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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 October 30, 2014 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 . 62It implements the mount protocol as described in RFC 1094, Appendix A and 63.%T "NFS: Network File System Version 3 Protocol Specification" , 64Appendix I. 65.Pp 66If the file system type is specified as ``oldnfs'', which implies this 67command is run as ``mount_oldnfs'', then it forces use of the old NFS 68client, which does not support the 69.Cm nfsv4 70option. 71.Pp 72By default, 73.Nm 74keeps retrying until the mount succeeds. 75This behaviour is intended for file systems listed in 76.Xr fstab 5 77that are critical to the boot process. 78For non-critical file systems, the 79.Cm bg 80and 81.Cm retrycnt 82options provide mechanisms to prevent the boot process from hanging 83if the server is unavailable. 84.Pp 85If the server becomes unresponsive while an NFS file system is 86mounted, any new or outstanding file operations on that file system 87will hang uninterruptibly until the server comes back. 88To modify this default behaviour, see the 89.Cm intr 90and 91.Cm soft 92options. 93.Pp 94The options are: 95.Bl -tag -width indent 96.It Fl o 97Options are specified with a 98.Fl o 99flag followed by a comma separated string of options. 100See the 101.Xr mount 8 102man page for possible options and their meanings. 103The following NFS specific options are also available: 104.Bl -tag -width indent 105.It Cm acregmin Ns = Ns Aq Ar seconds 106.It Cm acregmax Ns = Ns Aq Ar seconds 107.It Cm acdirmin Ns = Ns Aq Ar seconds 108.It Cm acdirmax Ns = Ns Aq Ar seconds 109When attributes of files are cached, a timeout calculated to determine 110whether a given cache entry has expired. 111These four values determine the upper and lower bounds of the timeouts for 112.Dq directory 113attributes and 114.Dq regular 115(ie: everything else). 116The default values are 3 -> 60 seconds 117for regular files, and 30 -> 60 seconds for directories. 118The algorithm to calculate the timeout is based on the age of the file. 119The older the file, 120the longer the cache is considered valid, subject to the limits above. 121.It Cm actimeo Ns = Ns Aq Ar seconds 122Set four cache timeouts above to specified value. 123.It Cm allgssname 124This option can be used along with 125.Fl o Cm gssname 126to specify that all operations should use the host-based initiator 127credential. 128This may be used for clients that run system daemons that need to 129access files on the NFSv4 mounted volume. 130.It Cm bg 131If an initial attempt to contact the server fails, fork off a child to keep 132trying the mount in the background. 133Useful for 134.Xr fstab 5 , 135where the file system mount is not critical to multiuser operation. 136.It Cm deadthresh Ns = Ns Aq Ar value 137Set the 138.Dq "dead server threshold" 139to the specified number of round trip timeout intervals before a 140.Dq "server not responding" 141message is displayed. 142.It Cm dumbtimer 143Turn off the dynamic retransmit timeout estimator. 144This may be useful for UDP mounts that exhibit high retry rates, 145since it is possible that the dynamically estimated timeout interval is too 146short. 147.It Cm fg 148Same as not specifying 149.Cm bg . 150.It Cm gssname Ns = Ns Aq Ar service-principal-name 151This option can be used with the KerberosV security flavors for NFSv4 mounts 152to specify the 153.Dq "service-principal-name" 154of a host-based entry in the default 155keytab file that is used for system operations. 156It allows the mount to be performed by 157.Dq "root" 158and avoids problems with 159cached credentials for the system operations expiring. 160The 161.Dq "service-prinicpal-name" 162should be specified without instance or domain and is typically 163.Dq "host" , 164.Dq "nfs" 165or 166.Dq "root" . 167.It Cm hard 168Same as not specifying 169.Cm soft . 170.It Cm intr 171Make the mount interruptible, which implies that file system calls that 172are delayed due to an unresponsive server will fail with EINTR when a 173termination signal is posted for the process. 174.It Cm maxgroups Ns = Ns Aq Ar value 175Set the maximum size of the group list for the credentials to the 176specified value. 177This should be used for mounts on old servers that cannot handle a 178group list size of 16, as specified in RFC 1057. 179Try 8, if users in a lot of groups cannot get response from the mount 180point. 181.It Cm mntudp 182Force the mount protocol to use UDP transport, even for TCP NFS mounts. 183(Necessary for some old 184.Bx 185servers.) 186.It Cm nametimeo Ns = Ns Aq Ar value 187Override the default of NFS_DEFAULT_NAMETIMEO for the timeout (in seconds) 188for positive name cache entries. 189If this is set to 0 it disables positive name caching for the mount point. 190.It Cm negnametimeo Ns = Ns Aq Ar value 191Override the default of NFS_DEFAULT_NEGNAMETIMEO for the timeout (in seconds) 192for negative name cache entries. If this is set to 0 it disables negative 193name caching for the mount point. 194.It Cm nfsv2 195Use the NFS Version 2 protocol (the default is to try version 3 first 196then version 2). 197Note that NFS version 2 has a file size limit of 2 gigabytes. 198.It Cm nfsv3 199Use the NFS Version 3 protocol. 200.It Cm nfsv4 201Use the NFS Version 4 protocol. 202This option will force the mount to use 203TCP transport. 204.It Cm minorversion Ns = Ns Aq Ar value 205Override the default of 0 for the minor version of the NFS Version 4 protocol. 206The only minor version currently supported is 1. 207This option is only meaningful when used with the 208.Cm nfsv4 209option. 210.It Cm pnfs 211Enable support for parallel NFS (pNFS) for minor version 1 of the 212NFS Version 4 protocol. 213This option is only meaningful when used with the 214.Cm minorversion 215option. 216.It Cm noac 217Disable attribute caching. 218.It Cm noconn 219For UDP mount points, do not do a 220.Xr connect 2 . 221This must be used if the server does not reply to requests from the standard 222NFS port number 2049 or replies to requests using a different IP address 223(which can occur if the server is multi-homed). 224Setting the 225.Va vfs.nfs.nfs_ip_paranoia 226sysctl to 0 will make this option the default. 227.It Cm nocto 228Normally, NFS clients maintain the close-to-open cache coherency. 229This works by flushing at close time and checking at open time. 230Checking at open time is implemented by getting attributes from 231the server and purging the data cache if they do not match 232attributes cached by the client. 233.Pp 234This option disables checking at open time. 235It may improve performance for read-only mounts, 236but should only be used if the data on the server changes rarely. 237Be sure to understand the consequences before enabling this option. 238.It Cm noinet4 , noinet6 239Disables 240.Dv AF_INET 241or 242.Dv AF_INET6 243connections. 244Useful for hosts that have 245both an A record and an AAAA record for the same name. 246.It Cm nolockd 247Do 248.Em not 249forward 250.Xr fcntl 2 251locks over the wire. 252All locks will be local and not seen by the server 253and likewise not seen by other NFS clients. 254This removes the need to run the 255.Xr rpcbind 8 256service and the 257.Xr rpc.statd 8 258and 259.Xr rpc.lockd 8 260servers on the client. 261Note that this option will only be honored when performing the 262initial mount, it will be silently ignored if used while updating 263the mount options. 264.It Cm noncontigwr 265This mount option allows the NFS client to 266combine non-contiguous byte ranges being written 267such that the dirty byte range becomes a superset of the bytes 268that are dirty. 269This reduces the number of writes significantly for software 270builds. 271The merging of byte ranges isn't done if the file has been file 272locked, since most applications modifying a file from multiple 273clients will use file locking. 274As such, this option could result in a corrupted file for the 275rare case of an application modifying the file from multiple 276clients concurrently without using file locking. 277.It Cm principal 278For the RPCSEC_GSS security flavors, such as krb5, krb5i and krb5p, 279this option sets the name of the host based principal name expected 280by the server. This option overrides the default, which will be 281``nfs@<server-fqdn>'' and should normally be sufficient. 282.It Cm noresvport 283Do 284.Em not 285use a reserved socket port number (see below). 286.It Cm port Ns = Ns Aq Ar port_number 287Use specified port number for NFS requests. 288The default is to query the portmapper for the NFS port. 289.It Cm proto Ns = Ns Aq Ar protocol 290Specify transport protocol version to use. 291Currently, they are: 292.Bd -literal 293udp - Use UDP over IPv4 294tcp - Use TCP over IPv4 295udp6 - Use UDP over IPv6 296tcp6 - Use TCP over IPv6 297.Ed 298.It Cm rdirplus 299Used with NFSV3 to specify that the \fBReaddirPlus\fR RPC should 300be used. 301For NFSV4, setting this option has a similar effect, in that it will make 302the Readdir Operation get more attributes. 303This option reduces RPC traffic for cases such as 304.Dq "ls -l" , 305but tends to flood the attribute and name caches with prefetched entries. 306Try this option and see whether performance improves or degrades. 307Probably 308most useful for client to server network interconnects with a large bandwidth 309times delay product. 310.It Cm readahead Ns = Ns Aq Ar value 311Set the read-ahead count to the specified value. 312This may be in the range of 0 - 4, and determines how many blocks 313will be read ahead when a large file is being read sequentially. 314Trying a value greater than 1 for this is suggested for 315mounts with a large bandwidth * delay product. 316.It Cm readdirsize Ns = Ns Aq Ar value 317Set the readdir read size to the specified value. 318The value should normally 319be a multiple of 320.Dv DIRBLKSIZ 321that is <= the read size for the mount. 322.It Cm resvport 323Use a reserved socket port number. 324This flag is obsolete, and only retained for compatibility reasons. 325Reserved port numbers are used by default now. 326(For the rare case where the client has a trusted root account 327but untrustworthy users and the network cables are in secure areas this does 328help, but for normal desktop clients this does not apply.) 329.It Cm retrans Ns = Ns Aq Ar value 330Set the retransmit timeout count for soft mounts to the specified value. 331.It Cm retrycnt Ns = Ns Aq Ar count 332Set the mount retry count to the specified value. 333The default is a retry count of zero, which means to keep retrying 334forever. 335There is a 60 second delay between each attempt. 336.It Cm rsize Ns = Ns Aq Ar value 337Set the read data size to the specified value. 338It should normally be a power of 2 greater than or equal to 1024. 339This should be used for UDP mounts when the 340.Dq "fragments dropped due to timeout" 341value is getting large while actively using a mount point. 342(Use 343.Xr netstat 1 344with the 345.Fl s 346option to see what the 347.Dq "fragments dropped due to timeout" 348value is.) 349.It Cm sec Ns = Ns Aq Ar flavor 350This option specifies what security flavor should be used for the mount. 351Currently, they are: 352.Bd -literal 353krb5 - Use KerberosV authentication 354krb5i - Use KerberosV authentication and 355 apply integrity checksums to RPCs 356krb5p - Use KerberosV authentication and 357 encrypt the RPC data 358sys - The default AUTH_SYS, which uses a 359 uid + gid list authenticator 360.Ed 361.It Cm soft 362A soft mount, which implies that file system calls will fail 363after 364.Ar retrycnt 365round trip timeout intervals. 366.It Cm tcp 367Use TCP transport. 368This is the default option, as it provides for increased reliability on both 369LAN and WAN configurations compared to UDP. 370Some old NFS servers do not support this method; UDP mounts may be required 371for interoperability. 372.It Cm timeout Ns = Ns Aq Ar value 373Set the initial retransmit timeout to the specified value, 374expressed in tenths of a second. 375May be useful for fine tuning UDP mounts over internetworks 376with high packet loss rates or an overloaded server. 377Try increasing the interval if 378.Xr nfsstat 1 379shows high retransmit rates while the file system is active or reducing the 380value if there is a low retransmit rate but long response delay observed. 381(Normally, the 382.Cm dumbtimer 383option should be specified when using this option to manually 384tune the timeout 385interval.) 386.It Cm timeo Ns = Ns Aq Ar value 387Alias for 388.Cm timeout . 389.It Cm udp 390Use UDP transport. 391.It Cm vers Ns = Ns Aq Ar vers_number 392Use the specified version number for NFS requests. 393See the 394.Cm nfsv2 , 395.Cm nfsv3 , 396and 397.Cm nfsv4 398options for details. 399.It Cm wcommitsize Ns = Ns Aq Ar value 400Set the maximum pending write commit size to the specified value. 401This determines the maximum amount of pending write data that the NFS 402client is willing to cache for each file. 403.It Cm wsize Ns = Ns Aq Ar value 404Set the write data size to the specified value. 405Ditto the comments w.r.t.\& the 406.Cm rsize 407option, but using the 408.Dq "fragments dropped due to timeout" 409value on the server instead of the client. 410Note that both the 411.Cm rsize 412and 413.Cm wsize 414options should only be used as a last ditch effort at improving performance 415when mounting servers that do not support TCP mounts. 416.El 417.El 418.Sh COMPATIBILITY 419The following command line flags are equivalent to 420.Fl o 421named options and are supported for compatibility with older 422installations. 423.Bl -tag -width indent 424.It Fl 2 425Same as 426.Fl o Cm nfsv2 427.It Fl 3 428Same as 429.Fl o Cm nfsv3 430.It Fl D 431Same as 432.Fl o Cm deadthresh 433.It Fl I 434Same as 435.Fl o Cm readdirsize Ns = Ns Aq Ar value 436.It Fl L 437Same as 438.Fl o Cm nolockd 439.It Fl N 440Same as 441.Fl o Cm noresvport 442.It Fl P 443Use a reserved socket port number. 444This flag is obsolete, and only retained for compatibility reasons. 445(For the rare case where the client has a trusted root account 446but untrustworthy users and the network cables are in secure areas this does 447help, but for normal desktop clients this does not apply.) 448.It Fl R 449Same as 450.Fl o Cm retrycnt Ns = Ns Aq Ar value 451.It Fl T 452Same as 453.Fl o Cm tcp 454.It Fl U 455Same as 456.Fl o Cm mntudp 457.It Fl a 458Same as 459.Fl o Cm readahead Ns = Ns Aq Ar value 460.It Fl b 461Same as 462.Fl o Cm bg 463.It Fl c 464Same as 465.Fl o Cm noconn 466.It Fl d 467Same as 468.Fl o Cm dumbtimer 469.It Fl g 470Same as 471.Fl o Cm maxgroups 472.It Fl i 473Same as 474.Fl o Cm intr 475.It Fl l 476Same as 477.Fl o Cm rdirplus 478.It Fl r 479Same as 480.Fl o Cm rsize Ns = Ns Aq Ar value 481.It Fl s 482Same as 483.Fl o Cm soft 484.It Fl t 485Same as 486.Fl o Cm retransmit Ns = Ns Aq Ar value 487.It Fl w 488Same as 489.Fl o Cm wsize Ns = Ns Aq Ar value 490.It Fl x 491Same as 492.Fl o Cm retrans Ns = Ns Aq Ar value 493.El 494.Pp 495The following 496.Fl o 497named options are equivalent to other 498.Fl o 499named options and are supported for compatibility with other 500operating systems (e.g., Linux, Solaris, and OSX) to ease usage of 501.Xr autofs 5 502support. 503.Bl -tag -width indent 504.It Fl o Cm vers Ns = Ns 2 505Same as 506.Fl o Cm nfsv2 507.It Fl o Cm vers Ns = Ns 3 508Same as 509.Fl o Cm nfsv3 510.It Fl o Cm vers Ns = Ns 4 511Same as 512.Fl o Cm nfsv4 513.El 514.Sh SEE ALSO 515.Xr nmount 2 , 516.Xr unmount 2 , 517.Xr nfsv4 4 , 518.Xr fstab 5 , 519.Xr gssd 8 , 520.Xr mount 8 , 521.Xr nfsd 8 , 522.Xr nfsiod 8 , 523.Xr showmount 8 524.Sh BUGS 525Since nfsv4 performs open/lock operations that have their ordering strictly 526enforced by the server, the options 527.Cm intr 528and 529.Cm soft 530cannot be safely used. 531.Cm hard 532nfsv4 mounts are strongly recommended. 533