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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: stable/9/sbin/mount_nfs/mount_nfs.8 271508 2014-09-13 13:36:17Z bz $ 30.\" 31.Dd August 5, 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 bg 122If an initial attempt to contact the server fails, fork off a child to keep 123trying the mount in the background. 124Useful for 125.Xr fstab 5 , 126where the file system mount is not critical to multiuser operation. 127.It Cm deadthresh Ns = Ns Aq Ar value 128Set the 129.Dq "dead server threshold" 130to the specified number of round trip timeout intervals before a 131.Dq "server not responding" 132message is displayed. 133.It Cm dumbtimer 134Turn off the dynamic retransmit timeout estimator. 135This may be useful for UDP mounts that exhibit high retry rates, 136since it is possible that the dynamically estimated timeout interval is too 137short. 138.It Cm fg 139Same as not specifying 140.Cm bg . 141.It Cm hard 142Same as not specifying 143.Cm soft . 144.It Cm intr 145Make the mount interruptible, which implies that file system calls that 146are delayed due to an unresponsive server will fail with EINTR when a 147termination signal is posted for the process. 148.It Cm maxgroups Ns = Ns Aq Ar value 149Set the maximum size of the group list for the credentials to the 150specified value. 151This should be used for mounts on old servers that cannot handle a 152group list size of 16, as specified in RFC 1057. 153Try 8, if users in a lot of groups cannot get response from the mount 154point. 155.It Cm mntudp 156Force the mount protocol to use UDP transport, even for TCP NFS mounts. 157(Necessary for some old 158.Bx 159servers.) 160.It Cm nametimeo Ns = Ns Aq Ar value 161Override the default of NFS_DEFAULT_NAMETIMEO for the timeout (in seconds) 162for positive name cache entries. 163If this is set to 0 it disables positive name caching for the mount point. 164.It Cm negnametimeo Ns = Ns Aq Ar value 165Override the default of NFS_DEFAULT_NEGNAMETIMEO for the timeout (in seconds) 166for negative name cache entries. If this is set to 0 it disables negative 167name caching for the mount point. 168.It Cm nfsv2 169Use the NFS Version 2 protocol (the default is to try version 3 first 170then version 2). 171Note that NFS version 2 has a file size limit of 2 gigabytes. 172.It Cm nfsv3 173Use the NFS Version 3 protocol. 174.It Cm nfsv4 175Use the NFS Version 4 protocol. 176This option will force the mount to use 177TCP transport. 178.It Cm noconn 179For UDP mount points, do not do a 180.Xr connect 2 . 181This must be used if the server does not reply to requests from the standard 182NFS port number 2049 or replies to requests using a different IP address 183(which can occur if the server is multi-homed). 184Setting the 185.Va vfs.nfs.nfs_ip_paranoia 186sysctl to 0 will make this option the default. 187.It Cm nocto 188Normally, NFS clients maintain the close-to-open cache coherency. 189This works by flushing at close time and checking at open time. 190Checking at open time is implemented by getting attributes from 191the server and purging the data cache if they do not match 192attributes cached by the client. 193.Pp 194This option disables checking at open time. 195It may improve performance for read-only mounts, 196but should only be used if the data on the server changes rarely. 197Be sure to understand the consequences before enabling this option. 198.It Cm noinet4 , noinet6 199Disables 200.Dv AF_INET 201or 202.Dv AF_INET6 203connections. 204Useful for hosts that have 205both an A record and an AAAA record for the same name. 206.It Cm nolockd 207Do 208.Em not 209forward 210.Xr fcntl 2 211locks over the wire. 212All locks will be local and not seen by the server 213and likewise not seen by other NFS clients. 214This removes the need to run the 215.Xr rpcbind 8 216service and the 217.Xr rpc.statd 8 218and 219.Xr rpc.lockd 8 220servers on the client. 221Note that this option will only be honored when performing the 222initial mount, it will be silently ignored if used while updating 223the mount options. 224.It Cm noncontigwr 225This mount option allows the NFS client to 226combine non-contiguous byte ranges being written 227such that the dirty byte range becomes a superset of the bytes 228that are dirty. 229This reduces the number of writes significantly for software 230builds. 231The merging of byte ranges isn't done if the file has been file 232locked, since most applications modifying a file from multiple 233clients will use file locking. 234As such, this option could result in a corrupted file for the 235rare case of an application modifying the file from multiple 236clients concurrently without using file locking. 237.It Cm principal 238For the RPCSEC_GSS security flavors, such as krb5, krb5i and krb5p, 239this option sets the name of the host based principal name expected 240by the server. This option overrides the default, which will be 241``nfs@<server-fqdn>'' and should normally be sufficient. 242.It Cm noresvport 243Do 244.Em not 245use a reserved socket port number (see below). 246.It Cm port Ns = Ns Aq Ar port_number 247Use specified port number for NFS requests. 248The default is to query the portmapper for the NFS port. 249.It Cm rdirplus 250Used with NFSV3 to specify that the \fBReaddirPlus\fR RPC should 251be used. 252For NFSV4, setting this option has a similar effect, in that it will make 253the Readdir Operation get more attributes. 254This option reduces RPC traffic for cases such as 255.Dq "ls -l" , 256but tends to flood the attribute and name caches with prefetched entries. 257Try this option and see whether performance improves or degrades. 258Probably 259most useful for client to server network interconnects with a large bandwidth 260times delay product. 261.It Cm readahead Ns = Ns Aq Ar value 262Set the read-ahead count to the specified value. 263This may be in the range of 0 - 4, and determines how many blocks 264will be read ahead when a large file is being read sequentially. 265Trying a value greater than 1 for this is suggested for 266mounts with a large bandwidth * delay product. 267.It Cm readdirsize Ns = Ns Aq Ar value 268Set the readdir read size to the specified value. 269The value should normally 270be a multiple of 271.Dv DIRBLKSIZ 272that is <= the read size for the mount. 273.It Cm resvport 274Use a reserved socket port number. 275This flag is obsolete, and only retained for compatibility reasons. 276Reserved port numbers are used by default now. 277(For the rare case where the client has a trusted root account 278but untrustworthy users and the network cables are in secure areas this does 279help, but for normal desktop clients this does not apply.) 280.It Cm retrans Ns = Ns Aq Ar value 281Set the retransmit timeout count for soft mounts to the specified value. 282.It Cm retrycnt Ns = Ns Aq Ar count 283Set the mount retry count to the specified value. 284The default is a retry count of zero, which means to keep retrying 285forever. 286There is a 60 second delay between each attempt. 287.It Cm rsize Ns = Ns Aq Ar value 288Set the read data size to the specified value. 289It should normally be a power of 2 greater than or equal to 1024. 290This should be used for UDP mounts when the 291.Dq "fragments dropped due to timeout" 292value is getting large while actively using a mount point. 293(Use 294.Xr netstat 1 295with the 296.Fl s 297option to see what the 298.Dq "fragments dropped due to timeout" 299value is.) 300.It Cm sec Ns = Ns Aq Ar flavor 301This option specifies what security flavor should be used for the mount. 302Currently, they are: 303.Bd -literal 304krb5 - Use KerberosV authentication 305krb5i - Use KerberosV authentication and 306 apply integrity checksums to RPCs 307krb5p - Use KerberosV authentication and 308 encrypt the RPC data 309sys - The default AUTH_SYS, which uses a 310 uid + gid list authenticator 311.Ed 312.It Cm soft 313A soft mount, which implies that file system calls will fail 314after 315.Ar retrycnt 316round trip timeout intervals. 317.It Cm tcp 318Use TCP transport. 319This is the default option, as it provides for increased reliability on both 320LAN and WAN configurations compared to UDP. 321Some old NFS servers do not support this method; UDP mounts may be required 322for interoperability. 323.It Cm timeout Ns = Ns Aq Ar value 324Set the initial retransmit timeout to the specified value. 325May be useful for fine tuning UDP mounts over internetworks 326with high packet loss rates or an overloaded server. 327Try increasing the interval if 328.Xr nfsstat 1 329shows high retransmit rates while the file system is active or reducing the 330value if there is a low retransmit rate but long response delay observed. 331(Normally, the 332.Cm dumbtimer 333option should be specified when using this option to manually 334tune the timeout 335interval.) 336.It Cm udp 337Use UDP transport. 338.It Cm vers Ns = Ns Aq Ar vers_number 339Use the specified version number for NFS requests. 340See the 341.Cm nfsv2 , 342.Cm nfsv3 , 343and 344.Cm nfsv4 345options for details. 346.It Cm wcommitsize Ns = Ns Aq Ar value 347Set the maximum pending write commit size to the specified value. 348This determines the maximum amount of pending write data that the NFS 349client is willing to cache for each file. 350.It Cm wsize Ns = Ns Aq Ar value 351Set the write data size to the specified value. 352Ditto the comments w.r.t.\& the 353.Cm rsize 354option, but using the 355.Dq "fragments dropped due to timeout" 356value on the server instead of the client. 357Note that both the 358.Cm rsize 359and 360.Cm wsize 361options should only be used as a last ditch effort at improving performance 362when mounting servers that do not support TCP mounts. 363.El 364.El 365.Sh COMPATIBILITY 366The following command line flags are equivalent to 367.Fl o 368named options and are supported for compatibility with older 369installations. 370.Bl -tag -width indent 371.It Fl 2 372Same as 373.Fl o Cm nfsv2 374.It Fl 3 375Same as 376.Fl o Cm nfsv3 377.It Fl D 378Same as 379.Fl o Cm deadthresh 380.It Fl I 381Same as 382.Fl o Cm readdirsize Ns = Ns Aq Ar value 383.It Fl L 384Same as 385.Fl o Cm nolockd 386.It Fl N 387Same as 388.Fl o Cm noresvport 389.It Fl P 390Use a reserved socket port number. 391This flag is obsolete, and only retained for compatibility reasons. 392(For the rare case where the client has a trusted root account 393but untrustworthy users and the network cables are in secure areas this does 394help, but for normal desktop clients this does not apply.) 395.It Fl R 396Same as 397.Fl o Cm retrycnt Ns = Ns Aq Ar value 398.It Fl T 399Same as 400.Fl o Cm tcp 401.It Fl U 402Same as 403.Fl o Cm mntudp 404.It Fl a 405Same as 406.Fl o Cm readahead Ns = Ns Aq Ar value 407.It Fl b 408Same as 409.Fl o Cm bg 410.It Fl c 411Same as 412.Fl o Cm noconn 413.It Fl d 414Same as 415.Fl o Cm dumbtimer 416.It Fl g 417Same as 418.Fl o Cm maxgroups 419.It Fl i 420Same as 421.Fl o Cm intr 422.It Fl l 423Same as 424.Fl o Cm rdirplus 425.It Fl r 426Same as 427.Fl o Cm rsize Ns = Ns Aq Ar value 428.It Fl s 429Same as 430.Fl o Cm soft 431.It Fl t 432Same as 433.Fl o Cm retransmit Ns = Ns Aq Ar value 434.It Fl w 435Same as 436.Fl o Cm wsize Ns = Ns Aq Ar value 437.It Fl x 438Same as 439.Fl o Cm retrans Ns = Ns Aq Ar value 440.El 441.Pp 442The following 443.Fl o 444named options are equivalent to other 445.Fl o 446named options and are supported for compatibility with other 447operating systems (e.g., Linux, Solaris, and OSX) to ease usage of 448.Xr autofs 5 449support. 450.Bl -tag -width indent 451.It Fl o Cm vers Ns = Ns 2 452Same as 453.Fl o Cm nfsv2 454.It Fl o Cm vers Ns = Ns 3 455Same as 456.Fl o Cm nfsv3 457.It Fl o Cm vers Ns = Ns 4 458Same as 459.Fl o Cm nfsv4 460.El 461.Sh SEE ALSO 462.Xr nmount 2 , 463.Xr unmount 2 , 464.Xr nfsv4 4 , 465.Xr fstab 5 , 466.Xr gssd 8 , 467.Xr mount 8 , 468.Xr nfsd 8 , 469.Xr nfsiod 8 , 470.Xr showmount 8 471.Sh BUGS 472Since nfsv4 performs open/lock operations that have their ordering strictly 473enforced by the server, the options 474.Cm intr 475and 476.Cm soft 477cannot be safely used. 478.Cm hard 479nfsv4 mounts are strongly recommended. 480