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NAME    [Toc]    [Back]

     mount_nfs - mount NFS file systems

SYNOPSIS    [Toc]    [Back]

     mount_nfs [-23PTUbcdilqs] [-D deadthresh]  [-I  readdirsize]
[-L leaseterm]
               [-R retrycnt] [-a maxreadahead] [-g maxgroups] [-o
               [-r readsize]  [-t  timeout]  [-w  writesize]  [-x
               rhost:path node

DESCRIPTION    [Toc]    [Back]

     The mount_nfs command calls the mount(2) system call to prepare and graft
     a remote NFS file system (rhost:path) on to the file  system
tree at the
     point  node.  This command is normally executed by mount(8).
It implements
 the mount protocol as described in RFC 1094,  Appendix
A and NFS:
     Network  File  System  Version 3 Protocol Specification, Appendix I.

     The options are as follows:

     -2      Use the NFS Version 2 protocol.

     -3      Use the NFS Version 3 protocol.  The default  is  to
try version 3
             first,  and  fall  back  to  version  2 if the mount

     -I readdirsize
             Set the readdir read size to  the  specified  value.
The value
             should  normally  be a multiple of DIRBLKSIZ that is
<= the read
             size for the mount.

     -P      The kernel always uses a  reserved  port  number  to
communicate with
             clients.   This option is ignored, and exists solely
for compatibility
 with older systems.

     -R retrycnt
             Set the retry count for doing the mount to the specified value.
             The default is 10000.

     -T       Use  TCP  transport instead of UDP.  This is recommended for
             servers that are not on the same LAN  cable  as  the
client.  (NB:
             This is NOT supported by most non-BSD servers.)

     -U       Force the mount protocol to use UDP transport, even
             mounts.  (Necessary for some old BSD servers.)

     -a maxreadahead
             Set the read-ahead count  to  the  specified  value.
This may be in
             the  range  of 0 - 4, and determines how many blocks
will be read
             ahead when a large file is being read  sequentially.
Trying a
             value  greater  than  1  for  this  is suggested for
mounts with a
             large bandwidth * delay product.

     -b      If an initial attempt to contact the  server  fails,
fork off a
             child  to  keep  trying the mount in the background.
Useful for
             fstab(5), where the filesystem mount is not critical
to multiuser

     -c       For UDP mount points, do not do a connect(2).  This
must be used
             for servers that do not reply to requests  from  the
standard NFS
             port  number  2049.   It  may  also  be required for
servers with more
             than one IP address (only necessary if replies  come
from an address
  other than the one specified in the mount request).

     -d      Turn off the dynamic retransmit  timeout  estimator.
This may be
             useful for UDP mounts that exhibit high retry rates,
since it is
             possible that the dynamically estimated timeout  interval is too

     -g maxgroups
             Set  the maximum size of the group list for the credentials to the
             specified value.  This should be used for mounts  on
old servers
             that cannot handle a group list size of 16, as specified in RFC
             1057.  Try 8, if users in a lot of groups cannot get
a response
             from the mount point.

     -i       Make  the  mount  interruptible, which implies that
file system
             calls that are delayed due to an unresponsive server
will fail
             with  EINTR  when a termination signal is posted for
the process.

     -l      Used with NFSV3 to specify that the ReaddirPlus  RPC
should be
             used.   This  option  reduces  RPC traffic for cases
such as ``ls
             -l'', but tends to  flood  the  attribute  and  name
caches with
             prefetched entries.  Try this option and see whether
             improves or  degrades.   Probably  most  useful  for
client to server
             network  interconnects  with a large bandwidth times
delay product.

     -o options
             Options are specified with a -o flag followed  by  a
comma separated
 string of options.  See the mount(8) man page for
possible options
 and their meanings.  The following NFS specific options are
             also available:

                     Cache  file  attributes for no more than num
seconds.  The
                     default is 60 seconds.

                     Cache file attributes for at least num  seconds.  The default
 is 5 seconds.

                     Cache  directory attributes for no more than
num seconds.
                     The default is 60 seconds.

                     Cache directory attributes for at least  num
seconds.  The
                     default is 5 seconds.

             noac    Disable attribute caching for both files and

                     Use specified port number for NFS  requests.
The default
                     is to query the portmapper for the NFS port.

     -r readsize
             Set the read data size to the specified  value.   It
should normally
  be  a  power of 2 greater than or equal to 1024.
This should be
             used for UDP mounts when the ``fragments dropped due
to timeout''
             value  is getting large while actively using a mount
point.  (Use
             netstat(1) with  the  -s  option  to  see  what  the
``fragments dropped
             due  to  timeout''  value is.)  See the -w option as

     -s      A soft mount, which implies that file  system  calls
will fail after
 Retry round trip timeout intervals.

     -t timeout
             Set  the initial retransmit timeout to the specified
value.  May
             be useful for fine tuning UDP mounts over  internetworks with high
             packet  loss rates or an overloaded server.  Try increasing the
             interval if nfsstat(1) shows high  retransmit  rates
while the file
             system is active or reducing the value if there is a
low retransmit
 rate but long response delay observed.  (Normally, the -d option
  should  be specified when using this option to
manually tune
             the timeout interval.)

     -w writesize
             Set the write data  size  to  the  specified  value.
Ditto the comments
  w.r.t.  the  -r option, but using the ``fragments dropped due
             to timeout'' value on  the  server  instead  of  the
client.  Note
             that  both the -r and -w options should only be used
as a last
             ditch effort at improving performance when  mounting
servers that
             do not support TCP mounts.

     -x retrans
             Set  the retransmit timeout count for soft mounts to
the specified

     In versions prior to OpenBSD 2.7, nfsiod daemons  were  running to improve
     performance  of client NFS I/O.  This is no longer done this
way.  Use
     sysctl(8)   or   modify   sysctl.conf(5)   to   adjust   the
vfs.nfs.iothreads value,
     which is the number of kernel threads created to serve asynchronous NFS
     I/O requests.

SEE ALSO    [Toc]    [Back]

     mount(2), fstab(5), mount(8), nfsd(8), sysctl(8), umount(8)

BUGS    [Toc]    [Back]

     Due to the way that Sun RPC is implemented  on  top  of  UDP
     datagram)  transport,  tuning  such mounts is really a black
art that can
     only be expected  to  have  limited  success.   For  clients
mounting servers
     that  are not on the same LAN cable or that tend to be overloaded, TCP
     transport is strongly recommended, but unfortunately this is
     to mostly 4.4BSD servers.

OpenBSD      3.6                          March      29,     1995
[ Back ]
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