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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 December 7, 2013 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 allgssname 122This option can be used along with 123.Fl o Cm gssname 124to specify that all operations should use the host-based initiator 125credential. 126This may be used for clients that run system daemons that need to 127access files on the NFSv4 mounted volume. 128.It Cm bg 129If an initial attempt to contact the server fails, fork off a child to keep 130trying the mount in the background. 131Useful for 132.Xr fstab 5 , 133where the file system mount is not critical to multiuser operation. 134.It Cm deadthresh Ns = Ns Aq Ar value 135Set the 136.Dq "dead server threshold" 137to the specified number of round trip timeout intervals before a 138.Dq "server not responding" 139message is displayed. 140.It Cm dumbtimer 141Turn off the dynamic retransmit timeout estimator. 142This may be useful for UDP mounts that exhibit high retry rates, 143since it is possible that the dynamically estimated timeout interval is too 144short. 145.It Cm fg 146Same as not specifying 147.Cm bg . 148.It Cm gssname Ns = Ns Aq Ar service-principal-name 149This option can be used with the KerberosV security flavors for NFSv4 mounts 150to specify the 151.Dq "service-principal-name" 152of a host-based entry in the default 153keytab file that is used for system operations. 154It allows the mount to be performed by 155.Dq "root" 156and avoids problems with 157cached credentials for the system operations expiring. 158The 159.Dq "service-prinicpal-name" 160should be specified without instance or domain and is typically 161.Dq "host" , 162.Dq "nfs" 163or 164.Dq "root" . 165.It Cm hard 166Same as not specifying 167.Cm soft . 168.It Cm intr 169Make the mount interruptible, which implies that file system calls that 170are delayed due to an unresponsive server will fail with EINTR when a 171termination signal is posted for the process. 172.It Cm maxgroups Ns = Ns Aq Ar value 173Set the maximum size of the group list for the credentials to the 174specified value. 175This should be used for mounts on old servers that cannot handle a 176group list size of 16, as specified in RFC 1057. 177Try 8, if users in a lot of groups cannot get response from the mount 178point. 179.It Cm mntudp 180Force the mount protocol to use UDP transport, even for TCP NFS mounts. 181(Necessary for some old 182.Bx 183servers.) 184.It Cm nametimeo Ns = Ns Aq Ar value 185Override the default of NFS_DEFAULT_NAMETIMEO for the timeout (in seconds) 186for positive name cache entries. 187If this is set to 0 it disables positive name caching for the mount point. 188.It Cm negnametimeo Ns = Ns Aq Ar value 189Override the default of NFS_DEFAULT_NEGNAMETIMEO for the timeout (in seconds) 190for negative name cache entries. If this is set to 0 it disables negative 191name caching for the mount point. 192.It Cm nfsv2 193Use the NFS Version 2 protocol (the default is to try version 3 first 194then version 2). 195Note that NFS version 2 has a file size limit of 2 gigabytes. 196.It Cm nfsv3 197Use the NFS Version 3 protocol. 198.It Cm nfsv4 199Use the NFS Version 4 protocol. 200This option will force the mount to use 201TCP transport. 202.It Cm minorversion Ns = Ns Aq Ar value 203Override the default of 0 for the minor version of the NFS Version 4 protocol. 204The only minor version currently supported is 1. 205This option is only meaningful when used with the 206.Cm nfsv4 207option. 208.It Cm pnfs 209Enable support for parallel NFS (pNFS) for minor version 1 of the 210NFS Version 4 protocol. 211This option is only meaningful when used with the 212.Cm minorversion 213option. 214.It Cm noconn 215For UDP mount points, do not do a 216.Xr connect 2 . 217This must be used if the server does not reply to requests from the standard 218NFS port number 2049 or replies to requests using a different IP address 219(which can occur if the server is multi-homed). 220Setting the 221.Va vfs.nfs.nfs_ip_paranoia 222sysctl to 0 will make this option the default. 223.It Cm nocto 224Normally, NFS clients maintain the close-to-open cache coherency. 225This works by flushing at close time and checking at open time. 226Checking at open time is implemented by getting attributes from 227the server and purging the data cache if they do not match 228attributes cached by the client. 229.Pp 230This option disables checking at open time. 231It may improve performance for read-only mounts, 232but should only be used if the data on the server changes rarely. 233Be sure to understand the consequences before enabling this option. 234.It Cm noinet4 , noinet6 235Disables 236.Dv AF_INET 237or 238.Dv AF_INET6 239connections. 240Useful for hosts that have 241both an A record and an AAAA record for the same name. 242.It Cm nolockd 243Do 244.Em not 245forward 246.Xr fcntl 2 247locks over the wire. 248All locks will be local and not seen by the server 249and likewise not seen by other NFS clients. 250This removes the need to run the 251.Xr rpcbind 8 252service and the 253.Xr rpc.statd 8 254and 255.Xr rpc.lockd 8 256servers on the client. 257Note that this option will only be honored when performing the 258initial mount, it will be silently ignored if used while updating 259the mount options. 260.It Cm noncontigwr 261This mount option allows the NFS client to 262combine non-contiguous byte ranges being written 263such that the dirty byte range becomes a superset of the bytes 264that are dirty. 265This reduces the number of writes significantly for software 266builds. 267The merging of byte ranges isn't done if the file has been file 268locked, since most applications modifying a file from multiple 269clients will use file locking. 270As such, this option could result in a corrupted file for the 271rare case of an application modifying the file from multiple 272clients concurrently without using file locking. 273.It Cm principal 274For the RPCSEC_GSS security flavors, such as krb5, krb5i and krb5p, 275this option sets the name of the host based principal name expected 276by the server. This option overrides the default, which will be 277``nfs@<server-fqdn>'' and should normally be sufficient. 278.It Cm noresvport 279Do 280.Em not 281use a reserved socket port number (see below). 282.It Cm port Ns = Ns Aq Ar port_number 283Use specified port number for NFS requests. 284The default is to query the portmapper for the NFS port. 285.It Cm rdirplus 286Used with NFSV3 to specify that the \fBReaddirPlus\fR RPC should 287be used. 288For NFSV4, setting this option has a similar effect, in that it will make 289the Readdir Operation get more attributes. 290This option reduces RPC traffic for cases such as 291.Dq "ls -l" , 292but tends to flood the attribute and name caches with prefetched entries. 293Try this option and see whether performance improves or degrades. 294Probably 295most useful for client to server network interconnects with a large bandwidth 296times delay product. 297.It Cm readahead Ns = Ns Aq Ar value 298Set the read-ahead count to the specified value. 299This may be in the range of 0 - 4, and determines how many blocks 300will be read ahead when a large file is being read sequentially. 301Trying a value greater than 1 for this is suggested for 302mounts with a large bandwidth * delay product. 303.It Cm readdirsize Ns = Ns Aq Ar value 304Set the readdir read size to the specified value. 305The value should normally 306be a multiple of 307.Dv DIRBLKSIZ 308that is <= the read size for the mount. 309.It Cm resvport 310Use a reserved socket port number. 311This flag is obsolete, and only retained for compatibility reasons. 312Reserved port numbers are used by default now. 313(For the rare case where the client has a trusted root account 314but untrustworthy users and the network cables are in secure areas this does 315help, but for normal desktop clients this does not apply.) 316.It Cm retrans Ns = Ns Aq Ar value 317Set the retransmit timeout count for soft mounts to the specified value. 318.It Cm retrycnt Ns = Ns Aq Ar count 319Set the mount retry count to the specified value. 320The default is a retry count of zero, which means to keep retrying 321forever. 322There is a 60 second delay between each attempt. 323.It Cm rsize Ns = Ns Aq Ar value 324Set the read data size to the specified value. 325It should normally be a power of 2 greater than or equal to 1024. 326This should be used for UDP mounts when the 327.Dq "fragments dropped due to timeout" 328value is getting large while actively using a mount point. 329(Use 330.Xr netstat 1 331with the 332.Fl s 333option to see what the 334.Dq "fragments dropped due to timeout" 335value is.) 336.It Cm sec Ns = Ns Aq Ar flavor 337This option specifies what security flavor should be used for the mount. 338Currently, they are: 339.Bd -literal 340krb5 - Use KerberosV authentication 341krb5i - Use KerberosV authentication and 342 apply integrity checksums to RPCs 343krb5p - Use KerberosV authentication and 344 encrypt the RPC data 345sys - The default AUTH_SYS, which uses a 346 uid + gid list authenticator 347.Ed 348.It Cm soft 349A soft mount, which implies that file system calls will fail 350after 351.Ar retrycnt 352round trip timeout intervals. 353.It Cm tcp 354Use TCP transport. 355This is the default option, as it provides for increased reliability on both 356LAN and WAN configurations compared to UDP. 357Some old NFS servers do not support this method; UDP mounts may be required 358for interoperability. 359.It Cm timeout Ns = Ns Aq Ar value 360Set the initial retransmit timeout to the specified value. 361May be useful for fine tuning UDP mounts over internetworks 362with high packet loss rates or an overloaded server. 363Try increasing the interval if 364.Xr nfsstat 1 365shows high retransmit rates while the file system is active or reducing the 366value if there is a low retransmit rate but long response delay observed. 367(Normally, the 368.Cm dumbtimer 369option should be specified when using this option to manually 370tune the timeout 371interval.) 372.It Cm udp 373Use UDP transport. 374.It Cm wcommitsize Ns = Ns Aq Ar value 375Set the maximum pending write commit size to the specified value. 376This determines the maximum amount of pending write data that the NFS 377client is willing to cache for each file. 378.It Cm wsize Ns = Ns Aq Ar value 379Set the write data size to the specified value. 380Ditto the comments w.r.t.\& the 381.Cm rsize 382option, but using the 383.Dq "fragments dropped due to timeout" 384value on the server instead of the client. 385Note that both the 386.Cm rsize 387and 388.Cm wsize 389options should only be used as a last ditch effort at improving performance 390when mounting servers that do not support TCP mounts. 391.El 392.El 393.Sh COMPATIBILITY 394The following command line flags are equivalent to 395.Fl o 396named options and are supported for compatibility with older 397installations. 398.Bl -tag -width indent 399.It Fl 2 400Same as 401.Fl o Cm nfsv2 402.It Fl 3 403Same as 404.Fl o Cm nfsv3 405.It Fl D 406Same as 407.Fl o Cm deadthresh 408.It Fl I 409Same as 410.Fl o Cm readdirsize Ns = Ns Aq Ar value 411.It Fl L 412Same as 413.Fl o Cm nolockd 414.It Fl N 415Same as 416.Fl o Cm noresvport 417.It Fl P 418Use a reserved socket port number. 419This flag is obsolete, and only retained for compatibility reasons. 420(For the rare case where the client has a trusted root account 421but untrustworthy users and the network cables are in secure areas this does 422help, but for normal desktop clients this does not apply.) 423.It Fl R 424Same as 425.Fl o Cm retrycnt Ns = Ns Aq Ar value 426.It Fl T 427Same as 428.Fl o Cm tcp 429.It Fl U 430Same as 431.Fl o Cm mntudp 432.It Fl a 433Same as 434.Fl o Cm readahead Ns = Ns Aq Ar value 435.It Fl b 436Same as 437.Fl o Cm bg 438.It Fl c 439Same as 440.Fl o Cm noconn 441.It Fl d 442Same as 443.Fl o Cm dumbtimer 444.It Fl g 445Same as 446.Fl o Cm maxgroups 447.It Fl i 448Same as 449.Fl o Cm intr 450.It Fl l 451Same as 452.Fl o Cm rdirplus 453.It Fl r 454Same as 455.Fl o Cm rsize Ns = Ns Aq Ar value 456.It Fl s 457Same as 458.Fl o Cm soft 459.It Fl t 460Same as 461.Fl o Cm retransmit Ns = Ns Aq Ar value 462.It Fl w 463Same as 464.Fl o Cm wsize Ns = Ns Aq Ar value 465.It Fl x 466Same as 467.Fl o Cm retrans Ns = Ns Aq Ar value 468.El 469.Sh SEE ALSO 470.Xr nmount 2 , 471.Xr unmount 2 , 472.Xr nfsv4 4 , 473.Xr fstab 5 , 474.Xr gssd 8 , 475.Xr mount 8 , 476.Xr nfsd 8 , 477.Xr nfsiod 8 , 478.Xr showmount 8 479.Sh BUGS 480Since nfsv4 performs open/lock operations that have their ordering strictly 481enforced by the server, the options 482.Cm intr 483and 484.Cm soft 485cannot be safely used. 486.Cm hard 487nfsv4 mounts are strongly recommended. 488