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NAMEmount_nfs: mount, umount — mount and unmount NFS file systems SYNOPSIS/usr/sbin/mount
[-l]
[-p|-v] /usr/sbin/mount
-a
[-F
nfs]
[-eQ] /usr/sbin/mount
[-F
nfs]
[-eQrV]
[-o
specific_options]
{host:path|directory} /usr/sbin/mount
[-F
nfs]
[-eQrV]
[-o
specific_options]
host:path
directory /usr/sbin/umount
-a
[-f]
[-F
nfs]
[-h
host]
[-v] /usr/sbin/umount
[-f]
[-v]
[-V]
{host:path|directory} DESCRIPTIONThe
mount
command mounts file systems.
Only
a superuser
can mount file systems.
Other users can use
mount
to list mounted file systems. The
mount
command attaches
host:path
to
directory.
host
is a remote system,
path
is a directory on this remote system and
directory
is a directory on the local file tree.
directory
must already exist, be given as an absolute path name and
will become the name of the root of the newly mounted file system.
If either
host:path
or
directory
is omitted,
mount
attempts to determine the missing value from an entry in the
/etc/fstab
file.
mount
can be invoked on any removable file system, except
/. If
mount
is invoked without any arguments,
it lists all of the mounted file systems from the file system mount table,
/etc/mnttab.
The
umount
command unmounts mounted file systems.
Only a superuser can unmount file systems. Options- -r
Mount the specified file system read-only. - -o specific_options
Set file system specific options according to a comma-separated list
chosen from words below.
- rw|ro
resource
is mounted read-write or read-only.
The default is
rw. - suid|nosuid
Setuid execution allowed or disallowed.
The default is
suid. - remount
If a file system is mounted read-only,
remounts the file system read-write. - bg|fg
If the first attempt fails, retry in the background, or,
in the foreground.
The default is
fg. - quota
Enables
quota
to check whether the user is over quota on
this file system; if the file system has quotas enabled on the server,
quotas will still be checked for operations on this file system. - noquota
Prevent
quota
from checking whether the user exceeded the quota on
this file system; if the file system has quotas enabled on the server,
quotas will still be checked for operations on this file system. - retry=n
The number of times to retry the mount operation.
The default is
1. - vers=NFS_version_number
By default, the version of NFS
protocol used between the client
and the server is the highest one available on both systems.
If the
NFS server does not support
NFS Version 3, then the
NFS mount will
use
NFS Version 2 . - port=n
Set server UDP port number to
n
(the default is the port customarily used for NFS servers). - proto=transp
Use the transport protocol
transp
for this mount.
Valid values for
transp
are
tcp
(connection-oriented) and
udp
(connectionless).
The default behavior is to attempt a
tcp
connection.
If the
tcp
connection attempt fails when defaulting to
tcp,
a
udp
connection will be attempted. - grpid
By default, the
GID associated with a newly created file will obey the System V
semantics; that is, the
GID is set to the effective
GID of the calling process.
This behavior may be overridden on a
per-directory basis by setting the set-GID bit of the parent
directory; in this case, the
GID of a newly created file is set to the
GID of the parent directory (see
open(2)
and
mkdir(2)).
Files created on file systems that are mounted with the
grpid
option will obey
BSD semantics independent of whether the set-GID bit of the
parent directory is set; that is, the
GID is unconditionally inherited from that of the parent directory. - rsize=n
Set the read buffer size to
n
bytes.
The default value is set by kernel. - wsize=n
Set the write buffer size to
n
bytes.
The default value is set by kernel. - timeo=n
Set the
NFS timeout to
n
tenths of a second.
The default value is set by kernel. - retrans=n
Set the number of
NFS retransmissions to
n.
The default value is
5. - soft|hard
Return an error if the server does not respond,
or continue the retry request until the server responds.
The default value is
hard. - intr|nointr
Allow (do not allow) keyboard interrupts to kill a process that is
hung while waiting for a response on a hard-mounted file system.
The default is
intr. - noac
Suppress attribute caching. - nocto
Suppress fresh attributes when opening a file. - forcedirectio
If
forcedirectio
is specified, then for the duration of the mount,
forced direct I/O is used.
If the filesystem is mounted using
forcedirectio,
data is transferred directly between client and server,
with no buffering on the client.
forcedirectio
is a performance option that is of
benefit only in large sequential data transfers.
Running applications and mapping memory with
mmap()
are not supported over
forcedirectio
mount points.
The default behavior is no
forcedirectio. - devs|nodevs
Allow (do not allow) access to local devices.
The default is
devs. - acdirmax=n
Hold cached attributes for no more than
n
seconds after directory update.
The default value is
60. - acdirmin=n
Hold cached attributes for at least
n
seconds after directory update.
The default value is
30. - acregmax=n
Hold cached attributes for no more than
n
seconds after file modification.
The default value is
60. - acregmin=n
Hold cached attributes for at least
n
seconds after file modification.
The default value is
3. - actimeo=n
Set
min
and
max
times for regular files and directories to
n
seconds.
actimeo
has no default; it sets
acregmin,
acregmax,
acdirmin,
and
acdirmax
to the value specified. - llock
By default, lock/unlock requests are sent to the server's
rpc.lockd
which enforces the requests.
With this option
set, the lock/unlock requests are not sent to the remote
rpc.lockd
and are enforced locally.
These local locks
are enforced much faster, but if other NFS clients access
the same data on the server, there is a risk of data corruption.
Consequently, this option must be used when only one NFS
client accesses the data on the server. - readdir
Disable the
READDIRPLUS
functionality, which is used by default on an NFS v3
mount point, and use the NFS v2
READDIR
functionality instead.
The performance of applications that read huge directories over NFS will
vary between v2 and v3 depending on the type of information they need.
The find command will be faster using the v3
READDIRPLUS
while the ls command will be faster using the v2
READDIR.
This option must be used on a case by case basis.
It has no effect on a v2 mount point.
- -O
Overlay mount.
Allow the file system to be mounted over an
existing mount point, making the underlying file system
inaccessible.
If a mount is attempted on a pre-existing
mount point without setting this flag, the mount
will fail, producing the error
device busy.
Options (umount)umount
recognizes the following options:
- -a
Attempt to unmount all file systems described in
/etc/mnttab.
All optional fields in
/etc/mnttab
must be included and supported.
If
-F
nfs
option is specified, all NFS file systems in
/etc/mnttab
are unmounted.
File systems are not necessarily unmounted in the order listed in
/etc/mnttab. - -f
Forcibly
unmount
a file system.
Without this option,
umount
does not allow a file system to be unmounted if a file on the file
system is busy.
Using this option can cause data loss for open
files; programs which access files after the file system has been
unmounted will get an error (EIO). - -F nfs
Specify the NFS file system type (see
fstyp(1M)). - -h host
Unmount only those file systems listed in
/etc/mnttab
that are remote-mounted from
host. - -v
Verbose mode.
Write a message to standard output
indicating which file system is being unmounted. - -V
Echo the completed command line, but performs no other action.
The command line is generated
by incorporating the user-specified options
and other information derived from
/etc/fstab.
This option allows the user to verify the command line.
NFS File Systems- Background vs. Foreground
File systems mounted with the
bg
option indicate that
mount
is to retry in the background if the server's mount daemon
(mountd)
does not respond.
mount
retries the request up to the count specified in the
retry=n
option.
Once the file system is mounted, each
NFS request made in the kernel waits
timeo=n
tenths of a second for a response.
If no response arrives, the
time-out is multiplied by
2
and the request is retransmitted.
When the number of
retransmissions has reached the number specified in the
retrans=n
option, a file system mounted with the
soft
option returns an error on the request; one mounted with the
hard
option prints a warning message and continues to retry the request. - Hard vs. Soft
File systems that are mounted read-write or that
contain executable files should always be mounted with the
hard
option.
Applications using
soft
mounted file systems may incur unexpected I/O errors. To improve
NFS read performance, files and file attributes are cached.
File modification times get updated whenever a write occurs.
However, file access times may be temporarily out-of-date
until the cache gets refreshed.
The attribute cache retains file attributes on the client.
Attributes for a file are assigned a time to be
flushed.
If the file is modified before the flush time, then the
flush time is extended by the time since the last modification
(under the assumption that files that changed recently are likely
to change soon).
There is a minimum and maximum flush time extension for
regular files and for directories.
Setting
actimeo=n
sets flush time to
n
seconds for both regular files and directories.
EXAMPLESTo mount an NFS file system:
mount serv:/usr/src /usr/src To mount an NFS file system readonly with no suid privileges:
mount -r -o nosuid serv:/usr/src /usr/src To mount an NFS file system over Version 3:
mount -o vers=3 serv:/usr/src /usr/src To unmount all file systems imported from a given host,
enter the following command as root:
umount -h mysystem.home.work.com -a The hostname must match what is in
/etc/mnttab
exactly (as shown by the
bdf
command).
For example, if
bdf
shows:
the
umount
command would be
FILES- /etc/mnttab
table of mounted file systems. - /etc/fstab
list of default parameters for each file system.
STANDARDS CONFORMANCEmount: SVID3 umount: SVID3 |
