MOUNT_NFS(8) Maintenance Commands and Procedures MOUNT_NFS(8)

NAME

mount_nfs - mount remote NFS resources

SYNOPSIS

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

DESCRIPTION

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.

Options

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.

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(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.

Hard versus 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 can incur unexpected I/O errors, file corruption, and
unexpected program core dumps. The soft option is not recommended.

Authenticated requests

The server can require authenticated NFS requests from the client. sec=dh
authentication might be required. See nfssec(7).

URLs and the public option

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).

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 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.

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 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.

Specifying Values for Attribute Cache Duration Options

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).

FILES

/etc/mnttab
table of mounted file systems

/etc/dfs/fstypes
default distributed file system type

/etc/vfstab
table of automatically mounted resources

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

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

SEE ALSO

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.

NOTES

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.

illumos March 12, 2016 illumos