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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 July 28, 2009 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 66By default, 67.Nm 68keeps retrying until the mount succeeds. 69This behaviour is intended for file systems listed in 70.Xr fstab 5 71that are critical to the boot process. 72For non-critical file systems, the 73.Cm bg 74and 75.Cm retrycnt 76options provide mechanisms to prevent the boot process from hanging 77if the server is unavailable. 78.Pp 79If the server becomes unresponsive while an NFS file system is 80mounted, any new or outstanding file operations on that file system 81will hang uninterruptibly until the server comes back. 82To modify this default behaviour, see the 83.Cm intr 84and 85.Cm soft 86options. 87.Pp 88The options are: 89.Bl -tag -width indent 90.It Fl o 91Options are specified with a 92.Fl o 93flag followed by a comma separated string of options. 94See the 95.Xr mount 8 96man page for possible options and their meanings. 97The following NFS specific options are also available: 98.Bl -tag -width indent 99.It Cm acregmin Ns = Ns Aq Ar seconds 100.It Cm acregmax Ns = Ns Aq Ar seconds 101.It Cm acdirmin Ns = Ns Aq Ar seconds 102.It Cm acdirmax Ns = Ns Aq Ar seconds 103When attributes of files are cached, a timeout calculated to determine 104whether a given cache entry has expired. 105These four values determine the upper and lower bounds of the timeouts for 106.Dq directory 107attributes and 108.Dq regular 109(ie: everything else). 110The default values are 3 -> 60 seconds 111for regular files, and 30 -> 60 seconds for directories. 112The algorithm to calculate the timeout is based on the age of the file. 113The older the file, 114the longer the cache is considered valid, subject to the limits above. 115.It Cm bg 116If an initial attempt to contact the server fails, fork off a child to keep 117trying the mount in the background. 118Useful for 119.Xr fstab 5 , 120where the file system mount is not critical to multiuser operation. 121.It Cm deadthresh Ns = Ns Aq Ar value 122Set the 123.Dq "dead server threshold" 124to the specified number of round trip timeout intervals before a 125.Dq "server not responding" 126message is displayed. 127.It Cm dumbtimer 128Turn off the dynamic retransmit timeout estimator. 129This may be useful for UDP mounts that exhibit high retry rates, 130since it is possible that the dynamically estimated timeout interval is too 131short. 132.It Cm fg 133Same as not specifying 134.Cm bg . 135.It Cm hard 136Same as not specifying 137.Cm soft . 138.It Cm intr 139Make the mount interruptible, which implies that file system calls that 140are delayed due to an unresponsive server will fail with EINTR when a 141termination signal is posted for the process. 142.It Cm maxgroups Ns = Ns Aq Ar value 143Set the maximum size of the group list for the credentials to the 144specified value. 145This should be used for mounts on old servers that cannot handle a 146group list size of 16, as specified in RFC 1057. 147Try 8, if users in a lot of groups cannot get response from the mount 148point. 149.It Cm mntudp 150Force the mount protocol to use UDP transport, even for TCP NFS mounts. 151(Necessary for some old 152.Bx 153servers.) 154.It Cm negnametimeo Ns = Ns Aq Ar value 155Override the default of NFS_DEFAULT_NEGNAMETIMEO for the timeout (in seconds) 156for negative name cache entries. If this is set to 0 it disables negative 157name caching for the mount point. 158.It Cm nfsv2 159Use the NFS Version 2 protocol (the default is to try version 3 first 160then version 2). 161Note that NFS version 2 has a file size limit of 2 gigabytes. 162.It Cm nfsv3 163Use the NFS Version 3 protocol. 164.It Cm nfsv4 165Use the NFS Version 4 protocol. 166This option will force the mount to use the experimental nfs subsystem and 167TCP transport. 168To use the experimental nfs subsystem for nfsv2 and nfsv3 mounts, you 169must specify the ``newnfs'' file system type instead of ``nfs''. 170.It Cm noconn 171For UDP mount points, do not do a 172.Xr connect 2 . 173This must be used if the server does not reply to requests from the standard 174NFS port number 2049 or replies to requests using a different IP address 175(which can occur if the server is multi-homed). 176Setting the 177.Va vfs.nfs.nfs_ip_paranoia 178sysctl to 0 will make this option the default. 179.It Cm noinet4 , noinet6 180Disables 181.Dv AF_INET 182or 183.Dv AF_INET6 184connections. 185Useful for hosts that have 186both an A record and an AAAA record for the same name. 187.It Cm nolockd 188Do 189.Em not 190forward 191.Xr fcntl 2 192locks over the wire. 193All locks will be local and not seen by the server 194and likewise not seen by other NFS clients. 195This removes the need to run the 196.Xr rpcbind 8 197service and the 198.Xr rpc.statd 8 199and 200.Xr rpc.lockd 8 201servers on the client. 202Note that this option will only be honored when performing the 203initial mount, it will be silently ignored if used while updating 204the mount options. 205.It Cm principal 206For the RPCSEC_GSS security flavors, such as krb5, krb5i and krb5p, 207this option sets the name of the host based principal name expected 208by the server. This option overrides the default, which will be 209``nfs@<server-fqdn>'' and should normally be sufficient. 210.It Cm noresvport 211Do 212.Em not 213use a reserved socket port number (see below). 214.It Cm port Ns = Ns Aq Ar port_number 215Use specified port number for NFS requests. 216The default is to query the portmapper for the NFS port. 217.It Cm rdirplus 218Used with NFSV3 to specify that the \fBReaddirPlus\fR RPC should 219be used. 220For NFSV4, setting this option has a similar effect, in that it will make 221the Readdir Operation get more attributes. 222This option reduces RPC traffic for cases such as 223.Dq "ls -l" , 224but tends to flood the attribute and name caches with prefetched entries. 225Try this option and see whether performance improves or degrades. 226Probably 227most useful for client to server network interconnects with a large bandwidth 228times delay product. 229.It Cm readahead Ns = Ns Aq Ar value 230Set the read-ahead count to the specified value. 231This may be in the range of 0 - 4, and determines how many blocks 232will be read ahead when a large file is being read sequentially. 233Trying a value greater than 1 for this is suggested for 234mounts with a large bandwidth * delay product. 235.It Cm readdirsize Ns = Ns Aq Ar value 236Set the readdir read size to the specified value. 237The value should normally 238be a multiple of 239.Dv DIRBLKSIZ 240that is <= the read size for the mount. 241.It Cm resvport 242Use a reserved socket port number. 243This flag is obsolete, and only retained for compatibility reasons. 244Reserved port numbers are used by default now. 245(For the rare case where the client has a trusted root account 246but untrustworthy users and the network cables are in secure areas this does 247help, but for normal desktop clients this does not apply.) 248.It Cm retrans Ns = Ns Aq Ar value 249Set the retransmit timeout count for soft mounts to the specified value. 250.It Cm retrycnt Ns = Ns Aq Ar count 251Set the mount retry count to the specified value. 252The default is a retry count of zero, which means to keep retrying 253forever. 254There is a 60 second delay between each attempt. 255.It Cm rsize Ns = Ns Aq Ar value 256Set the read data size to the specified value. 257It should normally be a power of 2 greater than or equal to 1024. 258This should be used for UDP mounts when the 259.Dq "fragments dropped due to timeout" 260value is getting large while actively using a mount point. 261(Use 262.Xr netstat 1 263with the 264.Fl s 265option to see what the 266.Dq "fragments dropped due to timeout" 267value is.) 268.It Cm sec Ns = Ns Aq Ar flavor 269This option specifies what security flavor should be used for the mount. 270Currently, they are: 271.Bd -literal 272krb5 - Use KerberosV authentication 273krb5i - Use KerberosV authentication and 274 apply integrity checksums to RPCs 275krb5p - Use KerberosV authentication and 276 encrypt the RPC data 277sys - The default AUTH_SYS, which uses a 278 uid + gid list authenticator 279.Ed 280.It Cm soft 281A soft mount, which implies that file system calls will fail 282after 283.Ar retrycnt 284round trip timeout intervals. 285.It Cm tcp 286Use TCP transport. 287This is the default option, as it provides for increased reliability on both 288LAN and WAN configurations compared to UDP. 289Some old NFS servers do not support this method; UDP mounts may be required 290for interoperability. 291.It Cm timeout Ns = Ns Aq Ar value 292Set the initial retransmit timeout to the specified value. 293May be useful for fine tuning UDP mounts over internetworks 294with high packet loss rates or an overloaded server. 295Try increasing the interval if 296.Xr nfsstat 1 297shows high retransmit rates while the file system is active or reducing the 298value if there is a low retransmit rate but long response delay observed. 299(Normally, the 300.Cm dumbtimer 301option should be specified when using this option to manually 302tune the timeout 303interval.) 304.It Cm udp 305Use UDP transport. 306.It Cm wsize Ns = Ns Aq Ar value 307Set the write data size to the specified value. 308Ditto the comments w.r.t.\& the 309.Cm rsize 310option, but using the 311.Dq "fragments dropped due to timeout" 312value on the server instead of the client. 313Note that both the 314.Cm rsize 315and 316.Cm wsize 317options should only be used as a last ditch effort at improving performance 318when mounting servers that do not support TCP mounts. 319.El 320.El 321.Sh COMPATIBILITY 322The following command line flags are equivalent to 323.Fl o 324named options and are supported for compatibility with older 325installations. 326.Bl -tag -width indent 327.It Fl 2 328Same as 329.Fl o Cm nfsv2 330.It Fl 3 331Same as 332.Fl o Cm nfsv3 333.It Fl D 334Same as 335.Fl o Cm deadthresh 336.It Fl I 337Same as 338.Fl o Cm readdirsize Ns = Ns Aq Ar value 339.It Fl L 340Same as 341.Fl o Cm nolockd 342.It Fl N 343Same as 344.Fl o Cm noresvport 345.It Fl P 346Use a reserved socket port number. 347This flag is obsolete, and only retained for compatibility reasons. 348(For the rare case where the client has a trusted root account 349but untrustworthy users and the network cables are in secure areas this does 350help, but for normal desktop clients this does not apply.) 351.It Fl R 352Same as 353.Fl o Cm retrycnt Ns = Ns Aq Ar value 354.It Fl T 355Same as 356.Fl o Cm tcp 357.It Fl U 358Same as 359.Fl o Cm mntudp 360.It Fl a 361Same as 362.Fl o Cm readahead Ns = Ns Aq Ar value 363.It Fl b 364Same as 365.Fl o Cm bg 366.It Fl c 367Same as 368.Fl o Cm noconn 369.It Fl d 370Same as 371.Fl o Cm dumbtimer 372.It Fl g 373Same as 374.Fl o Cm maxgroups 375.It Fl i 376Same as 377.Fl o Cm intr 378.It Fl l 379Same as 380.Fl o Cm rdirplus 381.It Fl r 382Same as 383.Fl o Cm rsize Ns = Ns Aq Ar value 384.It Fl s 385Same as 386.Fl o Cm soft 387.It Fl t 388Same as 389.Fl o Cm retransmit Ns = Ns Aq Ar value 390.It Fl w 391Same as 392.Fl o Cm wsize Ns = Ns Aq Ar value 393.It Fl x 394Same as 395.Fl o Cm retrans Ns = Ns Aq Ar value 396.El 397.Sh SEE ALSO 398.Xr nmount 2 , 399.Xr unmount 2 , 400.Xr nfsv4 4 , 401.Xr fstab 5 , 402.Xr gssd 8 , 403.Xr mount 8 , 404.Xr nfsd 8 , 405.Xr nfsiod 8 , 406.Xr showmount 8 407.Sh BUGS 408Since nfsv4 performs open/lock operations that have their ordering strictly 409enforced by the server, the options 410.Cm intr 411and 412.Cm soft 413cannot be safely used. 414.Cm hard 415nfsv4 mounts are strongly recommended. 416