SunOS man pages : mount_nfs (1)
Maintenance Commands mount_nfs(1M)
NAME
mount_nfs - mount remote NFS resources
SYNOPSIS
mount [ -F nfs ] [ generic_options ] [
-o specific_options ] [ -O ] resource
mount [ -F nfs ] [ generic_options ] [
-o specific_options ] [ -O ] mount_point
mount [ -F nfs ] [ generic_options ] [
-o specific_options ] [ -O ] resource mount_point
DESCRIPTION
The mount utility attaches a named resource to the file sys-
tem hierarchy at the pathname location mount_point, which
must already exist. If mount_point has any contents prior to
the mount operation, the contents remain hidden until the
resource is once again unmounted.
If the resource is listed in the /etc/vfstab file, the com-
mand line can specify either resource or mount_point, and
mount will consult /etc/vfstab for more information. If the
-F option is omitted, mount takes the file system type from
/etc/vfstab.
If the resource is not listed in the /etc/vfstab file, then
the command line must specify both the resource and the
mount_point.
A named resource can have one of the following formats:
host:pathname
Where host is the name of the NFS server host,
and pathname is the path name of the directory on
the server being mounted. The path name is
interpreted according to the server's path name
parsing rules and is not necessarily slash-
separated, though on most servers, this will be
the case.
nfs://host[:port]/pathname
This is an NFS URL and follows the standard con-
vention for NFS URLs as described in Internet RFC
2225 - NFS URL Scheme. See the discussion of
URL's and the public option under NFS FILE SYS-
TEMS below for a more detailed discussion.
nfs://host[:port]/pathname resources
A comma-
separated list of host:pathname and/or
See the discussion of Replicated file systems and
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failover under NFS FILE SYSTEMS below for a more
detailed discussion.
fix
A comma-
separated list of hosts followed by a :pathname suf-
See the discussion of Replicated file systems and
failover under NFS FILE SYSTEMS below for a more
detailed discussion
mount maintains a table of mounted file systems in /etc/mnt
tab, described in mnttab(4).
OPTIONS
See mount(1M) for the list of supported generic_options.
-o specific_options
Set file system specific options according to a
comma-separated list with no intervening spaces.
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.
bg | fg
If the first attempt fails, retry in the back-
ground, or, in the foreground. The default is
fg.
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
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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.
hard | soft
Continue to retry requests until the server
responds (hard) or give up and return an error
(soft). 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, which makes it possible for
clients to interrupt applications that may be
waiting for a remote mount.
noac Suppress data and attribute caching.
nocto Do not perform the normal close-to-open con-
sistency. When a file is closed, all modified
data associated with the file is flushed to the
server and not held on the client. When a file
is opened the client sends a request to the
server to validate the client's local caches.
This behavior ensures a file's consistency
across multiple NFS clients. When -nocto is in
effect, the client does not perform the flush on
close and the request for validation, allowing
the possiblity of differences among copies of
the same file as stored on multiple clients.
This option can be used where it can be
guaranteed that accesses to a specified file
system will be made from only one client and
only that client. Under such a condition, the
effect of -nocto can be a slight performance
gain.
port=n
The server IP port number. The default is
NFS_PORT. If the port option is specified, and
if the resource includes one or more NFS URLs,
and if any of the URLs include a port number,
then the port number in the option and in the
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URL must be the same.
posix Request POSIX.1 semantics for the file system.
Requires a mount Version 2 mountd(1M) on the
server. See standards(5) for information regard-
ing POSIX.
proto=<netid>
<netid> is a value of network_id field from
entry in the /etc/netconfig file. By default,
the transport protocol used for the NFS mount
will be first available connection oriented
transport supported on both the client and the
server. If no connection oriented transport is
found, then the first available connectionless
transport is used. This default behavior can be
overridden with the proto=<netid> option.
public
The public option forces the use of the public
file handle when connecting to the NFS server.
The resource specified may or may not have an
NFS URL. See the discussion of URL's and the
public option under NFS FILE SYSTEMS below for a
more detailed discussion.
quota | noquota
Enable or prevent quota(1M) 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.
remount
Remounts a read-only file system as read-write
(using the rw option). This option cannot be
used with other -o options, and this option
works only on currently mounted read-only file
systems.
retrans=n
Set the number of NFS retransmissions to n. The
default value is 5. For connection-oriented
transports, this option has no effect because it
is assumed that the transport will perform
retransmissions on behalf of NFS.
retry=n
The number of times to retry the mount opera-
tion. The default for the mount command is
10000.
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The default for the automounter is 0, in other
words, do not retry. You might find it useful to
increase this value on heavily loaded servers,
where automounter traffic is dropped, causing
unnecessary ``server not responding'' errors.
ro | rw
resource is mounted read-only or read-write. The
default is rw.
rsize=n
Set the read buffer size to n bytes. The default
value is 32768 when using Version 3 of the NFS
protocol. The default can be negotiated down if
the server prefers a smaller transfer size. When
using Version 2, the default value is 8192.
sec=mode
Set the security mode for NFS transactions. If
sec= is not specified, then the default action
is to use AUTH_SYS over NFS Version 2 mounts, or
to negotiate a mode over NFS Version 3 mounts.
NFS Version 3 mounts negotiate a security mode
when the server returns an array of security
modes. The client will pick the first mode in
the array that is supported on the client. Only
one mode can be specified with the sec= option.
See nfssec(5) for the available mode options.
secure
This option has been deprecated in favor of the
sec=dh option.
suid | nosuid
Allow or disallow setuid execution. The default
is suid.
timeo=n
Set the NFS timeout to n tenths of a second. The
default value is 11 tenths of a second for con-
nectionless transports, and 600 tenths of a
second for connection-oriented transports.
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 protocol, then
the NFS mount will use NFS Version 2 protocol.
wsize=n
Set the write buffer size to n bytes. The
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default value is 32768 when using Version 3 of
the NFS protocol. The default can be negotiated
down if the server prefers a smaller transfer
size. When using Version 2, the default value is
8192.
-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."
NFS FILE SYSTEMS
Background versus Foreground
File systems mounted with the bg option indicate that
mount is to retry in the background if the server's
mount daemon ( mountd(1M)) does not respond. mount
retries the request up to the count specified in the
retry=n option. (Note that the default value for retry
differs between mount and automount. See the descrip-
tion of retry, above.) 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 versus Soft
File systems that are mounted read-write or that con-
tain executable files should always be mounted with
the hard option. Applications using soft mounted file
systems may incur unexpected I/O errors, file corrup-
tion, and unexpected program core dumps. The soft
option is not recommended.
Authenticated Requests
The server may require authenticated NFS requests from
the client. Either sec=dh or sec=krb4 authentication
may be required. See nfssec(5).
URLs and the public option
If the public option is specified, or if the resource
includes and NFS URL, mount will attempt to connect to
the server using the public file handle lookup proto-
col. See Internet RFC 2054 - WebNFS Client Specifica-
tion. If the server supports the public file handle,
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the attempt is successful; mount will not need to con-
tact the server's rpcbind(1M), and the mountd(1M) dae-
mons to get the port number of the mount server and
the initial file handle of pathname, respectively. If
the NFS client and server are separated by a firewall
that allows all outbount connections through specific
ports, such as NFS_PORT, then this enables NFS opera-
tions through the firewall. The public option and the
NFS URL can be specified independently or together.
They interact as specified in the following matrix:
___________________________________________________________________
| | resource |
|____________________|______________________|______________________|
| style | | |
|____________________|______________________|______________________|
| | host:pathname | NFS URL |
|____________________|______________________|______________________|
| public option | + force public file | + force public file|
| | handle and fail | handle and fail moun-|
| | mountif not sup- | tif not supported. |
| | ported. | |
|____________________|______________________|______________________|
| | + use Native paths | + use Canonical paths|
|____________________|______________________|______________________|
| default | + use MOUNT protocol | + try public file|
| | | handle with Canonical|
| | | paths. Fall back to|
| | | MOUNT protocol if not|
| | | supported. |
|____________________|______________________|______________________|
A Native path is a path name that is interpreted
according to conventions used on the native operating
system of the NFS server. A Canonical path is a path
name that is interpreted according to the URL rules.
See Internet RFC 1738 - Uniform Resource Locators
(URL). Also, see EXAMPLES for uses of Native and
Canonical paths.
Replicated file systems and failover
resource can list multiple read-only file systems to
be used to provide data. These file systems should
contain equivalent directory structures and identical
files. It is also recommended that they be created by
a utility such as rdist(1). The file systems may be
specified either with a comma-separated list of
host:/pathname entries and/or NFS URL entries, or with
a comma -separated list of hosts, if all file system
names are the same. If multiple file systems are named
and the first server in the list is down, failover
will use the next alternate server to access files. If
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the read-only option is not chosen, replication will
be disabled. File access will block on the original if
NFS locks are active for that file.
File Attributes
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. Set-
ting actimeo=n sets flush time to n seconds for both regular
files and directories.
Setting actimeo=0 disables attribute caching on the client.
This means that every reference to attributes will be satis-
fied directly from the server though file data will still be
cached. While this guarantees that the client always has the
latest file attributes from the server, it has an adverse
effect on performance through additional latency, network
load, and server load.
Setting the noac option also disables attribute caching, but
has the further effect of disabling client write caching.
While this guarantees that data written by an application
will be written directly to a server, where it can be viewed
immediately by other clients, it has a significant adverse
effect on client write performance. Data written into
memory-mapped file pages (mmap(2)) will not be written
directly to this server.
EXAMPLES
Example 1: Mounting An NFS File System
To mount an NFS file system:
example# mount serv:/usr/src /usr/src
Example 2: Mounting An NFS File System Read-Only With No
Suid Privileges
To mount an NFS file system read-only with no suid
privileges:
example# mount -r -o nosuid serv:/usr/src /usr/src
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Example 3: Mounting An NFS File System Over Version 2, With
The UDP Transport
To mount an NFS file system over Version 2, with the UDP
transport:
example# mount -o vers=2,proto=udp serv:/usr/src /usr/src
Example 4: Mounting An NFS File System Using An NFS URL
To mount an NFS file system using an NFS URL (a canonical
path):
example# mount nfs://serv/usr/man /usr/man
Example 5: Mounting An NFS File System Forcing Use Of The
Public File Handle
To mount an NFS file system and force the use of the public
file handle and an NFS URL (a canonical path) that has a non
7-bit ASCII escape sequence:
example# mount -o public nfs://serv/usr/%A0abc /mnt/test
Example 6: Mounting An NFS File System Using A Native Path
To mount an NFS file system using a native path (where the
server uses colons (":") as the component separator) and the
public file handle:
example# mount -o public serv:C:doc:new /usr/doc
Example 7: Mounting an NFS file system using AUTH_KERB
authentication.
To mount an NFS file system using AUTH_KERB authentication:
example# mount -o sec=krb4 serv:/usr/src /usr/src
Example 8: Mounting a replicated set of NFS file systems
with the same pathnames.
To mount a replicated set of NFS file systems with the same
pathnames:
example# mount serv-a,serv-b,serv-c:/usr/man /usr/man
Example 9: Mounting a replicated set of NFS file systems
with different pathnames.
To mount a replicated set of NFS file systems with different
pathnames:
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example# mount serv-x:/usr/man,serv-y:/var/man,nfs://serv-z/man /usr/man
FILES
/etc/mnttab
table of mounted file systems
/etc/dfs/fstypes
default distributed file system type
/etc/vfstab
table of automatically mounted resources
ATTRIBUTES
See attributes(5) for descriptions of the following attri-
butes:
____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|_____________________________|_____________________________|
| Availability | SUNWcsu |
|_____________________________|_____________________________|
SEE ALSO
rdist(1), mountall(1M), mountd(1M), quota(1M), mkdir(2),
mmap(2), mount(2), open(2), umount(2), mnttab(4), attributes(5)
, nfssec(5), standards(5), lofs(7FS)
Internet RFC 1738- Uniform Resource Locators (URL)
Internet RFC 2054 - WebNFS Client Specification
Internet RFC 2225 - NFS URL Scheme
NOTES
An NFS server should not attempt to mount its own file sys-
tems. See lofs(7FS).
If the directory on which a file system is to be mounted is
a symbolic link, the file system is mounted on the directory
to which the symbolic link refers, rather than being mounted
on top of the symbolic link itself.
SunOS 4.X used the biod maintenance procedure to perform
parallel read-ahead and write-behind on NFS clients. SunOS
5.X made biod obsolete with multi-threaded processing, which
transparently performs parallel read-ahead and write-behind.
Since the root (/) file system is mounted read-only by the
kernel during the boot process, only the remount option (and
options that can be used in conjunction with remount) affect
the root (/) entry in the /etc/vfstab file.
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