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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 May 3, 2011 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 principal 225For the RPCSEC_GSS security flavors, such as krb5, krb5i and krb5p, 226this option sets the name of the host based principal name expected 227by the server. This option overrides the default, which will be 228``nfs@<server-fqdn>'' and should normally be sufficient. 229.It Cm noresvport 230Do 231.Em not 232use a reserved socket port number (see below). 233.It Cm port Ns = Ns Aq Ar port_number 234Use specified port number for NFS requests. 235The default is to query the portmapper for the NFS port. 236.It Cm rdirplus 237Used with NFSV3 to specify that the \fBReaddirPlus\fR RPC should 238be used. 239For NFSV4, setting this option has a similar effect, in that it will make 240the Readdir Operation get more attributes. 241This option reduces RPC traffic for cases such as 242.Dq "ls -l" , 243but tends to flood the attribute and name caches with prefetched entries. 244Try this option and see whether performance improves or degrades. 245Probably 246most useful for client to server network interconnects with a large bandwidth 247times delay product. 248.It Cm readahead Ns = Ns Aq Ar value 249Set the read-ahead count to the specified value. 250This may be in the range of 0 - 4, and determines how many blocks 251will be read ahead when a large file is being read sequentially. 252Trying a value greater than 1 for this is suggested for 253mounts with a large bandwidth * delay product. 254.It Cm readdirsize Ns = Ns Aq Ar value 255Set the readdir read size to the specified value. 256The value should normally 257be a multiple of 258.Dv DIRBLKSIZ 259that is <= the read size for the mount. 260.It Cm resvport 261Use a reserved socket port number. 262This flag is obsolete, and only retained for compatibility reasons. 263Reserved port numbers are used by default now. 264(For the rare case where the client has a trusted root account 265but untrustworthy users and the network cables are in secure areas this does 266help, but for normal desktop clients this does not apply.) 267.It Cm retrans Ns = Ns Aq Ar value 268Set the retransmit timeout count for soft mounts to the specified value. 269.It Cm retrycnt Ns = Ns Aq Ar count 270Set the mount retry count to the specified value. 271The default is a retry count of zero, which means to keep retrying 272forever. 273There is a 60 second delay between each attempt. 274.It Cm rsize Ns = Ns Aq Ar value 275Set the read data size to the specified value. 276It should normally be a power of 2 greater than or equal to 1024. 277This should be used for UDP mounts when the 278.Dq "fragments dropped due to timeout" 279value is getting large while actively using a mount point. 280(Use 281.Xr netstat 1 282with the 283.Fl s 284option to see what the 285.Dq "fragments dropped due to timeout" 286value is.) 287.It Cm sec Ns = Ns Aq Ar flavor 288This option specifies what security flavor should be used for the mount. 289Currently, they are: 290.Bd -literal 291krb5 - Use KerberosV authentication 292krb5i - Use KerberosV authentication and 293 apply integrity checksums to RPCs 294krb5p - Use KerberosV authentication and 295 encrypt the RPC data 296sys - The default AUTH_SYS, which uses a 297 uid + gid list authenticator 298.Ed 299.It Cm soft 300A soft mount, which implies that file system calls will fail 301after 302.Ar retrycnt 303round trip timeout intervals. 304.It Cm tcp 305Use TCP transport. 306This is the default option, as it provides for increased reliability on both 307LAN and WAN configurations compared to UDP. 308Some old NFS servers do not support this method; UDP mounts may be required 309for interoperability. 310.It Cm timeout Ns = Ns Aq Ar value 311Set the initial retransmit timeout to the specified value. 312May be useful for fine tuning UDP mounts over internetworks 313with high packet loss rates or an overloaded server. 314Try increasing the interval if 315.Xr nfsstat 1 316shows high retransmit rates while the file system is active or reducing the 317value if there is a low retransmit rate but long response delay observed. 318(Normally, the 319.Cm dumbtimer 320option should be specified when using this option to manually 321tune the timeout 322interval.) 323.It Cm udp 324Use UDP transport. 325.It Cm wcommitsize Ns = Ns Aq Ar value 326Set the maximum pending write commit size to the specified value. 327This determines the maximum amount of pending write data that the NFS 328client is willing to cache for each file. 329.It Cm wsize Ns = Ns Aq Ar value 330Set the write data size to the specified value. 331Ditto the comments w.r.t.\& the 332.Cm rsize 333option, but using the 334.Dq "fragments dropped due to timeout" 335value on the server instead of the client. 336Note that both the 337.Cm rsize 338and 339.Cm wsize 340options should only be used as a last ditch effort at improving performance 341when mounting servers that do not support TCP mounts. 342.El 343.El 344.Sh COMPATIBILITY 345The following command line flags are equivalent to 346.Fl o 347named options and are supported for compatibility with older 348installations. 349.Bl -tag -width indent 350.It Fl 2 351Same as 352.Fl o Cm nfsv2 353.It Fl 3 354Same as 355.Fl o Cm nfsv3 356.It Fl D 357Same as 358.Fl o Cm deadthresh 359.It Fl I 360Same as 361.Fl o Cm readdirsize Ns = Ns Aq Ar value 362.It Fl L 363Same as 364.Fl o Cm nolockd 365.It Fl N 366Same as 367.Fl o Cm noresvport 368.It Fl P 369Use a reserved socket port number. 370This flag is obsolete, and only retained for compatibility reasons. 371(For the rare case where the client has a trusted root account 372but untrustworthy users and the network cables are in secure areas this does 373help, but for normal desktop clients this does not apply.) 374.It Fl R 375Same as 376.Fl o Cm retrycnt Ns = Ns Aq Ar value 377.It Fl T 378Same as 379.Fl o Cm tcp 380.It Fl U 381Same as 382.Fl o Cm mntudp 383.It Fl a 384Same as 385.Fl o Cm readahead Ns = Ns Aq Ar value 386.It Fl b 387Same as 388.Fl o Cm bg 389.It Fl c 390Same as 391.Fl o Cm noconn 392.It Fl d 393Same as 394.Fl o Cm dumbtimer 395.It Fl g 396Same as 397.Fl o Cm maxgroups 398.It Fl i 399Same as 400.Fl o Cm intr 401.It Fl l 402Same as 403.Fl o Cm rdirplus 404.It Fl r 405Same as 406.Fl o Cm rsize Ns = Ns Aq Ar value 407.It Fl s 408Same as 409.Fl o Cm soft 410.It Fl t 411Same as 412.Fl o Cm retransmit Ns = Ns Aq Ar value 413.It Fl w 414Same as 415.Fl o Cm wsize Ns = Ns Aq Ar value 416.It Fl x 417Same as 418.Fl o Cm retrans Ns = Ns Aq Ar value 419.El 420.Sh SEE ALSO 421.Xr nmount 2 , 422.Xr unmount 2 , 423.Xr nfsv4 4 , 424.Xr fstab 5 , 425.Xr gssd 8 , 426.Xr mount 8 , 427.Xr nfsd 8 , 428.Xr nfsiod 8 , 429.Xr showmount 8 430.Sh BUGS 431Since nfsv4 performs open/lock operations that have their ordering strictly 432enforced by the server, the options 433.Cm intr 434and 435.Cm soft 436cannot be safely used. 437.Cm hard 438nfsv4 mounts are strongly recommended. 439