nfs
NFS(5) Linux Programmer's Manual NFS(5)
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 rsize=8192,wsize=8192,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 ker-
nel, currently 1024 bytes. (However, throughput is
improved greatly by asking for rsize=8192.)
wsize=n The number of bytes NFS uses when writing files to an
NFS server. The default value is dependent on the ker-
nel, currently 1024 bytes. (However, throughput is
improved greatly by asking for wsize=8192.)
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 time-
out cascade restarts at twice the initial value of the
previous cascade, again doubling at each retransmission.
The maximum timeout is always 60 seconds. Better over-
all performance may be achieved by increasing the time-
out 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 informa-
tion 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 direc-
tory should be cached before requesting fresh informa-
tion from a server. The default is 30 seconds.
acdirmax=n The maximum time in seconds that attributes of a direc-
tory 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.
retry=n The number of minutes to retry an NFS mount operation in
the foreground or background before giving up. The
default value is 10000 minutes, which is roughly one
week.
namlen=n When an NFS server does not support version two of the
RPC mount protocol, this option can be used to specify
the maximum length of a filename that is supported on
the remote filesystem. This is used to support the
POSIX pathconf functions. The default is 255 charac-
ters.
port=n The numeric value of the port to connect to the NFS
server on. If the port number is 0 (the default) then
query the remote host's portmapper for the port number
to use. If the remote host's NFS daemon is not regis-
tered with its portmapper, the standard NFS port number
2049 is used instead.
mountport=n The numeric value of the mountd port.
mounthost=name The name of the host running mountd .
mountprog=n Use an alternate RPC program number to contact the mount
daemon on the remote host. This option is useful for
hosts that can run multiple NFS servers. The default
value is 100005 which is the standard RPC mount daemon
program number.
mountvers=n Use an alternate RPC version number to contact the mount
daemon on the remote host. This option is useful for
hosts that can run multiple NFS servers. The default
value is version 1.
nfsprog=n Use an alternate RPC program number to contact the NFS
daemon on the remote host. This option is useful for
hosts that can run multiple NFS servers. The default
value is 100003 which is the standard RPC NFS daemon
program number.
nfsvers=n Use an alternate RPC version number to contact the NFS
daemon on the remote host. This option is useful for
hosts that can run multiple NFS servers. The default
value is version 2.
nolock Disable NFS locking. Do not start lockd. This has to be
used with some old NFS servers that don't support lock-
ing.
bg If the first NFS mount attempt times out, retry the
mount in the background. After a mount operation is
backgrounded, all subsequent mounts on the same NFS
server will be backgrounded immediately, without first
attempting the mount. A missing mount point is treated
as a timeout, to allow for nested NFS mounts.
fg If the first NFS mount attempt times out, retry the
mount in the foreground. This is the complement of the
bg option, and also the default behavior.
soft If an NFS file operation has a major timeout then report
an I/O error 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. This
allows an NFS filesystem to properly support the POSIX
pathconf command by querying the mount server for the
maximum length of a filename. To do this, the remote
host must support version two of the RPC mount protocol.
Many NFS servers support only version one.
nocto Suppress 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.
tcp Mount the NFS filesystem using the TCP protocol instead
of the default UDP protocol. Many NFS servers only sup-
port UDP.
udp Mount the NFS filesystem using the UDP protocol. This
is the default.
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), exports(5)
AUTHOR
"Rick Sladkey" <jrs@world.std.com>
BUGS
The posix, and nocto options are parsed by mount but currently are
silently ignored.
The tcp and namlen options are implemented but are not currently sup-
ported by the Linux kernel.
The umount command should notify the server when an NFS filesystem is
unmounted.
Linux 0.99 20 November 1993 NFS(5)
