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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 nfsv2 155Use the NFS Version 2 protocol (the default is to try version 3 first 156then version 2). 157Note that NFS version 2 has a file size limit of 2 gigabytes. 158.It Cm nfsv3 159Use the NFS Version 3 protocol. 160.It Cm nfsv4 161Use the NFS Version 4 protocol. 162This option will force the mount to use the experimental nfs subsystem and 163TCP transport. 164To use the experimental nfs subsystem for nfsv2 and nfsv3 mounts, you 165must specify the ``newnfs'' file system type instead of ``nfs''. 166.It Cm noconn 167For UDP mount points, do not do a 168.Xr connect 2 . 169This must be used if the server does not reply to requests from the standard 170NFS port number 2049 or replies to requests using a different IP address 171(which can occur if the server is multi-homed). 172Setting the 173.Va vfs.nfs.nfs_ip_paranoia 174sysctl to 0 will make this option the default. 175.It Cm noinet4 , noinet6 176Disables 177.Dv AF_INET 178or 179.Dv AF_INET6 180connections. 181Useful for hosts that have 182both an A record and an AAAA record for the same name. 183.It Cm nolockd 184Do 185.Em not 186forward 187.Xr fcntl 2 188locks over the wire. 189All locks will be local and not seen by the server 190and likewise not seen by other NFS clients. 191This removes the need to run the 192.Xr rpcbind 8 193service and the 194.Xr rpc.statd 8 195and 196.Xr rpc.lockd 8 197servers on the client. 198Note that this option will only be honored when performing the 199initial mount, it will be silently ignored if used while updating 200the mount options. 201.It Cm principal 202For the RPCSEC_GSS security flavors, such as krb5, krb5i and krb5p, 203this option sets the name of the host based principal name expected 204by the server. This option overrides the default, which will be 205``nfs@<server-fqdn>'' and should normally be sufficient. 206.It Cm noresvport 207Do 208.Em not 209use a reserved socket port number (see below). 210.It Cm port Ns = Ns Aq Ar port_number 211Use specified port number for NFS requests. 212The default is to query the portmapper for the NFS port. 213.It Cm rdirplus 214Used with NFSV3 to specify that the \fBReaddirPlus\fR RPC should 215be used. 216For NFSV4, setting this option has a similar effect, in that it will make 217the Readdir Operation get more attributes. 218This option reduces RPC traffic for cases such as 219.Dq "ls -l" , 220but tends to flood the attribute and name caches with prefetched entries. 221Try this option and see whether performance improves or degrades. 222Probably 223most useful for client to server network interconnects with a large bandwidth 224times delay product. 225.It Cm readahead Ns = Ns Aq Ar value 226Set the read-ahead count to the specified value. 227This may be in the range of 0 - 4, and determines how many blocks 228will be read ahead when a large file is being read sequentially. 229Trying a value greater than 1 for this is suggested for 230mounts with a large bandwidth * delay product. 231.It Cm readdirsize Ns = Ns Aq Ar value 232Set the readdir read size to the specified value. 233The value should normally 234be a multiple of 235.Dv DIRBLKSIZ 236that is <= the read size for the mount. 237.It Cm resvport 238Use a reserved socket port number. 239This flag is obsolete, and only retained for compatibility reasons. 240Reserved port numbers are used by default now. 241(For the rare case where the client has a trusted root account 242but untrustworthy users and the network cables are in secure areas this does 243help, but for normal desktop clients this does not apply.) 244.It Cm retrans Ns = Ns Aq Ar value 245Set the retransmit timeout count for soft mounts to the specified value. 246.It Cm retrycnt Ns = Ns Aq Ar count 247Set the mount retry count to the specified value. 248The default is a retry count of zero, which means to keep retrying 249forever. 250There is a 60 second delay between each attempt. 251.It Cm rsize Ns = Ns Aq Ar value 252Set the read data size to the specified value. 253It should normally be a power of 2 greater than or equal to 1024. 254This should be used for UDP mounts when the 255.Dq "fragments dropped due to timeout" 256value is getting large while actively using a mount point. 257(Use 258.Xr netstat 1 259with the 260.Fl s 261option to see what the 262.Dq "fragments dropped due to timeout" 263value is.) 264.It Cm sec Ns = Ns Aq Ar flavor 265This option specifies what security flavor should be used for the mount. 266Currently, they are: 267.Bd -literal 268krb5 - Use KerberosV authentication 269krb5i - Use KerberosV authentication and 270 apply integrity checksums to RPCs 271krb5p - Use KerberosV authentication and 272 encrypt the RPC data 273sys - The default AUTH_SYS, which uses a 274 uid + gid list authenticator 275.Ed 276.It Cm soft 277A soft mount, which implies that file system calls will fail 278after 279.Ar retrycnt 280round trip timeout intervals. 281.It Cm tcp 282Use TCP transport. 283This is the default option, as it provides for increased reliability on both 284LAN and WAN configurations compared to UDP. 285Some old NFS servers do not support this method; UDP mounts may be required 286for interoperability. 287.It Cm timeout Ns = Ns Aq Ar value 288Set the initial retransmit timeout to the specified value. 289May be useful for fine tuning UDP mounts over internetworks 290with high packet loss rates or an overloaded server. 291Try increasing the interval if 292.Xr nfsstat 1 293shows high retransmit rates while the file system is active or reducing the 294value if there is a low retransmit rate but long response delay observed. 295(Normally, the 296.Cm dumbtimer 297option should be specified when using this option to manually 298tune the timeout 299interval.) 300.It Cm udp 301Use UDP transport. 302.It Cm wsize Ns = Ns Aq Ar value 303Set the write data size to the specified value. 304Ditto the comments w.r.t.\& the 305.Cm rsize 306option, but using the 307.Dq "fragments dropped due to timeout" 308value on the server instead of the client. 309Note that both the 310.Cm rsize 311and 312.Cm wsize 313options should only be used as a last ditch effort at improving performance 314when mounting servers that do not support TCP mounts. 315.El 316.El 317.Sh COMPATIBILITY 318The following command line flags are equivalent to 319.Fl o 320named options and are supported for compatibility with older 321installations. 322.Bl -tag -width indent 323.It Fl 2 324Same as 325.Fl o Cm nfsv2 326.It Fl 3 327Same as 328.Fl o Cm nfsv3 329.It Fl D 330Same as 331.Fl o Cm deadthresh 332.It Fl I 333Same as 334.Fl o Cm readdirsize Ns = Ns Aq Ar value 335.It Fl L 336Same as 337.Fl o Cm nolockd 338.It Fl N 339Same as 340.Fl o Cm noresvport 341.It Fl P 342Use a reserved socket port number. 343This flag is obsolete, and only retained for compatibility reasons. 344(For the rare case where the client has a trusted root account 345but untrustworthy users and the network cables are in secure areas this does 346help, but for normal desktop clients this does not apply.) 347.It Fl R 348Same as 349.Fl o Cm retrycnt Ns = Ns Aq Ar value 350.It Fl T 351Same as 352.Fl o Cm tcp 353.It Fl U 354Same as 355.Fl o Cm mntudp 356.It Fl a 357Same as 358.Fl o Cm readahead Ns = Ns Aq Ar value 359.It Fl b 360Same as 361.Fl o Cm bg 362.It Fl c 363Same as 364.Fl o Cm noconn 365.It Fl d 366Same as 367.Fl o Cm dumbtimer 368.It Fl g 369Same as 370.Fl o Cm maxgroups 371.It Fl i 372Same as 373.Fl o Cm intr 374.It Fl l 375Same as 376.Fl o Cm rdirplus 377.It Fl r 378Same as 379.Fl o Cm rsize Ns = Ns Aq Ar value 380.It Fl s 381Same as 382.Fl o Cm soft 383.It Fl t 384Same as 385.Fl o Cm retransmit Ns = Ns Aq Ar value 386.It Fl w 387Same as 388.Fl o Cm wsize Ns = Ns Aq Ar value 389.It Fl x 390Same as 391.Fl o Cm retrans Ns = Ns Aq Ar value 392.El 393.Sh SEE ALSO 394.Xr nmount 2 , 395.Xr unmount 2 , 396.Xr nfsv4 4 , 397.Xr fstab 5 , 398.Xr gssd 8 , 399.Xr mount 8 , 400.Xr nfsd 8 , 401.Xr nfsiod 8 , 402.Xr showmount 8 403.Sh BUGS 404Since nfsv4 performs open/lock operations that have their ordering strictly 405enforced by the server, the options 406.Cm intr 407and 408.Cm soft 409cannot be safely used. 410.Cm hard 411nfsv4 mounts are strongly recommended. 412