MirOS Manual: mount_nfs(8)

MOUNT_NFS(8)             BSD System Manager's Manual              MOUNT_NFS(8)

NAME

     mount_nfs - mount NFS file systems

SYNOPSIS

     mount_nfs [-23bcdilsTU] [-a maxreadahead] [-g maxgroups] [-I readdirsize]
               [-o options] [-R retrycnt] [-r readsize] [-t timeout]
               [-w writesize] [-x retrans] rhost:path node

DESCRIPTION

     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 fails.

     -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 file system mount is not critical to mul-
             tiuser operation.

     -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 ad-
             dress 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
             short.

     -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 readdirsize
             Set the readdir read size to the specified value. The value
             should normally be a multiple of DIRBLKSIZ that is less than or
             equal to the read size for the mount.

     -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 "readdir plus" 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 performance improves or
             degrades. Probably most useful for client to server network in-
             terconnects with a large bandwidth-delay product.

     -o options
             Options are specified with a -o flag followed by a comma separat-
             ed string of options. The prefix "no" may be added to invert the
             behavior of default options that do not take arguments. See the
             mount(8) man page for possible options and their meanings.

             The following NFS specific options are also available:

             ac   Enable attribute caching for both files and directories (de-
                  fault).

             acregmax=num
                  Cache file attributes for no more than num seconds. The de-
                  fault is 60 seconds.

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

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

             acdirmin=num
                  Cache directory attributes for at least num seconds. The de-
                  fault is 5 seconds.

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

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

     -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 after timeout"
             value is getting large while actively using a mount point. (Use
             netstat(1) with the -s option to see what this value is.) See the
             -w option as well.

     -s      A soft mount, which implies that file system calls will fail
             after retrans round trip timeout intervals have been reached (see
             -x).

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

     -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 in-
             terval if nfsstat(1) shows high retransmit rates while the file
             system is active or reducing the value if there is a low re-
             transmit rate but long response delay observed. (Normally, the -d
             option should be specified when using this option to manually
             tune the timeout interval.)

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

     -w writesize
             Set the write data size to the specified value. Ditto the com-
             ments w.r.t. the -r option, but using the "fragments dropped
             after 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
             value. Defaults to 10.

     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

     nfsstat(1), mount(2), tcp(4), udp(4), fstab(5), mount(8), nfsd(8),
     sysctl(8), umount(8)

HISTORY

     The -P flag historically informed the kernel to use a reserved port when
     communicating with clients. In OpenBSD, a reserved port is always used.

BUGS

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

MirOS BSD #10-current           March 29, 1995                               2

Generated on 2014-07-04 21:17:45 by $MirOS: src/scripts/roff2htm,v 1.79 2014/02/10 00:36:11 tg Exp $

These manual pages and other documentation are copyrighted by their respective writers; their source is available at our CVSweb, AnonCVS, and other mirrors. The rest is Copyright © 2002‒2014 The MirOS Project, Germany.
This product includes material provided by Thorsten Glaser.

This manual page’s HTML representation is supposed to be valid XHTML/1.1; if not, please send a bug report – diffs preferred.