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 December 14, 2019 32.Dt MOUNT_NFS 8 33.Os 34.Sh NAME 35.Nm mount_nfs 36.Nd mount NFS file systems 37.Sh SYNOPSIS 38.Nm 39.Op Fl 23bcdiLlNPsTU 40.Op Fl a Ar maxreadahead 41.Op Fl D Ar deadthresh 42.Op Fl g Ar maxgroups 43.Op Fl I Ar readdirsize 44.Op Fl o Ar options 45.Op Fl R Ar retrycnt 46.Op Fl r Ar readsize 47.Op Fl t Ar timeout 48.Op Fl w Ar writesize 49.Op Fl x Ar retrans 50.Ar rhost : Ns Ar path node 51.Sh DESCRIPTION 52The 53.Nm 54utility calls the 55.Xr nmount 2 56system call to prepare and graft a remote NFS file system 57.Pq Ar rhost : Ns Ar path 58on to the file system tree at the point 59.Ar node . 60This command is normally executed by 61.Xr mount 8 . 62For NFSv2 and NFSv3, 63it implements the mount protocol as described in RFC 1094, Appendix A and 64RFC 1813, Appendix I. 65For NFSv4, it uses the NFSv4 protocol as described in RFC 7530, RFC 5661 and 66RFC 7862. 67.Pp 68By default, 69.Nm 70keeps retrying until the mount succeeds. 71This behaviour is intended for file systems listed in 72.Xr fstab 5 73that are critical to the boot process. 74For non-critical file systems, the 75.Cm bg 76and 77.Cm retrycnt 78options provide mechanisms to prevent the boot process from hanging 79if the server is unavailable. 80.Pp 81If the server becomes unresponsive while an NFS file system is 82mounted, any new or outstanding file operations on that file system 83will hang uninterruptibly until the server comes back. 84To modify this default behaviour, see the 85.Cm intr 86and 87.Cm soft 88options. 89.Pp 90The options are: 91.Bl -tag -width indent 92.It Fl o 93Options are specified with a 94.Fl o 95flag followed by a comma separated string of options. 96See the 97.Xr mount 8 98man page for possible options and their meanings. 99The following NFS specific options are also available: 100.Bl -tag -width indent 101.It Cm acregmin Ns = Ns Aq Ar seconds 102.It Cm acregmax Ns = Ns Aq Ar seconds 103.It Cm acdirmin Ns = Ns Aq Ar seconds 104.It Cm acdirmax Ns = Ns Aq Ar seconds 105When attributes of files are cached, a timeout calculated to determine 106whether a given cache entry has expired. 107These four values determine the upper and lower bounds of the timeouts for 108.Dq directory 109attributes and 110.Dq regular 111(ie: everything else). 112The default values are 3 -> 60 seconds 113for regular files, and 30 -> 60 seconds for directories. 114The algorithm to calculate the timeout is based on the age of the file. 115The older the file, 116the longer the cache is considered valid, subject to the limits above. 117.It Cm actimeo Ns = Ns Aq Ar seconds 118Set four cache timeouts above to specified value. 119.It Cm allgssname 120This option can be used along with 121.Fl o Cm gssname 122to specify that all operations should use the host-based initiator 123credential. 124This may be used for clients that run system daemons that need to 125access files on the NFSv4 mounted volume. 126.It Cm bg 127If an initial attempt to contact the server fails, fork off a child to keep 128trying the mount in the background. 129Useful for 130.Xr fstab 5 , 131where the file system mount is not critical to multiuser operation. 132.It Cm deadthresh Ns = Ns Aq Ar value 133Set the 134.Dq "dead server threshold" 135to the specified number of round trip timeout intervals before a 136.Dq "server not responding" 137message is displayed. 138.It Cm dumbtimer 139Turn off the dynamic retransmit timeout estimator. 140This may be useful for UDP mounts that exhibit high retry rates, 141since it is possible that the dynamically estimated timeout interval is too 142short. 143.It Cm fg 144Same as not specifying 145.Cm bg . 146.It Cm gssname Ns = Ns Aq Ar service-principal-name 147This option can be used with the KerberosV security flavors for NFSv4 mounts 148to specify the 149.Dq "service-principal-name" 150of a host-based entry in the default 151keytab file that is used for system operations. 152It allows the mount to be performed by 153.Dq "root" 154and avoids problems with 155cached credentials for the system operations expiring. 156The 157.Dq "service-prinicpal-name" 158should be specified without instance or domain and is typically 159.Dq "host" , 160.Dq "nfs" 161or 162.Dq "root" , 163although the form 164.Sm off 165.Aq Ar service 166@ 167.Aq Ar fqdn 168.Sm on 169can also be used if the local system's 170.Xr gethostname 3 171value does not match the host-based principal in the keytab. 172.It Cm hard 173Same as not specifying 174.Cm soft . 175.It Cm intr 176Make the mount interruptible, which implies that file system calls that 177are delayed due to an unresponsive server will fail with EINTR when a 178termination signal is posted for the process. 179.It Cm maxgroups Ns = Ns Aq Ar value 180Set the maximum size of the group list for the credentials to the 181specified value. 182This should be used for mounts on old servers that cannot handle a 183group list size of 16, as specified in RFC 1057. 184Try 8, if users in a lot of groups cannot get response from the mount 185point. 186.It Cm mntudp 187Force the mount protocol to use UDP transport, even for TCP NFS mounts. 188(Necessary for some old 189.Bx 190servers.) 191.It Cm nametimeo Ns = Ns Aq Ar value 192Override the default of NFS_DEFAULT_NAMETIMEO for the timeout (in seconds) 193for positive name cache entries. 194If this is set to 0 it disables positive name caching for the mount point. 195.It Cm negnametimeo Ns = Ns Aq Ar value 196Override the default of NFS_DEFAULT_NEGNAMETIMEO for the timeout (in seconds) 197for negative name cache entries. 198If this is set to 0 it disables negative name caching for the mount point. 199.It Cm nfsv2 200Use the NFS Version 2 protocol (the default is to try version 3 first 201then version 2). 202Note that NFS version 2 has a file size limit of 2 gigabytes. 203.It Cm nfsv3 204Use the NFS Version 3 protocol. 205.It Cm nfsv4 206Use the NFS Version 4 protocol. 207This option will force the mount to use 208TCP transport. 209.It Cm minorversion Ns = Ns Aq Ar value 210Override the default of 0 for the minor version of the NFS Version 4 protocol. 211The minor versions other than 0 currently supported are 1 and 2. 212This option is only meaningful when used with the 213.Cm nfsv4 214option. 215.It Cm oneopenown 216Make a minor version 1 or 2 of the NFS Version 4 protocol mount use a single 217OpenOwner for all Opens. 218This may be useful for a server with a very low limit on OpenOwners, such as 219AmazonEFS. 220It ca only be used with an NFSv4.1 or NFSv4.2 mount. 221It may not work correctly when Delegations are being issued by a server, 222but note that the AmazonEFS server does not issued delegations at this time. 223.It Cm pnfs 224Enable support for parallel NFS (pNFS) for minor version 1 or 2 of the 225NFS Version 4 protocol. 226This option is only meaningful when used with the 227.Cm minorversion 228option. 229.It Cm noac 230Disable attribute caching. 231.It Cm noconn 232For UDP mount points, do not do a 233.Xr connect 2 . 234This must be used if the server does not reply to requests from the standard 235NFS port number 2049 or replies to requests using a different IP address 236(which can occur if the server is multi-homed). 237Setting the 238.Va vfs.nfs.nfs_ip_paranoia 239sysctl to 0 will make this option the default. 240.It Cm nocto 241Normally, NFS clients maintain the close-to-open cache coherency. 242This works by flushing at close time and checking at open time. 243Checking at open time is implemented by getting attributes from 244the server and purging the data cache if they do not match 245attributes cached by the client. 246.Pp 247This option disables checking at open time. 248It may improve performance for read-only mounts, 249but should only be used if the data on the server changes rarely. 250Be sure to understand the consequences before enabling this option. 251.It Cm noinet4 , noinet6 252Disables 253.Dv AF_INET 254or 255.Dv AF_INET6 256connections. 257Useful for hosts that have 258both an A record and an AAAA record for the same name. 259.It Cm nolockd 260Do 261.Em not 262forward 263.Xr fcntl 2 264locks over the wire via the NLM protocol for NFSv3 mounts. 265All locks will be local and not seen by the server 266and likewise not seen by other NFS clients for NFSv3 mounts. 267This removes the need to run the 268.Xr rpcbind 8 269service and the 270.Xr rpc.statd 8 271and 272.Xr rpc.lockd 8 273servers on the client. 274Note that this option will only be honored when performing the 275initial mount, it will be silently ignored if used while updating 276the mount options. 277Also, note that NFSv4 mounts do not use these daemons and handle locks over the 278wire in the NFSv4 protocol. 279As such, this option is meaningless for NFSv4 mounts. 280.It Cm noncontigwr 281This mount option allows the NFS client to 282combine non-contiguous byte ranges being written 283such that the dirty byte range becomes a superset of the bytes 284that are dirty. 285This reduces the number of writes significantly for software 286builds. 287The merging of byte ranges is not done if the file has been file 288locked, since most applications modifying a file from multiple 289clients will use file locking. 290As such, this option could result in a corrupted file for the 291rare case of an application modifying the file from multiple 292clients concurrently without using file locking. 293.It Cm principal 294For the RPCSEC_GSS security flavors, such as krb5, krb5i and krb5p, 295this option sets the name of the host based principal name expected 296by the server. 297This option overrides the default, which will be ``nfs@<server-fqdn>'' 298and should normally be sufficient. 299.It Cm noresvport 300Do 301.Em not 302use a reserved socket port number (see below). 303.It Cm port Ns = Ns Aq Ar port_number 304Use specified port number for NFS requests. 305The default is to query the portmapper for the NFS port. 306.It Cm proto Ns = Ns Aq Ar protocol 307Specify transport protocol version to use. 308Currently, they are: 309.Bd -literal 310udp - Use UDP over IPv4 311tcp - Use TCP over IPv4 312udp6 - Use UDP over IPv6 313tcp6 - Use TCP over IPv6 314.Ed 315.It Cm rdirplus 316Used with NFSV3 to specify that the \fBReaddirPlus\fR RPC should 317be used. 318For NFSV4, setting this option has a similar effect, in that it will make 319the Readdir Operation get more attributes. 320This option reduces RPC traffic for cases such as 321.Dq "ls -l" , 322but tends to flood the attribute and name caches with prefetched entries. 323Try this option and see whether performance improves or degrades. 324Probably 325most useful for client to server network interconnects with a large bandwidth 326times delay product. 327.It Cm readahead Ns = Ns Aq Ar value 328Set the read-ahead count to the specified value. 329This may be in the range of 0 - 4, and determines how many blocks 330will be read ahead when a large file is being read sequentially. 331Trying a value greater than 1 for this is suggested for 332mounts with a large bandwidth * delay product. 333.It Cm readdirsize Ns = Ns Aq Ar value 334Set the readdir read size to the specified value. 335The value should normally 336be a multiple of 337.Dv DIRBLKSIZ 338that is <= the read size for the mount. 339.It Cm resvport 340Use a reserved socket port number. 341This flag is obsolete, and only retained for compatibility reasons. 342Reserved port numbers are used by default now. 343(For the rare case where the client has a trusted root account 344but untrustworthy users and the network cables are in secure areas this does 345help, but for normal desktop clients this does not apply.) 346.It Cm retrans Ns = Ns Aq Ar value 347Set the retransmit timeout count for soft mounts to the specified value. 348.It Cm retrycnt Ns = Ns Aq Ar count 349Set the mount retry count to the specified value. 350The default is a retry count of zero, which means to keep retrying 351forever. 352There is a 60 second delay between each attempt. 353.It Cm rsize Ns = Ns Aq Ar value 354Set the read data size to the specified value. 355It should normally be a power of 2 greater than or equal to 1024. 356This should be used for UDP mounts when the 357.Dq "fragments dropped due to timeout" 358value is getting large while actively using a mount point. 359(Use 360.Xr netstat 1 361with the 362.Fl s 363option to see what the 364.Dq "fragments dropped due to timeout" 365value is.) 366.It Cm sec Ns = Ns Aq Ar flavor 367This option specifies what security flavor should be used for the mount. 368Currently, they are: 369.Bd -literal 370krb5 - Use KerberosV authentication 371krb5i - Use KerberosV authentication and 372 apply integrity checksums to RPCs 373krb5p - Use KerberosV authentication and 374 encrypt the RPC data 375sys - The default AUTH_SYS, which uses a 376 uid + gid list authenticator 377.Ed 378.It Cm soft 379A soft mount, which implies that file system calls will fail 380after 381.Ar retrycnt 382round trip timeout intervals. 383.It Cm tcp 384Use TCP transport. 385This is the default option, as it provides for increased reliability on both 386LAN and WAN configurations compared to UDP. 387Some old NFS servers do not support this method; UDP mounts may be required 388for interoperability. 389.It Cm timeout Ns = Ns Aq Ar value 390Set the initial retransmit timeout to the specified value, 391expressed in tenths of a second. 392May be useful for fine tuning UDP mounts over internetworks 393with high packet loss rates or an overloaded server. 394Try increasing the interval if 395.Xr nfsstat 1 396shows high retransmit rates while the file system is active or reducing the 397value if there is a low retransmit rate but long response delay observed. 398(Normally, the 399.Cm dumbtimer 400option should be specified when using this option to manually 401tune the timeout 402interval.) 403.It Cm timeo Ns = Ns Aq Ar value 404Alias for 405.Cm timeout . 406.It Cm udp 407Use UDP transport. 408.It Cm vers Ns = Ns Aq Ar vers_number 409Use the specified version number for NFS requests. 410See the 411.Cm nfsv2 , 412.Cm nfsv3 , 413and 414.Cm nfsv4 415options for details. 416.It Cm wcommitsize Ns = Ns Aq Ar value 417Set the maximum pending write commit size to the specified value. 418This determines the maximum amount of pending write data that the NFS 419client is willing to cache for each file. 420.It Cm wsize Ns = Ns Aq Ar value 421Set the write data size to the specified value. 422Ditto the comments w.r.t.\& the 423.Cm rsize 424option, but using the 425.Dq "fragments dropped due to timeout" 426value on the server instead of the client. 427Note that both the 428.Cm rsize 429and 430.Cm wsize 431options should only be used as a last ditch effort at improving performance 432when mounting servers that do not support TCP mounts. 433.El 434.El 435.Sh COMPATIBILITY 436The following command line flags are equivalent to 437.Fl o 438named options and are supported for compatibility with older 439installations. 440.Bl -tag -width indent 441.It Fl 2 442Same as 443.Fl o Cm nfsv2 444.It Fl 3 445Same as 446.Fl o Cm nfsv3 447.It Fl D 448Same as 449.Fl o Cm deadthresh 450.It Fl I 451Same as 452.Fl o Cm readdirsize Ns = Ns Aq Ar value 453.It Fl L 454Same as 455.Fl o Cm nolockd 456.It Fl N 457Same as 458.Fl o Cm noresvport 459.It Fl P 460Use a reserved socket port number. 461This flag is obsolete, and only retained for compatibility reasons. 462(For the rare case where the client has a trusted root account 463but untrustworthy users and the network cables are in secure areas this does 464help, but for normal desktop clients this does not apply.) 465.It Fl R 466Same as 467.Fl o Cm retrycnt Ns = Ns Aq Ar value 468.It Fl T 469Same as 470.Fl o Cm tcp 471.It Fl U 472Same as 473.Fl o Cm mntudp 474.It Fl a 475Same as 476.Fl o Cm readahead Ns = Ns Aq Ar value 477.It Fl b 478Same as 479.Fl o Cm bg 480.It Fl c 481Same as 482.Fl o Cm noconn 483.It Fl d 484Same as 485.Fl o Cm dumbtimer 486.It Fl g 487Same as 488.Fl o Cm maxgroups 489.It Fl i 490Same as 491.Fl o Cm intr 492.It Fl l 493Same as 494.Fl o Cm rdirplus 495.It Fl r 496Same as 497.Fl o Cm rsize Ns = Ns Aq Ar value 498.It Fl s 499Same as 500.Fl o Cm soft 501.It Fl t 502Same as 503.Fl o Cm retransmit Ns = Ns Aq Ar value 504.It Fl w 505Same as 506.Fl o Cm wsize Ns = Ns Aq Ar value 507.It Fl x 508Same as 509.Fl o Cm retrans Ns = Ns Aq Ar value 510.El 511.Pp 512The following 513.Fl o 514named options are equivalent to other 515.Fl o 516named options and are supported for compatibility with other 517operating systems (e.g., Linux, Solaris, and OSX) to ease usage of 518.Xr autofs 5 519support. 520.Bl -tag -width indent 521.It Fl o Cm vers Ns = Ns 2 522Same as 523.Fl o Cm nfsv2 524.It Fl o Cm vers Ns = Ns 3 525Same as 526.Fl o Cm nfsv3 527.It Fl o Cm vers Ns = Ns 4 528Same as 529.Fl o Cm nfsv4 530.El 531.Sh SEE ALSO 532.Xr nmount 2 , 533.Xr unmount 2 , 534.Xr nfsv4 4 , 535.Xr fstab 5 , 536.Xr gssd 8 , 537.Xr mount 8 , 538.Xr nfsd 8 , 539.Xr nfsiod 8 , 540.Xr showmount 8 541.Sh HISTORY 542A version of the 543.Nm 544utility appeared in 545.Bx 4.4 . 546.Sh BUGS 547Since nfsv4 performs open/lock operations that have their ordering strictly 548enforced by the server, the options 549.Cm intr 550and 551.Cm soft 552cannot be safely used. 553.Cm hard 554nfsv4 mounts are strongly recommended. 555