mount_nfs
—
mount remote NFS resources
mount |
[-F nfs]
[generic_options] [-o
specific_options]
resource |
mount |
[-F nfs]
[generic_options] [-o
specific_options]
mount_point |
mount |
[-F nfs]
[generic_options] [-o
specific_options] resource
mount_point |
The mount
utility attaches a named
resource to the file system 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.
mount_nfs
starts the
lockd(8) and
statd(8) daemons if they are not
already running.
If the resource is listed in the
/etc/vfstab file, the command line can specify
either resource or mount_point,
and mount
consults
/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.
host can be an IPv4 or IPv6 address string.
As IPv6 addresses already contain colons, enclose host
in a pair of square brackets when specifying an IPv6 address string.
Otherwise the first occurrence of a colon can be interpreted as the
separator between the host name and path, for example,
[1080::8:800:200C:417A]:tmp/file
. See
inet(4P) and
inet6(4P).
- 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 is the case.
- nfs://host[:port]/pathname
- This is an NFS URL and follows the standard convention for NFS URLs as
described in RFC 2224,
NFS URL Scheme. See the discussion of URLs
and the public option under NFS
FILE SYSTEMS for a more detailed discussion.
- host:pathname
nfs://host[:port]/pathname
- host:pathname is a
comma-separated list of
host:pathname. See the
discussion of replicated file systems and failover under
NFS FILE SYSTEMS for a more
detailed discussion.
- hostlist pathname
- hostlist is a comma-separated list of hosts. See the
discussion of replicated file systems and failover under
NFS FILE SYSTEMS for a more
detailed discussion.
The mount
command maintains a table of
mounted file systems in /etc/mnttab, described in
mnttab(5).
mount_nfs
supports both NFSv3 and NFSv4
mounts. The default NFS version is NFSv4.
See mount(8) for the list of supported
generic_options. See
share_nfs(8) for a description of
server options.
-o
specific_options
- Set file system specific options according to a comma-separated list with
no intervening spaces.
The following list describes
specific_options:
- 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. See
File Attributes, below, for a
description of the effect of setting this option to 0.
See
Specifying
Values for Attribute Cache Duration Options, below, for a
description of how acdirmax,
acdirmin, acregmax,
acregmin, and actimeo are parsed on
a mount
command line.
- bg|fg
- If the first attempt fails, retry in the background, or, in the
foreground. The default is fg.
- forcedirectio|noforcedirectio
- 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. If the filesystem is
mounted using noforcedirectio, data is buffered on the
client. forcedirectio is a performance option that is of
benefit only in large sequential data transfers. The default behavior is
noforcedirectio.
- grpid
- By default, the GID associated with a newly created file obeys the System
V semantics; that is, the GID is set to the effective GID of the calling
process. This behavior can 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 obeys 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.
Note that NFSv4 clients do not support soft mounts.
- 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 can be waiting for a remote mount.
- noac
- Suppress data and attribute caching. The data caching that is suppressed
is the write-behind. The local page cache is still maintained, but data
copied into it is immediately written to the server.
- nocto
- Do not perform the normal close-to-open consistency. 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 possibility 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 are 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 URL must be the same.
- posix
- Request POSIX.1 semantics for the file system. Requires a mount Version 2
mountd(8) on the server. See
standards(7) for information
regarding POSIX.
- proto=netid|rdma
- By default, the transport protocol that the NFS mount uses is the first
available RDMA transport supported both by the client and the server. If
no RDMA transport is found, then it attempts to use a TCP transport or,
failing that, a UDP transport, as ordered in the
/etc/netconfig file. If it does not find a
connection oriented transport, it uses the first available connectionless
transport. Use this option to override the default behavior.
proto is set to the value of
netid or rdma.
netid is the value of the
network_id field entry in the
/etc/netconfig file.
The UDP protocol is not supported for NFS Version 4. If you
specify a UDP protocol with the proto option, NFS
version 4 is not used.
- public
- The public option forces the use of the public file
handle when connecting to the NFS server. The resource specified might not
have an NFS URL. See the discussion of URLs and the public option under
NFS FILE SYSTEMS for a more
detailed discussion.
- quota|noquota
- Enable or prevent quota(8) to check
whether the user is over quota on this file system; if the file system has
quotas enabled on the server, quotas are still 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 performs retransmissions
on behalf of NFS.
- retry=n
- The number of times to retry the
mount
operation.
The default for the mount
command is 10000.
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.
- rsize=n
- Set the read buffer size to a maximum of n bytes.
The default value is 1048576 when using connection-oriented transports
with Version 3 or Version 4 of the NFS protocol, and 32768 when using
connection-less transports. The default can be negotiated down if the
server prefers a smaller transfer size. “Read” operations
may not necessarily use the maximum buffer size. When using Version 2, the
default value is 32768 for all transports.
- 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, use a user-configured default
auth over NFS version 3 mounts, or to negotiate a mode
over Version 4 mounts.
The preferred mode for NFS Version 3 mounts is the default
mode specified in /etc/nfssec.conf (see
nfssec.conf(5)) on the
client. If there is no default configured in this file or if the server
does not export using the client's default mode, then the client picks
the first mode that it supports in the array of modes returned by the
server. These alternatives are limited to the security flavors listed in
/etc/nfssec.conf.
NFS Version 4 mounts negotiate a security mode when the server
returns an array of security modes. The client attempts the mount with
each security mode, in order, until one is successful.
Only one mode can be specified with the sec=
option. See nfssec(7) for the
available mode options.
- secure
- This option has been deprecated in favor of the
sec=dh option.
- timeo=n
- Set the NFS timeout to n tenths of a second. The
default value is 11 tenths of a second for connectionless transports, and
600 tenths of a second for connection-oriented transports. This value is
ignored for connectionless transports. Such transports might implement
their own timeouts, which are outside the control of NFS.
- 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 the client's default maximum, the next lowest version
attempted until a matching version is found. See
nfs(5) for more information on setting
default minimum and maximum client versions.
- wsize=n
- Set the write buffer size to a maximum of n bytes.
The default value is 1048576 when using connection-oriented transports
with Version 3 or Version 4 of the NFS protocol, and 32768 when using
connection-less transports. The default can be negotiated down if the
server prefers a smaller transfer size. “Write” operations
may not necessarily use the maximum buffer size. When using Version 2, the
default value is 32768 for all transports.
- xattr|noxattr
- Allow or disallow the creation and manipulation of extended attributes.
The default is xattr. See
fsattr(7) for a description of
extended attributes.
File systems mounted with the bg option indicate that
mount
is to retry in the background if the server's
mount daemon (mountd(8)) 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
description 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.
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 can incur unexpected I/O errors,
file corruption, and unexpected program core dumps. The soft
option is not recommended.
The server can require authenticated NFS requests from the client.
sec=dh authentication might be required.
See nfssec(7).
If the public option is specified, or if the
resource includes and NFS URL,
mount
attempts to connect to the server using the
public file handle lookup protocol. See RFC
2054, WebNFS Client Specification. If
the server supports the public file handle, the attempt is successful;
mount
does not need to contact the server's
rpcbind(8) and the
mountd(8) daemons 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 outbound connections through specific
ports, such as NFS_PORT
, then this enables NFS
operations 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
mount if not supported. mount if not supported.
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 RFC 1738,
Uniform Resource Locators (URL).
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 can 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 uses the next alternate server to access files. If the read-only
option is not chosen, replication is disabled. File access, for NFS Versions 2
and 3, is blocked on the original if NFS locks are active for that file.
To improve NFS read performance, files and file attributes are cached. File
modification times get updated whenever a write occurs. However, file access
times can 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.
Setting actimeo=0 disables
attribute caching on the client. This means that every reference to
attributes is satisfied directly from the server though file data is still
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 is 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)) are
not written directly to this server.
The attribute cache duration options are acdirmax,
acdirmin, acregmax,
acregmin, and actimeo, as described under
Options. A value specified for
actimeo sets the values of all attribute cache duration
options except for any of these options specified following
actimeo on a mount
command line. For
example, consider the following command:
example# mount -o acdirmax=10,actimeo=1000 server:/path /localpath
Because actimeo is the last duration option in
the command line, its value (1000) becomes the setting for all of the
duration options, including acdirmax. Now consider:
example# mount -o actimeo=1000,acdirmax=10 server:/path /localpath
Because the acdirmax option follows
actimeo on the command line, it is assigned the value
specified (10). The remaining duration options are set to the value of
actimeo (1000).
- /etc/mnttab
- table of mounted file systems
- /etc/dfs/fstypes
- default distributed file system type
- /etc/vfstab
- table of automatically mounted resources
- 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
- 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 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 8 Mounting a Replicated Set of NFS File Systems
with Different Pathnames
- To mount a replicated set of NFS file systems with different pathnames:
example# mount serv-x:/usr/man,serv-y:/var/man,nfs://serv-z/man /usr/man
rdist(1),
mkdir(2),
mmap(2),
mount(2),
open(2),
umount(2),
lofs(4FS),
inet(4P),
inet6(4P),
mnttab(5),
nfs(5),
nfssec.conf(5),
attributes(7),
fsattr(7),
nfssec(7),
standards(7),
lockd(8),
mountall(8),
mountd(8),
nfsd(8),
quota(8),
statd(8)
Callaghan and
Brent, RFC 2054,
WebNFS Client Specification,
October 1996.
Callaghan and
Brent, RFC 2224,
NFS URL Scheme, October
1997.
Berners-Lee,
Masinter, and McCahill,
RFC 1738, Uniform Resource
Locators (URL), December 1994.
An NFS server should not attempt to mount its own file systems. See
lofs(4FS).
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.
The NFS client service is managed by the service management
facility, smf(7), under the service
identifier:
svc:/network/nfs/client:default
Administrative actions on this service, such as enabling,
disabling, or requesting restart, can be performed using
svcadm(8). The service's status can be
queried using the svcs(1) command.