting large while actively using a mount point. 423(Use 424.Xr netstat 1 425with the 426.Fl s 427option to see what the 428.Dq "fragments dropped due to timeout" 429value is.) 430.It Cm sec Ns = Ns Aq Ar flavor 431This option specifies what security flavor should be used for the mount. 432Currently, they are: 433.Bd -literal 434krb5 - Use KerberosV authentication 435krb5i - Use KerberosV authentication and 436 apply integrity checksums to RPCs 437krb5p - Use KerberosV authentication and 438 encrypt the RPC data 439sys - The default AUTH_SYS, which uses a 440 uid + gid list authenticator 441.Ed 442.It Cm soft 443A soft mount, which implies that file system calls will fail 444after 445.Ar retrycnt 446round trip timeout intervals. 447.It Cm syskrb5 448This option specifies that a KerberosV NFSv4 minor version 1 or 2 mount 449uses AUTH_SYS for system operations. 450Using this option avoids the need for a KerberosV mount to have a 451host-based principal entry in the default keytab file 452(no 453.Cm gssname 454option) or a requirement for the user doing the mount to have a 455valid KerberosV ticket granting ticket (TGT) when the mount is done. 456This option is intended to be used with the 457.Cm sec Ns = Ns krb5 458and 459.Cm tls 460options and can only be used for 461NFSv4 mounts with minor version 1 or 2. 462.It Cm tcp 463Use TCP transport. 464This is the default option, as it provides for increased reliability on both 465LAN and WAN configurations compared to UDP. 466Some old NFS servers do not support this method; UDP mounts may be required 467for interoperability. 468.It Cm timeout Ns = Ns Aq Ar value 469Set the initial retransmit timeout to the specified value, 470expressed in tenths of a second. 471May be useful for fine tuning UDP mounts over internetworks 472with high packet loss rates or an overloaded server. 473Try increasing the interval if 474.Xr nfsstat 1 475shows high retransmit rates while the file system is active or reducing the 476value if there is a low retransmit rate but long response delay observed. 477(Normally, the 478.Cm dumbtimer 479option should be specified when using this option to manually 480tune the timeout 481interval.) 482.It Cm timeo Ns = Ns Aq Ar value 483Alias for 484.Cm timeout . 485.It Cm tls 486This option specifies that the connection to the server must use TLS 487per RFC 9289. 488TLS is only supported for TCP connections and the 489.Xr rpc.tlsclntd 8 490daemon must be running for an NFS over TCP connection to use TLS. 491.It Cm tlscertname Ns = Ns Aq Ar name 492This option specifies the name of an alternate certificate to be 493presented to the NFS server during TLS handshake. 494The default certificate file names are 495.Dq cert.pem 496and 497.Dq certkey.pem . 498When this option is specified, 499.Ar name 500replaces 501.Dq cert 502in the above file names. 503For example, if the value of 504.Ar name 505is specified as 506.Dq other 507the certificate file names to be used will be 508.Dq other.pem 509and 510.Dq otherkey.pem . 511These files are stored in 512.Pa /etc/rpc.tlsclntd 513by default. 514This option is only meaningful when used with the 515.Cm tls 516option and the 517.Xr rpc.tlsclntd 8 518is running with the 519.Fl m 520command line flag set. 521.It Cm udp 522Use UDP transport. 523.It Cm vers Ns = Ns Aq Ar vers_number 524Use the specified version number for NFS requests. 525See the 526.Cm nfsv2 , 527.Cm nfsv3 , 528and 529.Cm nfsv4 530options for details. 531.It Cm wcommitsize Ns = Ns Aq Ar value 532Set the maximum pending write commit size to the specified value. 533This determines the maximum amount of pending write data that the NFS 534client is willing to cache for each file. 535.It Cm wsize Ns = Ns Aq Ar value 536Set the write data size to the specified value. 537Ditto the comments w.r.t.\& the 538.Cm rsize 539option, but using the 540.Dq "fragments dropped due to timeout" 541value on the server instead of the client. 542Note that both the 543.Cm rsize 544and 545.Cm wsize 546options should only be used as a last ditch effort at improving performance 547when mounting servers that do not support TCP mounts. 548.El 549.El 550.Sh IMPLEMENTATION NOTES 551When neither the 552.Cm rsize 553nor 554.Cm wsize 555options are specified, the I/O size will be set to the largest value 556supported by both the NFS client and server. 557The largest value supported by the NFS client is defined by 558the tunable 559.Cd vfs.maxbcachebuf 560which can be set to a power of two up to 561.Cd kern.maxphys . 562.Pp 563The 564.Xr nfsstat 1 565command with the 566.Ic -m 567command line option will show what 568.Nm 569option settings are actually in use for the mount. 570.Sh COMPATIBILITY 571The following command line flags are equivalent to 572.Fl o 573named options and are supported for compatibility with older 574installations. 575.Bl -tag -width indent 576.It Fl 2 577Same as 578.Fl o Cm nfsv2 579.It Fl 3 580Same as 581.Fl o Cm nfsv3 582.It Fl D 583Same as 584.Fl o Cm deadthresh 585.It Fl I 586Same as 587.Fl o Cm readdirsize Ns = Ns Aq Ar value 588.It Fl L 589Same as 590.Fl o Cm nolockd 591.It Fl N 592Same as 593.Fl o Cm noresvport 594.It Fl P 595Use a reserved socket port number. 596This flag is obsolete, and only retained for compatibility reasons. 597(For the rare case where the client has a trusted root account 598but untrustworthy users and the network cables are in secure areas this does 599help, but for normal desktop clients this does not apply.) 600.It Fl R 601Same as 602.Fl o Cm retrycnt Ns = Ns Aq Ar value 603.It Fl T 604Same as 605.Fl o Cm tcp 606.It Fl U 607Same as 608.Fl o Cm mntudp 609.It Fl a 610Same as 611.Fl o Cm readahead Ns = Ns Aq Ar value 612.It Fl b 613Same as 614.Fl o Cm bg 615.It Fl c 616Same as 617.Fl o Cm noconn 618.It Fl d 619Same as 620.Fl o Cm dumbtimer 621.It Fl g 622Same as 623.Fl o Cm maxgroups 624.It Fl i 625Same as 626.Fl o Cm intr 627.It Fl l 628Same as 629.Fl o Cm rdirplus 630.It Fl r 631Same as 632.Fl o Cm rsize Ns = Ns Aq Ar value 633.It Fl s 634Same as 635.Fl o Cm soft 636.It Fl t 637Same as 638.Fl o Cm retransmit Ns = Ns Aq Ar value 639.It Fl w 640Same as 641.Fl o Cm wsize Ns = Ns Aq Ar value 642.It Fl x 643Same as 644.Fl o Cm retrans Ns = Ns Aq Ar value 645.El 646.Pp 647The following 648.Fl o 649named options are equivalent to other 650.Fl o 651named options and are supported for compatibility with other 652operating systems (e.g., Linux, Solaris, and OSX) to ease usage of 653.Xr autofs 5 654support. 655.Bl -tag -width indent 656.It Fl o Cm vers Ns = Ns 2 657Same as 658.Fl o Cm nfsv2 659.It Fl o Cm vers Ns = Ns 3 660Same as 661.Fl o Cm nfsv3 662.It Fl o Cm vers Ns = Ns 4 663Same as 664.Fl o Cm nfsv4 665.El 666.Sh SEE ALSO 667.Xr nfsstat 1 , 668.Xr nmount 2 , 669.Xr unmount 2 , 670.Xr lagg 4 , 671.Xr nfsv4 4 , 672.Xr fstab 5 , 673.Xr gssd 8 , 674.Xr mount 8 , 675.Xr nfsd 8 , 676.Xr nfsiod 8 , 677.Xr rpc.tlsclntd 8 , 678.Xr showmount 8 679.Sh HISTORY 680A version of the 681.Nm 682utility appeared in 683.Bx 4.4 . 684.Sh BUGS 685Since NFSv4 performs open/lock operations that have their ordering strictly 686enforced by the server, the options 687.Cm intr 688and 689.Cm soft 690cannot be safely used. 691For NFSv4 minor version 1 or 2 mounts, the ordering is done 692via session slots and the NFSv4 client now handles broken session slots 693fairly well. 694As such, if the 695.Cm nolockd 696option is used along with 697.Cm intr 698and/or 699.Cm soft , 700an NFSv4 minor version 1 or 2 mount 701should work fairly well, although still not completely correctly. 702For NFSv4 minor version 0 mounts, 703.Cm hard 704mounts without the 705.Cm intr 706mount option is strongly recommended. 707