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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 9, 2012 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 minorversion Ns = Ns Aq Ar value 179Override the default of 0 for the minor version of the NFS Version 4 protocol. 180The only minor version currently supported is 1. 181This option is only meaningful when used with the 182.Cm nfsv4 183option. 184.It Cm pnfs 185Enable support for parallel NFS (pNFS) for minor version 1 of the 186NFS Version 4 protocol. 187This option is only meaningful when used with the 188.Cm minorversion 189option. 190.It Cm noconn 191For UDP mount points, do not do a 192.Xr connect 2 . 193This must be used if the server does not reply to requests from the standard 194NFS port number 2049 or replies to requests using a different IP address 195(which can occur if the server is multi-homed). 196Setting the 197.Va vfs.nfs.nfs_ip_paranoia 198sysctl to 0 will make this option the default. 199.It Cm nocto 200Normally, NFS clients maintain the close-to-open cache coherency. 201This works by flushing at close time and checking at open time. 202Checking at open time is implemented by getting attributes from 203the server and purging the data cache if they do not match 204attributes cached by the client. 205.Pp 206This option disables checking at open time. 207It may improve performance for read-only mounts, 208but should only be used if the data on the server changes rarely. 209Be sure to understand the consequences before enabling this option. 210.It Cm noinet4 , noinet6 211Disables 212.Dv AF_INET 213or 214.Dv AF_INET6 215connections. 216Useful for hosts that have 217both an A record and an AAAA record for the same name. 218.It Cm nolockd 219Do 220.Em not 221forward 222.Xr fcntl 2 223locks over the wire. 224All locks will be local and not seen by the server 225and likewise not seen by other NFS clients. 226This removes the need to run the 227.Xr rpcbind 8 228service and the 229.Xr rpc.statd 8 230and 231.Xr rpc.lockd 8 232servers on the client. 233Note that this option will only be honored when performing the 234initial mount, it will be silently ignored if used while updating 235the mount options. 236.It Cm principal 237For the RPCSEC_GSS security flavors, such as krb5, krb5i and krb5p, 238this option sets the name of the host based principal name expected 239by the server. This option overrides the default, which will be 240``nfs@<server-fqdn>'' and should normally be sufficient. 241.It Cm noresvport 242Do 243.Em not 244use a reserved socket port number (see below). 245.It Cm port Ns = Ns Aq Ar port_number 246Use specified port number for NFS requests. 247The default is to query the portmapper for the NFS port. 248.It Cm rdirplus 249Used with NFSV3 to specify that the \fBReaddirPlus\fR RPC should 250be used. 251For NFSV4, setting this option has a similar effect, in that it will make 252the Readdir Operation get more attributes. 253This option reduces RPC traffic for cases such as 254.Dq "ls -l" , 255but tends to flood the attribute and name caches with prefetched entries. 256Try this option and see whether performance improves or degrades. 257Probably 258most useful for client to server network interconnects with a large bandwidth 259times delay product. 260.It Cm readahead Ns = Ns Aq Ar value 261Set the read-ahead count to the specified value. 262This may be in the range of 0 - 4, and determines how many blocks 263will be read ahead when a large file is being read sequentially. 264Trying a value greater than 1 for this is suggested for 265mounts with a large bandwidth * delay product. 266.It Cm readdirsize Ns = Ns Aq Ar value 267Set the readdir read size to the specified value. 268The value should normally 269be a multiple of 270.Dv DIRBLKSIZ 271that is <= the read size for the mount. 272.It Cm resvport 273Use a reserved socket port number. 274This flag is obsolete, and only retained for compatibility reasons. 275Reserved port numbers are used by default now. 276(For the rare case where the client has a trusted root account 277but untrustworthy users and the network cables are in secure areas this does 278help, but for normal desktop clients this does not apply.) 279.It Cm retrans Ns = Ns Aq Ar value 280Set the retransmit timeout count for soft mounts to the specified value. 281.It Cm retrycnt Ns = Ns Aq Ar count 282Set the mount retry count to the specified value. 283The default is a retry count of zero, which means to keep retrying 284forever. 285There is a 60 second delay between each attempt. 286.It Cm rsize Ns = Ns Aq Ar value 287Set the read data size to the specified value. 288It should normally be a power of 2 greater than or equal to 1024. 289This should be used for UDP mounts when the 290.Dq "fragments dropped due to timeout" 291value is getting large while actively using a mount point. 292(Use 293.Xr netstat 1 294with the 295.Fl s 296option to see what the 297.Dq "fragments dropped due to timeout" 298value is.) 299.It Cm sec Ns = Ns Aq Ar flavor 300This option specifies what security flavor should be used for the mount. 301Currently, they are: 302.Bd -literal 303krb5 - Use KerberosV authentication 304krb5i - Use KerberosV authentication and 305 apply integrity checksums to RPCs 306krb5p - Use KerberosV authentication and 307 encrypt the RPC data 308sys - The default AUTH_SYS, which uses a 309 uid + gid list authenticator 310.Ed 311.It Cm soft 312A soft mount, which implies that file system calls will fail 313after 314.Ar retrycnt 315round trip timeout intervals. 316.It Cm tcp 317Use TCP transport. 318This is the default option, as it provides for increased reliability on both 319LAN and WAN configurations compared to UDP. 320Some old NFS servers do not support this method; UDP mounts may be required 321for interoperability. 322.It Cm timeout Ns = Ns Aq Ar value 323Set the initial retransmit timeout to the specified value. 324May be useful for fine tuning UDP mounts over internetworks 325with high packet loss rates or an overloaded server. 326Try increasing the interval if 327.Xr nfsstat 1 328shows high retransmit rates while the file system is active or reducing the 329value if there is a low retransmit rate but long response delay observed. 330(Normally, the 331.Cm dumbtimer 332option should be specified when using this option to manually 333tune the timeout 334interval.) 335.It Cm udp 336Use UDP transport. 337.It Cm wcommitsize Ns = Ns Aq Ar value 338Set the maximum pending write commit size to the specified value. 339This determines the maximum amount of pending write data that the NFS 340client is willing to cache for each file. 341.It Cm wsize Ns = Ns Aq Ar value 342Set the write data size to the specified value. 343Ditto the comments w.r.t.\& the 344.Cm rsize 345option, but using the 346.Dq "fragments dropped due to timeout" 347value on the server instead of the client. 348Note that both the 349.Cm rsize 350and 351.Cm wsize 352options should only be used as a last ditch effort at improving performance 353when mounting servers that do not support TCP mounts. 354.El 355.El 356.Sh COMPATIBILITY 357The following command line flags are equivalent to 358.Fl o 359named options and are supported for compatibility with older 360installations. 361.Bl -tag -width indent 362.It Fl 2 363Same as 364.Fl o Cm nfsv2 365.It Fl 3 366Same as 367.Fl o Cm nfsv3 368.It Fl D 369Same as 370.Fl o Cm deadthresh 371.It Fl I 372Same as 373.Fl o Cm readdirsize Ns = Ns Aq Ar value 374.It Fl L 375Same as 376.Fl o Cm nolockd 377.It Fl N 378Same as 379.Fl o Cm noresvport 380.It Fl P 381Use a reserved socket port number. 382This flag is obsolete, and only retained for compatibility reasons. 383(For the rare case where the client has a trusted root account 384but untrustworthy users and the network cables are in secure areas this does 385help, but for normal desktop clients this does not apply.) 386.It Fl R 387Same as 388.Fl o Cm retrycnt Ns = Ns Aq Ar value 389.It Fl T 390Same as 391.Fl o Cm tcp 392.It Fl U 393Same as 394.Fl o Cm mntudp 395.It Fl a 396Same as 397.Fl o Cm readahead Ns = Ns Aq Ar value 398.It Fl b 399Same as 400.Fl o Cm bg 401.It Fl c 402Same as 403.Fl o Cm noconn 404.It Fl d 405Same as 406.Fl o Cm dumbtimer 407.It Fl g 408Same as 409.Fl o Cm maxgroups 410.It Fl i 411Same as 412.Fl o Cm intr 413.It Fl l 414Same as 415.Fl o Cm rdirplus 416.It Fl r 417Same as 418.Fl o Cm rsize Ns = Ns Aq Ar value 419.It Fl s 420Same as 421.Fl o Cm soft 422.It Fl t 423Same as 424.Fl o Cm retransmit Ns = Ns Aq Ar value 425.It Fl w 426Same as 427.Fl o Cm wsize Ns = Ns Aq Ar value 428.It Fl x 429Same as 430.Fl o Cm retrans Ns = Ns Aq Ar value 431.El 432.Sh SEE ALSO 433.Xr nmount 2 , 434.Xr unmount 2 , 435.Xr nfsv4 4 , 436.Xr fstab 5 , 437.Xr gssd 8 , 438.Xr mount 8 , 439.Xr nfsd 8 , 440.Xr nfsiod 8 , 441.Xr showmount 8 442.Sh BUGS 443Since nfsv4 performs open/lock operations that have their ordering strictly 444enforced by the server, the options 445.Cm intr 446and 447.Cm soft 448cannot be safely used. 449.Cm hard 450nfsv4 mounts are strongly recommended. 451