mount_nfs - mount NFS file systems
mount_nfs [-23PTUbcdilqs] [-D deadthresh] [-I readdirsize]
[-R retrycnt] [-a maxreadahead] [-g maxgroups] [-o
[-r readsize] [-t timeout] [-w writesize] [-x
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).
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
Set the readdir read size to the specified 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
clients. This option is ignored, and exists solely
with older systems.
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
This is NOT supported by most non-BSD servers.)
-U Force the mount protocol to use UDP transport, even
for TCP NFS
mounts. (Necessary for some old BSD servers.)
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.
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.
fstab(5), where the filesystem mount is not critical
-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
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
Set the maximum size of the group list for the credentials to the
specified value. This should be used for mounts on
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
from the mount point.
-i Make the mount interruptible, which implies that
calls that are delayed due to an unresponsive server
with EINTR when a termination signal is posted for
-l Used with NFSV3 to specify that the ReaddirPlus RPC
used. This option reduces RPC traffic for cases
such as ``ls
-l'', but tends to flood the attribute and name
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
Options are specified with a -o flag followed by a
string of options. See the mount(8) man page for
and their meanings. The following NFS specific options are
Cache file attributes for no more than num
default is 60 seconds.
Cache file attributes for at least num seconds. The default
is 5 seconds.
Cache directory attributes for no more than
The default is 60 seconds.
Cache directory attributes for at least num
default is 5 seconds.
noac Disable attribute caching for both files and
Use specified port number for NFS requests.
is to query the portmapper for the NFS port.
Set the read data size to the specified value. It
be a power of 2 greater than or equal to 1024.
This should be
used for UDP mounts when the ``fragments dropped due
value is getting large while actively using a mount
netstat(1) with the -s option to see what the
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.
Set the initial retransmit timeout to the specified
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
rate but long response delay observed. (Normally, the -d option
should be specified when using this option to
the timeout interval.)
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
that both the -r and -w options should only be used
as a last
ditch effort at improving performance when mounting
do not support TCP mounts.
Set the retransmit timeout count for soft mounts to
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
sysctl(8) or modify sysctl.conf(5) to adjust the
which is the number of kernel threads created to serve asynchronous NFS
mount(2), fstab(5), mount(8), nfsd(8), sysctl(8), umount(8)
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
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
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