mount_nfs(1M) manual page
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mount_nfs - mount remote NFS resources
mount [ -F nfs ] [
-r ] [ -m ] [ -o specific_options ] [ -O ] resource
mount [ -F nfs ] [ -r ] [ -m ] [ -o specific_options ] [ -O ] mount_point
SUNWcsu
mount 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.
If the resource is listed in the /etc/vfstab file, the command 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.
mount maintains a table of mounted file systems in
/etc/mnttab, described in mnttab(4)
.
- -r
- Mount the specified file system
read-only.
- -m
- Do not append an entry to the /etc/mnttab table of mounted file
systems
- -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(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.
- noquota
- Prevent quota(1M)
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 10000.
- 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
- 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.
- port=n
- The server IP
port number.
The default is NFS_PORT
.
- 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 32768 when using
Version 3 of the NFS
protocol. When using Version 2, the default value
is 8192.
- wsize=n
- Set the write buffer size to n bytes. The default value
is 32768 when using Version 3 of the NFS
protocol. When using Version
2, the default value is 8192.
- 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 100 tenths of a second for connection-oriented transports.
- 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
.
- 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.
- secure
- Use DES
authentication for NFS
transactions.
- posix
- Request
POSIX.1
semantics for the file system. Requires a mount Version 2 mountd(1M)
on the server.
- kerberos
- Use Kerberos authentication for NFS
transactions.
- noac
- Suppress data and attribute caching.
- 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.
- -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.’
- 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. 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
may incur unexpected I/O errors.
- Authenticated Requests
- The server may require
authenticated NFS
requests from the client. Either secure or kerberos authentication
may be required.
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.
Setting actimeo=n disables attribute caching on the client. This means
that every reference to attributes will be satisfied 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.
To mount an NFS
file system:
example# mount serv:/usr/src
/usr/src
To mount an NFS
file system read-only with no suid privileges:
example# mount -r -o nosuid serv:/usr/src /usr/src
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
- /etc/mnttab
- table of mounted file systems
- /etc/dfs/fstypes
- default
distributed file system type
- /etc/vfstab
- table of automatically mounted
resources
mountall(1M)
, mountd(1M)
, quota(1M)
, mkdir(2)
, mmap(2)
,
mount(2)
, open(2)
, umount(2)
, mnttab(4)
, lofs(7FS)
A NFS
server should
not attempt to mount its own file systems (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 obsoleted biod with multi-threaded processing, which
transparently performs parallel read-ahead and write-behind.
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