NFS
Section: File Formats (5)
Updated: 11 January 1993
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NAME
nfs - nfs fstab format and options
SYNOPSIS
/etc/fstab
DESCRIPTION
The
fstab
file contains information about which filesystems
to mount where and with what options.
For NFS mounts, it contains the server name and
exported server directory to mount from,
the local directory that is the mount point,
and the NFS specific options that control
the way the filesystem is mounted.
Here is an example from an /etc/fstab file from an NFS mount.
server:/usr/local/pub /pub nfs timeo=14,intr
Options
- rsize=n
-
The number of bytes NFS uses when reading files from an NFS server.
The default value is dependent on the kernel, currently 1024 bytes.
- wsize=n
-
The number of bytes NFS uses when writing files to an NFS server.
The default value is dependent on the kernel, currently 1024 bytes.
- timeo=n
-
The value in tenths of a second before sending the
first retransmission after an RPC timeout.
The default value is 7 tenths of a second. After the first timeout,
the timeout is doubled after each successive timeout until a maximum
timeout of 60 seconds is reached or the enough retransmissions
have occured to cause a major timeout. Then, if the filesystem
is hard mounted, each new timeout cascade restarts at twice the
initial value of the previous cascade, again doubling at each
retransmission. The maximum timeout is always 60 seconds.
Better overall performance may be achieved by increasing the
timeout when mounting on a busy network, to a slow server, or through
several routers or gateways.
- retrans=n
-
The number of minor timeouts and retransmissions that must occur before
a major timeout occurs. The default is 3 timeouts. When a major timeout
occurs, the file operation is either aborted or a "server not responding"
message is printed on the console.
- acregmin=n
-
The minimum time in seconds that attributes of a regular file should
be cached before requesting fresh information from a server.
The default is 3 seconds.
- acregmax=n
-
The maximum time in seconds that attributes of a regular file can
be cached before requesting fresh information from a server.
The default is 60 seconds.
- acdirmin=n
-
The minimum time in seconds that attributes of a directory should
be cached before requesting fresh information from a server.
The default is 30 seconds.
- acdirmax=n
-
The maximum time in seconds that attributes of a directory can
be cached before requesting fresh information from a server.
The default is 60 seconds.
- actimeo=n
-
Using actimeo sets all of
acregmin,
acregmax,
acdirmin,
and
acdirmax
to the same value.
There is no default value.
- port=n
-
The numeric value of the UDP port to connect to the NFS server on.
The default is the standard NFS port number 2049.
- retry=n
-
The number of times to retry a backgrounded NFS mount operation
before giving up.
The default value is 10000 times.
- bg
-
If the first NFS mount attempt times out, continue trying the mount
in the background.
The default is to not to background the mount on timeout but fail.
- fg
-
If the first NFS mount attempt times out, fail immediately.
This is the default.
- soft
-
If an NFS file operation has a major timeout then report an IO to
the calling program.
The default is to continue retrying NFS file operations indefinitely.
- hard
-
If an NFS file operation has a major timeout then report
"server not responding" on the console and continue retrying indefinitely.
This is the default.
- intr
-
If an NFS file operation has a major timeout and it is hard mounted,
then allow signals to interupt the file operation and cause it to
return EINTR to the calling program. The default is to not
allow file operations to be interrupted.
- posix
-
Mount the NFS filesystem using POSIX semantics.
- nocto
-
Supress the retrieval of new attributes when creating a file.
- noac
-
Disable all forms of attribute caching entirely. This extracts a
server performance penalty but it allows two different NFS clients
to get reasonable good results when both clients are actively
writing to common filesystem on the server.
All of the non-value options have corresponding nooption forms.
For example, nointr means don't allow file operations to be
interrupted.
FILES
/etc/fstab
SEE ALSO
fstab(5), mount(8), umount(8)
AUTHOR
"Rick Sladkey" <jrs@world.std.com>
BUGS
The bg, fg retry, posix, and nocto options are parsed by mount
but currently are silently ignored.
The umount command should notify the server
when an NFS filesystem is unmounted.
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- Options
-
- FILES
-
- SEE ALSO
-
- AUTHOR
-
- BUGS
-
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